Amazingly Original Pre-War OAHU Amp Gets a Tune-Up
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- Опубліковано 18 жов 2024
- As a change of pace from giant Fender Twins, I thought you might enjoy joining me for the evaluation and repair of an absolutely stunning pre-war Oahu (Valco) amplifier. We inspect the amp thoroughly, inside and out, discuss the very early and unusual tube set and the evolution of rectifier tubes, then begin a step-by-step repair of the somewhat troublesome circuit utilizing a typically inaccurate Valco schematic. Once the repairs are completed, the amp is subjected to an audio test to demonstrate its surprisingly good tone. In addition, we have an exciting announcement around the middle of the video that will be particularly interesting to loyal viewers and subscribers.....so don't miss it !!
If you enjoy videos like this one and would like to support our channel, please SUBSCRIBE and consider becoming a Patreon patron at this link: / uncledougsvintageamps or making a contribution to our PayPal account: dldcam@aol.com.
Here is the site for the cloth-covered 3-wire power cord: grandbrass.com...
Finally: Don't fret about the exposure of the gift card number......the card was used up (by Jack, ordering gourmet catnip) long before the posting of the video ;)
Congrats on 100K, Doug. Your dry sense of humor was the draw for me. Your electronics acumen keeps me coming back!
Thanks so much, Orion.
@@UncleDoug somehow didn't see this when you first uploaded... Glad to see you finally got your Play button 😀👍👍👍.
@@stevem.1853 I hope you enjoy it, Steve :)
@@UncleDoug the sound quality in the demo segment is the best I've heard from any of your video. if you have changed anything, it's made it even better 👍👍👍
Congratulations on the 100,000 subscribers. I as well as your followers greatly enjoy your educational videos. To have Uncle Doug as a teacher in a classroom would be an excellent experience, although You Tube is just fine. 100,000 followers is nothing to sneeze at. It is a valuable statistic that proves what you are teaching is very important and needed by 100,000 followers. I personally feel your contribution, dedication to teaching and your expressive personality is the best that UA-cam has to offer. Thank you for what you do.
Wow, thanks so much for your very nice comments, John. We really appreciate them :)
@@UncleDoug I second the sentiment Uncle Doug,,,,just a few observations,,,,I have missed your videos to the point I was concerned about the fact maybe no more videos,,,,and two,,,,I sorely miss the cat scans,,,hope all is well with the furry creatures as well !!!
@@tomstiel7576 It's nice to be missed, Tom. We're already working on our next video, so stay tuned :)
@@tomstiel7576 And I will "thirdle" it! Ha!
@@UncleDoug . . I'll 4th that. If I were raised with teachers like you I would be a lot smarter today :)
Glad you got your plaque, Doug. Back when you emailed me about it and said you didn't think you'd get one if you're not in the partner program, I told my wife I was thinking of sending you mine (which is still unopened on a shelf) as a thank you for being an inspiration to me and for being a friend. The only thing that stopped me was my wife said I should keep it and give it to one of my girls who might like to have it. But alas, all's well that ends well. Susan has given you your well-deserved mark of approbation.
Cool, Brad!
Greetings, Brad. It's always good to hear from you. Apparently, it was the backlog in plaque production that caused the delay, rather than punishment for allowing no revenue gathering by YT. But as my old, drunken granny used to say, "Better late than never"......a sentiment never shared by previous landlords and tax collectors :)
@@UncleDoug XD
@@UncleDoug This just goes to show you that you can learn from anyone, even a drunken Granny! I always learn from you Uncle Doug AND from Brad, unless he's ranting again and then... Wait! Brad's here?!! I gotta run Doug, got things to do!
Awe, man… why not display yours? It didn’t occur to me that you don’t have one on display until now. There’s nothing wrong with being recognized for a job well done from time to time. It’s no mean feat getting 100k subs! You’re good at what you do. No need to be all punk rock about it.Use it as a pedal box or in a cab or something,lol! A lot of times,when watching a new channel (as one does occasionally) I’ll notice how established they are by seeing their plaque before I look at the number of subs they have. If they get that big, they’re usually doing SOMETHING right.
i know this was 2 years ago . but still congrats on your award. Your wonderful knowledge of these circuits , has taught me loads . your a great teacher for sure.
