PRR varimu problem !!!

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flaheu

Well-known member
Joined
Feb 15, 2005
Messages
470
Location
Land of the chicon south - yep
Hello,

I've just built the prr varimu (only 1 channel is assembled for test).
I've used OEP A262A2E wired 600Ohm:600Ohm for both tranformers.
No audio is passing the limiter, instead i've got a big hum and 6vdc between out+ and ground !!!
I've check ten times everything, i can't figure it out !!
Can somebody give me some voltage to control, so i could try to fix it.
 
Do you have audio on the secondary of the second transformer? Follow the signal from the input to the output and look where it disapears. There is your problem.
As far as I know, the output of the PRR comp is unsymmetrical, so why out+? Is there also an out-?
 
Ok, i've no signal at the output, just a big hum, and yes when i say out + but
i meant signal.

When i'm home i'll post the pcb drawing i've used to make it with the oep transformers i've made on 160x100mm eurocard format (if someone is interested i'll make the pcb trace available).
MY electronic knowledge is very basic and with this project i'm completely lost, i've done already 4 greens (v14 boards) with no particular problem but with this one i don't know what to do anymore. I'll try to borrow a oscilloscope from one colleague of mine for the week-end and try to trace the signal.
 
An oscilloscope will definitely a big help.
But you can try the following: Disconnect the secondary of the second transformer and connect it to the output xlr and check if you have a signal.
It will be at low level. And look for solder shorts and wrong placed components (opamp).
 
OK here the pcb layout made from kent pcb

ftp://www.codarock.be/++RAPH%20PAS%20TOUCHE++/prr%20varimu

If somebody see any errors.....
There is no value but exept for the trannies every components are the same
at the same place.

Again sorry for my newbieness.

:? :? :?

Thanks in advance
 
Just replace ftp with http:
http://www.codarock.be/++RAPH%20PAS%20TOUCHE++/prr%20varimu/PRR%20VARIMU.LAY.pdf

EDIT: Too slow :wink: but not daring to delete this post, as this messed up the forum software in the past...
 
Ok i've checked my input TX with a sine wave 1000Hz and it was really dirty (big thick sine compared to the clean signal injected at the primary) on the scope with the probe on the secondary.

Maybe i magnetized the iron ?

I have ordered other trannies, and will check them before installation.
 

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