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jcmorrisii

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Hey guys! Recently did some repairs on a Sony 1271Q PVM and there very little information available to the public. So I wanted to share my experience with everyone in hopes that someone may find it useful and be able to save their own.

When I received the PVM it was obvious it had been through Hell and back, and some serious issues were occurring on the deflection board. Linearity , pincushion, h amp, you name it and there was an issue with it.
IMG_4642.jpg
So I reached out to Andy King, whom is very knowledgable about CRT repairs in general and hosts lots of public information of his website about repairing and maintaining CRTs. There was no information on this model PVM on his website and Andy said he had never worked on one before. But regardless, had some amazing tips and pointers on places to start looking for problems. One thing he mentioned may be causing the pincushion issue was loss of power going to the IC from a failed voltage regulator (IC504 on this model). It is supposed to generate 12v and send it to pin1 on the Pincushion IC. After probing pins 1 and 2 (for ground) see that we are getting perfect voltage, so thats not the problem.

So turning to the actual trimpots themselves.....these are really old open air trimmers, the type you would see in electronics from the 70s-80s. Very prone to corrosion and failure.
IMG_4767.jpg

SO as I start to probe these guys across legs 1-3 Im noticing that none are at the proper resistance and a few are open circuit?! THis cant be right , so i take some out of circuit to test further and confrim this to be true. Something was so out of wack it fried a few of these. Probably a board full of bad caps.

Most of the time trimmers don't out right fail, well this wasn't the case on this old bird. Two of them were reading 0L and most of the rest were WAY out of spec. Any time you tried to make an adjustment, the screen twisted and bounced around like you wouldn't believe, and some made no changes at all. So I went over the schematic and made a list of every single trimmer on the D Board.

List of Trimmers on D Board:

RV807 - 2.2K Ohm - U Pin Amp
RV805 - 330 Ohm - N. Pin Amp
RV811 - 470K Ohm - U. Pin Phase
RV804 - 1K Ohm - N. Pin Phase
RV806 - 3.3K Ohm - U. Horizontal Size
RV803 - 3.3K Ohm - N. Horizontal Size
RV503 - 2.2K Ohm - U. Vertical Size
RV501 - 220 Ohm - N. Vertical Size
RV504 - 22K Ohm - N. Linearity
RV502 - 10K Ohm - VCC
RV507 - 4.7K Ohm - V. Angle
RV558 - 220K Ohm - BOW
RV812 - 47K Ohm - H. Center
RV808 - N/A - H Center 1
RV753 - 4.7K Ohm - Y. BOW
RV751 - 4.7K Ohm - Horizontal Tilt
RV752 - 10K Ohm - Horizontal Amp
RV809 - 47K Ohm - H Center 2
RV802 - 5K Ohm - Horizontal Frequency



After replacing the bad trimmers, i was able to get some movement and control aspects of the Deflection circuit, but it was obvious the source of the problem that caused them to fail was still there.

Now to start pulling electrolytic capacitors and testing them for ESR, VLOSS, Capacitance. Every single one is an Elna, rated at 85C. I wont bore you with the ratings of every single cap but heres the take away: most of the 4.7-1UF caps were still within operational specs (but failing), but the large capacitance caps were gone. I couldn't even get reading on a few of them. Every single 330UF was bad. Heres a list of all the Electrolytic on the D Board and I make notes of the ones to look for that caused me issues.

D Board Capacitors:

C505 - 50V - 1uf
C507 - 50V - 1uf
C509 - 50V - 1uf
C511 - 25V - 10uf
C512 - 50V - 1uf
C515 - 50V - 100uf
C518 - 25V - 10uf
C519 - 50V - 1uf * BP / Bi Polar!!!!
C520 - 25V - 22uf
C521 - 25V - 470uf ** Cap Failed / 0L
C522 - 16V - 22uf
C523 - 16V - 22uf
C524 - 50V - 1uf
C527 - 16V - 470uf **High VLOSS, Low capacitance
C528 - 50V - 3.3uf
C529 - 50V - 1uf * BP / Bi Polar !!!
C532 - 50V - 1uf
C533 - 16V - 10uf
C535 - 25V - 100uf
C536 - 25V - 470uf **HIgh VLOSS, low capcitance
C537 - 50V - 2.2uf
C751 - 50V - 1uf
C752 - 50V - 2.2uf
C753 - 50V - 1uf
C756 - 50V - 1uf
C759 - 25V - 10uf
C760 - 25V - 47uf
C761 - 50V - 3.3uf
C762 - 25V - 22uf
C764 - 25V - 220uf ** Cap Failed / 0L
C766 - 50V - 1uf
C767 - 50V - 1uf
C769 - 25V - 47uf
C802 - 50V - 2.2uf
C804 - 50V - 1uf
C808 - 25V - 4.7uf
C816 - 50V - 2.2uf
C817 - 50V - 2.2uf
C818 - 25V - 22uf
C819 - 25V - 22uf
C821 - 50V - 2.2uf
C822 - 50V - 1uf
C823 - 16V - 10uf
C824 - 50V - 10uf
C825 - 16V - 330uf **High VLOSS, low Capacitance
C827 - 50V - 0.47uf **Cap Failed / 0L
C841 - 160V - 2.2uf
C843 - 50V - 1uf
C844 - 16V - 330uf
C846 - 35V - 330uf ** Cap Failed / 0L
C852 - 25V - 1000uf
C854 - 160V - 10uf
C855 - 160V - 33uf
C859 - 50V - 4.7uf
C860 - 25V - 47uf
C868 - 16V - 10uf
C870 - 25V - 47uf
C871 - 50V - 1uf
C873 - 16V - 470uf
C884 - 25V - 10uf
C887 - 16V - 47uf
C888 - 16V - 470uf


Ongoing more to come as I type it out..... :thumbsup: -
 
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