Thanks so much. I'm glad the videos have been helpful.
I wish you could see the smile on my face when your video showed up on my notifications. I'm sure I'm not the only one. Thanks Uncle Doug.
That's great to hear, Daniel. I hope you enjoy it :)
Mega dittos Uncle Doug you deserve it and we are glad to be here to have a part!
Thanks so much, John.
That is a sweet sounding little amp... now. Nice work Uncle Doug. Thank you, especially for the in-depth descriptions! You're the best. Congratulations on the plaque!
Thanks so much, Kort :)
Congratulations Uncle Doug on your UA-cam award! You must feel a bit proud to know you've reached the hearts and minds of so many of us.
You have taught me so much with your no nonsense, thorough explanations of how amps work. I am sorry that I have not been able to support you monetarily as I'm on a somewhat fixed income (oddly named it seems) BUT I do have a collection of all sorts of vintage tubes! If you ever need a hard to find tube please contact me and I will see if I have one for you. Of course I don't have extra GZ34's 😢 but I have The tubes you are showing in this video and many of my tubes are NOS. Anyway, thanks for being you and taking the time to teach.
Thanks so much, Tim. I'll keep your offer in mind. Meanwhile, our best to you and yours.
Great as always. my world stops when a new uncle Doug video gets posted!
Thanks so much, MP :)
43:07 Oh my goodness, UD! The imagery. 😂😂😂
Congratulations on your plaque! Well deserved.
I'm shocked that anyone could misconstrue my accurate description of events as being salacious ;) Thanks !!
Congrats on the milestone and "major award" Uncle Doug! 25 years ago, a fella brought a similar Oahu amp to me to try to get up and running. This was in the very beginning of my amplifier repair journey and all I had for reference information, was the Tube Amp Book and could not find anything similar and sadly had to return it to the customer--it was also badly hacked up by TV repairmen over the years, and I just couldn't make heads or tails of that little amp.
This example is museum quality. Thanks again for all you do for all of us!
Thanks for sharing, SC, and for your nice comments.
Keep the vids. coming they are "the best", and greatly enjoyed !
Thanks, RD. Will do :)
Congratulations, Uncle Doug. An award well deserved. And again, another great old school lesson on the early years of tube design. This video defined a great deal. So glad to see you back... I was having Uncle Doug withdrawals. And as always.. Thank you, Professor.
Thanks so much, y0 :)
The award could not go to a nicer guy, and as always a very informative and top notch video thanks for everything!
Thanks so much, GS :)
Congrats on a very well deserved Award. Hope to see you with many more.
Thanks so much, AZ.
glad to see you back. congrats
Thanks, SC :)
Congratulations Uncle Doug. It’s a good milestone to achieve. I have commented several times and find your videos highly informative and entertaining. Watching your videos has inspired me to and shaped my direction in building my own guitar amplifier. Thank you so much. I would love to share my own progress with you.
All the praise aside. Looking at that Oahu amplifier, it looks very similar to a Kay Amplifier that you did a year or 3 ago. Similar build, components, nice fret work, umbilical for the the field coil/speaker, and the additional choke. I like them both, but they are definitely odd.
Thanks so much, Aaron, for your nice comments and observations :)
Every time I rewatch these I get more from them! I just restored a 1927 Atwater Kent 37 with an 80 rec and transformers and caps potted in tar.(fun) I don't think those old guitar amps can scare me much anymore (thanks to you of course)
That's great to hear, Pete. I'm glad the videos are bolstering your confidence.
Terrific Video Uncle Doug!! Can't wait till it gets home to play its matching steel through it. Congrats on the 100,000 subs!! BigDave
Glad you liked it, Big Dave. It will be home soon :)
I am curious if the amp actually had shorting input jacks as shown on the schematic; amplifiers of this vintage often did not. Also note that a problem that can arise when the input stage has no grid-leak resistor is that a small voltage from the preamp tube grid can be fed backwards into the controls and pickups of the guitar, leading to crackling noises when the guitars volume is adjusted (which is the reason why you might see a capacitor between the input jack and the grid of the 1st preamp tube, to block DC from getting to the guitar's controls).
