[TechAssist] Pioneer Power Amp OUTPUT MODULE Shorts ASAP
- From: Bil Green <tv.vcrrepair@xxxxxxxxxxx>
- To: ".TECHASSIST @ freelists . org" <techassist@xxxxxxxxxxxxx>
- Date: Mon, 3 Nov 2003 22:31:16 -0800
Pioneer M-790 (and many other similar models)
Audio output transistors (6) shorted
Need the procedure to disable the Blow Trigger circuit so
the new outputs will not be ruined during testing. I don't
want to replace the module or boards, due to the high
repair bill.
These Pioneer power amps contain the output transistors
within a cube like circuit boards/ heat sink/ fan assembly.
And if it even thinks that something is wrong, it is designed
to pop the output transistors, and thus blow the fuse. Someone
should go to jail for this dirty trick.
"The action of the "Blow Trigger" line is to INTENTIONALLY blow
the outputs, so that the fuse will blow. It is a resistor ladder
arrangement, the summed output of which is zero volts under normal
conditions.
Interestingly, DC offset is NOT monitored. If any of the supplies
sags, the sum is no longer zero, and the BLOW line goes to .6volts
or so, at which point the bias is slammed HARD. For example a bad
cassette motor will cause the outputs to blow.
There are surface-mount transistors which can be shorted base-
emmiter to defeat the BLOW line for testing purposes."
--
Best regards,
Bil Green
2001 TV VCR
Mammoth Lakes, CA 93546
760-934-2001 mailto:tv.vcrrepair@xxxxxxxxxxx
*****************************************************************************
Classifieds! Buy or Sell!
http://sell.tech-assist.org
The Tech Address Book:
http://www.tech-assist.org/secure/tip/contact.htm
Add a Repair Tip Here, or Change/Remove your Email Address:
http://www.tech-assist.org/secure/tip/main.htm
Lost Password:
http://www.tech-assist.org and select "Lost your Login Info?".
Email Archives:
//www.freelists.org/archives/techassist/
Other related posts:
