[TechAssist] Re: [FIX] RCA MM102 chassis, standby 5v is low @ 1.4v
- From: "Jim Myers" <jr.myers@xxxxxxxxxxx>
- To: <techassist@xxxxxxxxxxxxx>
- Date: Sat, 18 Oct 2003 10:06:27 -0500
Maybe I made this one harder than it should have been, the problem was a
shorted rectifier on the secondary of the standby supply, CR14602. It
rectifies the negative 25 or so volts for the regulated negative 12 volt
source. Now on to the next problem......the convergence power supply is
dead.
**************************************************
Jim Myers
Since 1972
Telrad Electronic Services Co.
Fort Wayne, IN 46815
*************************************************
----- Original Message -----
From: "Gemini Computer & TV" <geminitv@xxxxxxxxxxxxxxxx>
To: <techassist@xxxxxxxxxxxxx>
Sent: Friday, October 17, 2003 1:46 PM
Subject: [TechAssist] Re: RCA MM102 chassis, standby 5v is low @ 1.4v
Here is an excerpt from an earlier email I sent on this chassis a while ago.
I suggest you call it quits on this one and you may concur after you read
the following:
This set was a nightmare, probably amongst the most difficult repairs I have
ever encountered. I was just told via my Thomson Field Rep and parts that
this board is now listed as NLA. I had finally figured out that the these
clock and data lines were being loaded down when Q18102 is in circuit (yes,
I had replacements on hand but it was not that easy!). Whenever the base and
collector are connected to the circuit it pulls it right down. There are no
shorts anywhere that I can find and I even cleaned the flux residue from the
entire board. I had traced the folis traces with the tiny, tiny rivets
through this double sided and solderded board all over the place and have a
multitude of surface mount components removed trying to isolate the source
of the load. Well for the first time in almost 28 years of doing this, I
must now concede defeat! I hope that if anyone ever runs across this in the
future, you remember to search the archives to check for the same symptoms
on these clock and data lines and call it quits because this was one dark
and dreary journey.
Bob Waterman, CET® #RI-28
Master Technician License #9109
Service Manager / Parts Manager
Gemini Computer, TV, & Security Alarms
(508)695-7302
(508)695-7769 FAX
geminitv@xxxxxxxxxxxxxxxx
geminitv@xxxxxxx
www.geminicomputertvsecurityalarms.com
----- Original Message -----
From: "Jim Myers" <jr.myers@xxxxxxxxxxx>
To: "TechAssist" <techassist@xxxxxxxxxxxxx>
Sent: Friday, October 17, 2003 2:36 PM
Subject: [TechAssist] RCA MM102 chassis, standby 5v is low @ 1.4v
> I think I have met my match with this MM102 chassis, the standby 5 is low
> but will be normal with the 20 some pin flex cable disconnected from the
I/O
> board yet no short or overload exist that I can find. Two other connectors
> to the I/O board must be connected that go to the tuners otherwise the 5v
> will be about 2.4 or 2.9 volts depending on which one is not connected. I
> can hear a relay close and then open when the 5 volts is normal but don't
> have any idea what that is telling me. Has anyone had this problem or
should
> I just retire early and blame it on Thomson?
> **************************************************
> Jim Myers
> Since 1972
> Telrad Electronic Services Co.
> Fort Wayne, IN 46815
> *************************************************
>
>
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