Other Amps

Hot rodding a Fender Bassman 10

1

Got this Bassman 10 in swap from DCBirdman. All original, unmolested. Gonna replace the electrolytic caps and burnt resistors, then do a little hot rodding. Make it more guitar oriented. It has a SS rectifier, but came with a 5volt winding and a chassis knockout for a tube socket. Probably use the useless polarity switch to go between SS and tube rectifier.

2

Already have the head cabinet made.

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Hey forgot about that one! You have a tube PA panel on it which is cool. I might have another beat Bassman 10 coming up -- still working on it.

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Please keep us informed. I have a 78 or 79' Bassman 10, completely stock. It ain't loud but does sound good for bass & has a funny, non- fender sound for guitar. (I love your cabinet.) I think there are mods to turn it into a Super Reverb without major surgery. Best wishes.

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I forgot. Check if yours has plastic shaft knobs. (Mine does.) They are made really cheap. The wiper portion of the pots are some kind of glued on metal particles, not a copper resistance ring. Wired in parallel in the tone stack, a bad pot that has a broken 250k, end to end screws up the entire circuit. (My temporary fix is to "dime" the entire amp.)

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Yea, all plastic shaft pots. They’re all pretty smooth though. I’ll clean them up and see where we are.

The Super Reverb territory is the plan. Some things just gotta go, like the SS recto and that rediculous bias-balance circuit.

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Common cracked 470R screen resistor.

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Tube rectifier socket in.

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There’s more than enough real estate here to add a two tube reverb circuit.

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Already two extra holes in the chassis front. Could easily add a Reverb control pot.

11

If by any chance you are going to rid the amp of the power cord, (with the red plug,) I will pay almost dearly for it. My FrankenChamp is begging for one of the darned things.

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Sorry 12Bars. I got it with the cord cut off.

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Thanks for the tread. I had to fire mine up for a stretch, (& my ears are only ringing, slightly.)

When I turn back the tone knobs on mine, it cuts the volume of the entire channel. (That's why I dime everything, for now.) This does not help my "On the Fence, Problematic Electromatic." I have a bag of 250k pots to solder in, but It's on my long list. This may help you;

If you put your VOM on the two outer tabs of the volume or tone pots you should get, roughly, ~ 250k. What I'm trying to say with mine... the VOM reads a completely open circuit on most of them.

If you pry open one of the potentiometers & look at the inside. The resistance band is made of powdered ferrite & is usually worn through. (It's not copper on copper, inside.)

In any case.. Rock On!

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I thought one of my Silverface Champs still had a red plug power cord. Nope, all replaced. I was gonna cut it off and send it to you.

I’ll keep my eyes peeled.

15

My "mixed bag" Champ has the tolex ripped off & a slap coat of varnish, shellac, (I don't know what applied?) It had a 2-prong cord that I replaced with a 3, but it ain't "Fender like." I have a Bendix 5992/6V6, & a Telefunken 12ax7. It's my baseline amp for dialing in a 6-string.

My Bassman 10 (before I got it,) was dropped upside down & I had to refabricate the back corner. I dripped on PC7 epoxy in layers. I was lucky, the tolex was there but the wood was gone. (I do need a side vent & a back panel.)**

However,,, it will be a much loved, ugly piece of crap no matter how much I do to it.

It was Fender's last piece of "Made in USA," tube driven, old school chassis design. When something eventually goes south in the thing I'll use your tutorial to eventually fix the thing properly.

I do have an older, P Bass Special, that I use my Bassman 10 to noodle on.

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If you add a pair of tubes for reverb AND add a rectifier tube...be careful that you aren't overloading the power transformer's current handling capabilities. It could be that the PT wasn't designed for that kind of load. An easy non-scientific test would be to feel how hot it gets with the added tubes after playing for a half hour. You'll know if it feels too hot.

The rectifier addition is probably ok by itself, though. They wouldn't have added the taps to that transformer if it couldn't handle THAT load.

Personally I wouldn't do either of those mods. Solid state rectification is going to give you higher voltages which translates to more headroom on tap with the right mods elsewhere. As for reverb, I'd just use a Hall of Fame pedal in front of it. Less hassle. Less risk of failure. Less expensive. More versatility. But that's just me.

17

Even though the added load of two 12AX7’s is minimal, I probably won’t add reverb. The PT is massive. I was just looking at all the empty space and thinking out loud. I’m really not into reverb at all and I don’t use pedals much.

The 5v tap and socket punch out in the chassis was an invitation I couldn’t refuse. I know most Gretsch players on this forum are “clean” players. Executives, Standels, etc. I really love the feel of a tube rectifier. I love the hair, the squish, the harmonics. Clean is not what this amp is about.

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People think they are hearing the rectifier tube but what they are actually hearing is the voltage change. The B+ voltage drops 50 volts or whatever (depending on which tube they use) and they hear the slightly lower headroom due to the drop in power as squishy and call it "sag" but true sag is rarely audible. You can get the voltage drop other ways like changing the resistor values on the rail or using a variac... but a tube rectifier doesn't hurt other than being a tad less reliable and eating more electricity. A bad tube rectifier could take out other components too I guess so there's that risk.

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Cooking up the new and improved Bassman 10.

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Good lookn cookn! Sounds good?

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Well, I plugged in after the cook, and initial opinion is that it is massive. Just a beast. Plenty clean headroom, very powerful. Overdrives nicely with everything up. May have to replace some (or all) of the pots. Positional loss of signal. I’ll give them all a good cleaning in the morning and see if that fixes it.


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