Ala Carte MENU: Plate Current vs Cathode Current @ 01:50 Proper SE Bias Procedure Discussion @ 04:35 Performance of Manual SE Bias Procedure @ 07:16 Performance of Eurotubes SE Bias Procedure @ 12:51 Comparison of Results for SE Amp Circuit @ 14:05 Manual Measurement of Screen Current @ 15:08 Open 1st Gift Box w/Jack & KC @ 16:39 Performance of Manual DE Bias Procedure @ 19:31 Performance of Eurotubes DE Bias Procedure @ 25:33 Comparison of Results for DE Amp Circuit @ 26:46 Open 3 more Gift Boxes @ 27:38 Final Discussion of Eurotubes Bias Probe @ 29:36 Build Your Own Bias Probe @ 32:08 Closing Statements @ 45:58 Car Show @ 47:27
Great video! I had an electronics instructor years ago that had been working on electronics for many decades. Some sage advice from him: “if you accidentally or intentionally touch the input of a rectifier while the circuit has power, it instantly becomes a Rectum-Frier”.
Uncle Doug, that was a masterfully done educational video. We love your amp videos and you have such a unique eloquent way of teaching us all!!! Bless you and your family.
A friend of mine used to own an amp repair business but closed a few years ago. He gave me a pair of these testers and they sure make biasing much easier. Thank you, Doug for teaching us that which cannot be found in any classroom today! I hope you are doing well, Good Sir!
Uncle Doug, Based on your posts I am pretty sure you are older than me by a few years, but wow, when I watch your videos do I ever connect with your "vibe", and I am guessing that there are thousands of others out there who feel the same. Please keep doing what you do. It is very educational and very important.
Thanks so much, Walter. I'm 73, and am glad to still be able to connect with the audience, instead of a rocking chair and Metamucil :) We definitely will continue for as long as we're able .
@@UncleDoug and I am 68 and a Fender-a-holic. Do you have any advice re my other post about the specifics of how to deal with my newly purchased vintage Fender Bassman?
The only suggestion I would make regarding making your own bias probe, is to chassis mount the tube socket, since output tubes can generate a lot of heat and wouldn't want to melt or singe the surface it rests on, and use recessed, isolated probe lead connections in same chassis to prevent inadvertent death sentence execution. As always, top notch teaching of tube theory, testing and appreciate you inviting us to your home, love of classic cars and pets. Miss Rusty.
Great video. I got one of these, after waiting for almost a year for these to be back in inventory at Eurotubes. I think it was worth it though, as it's not easy to find one that reads plate voltage. Only other one I found was a kit that plugged into an existing multi meter. Now it's been sitting for almost a year and I never yet had the need to bias anything. Soon I have a '71 Super Reverb arriving though and I'm going to want to check bias settings for the (new make) Telefunken 6L6GC's I have set aside. I believe for this amp it would require changing a bias resistor (it has a balance pot but not a bias, if I remember right). This video is a great reference on using this probe. This channel is a great reference library on tube amp function in general
THANK YOU David Freseto! (I hope I spelled that correctly). That was a very generous donation and I look forward for Uncle Doug to showcase your gifts. I can't wait for that Gibson Echo unit. Thank you Uncle Doug for another great video.
Uncle D- You really are so deserving. You give so much to the community in your depth (or shall I say "girth") of knowledge. I wish I had something to offer. God bless you, Brother... (Edit- You got to love those fighting men that came home from WW II and just jacked up a bunch of cars!! Started a culture..)
I thought this was a 55min video on tube biasing, watched 10mins then stopped. It stuck in my head though so a few days later I've watched the rest - Wow, what a tressure trove of random elements that together prove its not all maths and music theory, its a whole lifestyle - Please keep adding car meeting sections, hot rods is what kept me playing 30 years ago!
I think I'm addicted to these vids. I better go speak to someone. Lol... no seriously excellent to the point technologist makes it look so easy. Luv the concluding segments.
I bought one of these eurotubes bias probe devices some time ago and I really like it. I knew I was a bit too ignorant to attempt getting the readings manually, so doing my best to avoid the Dunning Kruger effect and potentially kill myself I spent the money on it and do not regret it. super happy to know that it's proven accurate by one of my favorite uncles! Thank you for sharing your knowledge.
My cat, Souixsie Queue, saw Jack and Casey on the screen, and had to get a closer look. THEN she saw her brand of treats. You've got a new 4 legged fan!!!
A most professional video. Wonderful generous patrons. That Gibson amp "David" sent is fabulous, not to mention the other items. I've purchased stuff from "Bob" at Eurotubes years ago and always recieved excellent quality and friendly service. Again, thanks for sharing your passion and patience in your videos/tutorials. The car shows are great! Keep your eyes peeled for an old Buick Roadmaster sometime, they have some nifty options on them. I had a few classic cars stolen when I was a younger that I miss. I recently seen an identical one that had been modified from a post into a hardtop and that was a 1950 Plymouth coupe deluxe with visor. The modifications to the body that they did made me wish I still had mine, so I could do the mods too. Absolutely beautiful! Mine was parked by a little old farm lady in 1964 just before she passed over. It had a imitation wood grain dash with a real cool large round clock with a ship on it too. It was stored there and during the Iraq war, metal prices went up and someone snatched it off the property before I could move it. So, who knows what happened to it? I reported it stolen, but the rural county law and state law weren't in the least bit interested in investigating it for some odd reason? Ya win some ya lose some. I believe it had a flat head 6. Pretty nice old car. Thanks!