The possibilities are legion for hum induction in an amplifier constructed like this. The 1st filter stage capacitor has its own ground ---- bolted, or riveted? ---- and the 2nd and 3rd stage filter caps have a separate ground several inches away through what looks to be a riveted-in-place terminal strip. Also the input jacks are bolted directly to the chassis without isolating launchers. All of this mechanical grounding was originally done to a heavily painted chassis without the factory taking pains to remove the paint around those holes, and 80 years later it can be pretty much guaranteed that there will be oxidation and galvanic corrosion underneath those bolts and input jacks, and especially at the riveted ground points for the terminal strips. Unfortunately it can be a big job to undo all those grounds and clean the metal and put them back together, and it's certainly not in everyone's budget, but it can be sonically rewarding (greatly lowering the hum and background noise floor) if one has the patience, or the budget, to do it.
One pointed comment pertaining to safety; I would recommend attaching the ground wire from the power cord *directly to the chassis* and not to the frame of the filter choke because you are relying on the 80-year-old bolted connections holding the choke in place to connect to ground electrically through the frame of that choke ( the bolts and the chassis are probably oxidized underneath the monting tabs of the choke). This also might tend to induce eddy currents into the chassis, increasing hum.
Thanks for all your excellent observations and suggestions, GU.
Bless you for sharing your wisdom with your growing community 109K plus!!!
Thanks, F1.
That amp looks like it just came out of the factory! I've never seen one in such pristine condition! Superb!!!
Thanks, BC. I agree.....it's a true "survivor".
Thanks again, very educational, your teaching skills really shine through. The paint is an inspection mark, we do that to indicate screws have been torqued and checked.
Glad you enjoyed the video, AK. Thanks for your input.
Congratulations on your UA-cam award you deserve it. Always enjoy your videos.
Thanks so much, Bob :)
Congratulations on the subscriber goalpost! Hopefully the same high quality of educational material just keeps coming. What a lovely channel.
Wow....thanks so much, Yup :)
I think that old amp has a beautiful tone. Very informative video. As always, thank you for sharing your wisdom. 👍
Thanks, Chad. We're glad you enjoyed it.
Hello
First, congratulations on UA-cam recognition for your fantastic broadcasts and lessons. You really deserve it. I am such an average listener very happy about it.
With great respect
Henry
Thanks so much, Henryk.
Congratulations!
Thanks, John :)
Congratulations! Your willingness to share your knowledge in a relaxed and humorous manner certainly deserve recognition. A beautiful vintage amp with great sound. I hope the kitties are well and not up to shenanigans.
Thanks so much, Andrew. Yes, they are doing well.....although often up to no good :)
WOW! UD, I remember when I started watching your wonderful channel, that you had like 50,000 subs! I am thrilled and very happy that you have crossed the 100,000 sub mark! That is a very monuments occasion indeed! I must now offer my thanks and deepest gratitude for starting me personally along the path of tube amp repair! I was interested in amps before I found your channel and found most of the information to be confusing and contradictory, your channel however, was and is clear and concise and I personally am forever indebted to you for sharing your vast knowledge of tube amps with us mere mortals, lol. Thanks for all you do and if anyone reads this and is interested in going on to work on tube amps I HIGHLY recommend UD's how a tube amplifier works videos to get you started!! Again, words cannot describe how grateful I am for the knowledge I have learned from watching your videos!! Peace! And greetings from Oklahoma!!
Wow....thanks so much for the wonderful comments, Jack. Viewers like you make it all worthwhile :)
Congratualations with the +100.000 subscribers and with the recognition you received for this event from You Tube. If there is one thing positive at the covid pandemic is that I discovered You tube, and more particular your channel. I graduated in Electronics in the mid eighties (for some reason we never learned about vacuumtubes, although all TV's in that era worked on vacuum tubes ...), but I never ended up working in electronics. It was by seeing your videos that my intrest in analoge electronics got a wake up. I digged up my old studybooks and looked for hours at your videos. Now am I building my first tube amp and I am very glad I rediscovered my intrest in electronics. Thank you!!
Thanks so much, William. It's great to hear that you are pursuing your interest in tube circuitry. We hope our videos continue to provide inspiration and information :)
Take it out to dinner and buy it flowers :-). UD you crack me up! Classic. Missed a cameo from the kitties though.
They boycotted the video because I wouldn't let them chew on the moustache handle.
