[AcdNrg]

Aesthetics aside, my concern it that the metal may connect to a neighbor module if that one is also "boxed". But as I didn´t finish final assemply, I can´t tell yet.

[AcdNrg]

[JPK]

Have you added the four 4mm spacers under the transformer?
If so, you could try to add some washers on the side that sticks out from the chassis.

[AcdNrg]

Yes, spacers are in place. Added 4 washers for aesthetics, double checking that there is enough room for PCB2. That is resolved now.

Still can´t finish the calibration though. Everything is fine except the Threshold Stage, where I get much higher voltages than expected and no effect of TR3 at +9dB:




4. PCB1 Voltage
V+ = 15.746
V- = -15.808
PASSED

LED check
PASSED

5. BIAS
TP2-TP3 = 3.003V
PASSED

6. Input Signal
Output at Chassis = 1.0004 VAC
PASSED

7. 0dB Gain
Output : 1.0004 / 1.0006 VAC
Makeup: up to 13.165 VAC
PASSED

9. 3V Adjust
3.001V
PASSED

CV Adjust
Bypassed: 2.451 VAC
Active: 0.9782 VAC
PASSED

10. Meter Adjust
8dB
PASSED

Threshold Adjust
JMP1 1-2 OK

1kHz at -6dB
Threshold -6dB SET
Bypassed: 6.151 VAC OK
Active:
fccw 6.143 FAIL
fcw 5.022 FAIL

1kHz at -18dB
Threshold -18dB SET
Bypassed: 1.5502 VAC OK
Active:
fccw 1.5472 FAIL
fcw 1.1994 FAIL

1kHz at +9dB
Threshold +9dB
Bypassed: 6.152 VAC OK
Active:
fccw: 6.139 VAC FAIL
fcw: 6.14 VAC FAIL


Measured onboard:
r35 4.6947 kOhm OK
r43 2.19 kOhm OK


What am I doing wrong? From a quick audio test, the compressor works and is doing something, but the threshold calibration is totally bonkers.

[JPK]

THRESHOLD adjust :
input 1kHz 6.15 VAC
Threshold -6dB
Bypassed: 6.151 VAC OK
Active:

In the THRESHOLD adjust conditions, with 6.15VAC at the input :

With JMP1 removed:
AC volts on TP4 : 2.8V (varying with trimmer TR3)
AC volts on TP5 : 2.8V (varying with trimmer TR3)

With JMP1 back in position 1-2:
DC volts on JMP1-pin1 : 4.7 VDC

[AcdNrg]

I get the 2.8 VAC on pin4 and 5 (2.799 + 2.798 ) against 0V

I don´t get any VDC on pin1 of JMP1 (marked by the dot), no matter if jumper is installed or not.

That said:
JMP1-pin1 to 0V = 0.0003 VDC
JMP1-pin2 to 0V = 0.0000 VDC
JMP1-pin3 to 0V = 3.001 VDC

For what it´s worth, on pin1 I get
12.336 VDC at Threshold set to -9dB
14.280 VDC at -12 dB
14.587 VDC at -15 dB
14.716 VDC at -18 dB

To be honest, I don´t know what I´m measuring here , so hopefully those numbers make some sense to you.

The compressor still works (from meter movements and musical material)

[JPK]

I don´t get any VDC on pin1 of JMP1
12.336 VDC at Threshold set to -9dB
These 2 lines seem contradictory.
Do you mean it is only at Threshold -6 that you get no DC on pin1?

[AcdNrg]

It seems I get 0 VDC on every setting higher than -9dB:

jumper JMP1 pin1-pin2 installed / not installed

-21 dB: 3.546 / 14.783
-18 db: 3.132 /14.717
-15dB: 2.686 / 14.587
-12 dB: 2.277 / 14.279
-9 dB: 1.811 / 12.321
-6 dB: 0.0024 (slowly falling to 0.000) / 0.0006
-3 dB: 0.0003 / 0.0003
0 dB: 0.0003 / 0.0003
etc. no change up to 12 dB

I made sure the jumper bridge has contact, even if the setup looks a little flimsy

[AcdNrg]

OK, it´s official now. I´m an idiot.

Since switching the threshold looked fishy, I decided to

- reflow all switch solder joints on the treshold switch
- reflow all connector joints on switchboard on PCB2

No change. Soooo, we´re in for the long run: Check all parts.

Low and behold, take a close look at D4



And that´s why DIODE Bridge Compressors will be known as Diodevil Bridge Compressors in my book from now on.

Let this be a warning to others to not build this kit over a long night with too many distractions...

Apologies for wasting your time and braincycles! I did a full calibration, all values within expected ranges, now I´m a happy man.

Best regards and thank you for your patience! 

[JPK]