Another great video. I’ve done lots of business with Eurotubes since they’re local to me. I shared this video with them. Hope you and the cats will be celebrating Cinco de Meow this weekend.
Thanks, Bill. I hope they are pleased with how well their probe performed. I found it to be a really nice instrument. I didn't realize that such an important cat holiday was upon us......I'll have to go shopping for catnip and play-toys :)
Great demonstration Uncle Doug, of how to use "and build if so desired" the bias probe.. Your gifts from viewers like Jim and others, are out of this world.. I'm expecting some grandmother to send you her Mary Kaye Strat she bought new! You'll have to finish the Corvette story in another video.. Be well, Tom
Thanks so much, Tom. I greet the mailman every day, hoping for a '59 LP or a nice Tweed Pro amp......but must admit that the latest hauls have been exceptional (as shown in the video) :)
Hi Doug...When I first started building amps, my buddy gave me some home made bias probes for the tube sockets. At some point, they got put in a box and mis-placed. I just started using my meter (an old Simpson 260 my dad gave me). I got fed up looking for my probes, so I finally got some new ones from Eurotubes. I was tempted to get these with the meters, but I felt I would just use my digital meters and save the money (I have an old Radio Shack one and a Fluke 77IV). A few years ago I finally bought an 87V Fluke. Those in your video from Eurotubes look great....easy to use, current and voltage on each tube. Super easy. I keep fighting the urge to get them. Great vid!
Thanks, Ireland. I agree that the purchase price may seem significant, but after having them for a couple years, I honestly can't imagine life without my Eurotubes bias probes.
Thank you so much for this tutorial! I am a novice amp tech and was able to use your manual method to check the bias on my own '78 Hiwatt. Seeing you walk through the entire process step-by-step was extremely helpful.
I just love the cats. Jack must be a union guy on his off day! Uncle Doug, not only are you super helpful tube amp creator, you take care of all the stragglers and homeless bum cats lurking around your yard. Since the strays can’t talk, I’ll say *THANK YOU* for them!
Actually, the Eurotubes probe was from Joseph V. , Dave, but I agree that David was also far more than generous. I've already begun work on the tweed Gibson.
THANKS UNCLE DOUG hope u have a great day. I saw the cobra then POOF aww man my fav !!!! blue 427 side oilier and white stripes!!! GIMME GIMME GIMME ;-)
Thank you for another great vid UD. I'm Glad you were blown away by my donations, They are worth the price of shipping for these master classes in amp restoration. BigDave.
You're quite welcome, BigDave, and thanks again for your great shipment. I am working steadily on the tweed Gibson GA-2RT and have it working quite well......even the reverb. Next will be the cosmetics. I think/hope you will be pleased with the result.
Today!!!! was the big day!!! first time power on the supro tremverb. perfect!!!! thanks verry much Uncle doug!!!!! used this bias method for the class a 6v6 and it came out on 12.6 watts, but the 6v6s by jj has a max of 14 watts so thats perfect. it will eat a 6v6 tube once a year, but the sound is just amazing!!! also checked temperatures of all components using a infrared temp. meter all seemed verry cool. thank again!!! greetings from holland!!!!
Love the video. Very clear and detailed amp tech info , unbelievably awsome viewer contributions, and sweet hot rods . Don't think it could get any better than that. Oh yeah, and the cat's. My 6 year old son likes to see Jack because he looks just like his black cat named Herman. Thanks for sharing your knowledge and adventures Uncle Doug.
First I must say thank you, David and Jim!! Any fodder for future videos is awesome!! Next, I have to say these educational vids are my favourites!! Thanks so much for sharing your knowledge with us! Oh and say hi to Jack and the rest of the kitty clan for me!!
Druel,druel! Old amps old cars. Love the biasing tool! I loved the black Ford. It is very similar to the last one I helped build. More engine than car.
it's also to RCA being in the great depression and seriously messing up on that radio, I've taken your advice about tube amplifier circuits and Carlson's lab about making it an awesome radio It was an original mess up and bad wire routing which led to an explosion! My cats Ozzy massive panther and Snowy my fluffy girl say hi to you and cat family, and you have taught me how to tune and make a tube amplifier sound awesome!
and hot chassis fivers have lower b plus but transformer radios have well yeah...I have used the knowledge you have given me and also Carlson to give old sets high AM band width and tight tuning especially on short wave too, and broadcast AM on them sounds like FM like it should. Don't ever touch B+ on a transformer radio or amp you will get whacked! It probably won't kill you but like my grandpa said it'll kick you like an electric horse! OUCH NO TOUCH! He worked on old school 480v three phase theater lighting...he knew.
