[TechAssist] Re: VS-5004R FIXED (Inter. Power On)

Bil, I have experienced the exact same problem on an Emerson TC0918 several 
weeks ago. This was an AC/DC TV that Worked fine on +12v DC but did not work 
on AC. I Replaced IC501 STR12006 NTE7095 and it still would not power on 
with AC. Touching pin 3 of IC501 with my volt meter would make the set turn 
on, and I also noticed how C504 main cap stayed fully charged at all times 
after unplugging set (Chemwick discharge! LOL) so I quickly noted the main 
cap was not discharging down hardly any at all over time, futher 
troubleshooting found an Open R507 330K 1W Resistor coming right off the 
main cap (was open) which was in the bleed down line of the main cap and 
that 330K resistor fixed the entire problem. The resistor was located right 
next to T501. Now I know when I touch any pin on a Voltage reg IC with my 
voltmeter and it turns on, to look for an open resistor usually of high 
value somewhere in the circuit (around the 100's of K ohm value usually). 
And also to make note if the main filter cap is staying fully charged, If so 
I usually can quickly trace the open resistor by following the traces off 
the positive lead of main filter cap. In past I had had one or two sets with 
this same problem and had no print and gave up on them, now I will always 
know what to do and it has worked for me! - Very good thing to know for 
future troubleshooting.

Dan Garris
Garris TV
New Bern, NC
DGarris@xxxxxxxxxxx


>From: Bil Green <tv.vcrrepair@xxxxxxxxxxx>
>Reply-To: techassist@xxxxxxxxxxxxx
>To: ".TECHASSIST @ freelists . org" <techassist@xxxxxxxxxxxxx>
>Subject: [TechAssist] VS-5004R FIXED (Inter. Power On)
>Date: Sun, 31 Oct 2004 01:48:37 -0800
>
>Mitsubishi VS-5004R PTV
>Using STRS6301 SMPS IC
>
>The original symptom was no power. Replaced the usual caps in the SMPS
>(47mF, 100V - 10mF, 100V - etc.). All the electros near both power ICs
>tested bad. Replaced the STRS6301 IC.
>
>Then the set still would not turn on unless I applied the meter probe
>to pin one of the STRS6301 (to check for 155VDC) while the on-off
>relay was on. The set would then power up just fine, good picture,
>etc. Removing the meter probe didn't cause the set to turn off.
>
>After checking all the resistors I found that the 270k, 1/8W resistor
>in the primary winding was open. It made sense since this resistor
>was in the same part of the circuit as pin 1 of the IC (touching the
>probe to pin 1 made the set turn on).
>
>Now the set turns on fine. I posted this because too often large value
>resistors have a small voltage across them and won't check properly
>(as in this case) and it's easy to assume the resistor is OK and not
>bother to check it out-of-circuit.
>
>It's not always the low value resistors that blow out.
>
>
>Bil Green
>PC 1000
>Mammoth Lakes, CA 93546
>760-924-1000
>
>
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