Congrats Uncle Doug,much desrved award,its a testament to your excellent and straightforward teaching skills that even an electrocutional hazard old mechanic can understand! cheers!
Thanks so much, Ted. Be careful :)
You are still, the man, Uncle Doug.
Thanks, Shannon :)
That sounds really good
Congratulations on your UA-cam Plaque!! Another great and informative video, thanks UD
Thanks for sending me the amp, Big Dave. It will be on the way home quite soon :)
Hey Uncle Doug.
Congratulations on 100K.
Now as for people that think the plaques are silly. Well there are over 100,000 people on this planet that don't think they're silly. 100,000 people who are interested in what you have to say, who's lives have been enriched by your knowledge. Mine certainly has.
Well done.
Wow.....very nicely said, Nick......and I agree 100%.
Awesome, display your award with pride, you have earned it.
Thanks, Pat. Will do :)
Big fan for many years here, thank you for sharing your knowledge & preserving these pieces of history so carefully. Bravo!
You're welcome, GM :)
Congratulations for your UA-cam channel...... thanks for all your hard and enjoyable work. 🙏👍
Thanks, Mr. McGee :)
I agree doug its beautiful and if you are that excited about an amps appearance , the sound wont dissapoint
Thanks, IA :)
Was just thinking I wish there was a new Uncle Doug video. Looked at UA-cam, and there it was. Damn going to try to try that again tomorrow.
Thanks, Shawn. Wait a few weeks......and it will happen.
Hello again uncle Doug. I’ve been chasing an old mystery amp for a week and half. After identifying a coke bottle 80 and 6n6 sitting in a chassis that looked familiar I put in a successful bid. One poorly lit photo barely showed a domino capacitor so I knew it was much older than advertised.
It’s a single ended Oahu and sounds beautiful. After researching and many identifying photos mine is the only one without a power light or fuse.
The seller played it for me. He insisted.
The chassis is absolutely spotless and has been minimally upgraded. Utah field coil 8”
What I’ve learned from your videos and teaching style is paying off but I’ve only scratched the surface of what I need to. Thanks again. Bob
It sounds like a wonderful old amp, Bob. We're glad our videos have helped you gain both knowledge and appreciation of these old gems :)
After finishing the video I see your plaque from UA-cam. Congratulations
Just to add to the description of the Oahu, the solder dye is bright blue and the cabinet has the same wallpaper sort of alligator or laquer checking texture. No markings serial model#s. Off volume pot has a number showing manufacture code 303 which is either sprague or possibly a military spec. It looks different than your video but chassis is identical
@@Cdog5279 Thanks, Bob. No doubt you have an early Valco amp. Perhaps at the time of its production, they were not labeling them with subsidiary names like Gretsch, Oahu, National, etc.
Ok I can’t send photos on UA-cam or maybe I can. I guess I’ll have to post a video
@@Cdog5279 Why would this be necessary, Bob? The amp has been accurately identified as an early Valco product.
Two thumbs up Doug. Going to be late getting into my own shop this morning, Got a Uncle Doug vid to watch. That's almost like Christmas morning.
Thanks, Martin. I hope you enjoy it :)
Congratulations Uncle Doug! And thank-you for the wonderful videos!
Thanks, David. It was our pleasure.
Such interesting material for tons of people. I don't know diddly about old tube amps other than I like them. I really like to hear and see you talk about them.
Thankyou Doug.
You're welcome, Roger :)
Congrats on your 100k plaque! And thank you for another very well put together video on tube amp repair.
Thanks, Robert. Glad you enjoyed it :)
Wow! You got the OAHU sounding pretty again Uncle Doug! Great Job!
Glad you liked it, Tom.
Dear uncle Doug, congratulations to your 100K. You definitely deserve it 🙂 if not more . For me you and your videos belonging to the kind of content that made UA-cam so famous and unique and is the reason I still have it. It is honest, educational, non profit, and with a lovely sense of humour. You are one big influence that brought me into electronics and I hope you ll stay on air many years.
Wow....Thanks so much for the very nice comments, Doc. We really appreciate them :)
Very nice range of tones. Enjoyed this one and the very good explanations of the technical circuitry...