You never fail to amaze! The probe part components are available on several sites on the web. I think building your own probe, like building anything, you know exactly what is in it and, most important, how it works! Like you said, the Euro tester is nice and accurate, but you can build one for under $20. Go figure. If you build it yourself, you can fix it yourself. It's a no-brainer! The cars ARE wonderful! In the early 50s we moved from Mo. to Roswell, N.M.. My dad bought a late model Hudson Wasp. It was, in his words, the best damned car he ever owned and he had many. We moved back to Mo. a few years later to help my Grandfather and the Hudson got repossessed. My Dad never got over it! Oh well. I learned a valuable lesson about over extending yourself. Thank you so much for sharing! Can't wait for the videos on those amps you got in the mail! Love them kitties! Thanxz
You're welcome, ATL. I have already started on the tweed Gibson GA-2RT and it is turning out to be a great amp......so stay tuned :) Thanks for all your nice comments.
I have their original probe, same probe but plugs right into the multimeter set to mA. I finally got to do a comparison using the ST70 restoration by using the Voltage/mA on the St70 outputs
Excellent. I have a Compu Bias unit that is similar but has two leads so it will measure two tubes at the same time. Also gives a direct display of Plate Voltage, Plate Current, and Plate Dissipation. Makes bias adjustments a breeze. Pricey, but one of the biggest positives is that it improves safety by eliminating the need to insert your hands in the HV multiple times. If you Google it, you can see some excellent photos of it in action.
Another super video, Uncle Doug. The Eurotubes device looks like a great buy if one has to bias a lot of amps, as in a repair shop situation. For us who only own several tube amps, the traditional bias method will suffice very nicely.
@@UncleDoug Yes, you are correct, but I would hazard to guess that anyone who has very little knowledge or is not interested in gaining such knowledge of how to bias their tube amp should pay a pro for that service, as it can save their life in the worse scenario.. or at least save them from causing expensive damage to their tube amp. But as a handy probe to see if your amp is biased correctly or not and take safe corrective action from there.. then it is worth buying it.
I am not advocating that they also try to adjust the bias themselves, Jay. As I explain in the video, the probe will allow them to monitor their bias and then seek professional assistance when necessary.
@@UncleDoug Right on, Uncle Doug. I get what you are saying. That would be ideal for most amp owners, who want optimum performance but will not work on their amp. Seeking pro help makes the most sense for them.
Very cool little gadget, and fairly easy to copy. Thank you for taking time to show it! The black '34 was impressive, the T-bucket does look odd. Just when you said "tasteful flames", I was thinking "orange kelp". :))
I really enjoyed this video. Right about the time I started thinking about what might be inside the Eurotube unit, you started talking about how to make one. Perfect timing! I had pretty much sketched out what you had but was trying to figure out how I could power the meters from the filament voltage so I would not have to use external meter(s) to make the measurements. I would need two fully isolated supplies to power the meters which could easily be done off the filament voltage if it was in the 6vac to 12vac range; but then I hit a dead end when I thought about the much higher filament voltage tubes such as the 50L6......
At 8:30, the manner in which the multimeter leads are connected between pin 8 of the rectifier and pin 3 of the output tube can also be used to measure actual plate current *directly* by means of the "transformer shunt method", whereby you set the multimeter to measure current in milliamps, change where the probe cables actually plug into the milliamp meter if required ( as it often for invariably is), and turn the amp on. This isn't recommended for the inexperienced or faint of heart, but it will give you a direct in-circuit plate current reading, without any math involved. Just one caveat: most multimeters require you to use a different input jack or even pair of input jacks when measuring current, compared to measuring voltage or resistance, and if you try to use the multimeter to measure current directly but you've forgotten to change which input jacks on the meter you have plugged the test-lead cables into, at best you will blow a fuse on the meter, and at worst you will blow the meter to smithereens! Don't ask me how I know this....😣
Excellent installment, Doug! This will be the go-to reference for bias measurements on UA-cam. I know you've covered this stuff before, but a nice companion piece to this one might be about the decision process that goes into selecting a particular plate dissipation. Would be great to bring up some sine wave test tones on the 'scope and show how they're distorted by the output tubes in different ways under different biases as well.
Thanks so much, AQ. The determination of PD value has been covered before several times, but the bias to sine wave analysis is a great suggestion. I will keep this in mind for the future.
nice instructional video. had a watch last night and the old grey matter dragged up a memory from college regarding DVM accuracy i seem to remember we were told to pretty much ignore the last digit displayed so for 23.33 we would take it as 23.3 and 23.37 would be 23.4 as the meters were not precision instruments. there is probably more to it than that for sure and that was mid 1980's but as I said the grey matter thought about that and your results and thought they would be even closer between the two sets for manual and with that nice piece of kit if taking that view of the meters. but of course it all falls down with the one displaying 263V as there was no decimal to worry about. now to watch the end with the hotrods, what a great mix of viewing pleasure.
