Super lead hum ballance, resistors on V1

martin g · Post by **martin g** » Sun Feb 27, 2005 1:04 pm

Hello I'm Martin from Poland I've just get my first marshall super lead serial sl/a 10252 (no letter). I asked about that on topic
I looked inside on ptp board and I found that it has little mod (Transformer for phones on speaker out 2:shock:). What value of resitors r7 r8 should be? (going to V1) pin 1&6 on schematic is 2* 100k I have 2* 50 k. When I turn on the amp it's a little hum in speakers, What do you think about ad hum ballance like in the new reissue? What about big capacitor among v1 v2 500V what value should be - mine has got 2 *40 uF. What cap change to add little smooth tone to chann1 ( to treble)
Thanks for any advice

Dax · Post by **Dax** » Sun Feb 27, 2005 1:47 pm

Post some closeup pictures of thr Circuit Board, and, oh yeah, REMOVE THAT FRICKIN PHONES MOD!!!! We can help alot more with some pic's.

Dax-The-Ax · Post by **Dax-The-Ax** » Sun Feb 27, 2005 2:00 pm

I would install the correct 100K resistors and Remove the bright cap off of the channel I Volume Pot. That might make it a little smoother.

martin g · Post by **martin g** » Sun Feb 27, 2005 3:50 pm

Thanks a lot I've just removed this transformer and send the pictures in attach, there will be this transformer on pictures near pwr tube. How about big cap among v1&v2, mine has 2* 40 uF I've read on schematic that should be 2*50uF. When I turn the volumes down I hear the sound in cab, is it normal? What about output transformer it's probably older than 1969. What about this hum ballance is t worth to put hum ballance?

Flames1950 · Post by **Flames1950** » Sun Feb 27, 2005 5:52 pm

The bright caps on the ch. I volume and the channel mixer resistors will cause you to hear sound through the amp when the volumes are at zero, and will cause one channel's volume knob setting to affect the other channel's sound. Nothing unusual there.
If you have 50K resistors instead of 100K's on the first tube's plates you're getting less overdrive and volume, and too clean a sound from the amp. The correct 100K values should give you plenty of singing distortion when you're cranked up.
While you could add a hum balance it just shouldn't be necessary. Thousands of these amps sound great with no need for a hum balance, there's something else that would need to be fixed if there's too much hum. May be ready for a cap job (changing all the 50uF/50uF cans) or the tubes could cause humming if they're going bad.

martin g · Post by **martin g** » Mon Feb 28, 2005 3:02 am

Thanks a lot