Bassman Ten mods

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6V6
Junior tube assistant
Posts: 1
(4/15/04 6:51 am)
  Bassman Ten mods
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 I recently aquired a Bassman Ten and after reading everything on this site for the last 3 months have decided to do my first rebuild on it. I have modified some of my other amps before and understand about biasing and the pre / power amp stages. My first questions are :-
1. The wiring from the PT, do I earth red/yellow wire or tape it off.
2. Can I still use the 220uf/285V filter caps, what effect will they have.
3. Also I think I read somewhere that they used the large 2.7k/10w and 30k/20w resistors as the choke, whats the difference compared to a transformer choke.

Any help or other suggestions would be great.
 
ganzonimx
Hey get your own solder
Posts: 463
(4/16/04 8:59 am)
  Re: Bassman Ten mods
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 I'll try to answer your question...

1. The wiring from the PT, do I earth red/yellow wire or tape it off.

The red/yellow in Fender PT's wire is the center tap of the HV winding, it hast to stay grounded.

2. Can I still use the 220uf/285V filter caps, what effect will they have.

I don't know what cap you ar talking about. If it the cap is Ok it will serve you.

3. Also I think I read somewhere that they used the large 2.7k/10w and 30k/20w resistors as the choke, whats the difference compared to a transformer choke.

The choke/cap network smoothes out the ripple in B (L/C-network). A resistor/cap network (R/C-network) does the same. As the choke is in a part of the power line where current changes (between node of PT center tap and screen supply node), the R/C-Network in this place would produce sag as the voltage drop over the resistor increases with growing current flow. If the reisor is not to big it's not that obvious. Earlier amps like the 5e3 have a resistor in place of the choke. Replacing it with a choke gives a smother response of the amp. A 2.7K might be ok, a 30K will give probably ugly sag. (.. that's what I did understand... )

Cris
 
6V6
Posts: 2
(4/17/04 6:41 pm)
  bassman ten mods
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 If you look at the Bassman Ten 70 watt schem. the red/yellow CT connects to 2 220/285V caps which join to the bias supply. I have looked at all the other schems and these are usually alot lower. Any ideas.

Thanks.
 
ganzonimx
Hey get your own solder
Posts: 465
(4/18/04 12:35 pm)
  Re: bassman ten mods
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 Are you looking at a layout diagram ore at a schematic?

The schematic I look at (has two 50uF/70V caps in the bias circuit - are you talking about these caps? You need these caps for the filtering of the bias supply, but I don't think that they are that fat with such a high voltage rating.

Then there are also two 70uf/350V caps (in series, paralleled by the bleeder resistors) that connect from b to ground (first filter stage), followed down the power rail from tree 20uF/500V filter caps.

Cris
 
Tiny Daddy
I will work on all amps
Posts: 621
(4/19/04 7:20 am)
  Re: bassman ten mods
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 I see those caps on the Bassman 135 and Super Bassman. Doug sells replacements. I suppose you could try 100uF but why?
 
ganzonimx
Hey get your own solder
Posts: 466
(4/19/04 10:51 am)
  Re: bassman ten mods
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 TD!

dou you have a Super Bassman Schematic that is readable? I never saw one, - it is different from the Bassman 135.

Chris
 
Tiny Daddy
I will work on all amps
Posts: 622
(4/19/04 9:42 pm)
  Re: bassman ten mods
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 Chris,

I was just looking at the schematics at schematicheaven.com
 
6V6
Posts: 3
(4/25/04 8:20 am)
  bassman ten mods
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 If you've got the Tube Amp Book (vol 3) by Aspen Pittman, the schematic for my Bassman is on page 377. If you follow the red/yellow wire it connects to the large caps I'm referring to. Also when I measured the of the CT it was 562V. Is this too much for 6l6's.
 
bnwitt
Senior tube assistant
Posts: 344
(4/25/04 9:42 am)
  Re: bassman ten mods
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 Pittman's schematic shows the ultra linear 70 watt version. Schematic Heaven's is the 50 watt version. I guess your's is the 70 watt UL as well. You should follow the Pittman schematic in your rewire and don't ground the red/yellow wire. As far as the 562v B+, that is part of the extra 20 watts the ultra linear version delivers. You're definitely gonna want some good 6L6GT's. The 70 watt version has a bridge rectifier layout and hence no PT HT center tap to ground.

Edited by: bnwitt at: 4/25/04 1:29 pm
 
 
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