Ala Carte MENU:
Plate Current vs Cathode Current @ 01:50
Proper SE Bias Procedure Discussion @ 04:35
Performance of Manual SE Bias Procedure @ 07:16
Performance of Eurotubes SE Bias Procedure @ 12:51
Comparison of Results for SE Amp Circuit @ 14:05
Manual Measurement of Screen Current @ 15:08
Open 1st Gift Box w/Jack & KC @ 16:39
Performance of Manual DE Bias Procedure @ 19:31
Performance of Eurotubes DE Bias Procedure @ 25:33
Comparison of Results for DE Amp Circuit @ 26:46
Open 3 more Gift Boxes @ 27:38
Final Discussion of Eurotubes Bias Probe @ 29:36
Build Your Own Bias Probe @ 32:08 Closing Statements @ 45:58
Car Show @ 47:27
Always a good day when there is a new Uncle Doug video.
Thanks, Ken :)
@@UncleDoug I retired this week, so now I have time to watch even more.
@@kendavis8046 GOOD FOR YOU-!!!
Great video!
I had an electronics instructor years ago that had been working on electronics for many decades. Some sage advice from him: “if you accidentally or intentionally touch the input of a rectifier while the circuit has power, it instantly becomes a Rectum-Frier”.
I would think this would even more true if you actually sat on the hot wire :)
Uncle Doug, that was a masterfully done educational video. We love your amp videos and you have such a unique eloquent way of teaching us all!!!
Bless you and your family.
Thanks so much, F1. We really appreciate your kind words.
If I could thumbs up this comment 100 times I would---thanks Uncle Doug!!
Wow......thanks, SC :)
A friend of mine used to own an amp repair business but closed a few years ago. He gave me a pair of these testers and they sure make biasing much easier. Thank you, Doug for teaching us that which cannot be found in any classroom today! I hope you are doing well, Good Sir!
You're lucky to have such a generous friend, Earl. So glad you enjoy our videos.
Thanks Uncle Doug, you're the best!
You'r welcome, James. Thanks !!
The best channel in the whole internet! Thanks Uncle Doug!
Wow, thanks, Luis :) Our pleasure.
Uncle Doug, Based on your posts I am pretty sure you are older than me by a few years, but wow, when I watch your videos do I ever connect with your "vibe", and I am guessing that there are thousands of others out there who feel the same. Please keep doing what you do. It is very educational and very important.
Thanks so much, Walter. I'm 73, and am glad to still be able to connect with the audience, instead of a rocking chair and Metamucil :) We definitely will continue for as long as we're able .
@@UncleDoug and I am 68 and a Fender-a-holic. Do you have any advice re my other post about the specifics of how to deal with my newly purchased vintage Fender Bassman?
Uncle Doug, a most fantastic specimen of human being. Thanks for your work and for showing it.
You are quite welcome, MJ :) Thanks !!!
The only suggestion I would make regarding making your own bias probe, is to chassis mount the tube socket, since output tubes can generate a lot of heat and wouldn't want to melt or singe the surface it rests on, and use recessed, isolated probe lead connections in same chassis to prevent inadvertent death sentence execution.
As always, top notch teaching of tube theory, testing and appreciate you inviting us to your home, love of classic cars and pets. Miss Rusty.
Thanks so much, Steve, for your nice comments and your good advice.
Great video. I got one of these, after waiting for almost a year for these to be back in inventory at Eurotubes. I think it was worth it though, as it's not easy to find one that reads plate voltage. Only other one I found was a kit that plugged into an existing multi meter. Now it's been sitting for almost a year and I never yet had the need to bias anything. Soon I have a '71 Super Reverb arriving though and I'm going to want to check bias settings for the (new make) Telefunken 6L6GC's I have set aside. I believe for this amp it would require changing a bias resistor (it has a balance pot but not a bias, if I remember right). This video is a great reference on using this probe. This channel is a great reference library on tube amp function in general
Thanks so much, M. We're glad our videos are helpful :)
THANK YOU David Freseto! (I hope I spelled that correctly). That was a very generous donation and I look forward for Uncle Doug to showcase your gifts. I can't wait for that Gibson Echo unit.
Thank you Uncle Doug for another great video.
Amen, Rick. I have been working on the tweed Gibson GA-2RT and have it working nicely. Next will be the cosmetics......so stay tuned :)
I learn so much from all of your videos. Plus we get gut shots of some real gems. Thanks Uncle Doug.
Our pleasure, Jason :)
Uncle D- You really are so deserving. You give so much to the community in your depth (or shall I say "girth") of knowledge. I wish I had something to offer. God bless you, Brother... (Edit- You got to love those fighting men that came home from WW II and just jacked up a bunch of cars!! Started a culture..)
Thanks so much, Abe. Your kind words are reward enough :)
I thought this was a 55min video on tube biasing, watched 10mins then stopped. It stuck in my head though so a few days later I've watched the rest - Wow, what a tressure trove of random elements that together prove its not all maths and music theory, its a whole lifestyle - Please keep adding car meeting sections, hot rods is what kept me playing 30 years ago!
Thanks so much for your nice comments, Prince. We will :)
Thanks Uncle Doug, good review of measuring for tube biasing.
Cheers,
You're welcome, Eddy.
David, thank you! Your generous gift will bring hundreds (?thousands) of viewers more UD videos!
Yes it will, Cass. I'm working on the tweed Gibson as we speak :)
You've quite the talent for sharing *great detail* very clearly, Uncle Doug.
Plus, there's cats, too.
Thanks from all of us, M :)
That’s a lovely gift from David. I have to say all my vintage radio friends have always been generous.
Indeed. I was overwhelmed by his generosity. I believe we have the nicest, most generous viewers on all of UA-cam :)
Fantastic instruction! The Eurotube tester is certainly convenient but I appreciate your snippet of the DIY method, as well!
Glad you enjoyed the video, Jeff.
Classic cars and tube amps. Sounds like a great TV channel.
Keep watching, Jay. We also feature drone flights, desert excursions, and hot rod rides.
tube amps, cats, dogs, hot rods, education, if this was the only channel on UA-cam it would be worthwhile.
Thanks, Reg. We try to cover all the important bases :)
Excellent, Thanks for the video Uncle Doug & Warm Greetings from the Sunshine Coast, Australia
You're welcome, Ollie. Likewise from the Sunny Southwest, USA :)
Very good, Doug.
Thanks, Ted.
I think I'm addicted to these vids. I better go speak to someone. Lol... no seriously excellent to the point technologist makes it look so easy. Luv the concluding segments.
Thanks, Doc.
I bought one of these eurotubes bias probe devices some time ago and I really like it. I knew I was a bit too ignorant to attempt getting the readings manually, so doing my best to avoid the Dunning Kruger effect and potentially kill myself I spent the money on it and do not regret it. super happy to know that it's proven accurate by one of my favorite uncles! Thank you for sharing your knowledge.
Not saying your old because obviously you're young at heart BUT I wish my uncle was as coooool as you.. Thanks for all that information, a real legacy
You're quite welcome, JR......and thanks for the nice comments :)
My cat, Souixsie Queue, saw Jack and Casey on the screen, and had to get a closer look. THEN she saw her brand of treats. You've got a new 4 legged fan!!!
Make sure she subscribes, SD......we need all the help we can get to reach 100K ;)
A most professional video.
Wonderful generous patrons. That Gibson amp "David" sent is fabulous, not to mention the other items.
I've purchased stuff from "Bob" at Eurotubes years ago and always recieved excellent quality and friendly service.
Again, thanks for sharing your passion and patience in your videos/tutorials.
The car shows are great!
Keep your eyes peeled for an old Buick Roadmaster sometime, they have some nifty options on them.
I had a few classic cars stolen when I was a younger that I miss.
I recently seen an identical one that had been modified from a post into a hardtop and that was a 1950 Plymouth coupe deluxe with visor. The modifications to the body that they did made me wish I still had mine, so I could do the mods too.
Absolutely beautiful!
Mine was parked by a little old farm lady in 1964 just before she passed over.
It had a imitation wood grain dash with a real cool large round clock with a ship on it too.
It was stored there and during the Iraq war, metal prices went up and someone snatched it off the property before I could move it. So, who knows what happened to it?
I reported it stolen, but the rural county law and state law weren't in the least bit interested in investigating it for some odd reason?
Ya win some ya lose some.
I believe it had a flat head 6.
Pretty nice old car.
Thanks!
Thanks for sharing, Amo.
The most informative video about biasing. Thank you very much!
I'm glad to hear it, Alex. Thanks :)
Very nice DIY bias probe.
Thanks, RB.
Another great video. I’ve done lots of business with Eurotubes since they’re local to me. I shared this video with them. Hope you and the cats will be celebrating Cinco de Meow this weekend.
Thanks, Bill. I hope they are pleased with how well their probe performed. I found it to be a really nice instrument. I didn't realize that such an important cat holiday was upon us......I'll have to go shopping for catnip and play-toys :)
Thanks to all the gentlemen that generously gave to Uncle Doug, and thanks to you Uncle Doug for another great video.
You're welcome from all of us, Brian. Thanks !!!
Great demonstration Uncle Doug, of how to use "and build if so desired" the bias probe.. Your gifts from viewers like Jim and others, are out of this world.. I'm expecting some grandmother to send you her Mary Kaye Strat she bought new! You'll have to finish the Corvette story in another video.. Be well, Tom
Thanks so much, Tom. I greet the mailman every day, hoping for a '59 LP or a nice Tweed Pro amp......but must admit that the latest hauls have been exceptional (as shown in the video) :)
Wow! Great video Uncle Doug and thanks to David too. So generous. Amazing!
