[TechAssist] Re: JVC AV-27050, AV-32050 power supply grief
- From: "Peter oliver" <oliver_peter1@xxxxxxxxxxx>
- To: techassist@xxxxxxxxxxxxx
- Date: Wed, 06 Aug 2003 04:06:26 +0000
Studied one simmilar last year a AV27D201 uses the STRF6626 in the power
supply. Set worked but onky so-so. That partuclar power supply uses active
feedback from the Error amp probabbly a SE135 or simmilar. Pin 2 common
needs to be held to ground to keep error from triggering an off state but
there is also active feed back from the circuit across PC901 (the opto
isolator) I would suspect that the feedback signal is impropper from parts
along the turn on/regulation path the last leg is Q943 and D942 a Zener (At
least with the D201 chassis I am assuming yours is simmilar) Check the path
of transistors back from the opto-isolator and parts on the secondary side
of the transformer. The reason these sets are such a pain is that there is
an active feedback-reguation circuit and all of the parts need to be right
for it to work, Lighting does funny things to parts that make faults
difficult at times to follow. On 27D201 I mentioned the set would run if I
had the Damaged-leaky Q943 in the set and put a 1k resistor accross D903
(basicly manually set the regualtion voltage) the only problem was the HV
and filiments never shutdown in that state. I rember a posting reciently on
a lighting damaged set simmilar to yours that required replacement of the
parts you mentioned some of the transistors and the error amp.
Peter Oliver
Tucson Radio TV
From: "art bevilacqua" <abevilac@xxxxxxxxxxxxx>
Reply-To: techassist@xxxxxxxxxxxxx
To: <techassist@xxxxxxxxxxxxx>
Subject: [TechAssist] JVC AV-27050, AV-32050 power supply grief
Date: Tue, 5 Aug 2003 23:13:33 -0400
We've found and replaced a number of bad parts on this unit, D905, D903,
Q912 regulator, IC901 STRF6626. I have a Sams for the set. I checked =
many
other diodes in the primary of the power supply but found nothing more.
After this, the 14 volt supply only comes up to 6.9 volts (or the power
supply shuts down with the result that we see 6.9V). I replaced C926 on =
the
14 volt line and saw the 14 volt line come up to 12 volts, and the thing
almost powered up, with a shot of high voltage. But now we are back to =
6.9.=20
I know everyone hates these sets, especially when lightning is involved, =
but
somebody must have a training document or procedure for working through =
this
type of problem. I want to conquer this thing so future similar repairs =
will
become routine. Also, I understand many of the JVC models use similar =
power
supplies, the AV-32050 for example.
Remember the old Sony's with the weird SGS horizontal output? That was
another case where the set would gobble new parts and almost kill you, =
until
we found a Sony procedure for energizing the horizontal section with an
external 35 volt supply so that waveforms could be checked. Once we got
through one using the good procedure, all future ones were easy.
What do you say we try to collect some knowledge or procedures on these
sets?
Art Bevilacqua
Essex Radio and TV
40 Main Street
Essex, MA 01929
*****************************************************************************
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/
_________________________________________________________________
MSN 8 with e-mail virus protection service: 2 months FREE*
http://join.msn.com/?page=features/virus
*****************************************************************************
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:
