Bassman head circuit identification

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tremblaylive
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Bassman head circuit identification

Post by tremblaylive »

Hi guys,

I've recently acquired a Fender Bassman head, but the sticker inside the chassis has taken quite a beating (and even so, i've seen multiple sources mention that they are sometimes inaccurate)

I want to identify which circuit I have, and was wondering what the key things I should look for are?

Things of note: The tolex is black, knobs are not original (chicken heads), there are 6 tubes total (so I guess this isn't a tube-rectified model?), there is a presence control on the front panel.
It hasn't been recapped (so I guess that's the first thing I should be looking to do... Would the caps be useful for identification purposes, or are they always the same?)

Based on what I have read online, I may have a 6G6-B, but i'm really no expert.

Also, what kind of speaker setup would you suggest? Currently on the lookout for a cab for this bad boy 8)

Thanks!
tubeswell
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Re: Bassman head circuit identification

Post by tubeswell »

Need pictures and serial numbers.
Last edited by tubeswell on Sun Apr 30, 2017 8:19 pm, edited 1 time in total.
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martin manning
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Re: Bassman head circuit identification

Post by martin manning »

6G6-A and -B are blonde, but there are exceptions. See here: http://www.thevintagesound.com/ffg/
tremblaylive
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Re: Bassman head circuit identification

Post by tremblaylive »

I will try to post pictures when I can open it up again.

Is there anything in particular I should be photographing that is a "dead giveaway"?

Also, for a speaker cab -- would a 1x12 cab with a Tone Tubby Alnico Red 50w 8 ohm speaker stand up to the abuse of the bassman? (Assuming its volume will likely never go higher than 7-8)

Thanks!
tremblaylive
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Re: Bassman head circuit identification

Post by tremblaylive »

Also Martin, I looked on the site you provided -- the front panel layout of my amp is similar to the blonde ones (there are no deep or bright switches), even though the tolex is black...

It seems to fall into the exceptions on the 6G6-A Blonde bassman page.

Now... The amp powers up fine, I cleaned the pots with contact cleaner as they were all scratchy. Now, on the Normal side, the treble control brings in a bit of a hum (maximum treble = maximum hum, no treble = no hum), and the bass side inputs seem to not work at all.

Is it possible that i'm just not driving the bass side hard enough? (Currently running through an 8 ohm speaker that is wayyyy overbuilt for this amp -- an EVM12L)

The clean side sounds very nice with my strat, but i'd love to get this amp working as it should (pretty sure it's going to need to be re-capped as one of the big ones leaked slightly)

So much to think about..!
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martin manning
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Re: Bassman head circuit identification

Post by martin manning »

Could be one of those exceptions! 6G6-A and -B do not have a bias pot. AB165 has a bias balance pot with a center tap, while AA864 has a normal bias pot. Get some model numbers and date codes from the transformers.

Yes, re-cap for sure. Could be a number of things on the non-working channel. Are you going to work on it yourself?
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ToneMerc
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Re: Bassman head circuit identification

Post by ToneMerc »

Sounds like a tuxedo blonde Bassman


TM
tremblaylive
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Re: Bassman head circuit identification

Post by tremblaylive »

I definitely want to start learning about tube amps and working on them. First thing that I want to do is build a stand so I can sit the chassis in it upside down so that I can properly prod around.

Next time I open it up I will check what the bias setup is and report back :)

I'm stoked if it really is one of the blondes, those circuits seem to be some of the more sought-after ones!
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ToneMerc
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Re: Bassman head circuit identification

Post by ToneMerc »

tremblaylive wrote: Mon May 01, 2017 12:52 am I definitely want to start learning about tube amps and working on them. First thing that I want to do is build a stand so I can sit the chassis in it upside down so that I can properly prod around.

Next time I open it up I will check what the bias setup is and report back :)

I'm stoked if it really is one of the blondes, those circuits seem to be some of the more sought-after ones!
The fact that it has a black tolex and black faceplate with a presence knob leads to a 6g6b. BTW the tuxedo reference is the transitional model that has the later blond circuit with black tolex, faceplate, handle and white knobs.

TM
tremblaylive
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Re: Bassman head circuit identification

Post by tremblaylive »

ToneMerc wrote: Mon May 01, 2017 1:22 am
tremblaylive wrote: Mon May 01, 2017 12:52 am I definitely want to start learning about tube amps and working on them. First thing that I want to do is build a stand so I can sit the chassis in it upside down so that I can properly prod around.

Next time I open it up I will check what the bias setup is and report back :)

I'm stoked if it really is one of the blondes, those circuits seem to be some of the more sought-after ones!
The fact that it has a black tolex and black faceplate with a presence knob leads to a 6g6b. BTW the tuxedo reference is the transitional model that has the later blond circuit with black tolex, faceplate, handle and white knobs.

TM
Thanks TM! Now to figure out which speakers to use with it :) (And fix the bass channel, so I can get some jumped goodness! :D)
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M Fowler
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Re: Bassman head circuit identification

Post by M Fowler »

I picked up a 6G6-A from local pawn shop for $325. and it has a loose black tolex put on it, blonde tolex is gone.

Based on serial number and tube chart it is a 1962 6G6-A and will get new blonde tolex and early grille cloth not the oxblood cloth.
Fender Bassman 6G6a 01.jpg
17240625_10208022267986087_8196783240664273999_o.jpg
Marks 6g6a tube chart.jpg
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ToneMerc
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Re: Bassman head circuit identification

Post by ToneMerc »

tremblaylive wrote: Mon May 01, 2017 12:07 pm

(And fix the bass channel, so I can get some jumped goodness! :D)
* clip off or just lift one leg of the bypass cap on V2b's 100k plate resistor.

* change those .25 coupling caps to .022

* change 1M resistor to 33K to 56K.

* change .00025 to 330 to 390pf

TM
Last edited by ToneMerc on Mon May 01, 2017 2:39 pm, edited 1 time in total.
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ToneMerc
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Re: Bassman head circuit identification

Post by ToneMerc »

Dup
Stevem
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Re: Bassman head circuit identification

Post by Stevem »

No Bass channel function at all, Are all 4 small preamp tubes in the amp and there filaments lighted up?
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Re: Bassman head circuit identification

Post by scooter_trasher »

M Fowler wrote: Mon May 01, 2017 1:36 pm I picked up a 6G6-A from local pawn shop for $325. and it has a loose black tolex put on it, blonde tolex is gone.

Based on serial number and tube chart it is a 1962 6G6-A and will get new blonde tolex and early grille cloth not the oxblood cloth.Fender Bassman 6G6a 01.jpg17240625_10208022267986087_8196783240664273999_o.jpgMarks 6g6a tube chart.jpg
I wanna shop where you shop, this beat up one went for $1225 on fleabay , I almost puked :)
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