Thanks, Jon. Amen on the thanks to Joseph V.
Uncle Doug Amen indeed! Joseph, Jim and David appreciated.
Be a radiator, not a sink!
Well said, Jon.
Hi Doug...When I first started building amps, my buddy gave me some home made bias probes for the tube sockets. At some point, they got put in a box and mis-placed. I just started using my meter (an old Simpson 260 my dad gave me). I got fed up looking for my probes, so I finally got some new ones from Eurotubes. I was tempted to get these with the meters, but I felt I would just use my digital meters and save the money (I have an old Radio Shack one and a Fluke 77IV). A few years ago I finally bought an 87V Fluke. Those in your video from Eurotubes look great....easy to use, current and voltage on each tube. Super easy. I keep fighting the urge to get them. Great vid!
Thanks, Ireland. I agree that the purchase price may seem significant, but after having them for a couple years, I honestly can't imagine life without my Eurotubes bias probes.
Thank you so much for this tutorial! I am a novice amp tech and was able to use your manual method to check the bias on my own '78 Hiwatt. Seeing you walk through the entire process step-by-step was extremely helpful.
Glad it helped, Sage. Best of luck with all your projects :)
Welll done video of the manual bias and the Eurotube Bias Probe.
I just love the cats. Jack must be a union guy on his off day!
Uncle Doug, not only are you super helpful tube amp creator, you take care of all the stragglers and homeless bum cats lurking around your yard. Since the strays can’t talk, I’ll say *THANK YOU* for them!
You (and they) are quite welcome, Matt. We enjoy you all.
Best instructional videos on you tube. Thank You
Wow.....thanks so much, Gerald.
Thanks UD! I learn something every time I see the videos you post.
That was some mail call.
Thanks David.
Thank Jim
You're welcome, JJ.......and thanks, generous donors.
...a real mail call haul(?)
THANK YOU for your generosity, David! More learning ahead.
Uncle Doug - This vid was SO informative!
Actually, the Eurotubes probe was from Joseph V. , Dave, but I agree that David was also far more than generous. I've already begun work on the tweed Gibson.
Great! That's exactly what I was looking for, how to make my own tube bias probe
Good luck with your project, Alex.
I have two of these. Very much worth the money
Thanks for the positive report, Wayne.
Thanks Uncle Doug, this topic is (currently) out of my pay grade, but I remain teachable. :)
You're welcome, Brad.
THANKS UNCLE DOUG hope u have a great day. I saw the cobra then POOF aww man my fav !!!! blue 427 side oilier and white stripes!!! GIMME GIMME GIMME ;-)
You're welcome, Ken :)
Hello from Canada, Toronto Ontario. Like Always your Videos are educational, Thank you for your efforts.
You're welcome, V. Likewise from the Sunny Southwest :)
Thanks Doug for a new project to build and assist in my amp restorations.
You're welcome, Thomas :)
Thank you for another great vid UD. I'm Glad you were blown away by my donations, They are worth the price of shipping for these master classes in amp restoration. BigDave.
You're quite welcome, BigDave, and thanks again for your great shipment. I am working steadily on the tweed Gibson GA-2RT and have it working quite well......even the reverb. Next will be the cosmetics. I think/hope you will be pleased with the result.
I use this guy. Love it. It’s great
Thanks for sharing, Mike.
Thank you for sharing this information to help us with this hobby
You're welcome, Jess.
Thanks Doug for another excellent informative video.......................................Berni
You're welcome, Berni :)
always look at your videos you give a teaching lesson like no other and i thank you for being a part of my educational on electroniics
You're quite welcome, Wifredo. We appreciate your nice comments.
Today!!!! was the big day!!! first time power on the supro tremverb. perfect!!!! thanks verry much Uncle doug!!!!! used this bias method for the class a 6v6 and it came out on 12.6 watts, but the 6v6s by jj has a max of 14 watts so thats perfect. it will eat a 6v6 tube once a year, but the sound is just amazing!!! also checked temperatures of all components using a infrared temp. meter all seemed verry cool. thank again!!! greetings from holland!!!!
That's great news, Jeff. Congratulations on the success of your Supro TV build. We hope it gives you many years of enjoyment.
Great educational video, thanks Uncle Doug!
Glad you enjoyed it, Bob :)
Excellent video!
Thanks, Dale.
Marvelous Doug! Really a great vid as usual, thnx !
Learn something new every time, Always good stuff
Thanks, Matthew.
Love the video. Very clear and detailed amp tech info , unbelievably awsome viewer contributions, and sweet hot rods . Don't think it could get any better than that. Oh yeah, and the cat's. My 6 year old son likes to see Jack because he looks just like his black cat named Herman. Thanks for sharing your knowledge and adventures Uncle Doug.
You're welcome, Scott. Thanks !!!! Regards to Herman :)
First I must say thank you, David and Jim!! Any fodder for future videos is awesome!! Next, I have to say these educational vids are my favourites!! Thanks so much for sharing your knowledge with us! Oh and say hi to Jack and the rest of the kitty clan for me!!
