How to quickly repair Fender Bassman guitar amp negative bias failure 

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.

I just bought one of these Terry. As always, your videos are informative and on point. Thanks mate 👌👌

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!

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.

Dang I love these vids and I just play Geeter for 50+ years

Nice fix Terry.. Thanks for sharing and the expert info..Ed..UK..😀

Hi Terry, Please give us radio guys a little love.

Looking good!Enjoyed.

Good easy fix my friend. Makes you wonder how they blew that diode.... or was it just weak... you never know... Great fix

Fender built some tuff stuff thanks

Another save by D-lab.

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

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.

10:18 - I'm still curious what caused that pop!

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?

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 RU-vid page on there as well.

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.

28 ma is awfully cold bias for those 6L6GC's ! closer to 38 ma would sound so much better !!

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.

going there now Mr. T

I noticed you have 'shop hours' . . .did you retire ? ? ? If so, you have a great future in HR/Amp repair.

Just sent you a miserly donation via PAYPAL. Yay! At least it's something, finally!

link in the description?

There's that honking big screw by the orange Spragues. Is that normal?

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

That's a nice looking amp stand. Is it home-made?

10:10 cheers!

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..???

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.

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.

Nice George Bush imitation! Not gonna do it.!

...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.