How to quickly repair Fender Bassman guitar amp negative bias failure
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- Опубліковано 28 лип 2024
- Fender Bassman dead! I expected the worst (Power transformer) After a quick checkout, the problem ended up being a open negative bias diode. Easy cheap fix. Contacted the owner, have a few more items to address, but the Bassman is operating again! Please keep in mind, this is an initial inspection and revival of the amp, Not a full repair. That will be wrapped up later.
Here is the new website: d-labelectronics.com - Навчання та стиль
Nice little repair. One of the Bassman 50s I did on my channel recently came back, and while the customer was here I quickly discovered major hum, and opened the dog box to immediately see the terminal completely broken off one of the main filter caps in series. Replaced it, tested the amp, which was so dead silent I didn’t think it was on. We plugged a guitar in and had fun with it.
Hey Terry, I like your videos, & it's always nice to see a wine bottle on the bench. You're a funny guy, a glass of wine in hand & excellent vintage gear in the shop. You know your stuff though & I give credit where credit is due. It's just how some of us are "wired" I'd have to say. I've been a tech. since 1976, @13 yrs. old & excelled quickly in this field. Like so many of us, it all started out with CB for me & I loved it. Total satisfaction in the Electronics field. -Yeah- the thrill of it all! There are many people here posting videos ranging somewhere between guessing, yet unfortunately smoking up priceless cool stuff but -really wanting to learn though ...and the laid back Tech who knows the deal. No offense meant to some of these guys, at all. I just enjoy the vid's where things fall into place sort of like a bottle of good wine on the BENCH, a clean bench setup, and of course -communication gear & Amps all within view as you move on to the next job. And BTW: "Fender Bassman" ? **You know Jack Cassaday IS the Bassman** right? Keep up the good work!
I just bought one of these Terry. As always, your videos are informative and on point. Thanks mate 👌👌
Quick indeed!! I see the website - nice touch with your helper! Didn't know your a BC guy... used to train there so I know I'm in good hands.
Great video Terry. Sorry to hear about your wife's mother. I'm a little late on that, but I just heard today. Thanks again for the help today also, I really appreciate it.
Dittos on that. God bless to you and family.
Nice fix Terry.. Thanks for sharing and the expert info..Ed..UK..😀
Dang I love these vids and I just play Geeter for 50+ years
Hi Terry, Please give us radio guys a little love.
Looking good!Enjoyed.
Fender built some tuff stuff thanks
As a 59-year user, with 35 on weekend stages, I can attest to that!
Terry, I'm desperate to know more about my Fender DR2 amp circuitry, I'm a retired electronics tech, but solid state, the DR2 input system is doing my head in, if you ever get one of these I'll gladly make a contribution, love the channel, Gary , England
Good easy fix my friend. Makes you wonder how they blew that diode.... or was it just weak... you never know... Great fix
Hi Ron, Thanks for the $$, very cool of you Sir. I will be making a follow up video of this amp maybe discover other issues. Had to see what the customer wanted first.
Another save by D-lab.
I enjoy watching your videos. I took your advice a purchased a leader LAG 25 and I'm curious if you have an owner or service manual for yours. I'm not sure what the output voltage is supposed to be since it drops to zero when I turn it to the x1 on the output multiplier. This unit is like brand new and don't want to get into it until I know for sure what the specs are supposed to be.
Great website Terry. I used to have a website with GoDaddy myself. I liked how you could customize it the way you want it. You should put a link you your UA-cam page on there as well.
Great idea man, will do, Thank you!
Hey Terry, I don't know if it would interest you to do so, but you could get a cheap looper pedal to test your amps rather than the signal generator. Not that there's anything wrong with the signal generator of course, but you could have a friend play some chords and lead lines into the looper pedal and then get actual guitar sounds through the guitar amps.
I was thinking the same thing.
