Fender Bassman 10 - Service, Repair, Breakdown, Tone Mods

[@PaulLebow]

Just saw this - Really informative! I've had a BM-10 chassis only for 30 years. Used as a tube amp learning platform. Put in the bias pot and precision 1 ohm resistors to measure current back then. Thanks very much for the insights. I grabbed mine form of the attic and ready to dig in.

[@wtangodelta1715]

THANKS KDJ!!!!!! I recently scored an unadulterated Bassman Ten (minus the cab and speakers) for a song, figuring I'd get around to unlocking the potential of the amplifier some day. Thanks to you that day has basically arrived, and the process has begun...Thanks for doing the real work (the analysis) for me! I'm going to run along now...I'm off to plug and chug, as it were, to free this amp from oppression :) Cheers Mate!!!

[@TRtribal]

Did one of these once. Complete recap, and had to replace a blown driver. Finding a replacement 10" 32ohm speaker was fun.

[@williambock1821]

My friend had one of those that was used for bass ,actually! I’m not sure what happened to it but back in the 90’s was the last time I saw it. It worked pretty well for the 3 piece band we had. I played drums. I was wondering a bit about some of the mods you made till I heard the results. Sounds great!

[@PaulLebow]

Seems that removing the negative feedback gives the major impact to get away from the ultra clean tone.

[@rockinws6567]

Very good, I'm diggin it. I may grab one of these and do similar.

[@randr10]

I have one of these that sat for over a decade and the tubes are getting so hot it feels like standing next to a campfire when I stand behind the amp. The tubes that were in it red plated when I first kicked it on and burned up the fuse. I found that the power to the transformer was setting on top of one of the tube pins and they got so hot the insulation burned and the tube pin was either arcing to the input power or the two pins were carbon tracking along the burned insulation. I rerouted that and spliced that section of transformer wire out, put a different set of power tubes in it and it sounds good and doesn't blow fuses anymore, but that heat is way more intense than I ever remember a tube amp giving off. I'm wondering now if this bias resistor might be the problem and that I could fix it with that 30k control pot trick you did? I noticed some minor differences on mine too. That balance control pot has a resistor to ground coming off of it and that's missing on mine, and that pair of green components in series have a white 2250 ohm resistor there instead, but otherwise it's identical under there. And yes, this thing has a very flat tone when you play a guitar through it. Sounds very 60s-ish bass when you run a bass guitar through it though.

[@KleyDeJong]

@@randr10 Yeah an adjustable bias pot is a nice addition.

[@JammyCrackcorn]

Should have used axial Capacitors under the Doghouse…

[@peterhurst6263]

I did every mod here except for the pentode triode, cause I didn’t find good enough directions to feel competent doing that one. I don’t feel like I have quite as much gain as shown at the end of the video. Maybe the pent/tri mod helps, but I’m a little disappointed and wanting more. Wish I knew what else to do.

[@stringlocker]

Haha you seem to know what you're doing. Pretty rare. Sounds awesome

[@Matan2222222]

Hello Kley! Great Video! Do you have any solutions for the huge low end that the blackface amp produce. Tried many speakers with my 1965 Vibrolux but the bass get’s really lost on volume 5 or more

[@KleyDeJong]

I usually run the bass control at 2 or 3. Treble at 6 or 7. Speakers are a great idea as well. Past that there are a number of ways you could shift the overall EQ to be brighter. I'd look at the bass and treble capacitors and the pot values. I'd use the tone stack calculator to dial in an idea on paper the test at length. You could also send it to me and I'd be happy to give it a deep dive on a video!

[@Matan2222222]

@@KleyDeJong I wish could! I’m from Israel! Thank you for the fast response. I’ll keep watching your videos!

[@robimiara7444]

You practically destroyed that poor amp

[@stanislavmigra]

Thats one hell of an amp. And very good video, with informative details. Perfect demonstration of impact of negative feedback (or lack there of). Great work. Interesting, that you installed the penthode/triode switch, as Uncle Doug is not a fan of that, as he thinks the triode mode is not very good for audio. ps: I will very probably live only in the "Tweed mode" just rideing volume on guitar. But hooking AB switcher will allow for very nice dirty/clean channel switching, without jumping too much in character of sound (what is often problem on modern multichannel amps).

[@chuckwn]

Thanks for your helpful video. I just acquired one of these and got it back up and running. I’m curious how you get all the overdrive in your demo? I can’t get mine to break up. Also sounds like there is some reverb in there. Are you using pedals?

[@KleyDeJong]

One mod I did on channel one was to remove the resistors that make a voltage divider on the input before v1. That was sending some of that input signal to ground.

[@chuckwn]

@@KleyDeJong I really like the sound of your modified channel 1. Unmodified, channel 1 does not sound good on mine. Still curious how you are getting the reverb and additional drive?

[@levijessegonzalez3629]

thinking about buying one. 2 speakers are blown... are the speakers really 32 ohms? if that's the case would I be better off replacing them with all four new speakers?

[@lgs6692]

i have a an old bassman10 in original state, but a few rca 35604 diodes in powersupply are dead, what would you replace them with ? (running the amp at 230 volt) Of coarse i am going to recap it. an i might do some of your (reverseable) mods to it , Nice Job

[@KleyDeJong]

I've been using 1n4007 with good success

[@georyans]

Taking out the 220p in the tone stack is a mistake plug in those values in the Weber tone stack program and you will see what it does

[@JammyCrackcorn]

When you used the bulb limiter…it dimmed down but when you removed the tester meter…it lit up Brite…shows high Brite bulb!!

[@Phillip-y6d]

I had one of these in the 80s and damned can't remember what happened to it. maybe traded it in for something dam

[@Allenbass7]

I want to mention that if you are unaware of what the reference of "death cap" is to, or what the DANGERs are in using an amp with this wiring schematic - it should be promptly understood. I recently inherited a Bassman 10 and I am so glad that I have not plugged it in or turned it on yet at all. I will not even try until this is reworked... If you look it up, there is a capacitor in the circuit which can fail and result in the guitar going straight into "main" voltage (i.e. straight into the wall). Appalling.

[@theedrstrangelove]

I have 2 from like '78 and they are plywood except for the front.

[@deadcityamps2731]

Should have changed hum balance to blackface bias.

[@jamesbracken4618]

You need to replace those with 500 volt capacitors not 450 volt, They wont last.

[@SteverRob]

Yep. I'd punch a hole and install a tube rectifier. That'll bring B+ down too.

[@juniormint3136]

Fender specifies 600v for all the capacitors in that amp

[@lancemartin8465]

Brown box helps

[@sonnysilversmith2156]

I can get the same sound using a good eq, boss chorus pedal, a donner compressor, fender hammer tone fuzz, wampler moxie od, and a mini reverb pedal from unfortunately china… thru a Squire 60’s Classic Vibe Sunburst Strat.

[@stanleyjoyce7674]

j hooked the filter caps. not good. sloppy

[@JammyCrackcorn]

Axial caps should have been used…