Brownface Potentiometers
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Brownface Potentiometers
Just getting parts together for a brownface pro 6g5a build and having problems getting hold of the 10m ra pot, i can get the 3m ra pot quite easily so can i use the 3m ra pot instead of the 10m one and would i have to alter any of the components connecting to the pot?
Regards
Regards
- martin manning
- Posts: 13209
- Joined: Sun Jul 06, 2008 12:43 am
- Location: 39°06' N 84°30' W
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Re: Brownface Potentiometers
Checked that earlier and they wanted $83.15 postage for a $2.22 part to the UK
but thanks Martin
but thanks Martin
- martin manning
- Posts: 13209
- Joined: Sun Jul 06, 2008 12:43 am
- Location: 39°06' N 84°30' W
3 others liked this
Re: Brownface Potentiometers
You didn't't say you are in UK ;^)
I would try this:
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Re: Brownface Potentiometers
Thank you Martin that is exactly what i wanted just wish i had the brains to figure it out myself but alas its not my forte and have to rely on wonderful people like yourself so thank you once again.
Regards
Regards
Re: Brownface Potentiometers
Implemented the changes that Martin supplied but things are not as expected and the sound output is heavily distorted on volume 1 on both channels but the tremolo works as expected but heavily distorted, the voltages on v4 are not good either with 0v on pin 8(70v) and pin 6 showing 400v(295) the 56k resistor showing 404v on side and 400v on the other so only a 4v drop.The bias is causing me a problem too as i cant get the tubes hot enough got a range on pin from -50v to -60v but can only get it to 43% despite changing the input resistor to 220 ohms from 1k infact got up to 50% on a 470 ohm resistor.
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- martin manning
- Posts: 13209
- Joined: Sun Jul 06, 2008 12:43 am
- Location: 39°06' N 84°30' W
Re: Brownface Potentiometers
What if you pull the trem tubes out and try the normal channel? Pretty sure I checked out the 10M pot replacement with a simulation.
Re: Brownface Potentiometers
If you want to bias the tubes hotter (ie, less negative bias on pin 5 of the output tubes) then you need a larger resistor before the diode.
Re: Brownface Potentiometers
Tried that and lost any volume now
- martin manning
- Posts: 13209
- Joined: Sun Jul 06, 2008 12:43 am
- Location: 39°06' N 84°30' W
Re: Brownface Potentiometers
Have you made a voltage survey and compared it to the Fender schematic?
Re: Brownface Potentiometers
All voltages except V4 pin 6 at 404v(295v) V4 pin 8 at 0v(70v) and V6 pin 6 at 365v(290v) and pin 1 at 265v(295v) rest are within 10% of schematic.
- martin manning
- Posts: 13209
- Joined: Sun Jul 06, 2008 12:43 am
- Location: 39°06' N 84°30' W
Re: Brownface Potentiometers
Looks like V4 is not conducting any current. Measure resistance from pin 8 to ground. You should see 57.5k.
Re: Brownface Potentiometers
And i get 58.87k both resistors measure ok. Pin 7 reads 57.4k
- martin manning
- Posts: 13209
- Joined: Sun Jul 06, 2008 12:43 am
- Location: 39°06' N 84°30' W
Re: Brownface Potentiometers
There must be some wiring error, bad socket pin connection, or bad solder joint. You should see 60-70V across both of the 56k's. Based on the V6 voltages something is off in the phase inverter too.
Re: Brownface Potentiometers
Changed tube on V4 and now get on pin 6 307v and pin 8 65v will now have a look at the phase invertor. Strange that as thats the 4th tube i tried in V4 and all the others work fine in a 5e3.