Hi Terry, I'm so sorry to hear about your Mother in Law. Great videos! I've been watching for a few years now but have just subscribed. Thanks again for the Variac. I've noticed that you are now again using a manual range meter but tried an auto range meter for a while and before you were not a big fan of auto range meters. What are your thoughts now?
28 ma is awfully cold bias for those 6L6GC's ! closer to 38 ma would sound so much better !!
Initial checkout value only
10:18 - I'm still curious what caused that pop!
Lots of external noises in my shop
going there now Mr. T
But why did the diode fail? This doesn't give me a warm fuzzy. Did the old diode have a low PIV that got taken out in an electrical spike? Looking at the schematic, I don't think a shorted output tube could do that.
Have no idea man
Overheating ( Thermal runaway) ? The failure of another component ( simply to check, if the ampli not work again)? Overcurrent ? Overvoltage ? Simply aged or stressed ? Diodes can fail open, closed, and in between ( fail closed and open failure is a subsequent event) .Who knows.
link in the description?
Why did you not check for matching, then measure and set the plate/watt dissipation for the highest current draw pt, which would, I defend, be the more correct way to set the pt bias for a properly matched (or unmatched) set of pt's, instead of "good enough for me"..??? Based on what.?? The other problem I see is "a really cheap repair".. Yes, the parts are cheap, but discovering the problem and setting a course of action is not.. Would you divulge what you ultimately charged for the repair..???
There will be a part 2 with more info, This was just initial inspection and revive
@@d-labelectronics As a suggestion, you might include the "part two" and possible outline of the next procedures, as many boob toobers will think the service is completed, no matter if the client wants more work done or not..
There's that honking big screw by the orange Spragues. Is that normal?
How can a screen
Grid be shorted and burn the screen resistor? screen grid is
Far away from the plate or cathode and heater but it is next to G1 control grid. Far from G3 suppressor grid in a pentode.beam
Power tetrodes
Don't have a G3 but beam confining plates
Connected to the cathode. I know the heater can get shorted to the cathode the heater inside the cathode is insulated
With aluminum oxide
That can fail. The cathode is coated with
Strontium oxide barium oxide or both so how can Grid 2 screen grid get shorted to anyting and show up on a tester or a burnt screen resistor? What does it short out to?
This may sound like a funny question. I just don't see how.
Just sent you a miserly donation via PAYPAL. Yay! At least it's something, finally!
Very nice of you. Thank you for thinking of me. Plan to review the donations on my next vid.
Hi i have a 66 bassman. There are 7 Diodes in the biasboard. Will they be ok after 60 years or is it better to change them all to 1n4007 diodes. If they are to change can 1 insert only one 1 n4007 instead of the three or better install also 3 new Diodes.because one new is rated with 1000v. Thank you and Greetings from Germany
I noticed you have 'shop hours' . . .did you retire ? ? ? If so, you have a great future in HR/Amp repair.
Not Yet, Hope to soon. Yes, I need to edit the hours
@@d-labelectronics I guarantee you, when you do and do amp/HR repair work, you will definitely have to hire a good 'assistant' (preferably a knowledgeable young one) to help you with the work...you do 'outstanding work' along with UD !
10:10 cheers!
That's a nice looking amp stand. Is it home-made?
mojotone sells them
@@d-labelectronics thank you.
Did the female Amplifier Tech slip up?
Are you open ?
DOA. Bassman needs one of them heart paddle things ... BTW: If you go on the Internet and get NOW brand Sunflower Lecithin in 1200 mg, and take 6-10 / day, they will clean out your (everybody's) arteries, so YOU don't need that heart paddle thing. lynncapehartwellness.com blog 6
I wondered how often those SS rectifiers failed. When rectifiers go, amp no go.
...the amplifier HUMS because it doesn't know the WORDS-(?)
Interesting videos but these amplifier repairs are all starting to look the same. There must be other stuff to work on.
Yes Sir, good input, was just talking to my son about the same thing. Plan for new content soon
Nice George Bush imitation! Not gonna do it.!