PYE Compressor/Limiter Thread *boards shipping* BOM up!

[Spencerleehorton]

ok, i'll do a DC voltage sweep across all the transistors and the oscillator, report back.

 

[Spencerleehorton]

oscillator 1 is on channel 1 = DC = - 0.299 at CW and AC = -0.407v
oscillator 2 is on channel 2 = DC = -0.302 at CW and AC = -0.400v

I'm going through the transistors now, going to make a chart.

 

[marcn]

Did you probe the voltage at cathodes of D5/D6 under the various ratios?

 

[Spencerleehorton]

d5/d6 on pcb 1 = pos1 = 0v, pos2 = -8.37, pos3 = -8.17, pos4 = -7.73

im gonna check my wiring again on pcb 2 as the voltage doesnt change at all!!!

 

[Spencerleehorton]

voltages on audio path:

TR1
E = -16.64
B = 17.4
C = -17.96

TR4
E = -6.82
B = -6.18
C = 0v

TR11
E = 0v
B = 0v
C = 0v

 

[Spencerleehorton]

i've managed to work out how to set the frequency to 250khz now but nothing seems to have changed, doesnt seem to operate?
vu meter doesnt  move?

 

[Ilya]

Forget the VU for now. Do you have an audio path working? Is it clean? You need to use component values NOT in the brackets - this is important!

Put a scope probe on the base of TR11 and set any ratio except 1:1. Feed an input signal and observe the waveform on the scope. Increase the volume of input signal and see if there's any change in the waveform at the base of TR11. If everything works correctly, you should see how spikes become narrower when you increase the volume of input signal.

 

[Spencerleehorton]

channel 1 the audio path isnt clean, but i have had a play with all the trimmers again so they could be set to anything!!!
but there does seem to be movement to the wave form when using the controls, not a lot but something.

channel 2 seems better audio path but no movement to audio waveform.

 

[Ilya]

R23 is the only trimmer in the audio path, you need to set it so that there's minimum distortion. Other trimmers are in the sidechain and it's better to set them to the pretrimmed values indicated in the schematic.

Don't move contols. Change the input signal volume and see if there's any change at the base of TR11. Set your threshold to the lowest possible setting to make sure you're hitting the threshold.

 

[Spencerleehorton]

both channels have good waveforms up till TR7 base.

at TR8 base looks bad.

tested TR11 base and only getting top part of waveform.

I have used all resistor values not in brackets.

 

[Ilya]

TR11 waveform has nothing to do with the input waveform. It's a control waveform that turns the transistor on and off, so it shouldn't resemble the input waveform at all.

Now,  TR7 is a buffer that feeds the sidechain transformer. What do you get at the emitter of TR7? You may also check the emitter of TR5 and see if there's any clipping (not symmetrical) or rectification going on. If it is, the DC bias at the base of TR5 is incorrect and you may need to adjust it with R20. The same logic applies to TR7, but here the DC bias is set by the previous stage (TR5).

If you get crap at TR8 this means the signal corrupts somewhere earlier. I suspect the TR5-TR7 region is the culprit.

 

[shot]

When you fiddle to much with R23 it can cause shutdown of audio signal. Maybe Spence has set the value of this trimmer to off and that is why it's not passing audio anymore.

Spence, did you happen to desolder this (or any other) trimmer and later solder it back?

My situation was that one trimmer was burnt. They are very fragile and too much heat can burn them.
And specifically this pcb has very narrow holes for components so taking components out is a hassle and requires a lot of heating. Maybe that's the way you've burned it.

As a precaution, I would take all the trimmers out, throw them in trash, get new ones and set them to preferred values before soldering them in. At least trimmers are cheap and it's a half'n hour job

And once you do that DO NOT rotate trimmers anymore. That way you'll know that the problem has got nothing to do with them. Then you can go searching for problems elsewhere! See, trimmers on wrong values can cause a domino effect on other components. You'll never know what is wrong unless you know you got your trim values on a correct spot.
After you get all your audio passing and compression going on on all ratios and speeds, only then you start calibrating meter and overall responsiveness of the unit (read: rotating trimmers)


Luka

 

[Spencerleehorton]

the trimmers are fine as i can put my MM on them and when i turn them they function.

Channel 2 now seems to pass audio nicely but channel 1 waveform doesnt look right.

Im not getting compression, i do not have a bypass switch either as i dont think its possible?

 

[Spencerleehorton]

channel 1 is good up until Tr7 emitter and R27 / C15.
Tr6 is all good along with Tr5.
Ive changed TR8, TR9 and TR 10 and its still bad waveform.
Ive tested all resistors around the output back to the output pot and all are good.
I'll draw out a diagram to show how ive connected the lorlins just to make sure i havent cocked all that up!!!

 

[Spencerleehorton]

this is very crude but this is how i figured it would work!!!

 

[shot]

this is very crude but this is how i figured it would work!!!

There's an error - Pins 6 & 7 are swapped!
Third switch (ratio) section B resistors need to sum to pin 7 and section C resistors need to sum to pin 6

And also you have first position of the decay switch doing the longest time. Pin 1 on that switch should be 100ms and pin 6 be 3200ms.

 

[Spencerleehorton]

Ok, I've either wired it wrong or drawn it wrong either way I'll correct and report back!

 

[Spencerleehorton]

Found 39R resistor which should have been 39k, changed and I'm now getting signs of compression and meter is moving a little, this is on channel 1, channel 2 was good but not now I need to test again as it seems low output compared to channel 1.
Testing all voltages does seem to help me track down what area is off as I can compare to channel 1 now.

 

[Spencerleehorton]

Got both channels passing audio good now.
Couple of mistakes with resistors!
Channel 1 seem to compress a little and meter moves but it's all the way to the left, can I adjust the meter?

 

[Ilya]

You need to make your unit compress properly. Do you have your sidechain tx connected correctly? It should be connected in 1:4 step-up ("4" side goes to diode bridge in the sidechain).