Glad you enjoyed it, Dave :)
Thanks for another great video and especially the rectifier tutorial. I love little vintage tube amps that I can actually lift. I rescue them from disrepair using similar approaches as you, and so I love your videos. Your videos have all of the fun of amp repair, but none of the frustration (you fast forward through the hair pulling parts, that is very kind), so thank you again for sharing your hobby and knowledge. The Oahu owner really has a great amp now!
Thanks so much, George :)
You earned it Unc!!! You lay down some sweet videos and so many teachable moments. Shame you haven't cobbled together a DVD collection to educate the young ones. Who knows, maybe that's forthcoming. Love you, Bro!!!
Thanks so much, Abe. Likewise :)
Kind sir, YOU ARE THE BEST! Thank you.
Thanks, Mike :)
Congrats on hitting 100,000 subscribers! I'm glad to account for at least one of those subscriptions. This amp is an absolute beauty.
Thanks so much, Greg :)
It is always a red letter day when a new Uncle Doug video is posted. Thanks.
I hope you enjoy it, Jeff :)
'"Take her out to dinner and buy her flowers" got me chuckling Doug !!
Glad you enjoyed it, AG.
Very Good Video Uncle Doug!
I Grew Up learning on circuits similar to the Oahu amp.
I had an old ValveCo amp I played through practically the same circuit as your Oahu.
Greetings, MP. Thanks for sharing :)
Hey uncle Doug great to hear from you
You too, Stevie :)
UD Rusty, Jack, Casey and Ollie congratulations on getting over 100,000 subscribers, thats a remarkable achievement. im glad to see Google/UA-cam are not the evil dark side and recognized you all even though you dont allow them to profit from your content.
the amp sounds fantastic! im sure glad in this day of consumption and throw away after a few years of use, that you keep this great historic equipment alive and useful.
Thanks, Russell. Apparently they do make money from my channel but simply don't share it with me. To be honest, I don't care.
Uncle Doug, you are my Rock, when it comes to working on Amplifiers. As you know, it's been a few years now, since I became inspired to learn this stuff.
There's a couple other channels I watch.
But when I am looking for die hard, bottom line, correct information. I ALWAYS go back to see what you have to say on a given subject.
Thank you, for keeping me and many others inspired!
Wow, thanks so much for the very kind words, DW. It's always great to hear from you :)
Congrats! This channel has been a great education for me, thanks for sharing your knowledge.
That's good to hear, Kevin :)
Congratulations Uncle Doug
Thanks, Dave :)
Congratulations on your subscribers award Uncle Doug!! and thanks for another video treasure :)
Thanks, Shawn.....glad you enjoyed it :)
Congratulations Doug, 'keep on rockin'...
Thanks, Rob. Will do :)
Congratulations Uncle Doug, you are well deserved for this award. Thank you for another great video, this amp sounds fabulous.
Thanks so much, Asaf :)
Congratulations Uncle Doug!
Thanks, Fred.
'...Had to take it out to dinner and buy it flowers...' You sir, are a wag. I learn ever more watching your content. Congratulations on the 100k - fully merited.
Thanks so much, Phil :)
Awesome and congratulations! You’re doing an absolutely great job for the community on your YT video channel. I have liked and truly subscribed. 👍
Wow, GD. Thanks so much for commenting and subscribing :)
43:09 and just when you were hoping for a cheap date Uncle Doug :) Congrats on the 100K viewers and many more to come
So true......Thanks, Pedro :)
That amp has the exact same handle as the Gibson EH-150. The grille cloth is absolutely amazing!! And congratulations for the 100K!
Yes, it does. Thanks, V.
Another fantastic video to brighten my day. Congratulations on the YT plaque. Thoroughly deserved!!
There are some great amp channel's on here but Uncle Doug is the go to and best!!
I eagerly await the next episode 🙂
Wow....thanks so much, Richard :)
@@UncleDoug no thank you!!
Congrats Doug! I always watch your videos and love the sense of humor, especially when it pertains to Juarez.
Thanks so much, Scott. It was a big part of my youth and I guess it shows in my comments ;)
Sounds super clean. A simple design from the past but still sounds good. Wow you made someone happy for sure. All the best UD .
Thanks, J&B :)
Congratulations Unlce Doug! Your a wealth of knowledge for Us! Thank you greatly for sharing it!
Thanks, Anthony :)
That debit card addition is brilliant!
Glad you liked it, Jeff.
