DIY Class A/B Amp The "Wolverine" build thread

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#4,083
Yes, parallel 18k.

I am also uploading some more pics in case. I didn't realise the file size limit could be over 2mb
 

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#4,084
Check settings of your bench-PSU negative rail for right voltage and no current limiting.
In #4070 you reported measuring the correct voltage over Q102 (TP106 to neg rail - 1.2V)
This together with reported values in #4081 (TP106 to ground 10 V) points to a problem with the negative rail
 
#4,086
This problem is really vexing, thanks for the suggestions so far... beats staring at the board. To summarise so far:


I am currently trying to test the boards with a 30V supply. It’s a Korad KA3005D

The issue:
D108 doesn’t light up on either of my two boards

The status:
  • The voltage across R111A and R111b is just below 800mv (750-790)
  • TP-105 to pos power rail is 1.2V (TP-105 (DMM -) and the positive power rail connection)
  • TP-106 to neg power rail is 1.2V (TP-106 (DMM +) and the negative probe on the negative rail)
  • TP106 to GND is roughly at ±19V
  • TP105 to GND is roughly ±-9V
  • V+ to GNB is ± +20V
  • V- to GND is ± -10V
  • The board pulls around 23mA from the PSU
    Jumper and R17 9k are installed, and input is shorted.
  • R109 is set to 500R across pins 1&2

What I have done:
  • Switched out all leds and tested them after replacing them
  • Switched out:
  • Q103
  • Q107, Q108
  • Took out and tested Q101, Q102, Q104, Q105, Q106
  • Changed PSU leads and tested using an older bench PSU.
 
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#4,090
It is ± +30V, -30V now.

Other:
Voltage to rail between D107 and RLED1 is 1.2V (TP05 1.2V)
Voltage to rail between D108 and RLED2 is 1.3V(TP06 1.3V)

I shifted to Testing at 20V
0V to between TP05 and RLED1 is 1.2V
0V to between RLED1 and D107 is 18V
0V to between TP06 and RLED2 is 18.6V
0V to between RLED2 and D108 is 18.9V!

The Red Led is still not lit, but I think I must review everything again.
 
#4,091
Strange indeed, definitely something wrong with the rails.

Sticking with 30V rails for now

Check rail fuses
Check continuity between ground and all transistor legs
What are you getting between TP3 and TP4
Might pay to fill the unused pads on R7 and R8
Might need to switch to testing in isolation
Stuart has provided a testing IPS at 30V (with 64V components) and EF3-X in the dropbox and build guide
 
Last edited:
#4,093
Yeah something might be pulling a rail down.

I would print out / digitally mark up the schematic. Leave your DMM- on the amp GND and probe and markup the schematic with all the voltages you are getting.

If using 30V rails I would expect TP105 to GND would be ~ +27V while TP106 would be ~ -27V.
 
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