Again needing help fixing Orion HCCA 225 Digital Reference

Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
I just bypassed as much of the trace as possible (see pic) and the voltage remains at -2.5v. I'm thinking we have something else causing the problem.
 

Attachments

  • 20180617_232953.jpg
    20180617_232953.jpg
    958 KB · Views: 47
With jumper removed I'm getting -5.5v on pin 5 of the opto-coupler.


All 3 of the muting transistor are still out of the board.


Can you attach a pic showing me the location of the 1M resistor and capacitor?
Voltage reading on the square pad of the front two muting transistor is 0.0v. Voltage on the one by the transformer is -5.5v.
 
Your guess is as good as mine. When I lifted the leg before it dropped to -21.0v almost immediately. That was prior to cleaning the part of the board with the suspect trace. After that is when it started working in reverse voltage was at -17.5v but after a few minutes of play it rose to -2.5v. The voltage since then has not dropped below -6.5v.
 
Last edited:
The voltage readings I'm getting are/have been inconsistent. The DC voltage at the junction of the diode and the 100k resistor is -8.4v. At the same time the reading on the 4 pin of the opto-coupler is -9.2v. Note: when I touch the probe to the leg of the opto-coupler -9.2v is the initial reading, if I hold the probe there the voltage rises.



Yes, I'm still using the RCA shield as a ground reference.
 
We covered just about everything. You'll have to go back and redo the tests. Start by lifting the end of the 100k that's not connected to the diode. Does that allow the -20v to develop?

If so, recheck the board for leakage/electrolyte contamination by running one prove over the top of the board with the other probe grounded.
 
Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.