Jimmy's 400 Rev D in for Warranty

laatsch55 said:
The frustration continues...got a blizzard comin, all my wells tucked in for a 3 day storm if it gets that bad. 9- 20 Inches of snow and 60 mph winds....this should be fun.

Jut a slight movement of the upper right corner of the board....
Click to expand...

Good luck Lee, Hope you and Jani are ok :)
 
Update....

After shorting out a low voltage regulator TO-220, and rebuilding the entire low voltage section, I am back on the original problem.......probe slip...
 
Joe, do I isolate the base drives in a quasi D the same way I would on a full comp?
 
Hi Lee
Please clarify your question a bit more so I can properly answer your question.
 
Preserved for posterity now.

Control board debug instructions

These are quick checks you can perform on your control board to ensure it is regulating properly.

Quasi-Comp Configuration, all PCB artwork revisions

  • Pad references that follow will include L or R and will depend on the channel you are testing. The L an R are left off of Pad and component references for simplicity.
  • Detach and tape off wires going to Pads 9, 8, 6, 4, and 3.
  • Tack a jumper wire between Pad 3 and 12.
  • Tack a jumper wire between Pad 8 and 6.
  • Tack a 47 ohm 1/2W resistor between Pads 9 and 6.
  • Tack a second 47 ohm 1/2W resistor between Pads 4 and 6.
  • Bring up on DBT and Variac and ensure that the output on Pad 6 is zero or no more than 15 mV.
  • Check that you have B+ on Pad 11.
  • Check that you have B- on Pad 12
  • Ensure that the voltage across each of the 47 ohm 1/2W resistors is less than 2V and the voltage on the 47 ohm 1/2W resistor tacked between Pads 9 and 6 varies as you adjust the bias potentiometer.
  • If all good on the control board search for your problem on the backplane or backwall.
  • If not all good on the control board, use this configuration to debug what is wrong with the control board.
Full-Comp Configuration, PCB artwork Revision D, E and G1

  • This set of instructions assumes you have the White Oak Audio Backplane Kit installed.
  • Pad references that follow will include L or R and will depend on the channel you are testing. The L an R are left off of Pad and component references for simplicity.
  • Detach and tape off wires going to Pads 9, 8, 6, 4, and 3.
  • Tack a jumper wire between Pad 8 and 6.
  • Tack a 47 ohm 1/2W resistor between Pads 9 and 6.
  • Tack a second 47 ohm 1/2W resistor between Pads PNP and 6.
  • Bring up on DBT and Variac and ensure that the output on Pad 6 is zero or no more than 15 mV.
  • Check that you have B+ on Pad 11.
  • Check that you have B- on Pad 12
  • Ensure that the voltage across each of the 47 ohm 1/2W resistors is less than 2V and the voltage on each 47 ohm 1/2W resistor varies as you adjust the bias potentiometer.
  • If all good on the control board search for your problem on the backplane or backwall.
  • If not all good on the control board, use this configuration to debug what is wrong with the control board.
 
Electron Herders at their finest, love this stuff! (Even though most of it goes over my head :evil4:)
 
I would read his post in full 3 times then follow step by step. Variac? Dim bulb? Eh?
 
Jumpered as in the directions..
 

Attachments

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Measurements

Left channel
Plus lead on 6 neg lead on ground----------40mv
Plus lead on 9, neg lead on 6--------------+.566vdc
Plus lead on 4, neg lead on 6 ------------ -.218vdc
Adjustment range on pad 9 to pad 6 47 ohm is +.594 vdc to +.841vdc

Right channel
Plus Lead on 6, neg lead on ground----------36 mv
Plus lead on 9, neg lead on 6--------------- +.571vdc
Plus lead on 4, neg lead on 6--------------- -.238vdc
Adjustment range on pad 9 to pad 6 47 ohm is + .572 vdc to + .813 vdc
 
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