[greyskull]

Hi there, I've just finished putting this together, and I can't get the balance to read 0 Volts between tp1 and tp2. It only goes down to 5.9 volts before the trim pot hits the end of its travel. I've stopped at this point before breaking anything!

Initial conditions:
IN pot @ max
OUT pot @ min
REC pot @ max
Bypass toggle @IN
All Push buttons @UP
Input signal: Sinus 1kHz, 1VAC
Jumper JMP1: removed

Results:
TP1 = 34.8 VDC (black probe on 0V)
TP2 = 40.7 VDC (black probe on 0V)

TP1 = TP2 = 0.82 VAC
TP3 = TP4 = 0 VAC
Output: 1.12 VAC (between XLR pins 2&3)

[JPK]

Check the solder joints on R6, R7, R9, R10, Q1, Q2.
Check that TR2 is working properly: Resistance going from 0 to 1k between center pin and one side pin and goinf from 1k to 0 on the other side pin.
Check again the balance setting after removing U4.

[greyskull]

Thanks for getting back so fast JP.

I've re-flowed all of those and am getting the same readings with U4 pulled out of circuit and still not able to adjust balance to 0.


TP1 = 34.8 VDC (black probe on 0V)
TP2 = 40.7 VDC (black probe on 0V)

TP1 = TP2 = 0.82 VAC
TP3 = TP4 = 0 VAC


Picture attached in case I've done something stupid.
Many thanks again

[JPK]

TP3 = TP4 = 0 VAC
Were you able to get 9VAC in step 6?
If true, then you may have a defective tube. Contact me here for a replacement.

[greyskull]

Thanks JP.

Unit is passing audio and output is up to 14.1V when out Is Maxed.

I've checked continuity between legs of tube and board to be sure, so I Think you're right!
I'll be in touch Via form/Email. Thanks again.


Guy

[greyskull]

Hi JP,
Either I'm extremely unlucky or very stupid.
With the new Tube I was just about able to get the voltage down to 0 between tp 1 and 2 in step 7
BUT in Step 8, TR 1 doesn't seem to affect anything.
Similarly, adjusting TR5 further down, has no affect.

Could it be I've had two tubes each with one half bad? In any case should I send the unit in at this point to prevent you being further out of pocket?

I followed the rest of the instructions to the end, and whilst I wasn't able to calibrate the unit within spec, it works, in so far as it passes audio and compresses, albeit with an increased noise floor as you turn the attack - which would lead me to think that the tube halves are not balanced.

Any help gratefully received.

Many thanks.
Guy

[JPK]

BUT in Step 8, TR 1 doesn't seem to affect anything.
Check That TR1 is working : 0 to 1k3 (approximately, in circuit).
Check the solder joints of R3, R4.
Where you able to do the sub-steps of step 8, before TR1 adjust?
How many DC Volts did you get on TP6 and on U4-pin6 (against 0V), when you did this:
?  Adjust TR4 (Vref) until you read 3.0VAC.

In all cases, we can fix it for you, contact me here.

[greyskull]

Hi JP,

Yes it's range is 0 - 1.3 k in circuit.

On step 7 I can only get down to .68 V with the trimmer at max travel


On step 8 adjusting Tr1 only goes down to 3.53 V at the maximum travel.
Turning TR1 Back to the max position as per instructions, At this point TP6 = -1.73 V if black probe is on 0 TP and U4 Pin 6 is -1.73 V if black probe in on 0 Tp.
Help!
Many thanks
Guy

[JPK]

On step 7 I can only get down to .68 V with the trimmer at max travel
So the problem was not the tube.

I think you will need to send your compressor to us for a check. Please contact me.