bassman 6g6b bass channel mod?

[jamme61]

just p/u a 1962 blonde fender bassman. Beat up on the outside but the inside is in perfect- non mod condition.. My question, is there a simple mod for the bass channel side? Anyone mod the bass side of the amp? Interested in any info on this. Thanks

layout here
http://www.thevintagesound.com/ffg/sche ... layout.gif

update:
I like to tweak the bass channel of the 6G6-b not totally change it. any ideas thanks ahead of time.

IF your bass channel sounds Bright with little bass go to this link
http://www.fenderforum.com/forum.html?d ... ber=549123

[ToneMerc]

just p/u a 1962 blonde fender bassman. Beat up on the outside but the inside is in perfect- non mod condition. Had to change two plate resistors and two cathode caps and add bias pot- quiet as a mouse, sounds great. My question, is there a simple mod for the bass channel side? seen some talk of making this side a JTM 45. Anyone mod the bass side of the amp? Interested in any info on this. Thanks

layout here
http://www.thevintagesound.com/ffg/sche ... layout.gif

Ive built a couple and modded the bass channel only, they are great amps.

1. remove ceramic cap on v2b, try that only first if you want to leave it pretty much stock.
2. change bass chan couplers from ,1 &.25 to .02.
3. change bass chan slope resistor and treble cap to typical Marshall range values, I like 43k and 390pf.

YMMV

TM

[jamme61]

thanks, i did remove that cap already (big improvement) it does seem to be pretty bight channel right now. The slope resistor mod will give me more mids right? thanks for the help

[billyz]

Here's mine.
http://www.billyz.net/Fender%20Bassman% ... 20mod.html

Based on the express of course.

[jamme61]

Thanks! checkin this out right now

hey thanks for this but this is based off the ab165 I was hoping just to tweak the bass channel of the 6G6-b not totally change it. any ideas thanks a head of time.

[billyz]

Works for the 6g6 as well, less
Work to do. Move the treble control to the standard tone stack change a few resistors and caps , wha la .

[jamme61]

Works for the 6g6 as well, less
Work to do. Move the treble control to the standard tone stack change a few resistors and caps , wha la .

thanks again not sure I want to do it? I'd have to change some pots too. The bass channel is brighter and has less bass then the normal channel, on my amp? I did remove (.001 cap) on the plate resistor but the rest of it looks stk. I had a bassman ab165 and the bass channel sounded really bad, this one is pretty good. starting to grow on me.

[jamme61]

FYI update: found that my 1964 bassmans Bass channel is some kind of fender factory change that's not on any schematics. My Bass channel was very bright with very little bass. Once I wired it back to the schematic, all the bass came back. sounds great. Here is a link where I found all the info.

http://www.fenderforum.com/forum.html?d ... ber=549123

[john l]

Sorry to resurrect this thread.

So I have a 6G6B and my bass channel is also pretty trebly with little bass that this thread mentions but all the pics of the correct way to wire it have been lost in threads that are linked. Can anyone help me fill in the blanks. As it stands mine is wired like the 6G6B layout is drawn but apparently this isn't accurate?

[martin manning]

Reading a bit at the above fender forum link it appears that the 6G6-B schematic and layout have the correct wiring for the bass channel, but some transition-era amps were wired differently (incorrectly?), resulting in a loss of low end. I would start by checking what you have against the schematic.

[Roe]

I tried tweaking the 6g6b bass channel. Reducing the 2nf snubber cap helps. but the best solution was to rebuild it to a k50 preamp

[john l]

Despite having more than a few builds under me im ashamed to say that my schematic Kung fu isn’t very strong Martin. I was hoping for some help deciphering the differences between it and the layout.
If it were a clone I’d dive right in and start figuring it out but since it’s orignial I’d like to just do what needs to be done.

[martin manning]

Reading that thread again it seems a little confused, referring to both the bass channel and the normal channel. I think the gist of it is this:

"When I compared to the 6G6-B schem, the normal channel's bass pot had the brown wire tied to the middle terminal (along with the yellow wire from the 70k tap from the treble pot) instead of directly to the 70k tap. And the bass channel's bass pot (5k incidently, not 25k according to the schem) was weird, it had a 4700 ohm resistor on the terminal connecting it to ground that normally (according to the schem) is not connected. The other terminal that normally (again according to the schem) has a 820 ohm resistor connecting it to ground was simply bent and grounded to the back of the pot. Also the yellow wire going from same terminal to the 0.25uF cap was missing."

The brown wire going to the middle lug of the bass pot could be connected to either the treble pot tap or the bass pot center lug with no effect, as long as there is a short wire from the treble tap to the bass middle. The error seems to be the wire from the .25uF cap going straight to ground, and the lack of an 820R between the bass pot and ground. It's unclear whether the bass pot was changed to 25k or not. This is all on the normal channel, but another poster says his bass channel had something similar.

Is yours a brown amp or a black tolex/white knob transition amp? Does it appear to be wired as described above or as shown in the Fender 6G6-B layout drawing?

[john l]

Yeah it’s confusing to me as well
Here’s how mine is wired

https://imgur.com/gallery/euXSWsN

Normal channel

https://imgur.com/gallery/nl2Ptte

Bass channel

https://imgur.com/gallery/3Qr2yNt

[martin manning]

Looks like yours is wired like the Fender layout, which is as it should be. If you are having issues, I wonder if the grounds that are made through the pot bushings are good? It looks pretty clean in there, but maybe removing, cleaning, and retightening them would help. You could check resistance from the pot cases to the brass plate to get a clue. The board grounds (soldered to the brass plate) look good.