You're quite welcome, Jack. It's always good to hear from you. The kitties are waving back :)
Druel,druel! Old amps old cars. Love the biasing tool! I loved the black Ford. It is very similar to the last one I helped build. More engine than car.
Thanks, Bob. I agree :)
Ótimo fim de semana para o Sr.obrigado por mostrar esquemas detalhado Sul do Brasil
De nada, Jorge. Have a great weekend :)
@@UncleDoug thanks my friend
Thank you so much! Very helpful.
Glad to hear it, Tommy.
it's also to RCA being in the great depression and seriously messing up on that radio, I've taken your advice about tube amplifier circuits and Carlson's lab about making it an awesome radio It was an original mess up and bad wire routing which led to an explosion! My cats Ozzy massive panther and Snowy my fluffy girl say hi to you and cat family, and you have taught me how to tune and make a tube amplifier sound awesome!
and hot chassis fivers have lower b plus but transformer radios have well yeah...I have used the knowledge you have given me and also Carlson to give old sets high AM band width and tight tuning especially on short wave too, and broadcast AM on them sounds like FM like it should. Don't ever touch B+ on a transformer radio or amp you will get whacked! It probably won't kill you but like my grandpa said it'll kick you like an electric horse! OUCH NO TOUCH! He worked on old school 480v three phase theater lighting...he knew.
Thanks for all your nice comments, G, and regards to Ozzy & Snowy.
@@UncleDoug I think you should name fuzzy girl cat amber and invite her inside!!
Pretty amazing the way
The mind works once
You gain knowledge
On things good idea
On making your own current probes for electron tube biasing.
Thanks, Dwight.
Great video Doug. A video that certainly needed to be done.
Thanks, Bryan.
Nice video and lesson Doug, thanks!!
You're welcome, Robert.
You never fail to amaze! The probe part components are available on several sites on the web. I think building your own probe, like building anything, you know exactly what is in it and, most important, how it works! Like you said, the Euro tester is nice and accurate, but you can build one for under $20. Go figure. If you build it yourself, you can fix it yourself. It's a no-brainer! The cars ARE wonderful! In the early 50s we moved from Mo. to Roswell, N.M.. My dad bought a late model Hudson Wasp. It was, in his words, the best damned car he ever owned and he had many. We moved back to Mo. a few years later to help my Grandfather and the Hudson got repossessed. My Dad never got over it! Oh well. I learned a valuable lesson about over extending yourself. Thank you so much for sharing! Can't wait for the videos on those amps you got in the mail! Love them kitties! Thanxz
You're welcome, ATL. I have already started on the tweed Gibson GA-2RT and it is turning out to be a great amp......so stay tuned :) Thanks for all your nice comments.
Another great video Uncle Doug! Glad the probe is accurate
Thanks, Big Joe. So am I :)
Another great video! When I build mine I think I'll install the tube socket in the junction box.
Thanks, KT. I can imagine all sorts of neat modifications that would make the test unit better and easier to use. Good luck.
Awesome build! Love the cars too! I see myself making an amp probe soon. Thank you for all the great ideas.
You're quite welcome. Good luck.
thanks for sharing!! glad ppl are feeding your kitties too,.,.,🌿
You're welcome, Sadie. Yes, our viewers are very kind and generous.
I have their original probe, same probe but plugs right into the multimeter set to mA. I finally got to do a comparison using the ST70 restoration by using the Voltage/mA on the St70 outputs
Yes, I understand that they sell the probes separately.
Excellent. I have a Compu Bias unit that is similar but has two leads so it will measure two tubes at the same time. Also gives a direct display of Plate Voltage, Plate Current, and Plate Dissipation. Makes bias adjustments a breeze. Pricey, but one of the biggest positives is that it improves safety by eliminating the need to insert your hands in the HV multiple times. If you Google it, you can see some excellent photos of it in action.
Thanks for your input, John.
Another super video, Uncle Doug.
The Eurotubes device looks like a great buy if one has to bias a lot of amps, as in a repair shop situation.
For us who only own several tube amps, the traditional bias method will suffice very nicely.
Thanks, Jay. I think it will also be useful for those who don't know how to manually check or adjust bias.
@@UncleDoug Yes, you are correct, but I would hazard to guess that anyone who has very little knowledge or is not interested in gaining such knowledge of how to bias their tube amp should pay a pro for that service, as it can save their life in the worse scenario.. or at least save them from causing expensive damage to their tube amp. But as a handy probe to see if your amp is biased correctly or not and take safe corrective action from there.. then it is worth buying it.
I am not advocating that they also try to adjust the bias themselves, Jay. As I explain in the video, the probe will allow them to monitor their bias and then seek professional assistance when necessary.
@@UncleDoug Right on, Uncle Doug.
I get what you are saying.
That would be ideal for most amp owners, who want optimum performance but will not work on their amp.