Congrats on 100k subs. Started watching you around 2016 and was coming back for your repairs but also for your personality. Always can hear you are talking about something you really like and that is so nice to watch and listen to. Cheers.
Thanks so much, Michael :)
Greetings uncle doug! Is so nice see a brand new video of yours. Thank you so much!
I hope you enjoyed it, Demian :)
You are a true historian Uncle Doug. We need more of you to stop history repeating itself.
Beautiful amp wonderful restoration work. Joy.
Thanks so much, IL.
Congrats on reaching 100 000 tube twiddling maniacs around the globe Uncle Doug. Could you ever imagine reaching this milestone when you began this channel..! Kudos to your warm humour, steadfast principles and the helpful contribution of ole Rusty, Jack and the rest of the 4 legged furry crew, thanks for all the joy you have given us. .. greetings from South Africa.
Thanks so much for your very kind comments, Alex. Honestly, no, we never dreamed of reaching 100K. Early on, I was glad to have ANY subscribers :)
Congrats, Uncle Doug - you're the best. I came across your videos years ago and they helped me learn so much about tube amp repair and restoration. I'm so glad you're still producing great videos. Love that you passed 100,000 subscribers - Here's to 100,000 more!
Thanks so much, JC :)
Very deserving award, congratulations
Thanks, OG :)
Congratulations for 100 000 subscribers, trust you will go for the next 100k. Great video with lots of useful information. Regards from Germany, Thomas
Thanks, Thomas. We are indeed :)
That is a very handsome plaque. Richly deserved.
Thanks so much, Allan.
Congrats on the 100 kilosubscribers! Here's to 1 meg!! I think a black, brown, green, silver frame would look great with the plaque.
Very cool little amp with a really sweat sound. I noticed the teardrops on the schematic about halfway through the video. Well done, sir, as always!
Thanks so much, Tim. I think it was sweat.....and brake fluid from a 1929 Model A Roadster ;)
@@UncleDoug LOL - I see what I did there. I think I have spring on the brain. We just got dumped on with another 7" of snow... No sweat here!
Uncle Doug - welcome back. Congrats on your UA-cam plague. I've been playing bass guitar for 51 years and have gone from all tube amplifiers to all transistor and now have a hybrid model. I would normally have bypassed your section on the various tube types but I found it interesting, and your detailed descriptions so engaging that I watched the entire segment. Thank you.
Thanks for your nice comments, Paul. We're glad you enjoyed the video :)
Congratulations uncle Doug love watching you repair amplifiers and leaning about them.
Thanks, Fred :)
Wow, that's a fab specimen of an old amp..! Love the repair and excellent valve and circuit explanation. Congrats' on your plaque Doug, so well deserved..Well done you... More knowledge absorbed... Thanks for sharing..Ed..UK..😁
Thanks so much for the very nice comments, Ed :)
100K and more to come Uncle Doug! Thanks and well done to you :)
Cheers Good Sir!
We appreciate it, Rick :) Likewise.
Wow! That amp puts out some rich harmonics!
I'm sure it would, Maurice :)
WOW! Congrats for the 100k+ subscribers, Maestro!
Thanks so much, FW :)
Congratulations on the award. Well deserved!
Thanks, Brian :)
Congratulations Doug!
Thanks, Dino :)
Congratulations Uncle Doug! Woohoo!!
Thank you, Rick :)
Congratulations on your 100,000 subscribers award! So glad to see you get recognition for your well done and enjoyable work on your videos.
Thanks so much, Scott.
Congrats on your award. Greatly deserved.
Thank you very much!
Congratulations! I love your channel because I used to repair a lot of vintage gear but back then it wasn't vintage.
Thanks, Mr. Pile :)
Good to see you again, Uncle Doug! I saw a Patreon payment sent, got exited so checked and there ya go! Another Uncle Doug video! WooHoo!
Thanks, Maurice. I hope you enjoyed it :)
Nice to see you here agai, Doug!
Thanks, you too, FW :)
@43:16 - wow😆 Uncle Doug ...just ... wow!
Glad you liked it, TC.
I really enjoyed this video. Thank you for always sharing your priceless knowledge with us. You are a pillar in the vintage amp world, and in my life! Congrats on the 100K subs. We love you Uncle Doug!!!
Wow, thanks so much, Colleen. It's always great to hear from you :)