Techtalk

Ok I tried a few things all of which made no difference: 1. Connected the center tap secondary of the edcor output to ground. This should have better balanced the output signals in the hope that the two channels would cancel each other out on noise. But it did not work. 2. Shielded the power lines ....

Hum increases with more gain as well.
At max gain with no input hum is peak at -40dBu

Did you end up getting some telefunkens from ebay to solve your problem after all?

Also did you only have to replace v101 and v201?

-Chuck

Huuuuuuummmmmmmm damnit! Here's a snapshot http://pillarsofnein.com/diy_projects/LA2A_Stereo/Photos/la2a_hum.jpg Centered around 70Hz and some nasty high end stuff Followed the correct star grounding scheme and made sure to ground the XLR and shielded the gain and peak. Tubes : JJ ECC803 Electro Har...

ahhh Fixed ! The 1K resistor 118 was not soldered on one side! :oops: That was easy once I saw way more voltage drop on one side then the other. Got lucky that time but will have to see how it sounds now. Volker, What side do I put the 3.9K on the Vu. I read it should be on the negative side? Is tha...

Ok the voltages do seem off

Node at :
10K (R117) input to the 12BH7A and Solen 100n

Working one = 250 VDC
Broken one = 340 VDC

CJ's Voltage chart = 210 VDC

I expect little higher since the Sidechain is pulled out but 340VDC is too high here for sure

What could be the cause?

-Chuck

OK I'm back Hey Volker did you mean pull everything except leave in the Voltage Amp 12AX7 (V201) and the Cathode Follower 12BH7A (V202) ??? Is that correct? Will this show my gain structure in both channels only for debugging and possibly matching the tubes better... or finding a bad one. -Chuck

I'll have to wait until tommorow it's 2am and sleepy + 250VAC = danger

Ask me about how I almost killed myself with the Vari Mu !! I was literally knocked on the floor when the chassis became hot....

Thanks that is a good tip to try I'll get back to you tomorrow.


-Chuck

Well fired #1 up !! So I am getting unequal clipping (only on bottom of wave) on channel 2 at about 3V p-p while the channel 1 will gain up until the transformer clips and whole thing breaks apart way above 3V p-p I measured the heaters to be all at 6VAC. So my transformer is a little weak but will ...

I keep getting logged out ! Anyway sorry here is the one I meant to post

see above question ... double post

btw, why is it 12V in series, not 12,6V ? I don't understand the question Here is the transformer I picked out http://www.antekinc.com/AN-1T250.pdf AN-1T250 $29.00 USD 250 0 250 VAC 6.3 @ 3amps (tested this coil at 3.5amp saw drop to just above 6VAC) 12.6 @ 2 amps The price is good since I need 3 o...

Anyone have some thought on my question above. I need to order my power trannys to finish both this and the Analag.

Thanks guys

-Chuck

Bernd! That looks nice! Mine is soon to come ... I have one question concerning power supply again: My current torriod when I put a dummy load on the 6.3VAC tap and setup a current draw of 3.5 amps the voltage dropped (IR drop) to almost 6VAC is this still ok for the tube heaters? thoughts? I think ...

hahahah ! I just was reading that site and Kev's too when you replied! too funny. Well the link are all dead it seems so I will contact CJ and see if he will fix them. Maybe I will move this disscusion to the Drawing Board as well as Jacob's Vactrol sub for the T4B. I will try both out and experimen...

I can't afford the T4Bs! Anyone willing to take one apart and reverse engineer it???

Comeon! how hard could it be???

-ChuckD