Drip opto4 La2a troubles

[Chryst]

Hi guys,

I hope I'm abiding the rules by posting here...

I've build an Drip La2a and I've been troubleshooting the unit for a while now, but I can't figure out what's wrong. The voltages seem ok. And it sort of passes audio, but way too soft and it does compress (because of the soft signal I think). I've tried to probe the audio and it does not really seem to pass the input transformer well. I got another transformer from Sowter, but this one has the same problem.

The transformer should pass the audio louder than the input signal right? Is there a different way to test the transformer except for checking the resistance and seeing if audio passes? I also thought that the pin 6 should connect to the metal housing, but my meter says there is no connection. Could this be a problem?

Thanks guys! Really, really appreciate it!

 

[CJ]

check the ac volts after the V1 coupling cap while injecting a 1 volt signal.

or use 0.1 volts if you want,

a 12ax7a has a mu of 100, so you should see a bit less than 100 times your input signal.

then just follow the trail til the signal suddenly drops,

you have 2 amplifiers, one to amplify the signal and the other to light up the EL panel.

first get the signal amp going and we can worry about compression later.

in fact, pull the T4 module in case it is somehow clamping the signal,

 

[Chryst]

Hey CJ,

Sorry for the slow reaction. I thought I would receive an email when someone replied, but that wasn't the case. So I just discovered your reply.
I've tried to measure the circuit as you said. The amazing discovery was that pulling the T4's caused one 'connection foot' to break, but suddenly the La2a worked!!! I think there was a bad connection, but I'm very, very happy now with my working machine.
Thanks for your help. You have put months of troubleshooting to an end. Hero!