Seeking pro help makes the most sense for them.
i made one of these for $20 ... this was a cool video love the cars
Thanks, Jamie.
Very cool little gadget, and fairly easy to copy. Thank you for taking time to show it! The black '34 was impressive, the T-bucket does look odd. Just when you said "tasteful flames", I was thinking "orange kelp". :))
You're welcome, Andrew. Flames are a polarizing feature :)
Very cool! Thanks for the demonstration.
You're welcome, GL.
Always awesome learning experience with your videos, thanks for sharing!
You're welcome, Vince.
I think I will make one of those. Thanks for the gear donners and to you for making it possible.
I agree, Daniel. Thanks !!
41:34 That's too funny! Great job as always. Sweet cars too.
Thanks, Mr. B. It's not funny if you forget to run the wires properly :)
@@UncleDoug I did it once with a RCA cable I believe. But, that's only a couple wires.
@@UncleDoug Maybe a guitar cord as well. I don't know what I was smoking. Maybe the smoke from the rosin :-)
Wow fantastic, i would love a tube tester but way out of my budget in the UK, what a great gift
I agree, Wayne......very generous.
Yet another awesome contribution, sir! Thanks!
You're welcome, Fabio :)
Thanks David for your generous donation so we can learn more about vintage tube amplifiers from Uncle Doug in future videos!
Amen, Tony. Thanks !!!
I really enjoyed this video.
Right about the time I started thinking about what might be inside the Eurotube unit, you started talking about how to make one. Perfect timing!
I had pretty much sketched out what you had but was trying to figure out how I could power the meters from the filament voltage so I would not have to use external meter(s) to make the measurements.
I would need two fully isolated supplies to power the meters which could easily be done off the filament voltage if it was in the 6vac to 12vac range; but then I hit a dead end when I thought about the much higher filament voltage tubes such as the 50L6......
The probes won't work with 50L6's, Dennis, only the 6V6, 6L6, etc. family of tubes.
Thanks Uncle! cheers from Colombia
You're welcome, Alex :)
I've never seen this one before Uncle Doug I better pay attention to this.
Yes, indeed, Mark. It is a very useful device.
Gosh you're pleasant to listen too.
That's nice to hear. Thanks, Rev.
I have 4 of those probes to watch all 4 tubes while adjusting
That would be the ideal set up for 4 output tubes, CS.
great one Uncle Doug
Thanks, Carlos.
At 8:30, the manner in which the multimeter leads are connected between pin 8 of the rectifier and pin 3 of the output tube can also be used to measure actual plate current *directly* by means of the "transformer shunt method", whereby you set the multimeter to measure current in milliamps, change where the probe cables actually plug into the milliamp meter if required ( as it often for invariably is), and turn the amp on. This isn't recommended for the inexperienced or faint of heart, but it will give you a direct in-circuit plate current reading, without any math involved. Just one caveat: most multimeters require you to use a different input jack or even pair of input jacks when measuring current, compared to measuring voltage or resistance, and if you try to use the multimeter to measure current directly but you've forgotten to change which input jacks on the meter you have plugged the test-lead cables into, at best you will blow a fuse on the meter, and at worst you will blow the meter to smithereens! Don't ask me how I know this....😣
Doug, you and I are in general agreement as car critics ;) Great video as always!
Thanks, Bill. I'm glad someone else shares my views :)
Sweet video! Love the time stamps as well
I'm glad you enjoyed it, Bill.
Excellent installment, Doug! This will be the go-to reference for bias measurements on UA-cam.
I know you've covered this stuff before, but a nice companion piece to this one might be about the decision process that goes into selecting a particular plate dissipation. Would be great to bring up some sine wave test tones on the 'scope and show how they're distorted by the output tubes in different ways under different biases as well.
I concur. Lol. Uncle Doug is thorough but most importantly very easy to understand.
Thanks so much, AQ. The determination of PD value has been covered before several times, but the bias to sine wave analysis is a great suggestion. I will keep this in mind for the future.
Thanks UD!! Another beauty!!
You're welcome, UB :)
42:27 - A lid from an aerosol can! Great new 'killer app' :)
I keep a bunch of junk like that around. You never know when it will come in handy :)
Thank you for another great video.....
You're welcome, Doc.
Another great video, as usual, thanks!
You're welcome, Jeff :)
wow, killer white '66 Vette... And a Twin-H Hudson!
Yes, indeed, Bruce :)
nice instructional video. had a watch last night and the old grey matter dragged up a memory from college regarding DVM accuracy i seem to remember we were told to pretty much ignore the last digit displayed so for 23.33 we would take it as 23.3 and 23.37 would be 23.4 as the meters were not precision instruments. there is probably more to it than that for sure and that was mid 1980's but as I said the grey matter thought about that and your results and thought they would be even closer between the two sets for manual and with that nice piece of kit if taking that view of the meters. but of course it all falls down with the one displaying 263V as there was no decimal to worry about. now to watch the end with the hotrods, what a great mix of viewing pleasure.
Thanks for your input, Mr. G :)