CTC169BJ2 from PS35652 no 5v Stnby


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CTC169BJ2 from PS35652 no 5v Stnby

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jerryp49
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Apr 17, 2005, 4:54 PM

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CTC169BJ2 from PS35652 no 5v Stnby	Can't Post

Hello all, I'm new to the forum but seak your advise. I'm a ham so know a bit about electronics but have hit a wall on this one. My set will not turn on and have done all the usual fixes such as the HOT, Flyback, several CRxxxx diodes and caps. The 143vdc stan-by voltage is good as well as the 12vdc but I can not get any 5vdc stand by. I did check the Q4601 transistor which is good. Without a schematic I can't find where to look from here.

Any thoughts from the pros? Thanks, Jerry

mel
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Apr 17, 2005, 10:06 PM

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Re: [jerryp49] CTC169BJ2 from PS35652 no 5v Stnby [In reply to]	Can't Post

I suspect that your problem may a shorted zener diode CR606 but it could also be that CR709, CR710 or Q703 are bad. The power supply in this set is so complicated that it could be any number of other things. You can go to www.forum.eserviceinfo.com and download the schematic for this set for free. When you try to open it, it will say that it is password protected but ignore the warning and just open it. You might also want to check out www.FreeFlatScreens.com/?r=10948674 for an opportunity to earn a free replacement for this set with a little effort on your part.

jerryp49
New User

Apr 18, 2005, 12:11 AM

Post #3 of 12 (1630 views)
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Re: [mel] CTC169BJ2 from PS35652 no 5v Stnby [In reply to]	Can't Post

Hi Mel, Thanks for all the suggestions. I was given the free download sight earlier today and am going through the trace for the failure now. That is a great tool to have right on the computer! Hope I can track it down. I really love this set and had it going right after I replaced to HOT and then it went again with loss of the HOT again. This time replace a lot of the recommended parts with it but the best I ever got was a little clicking from the relay with no start. Now the 5V is gone as well.

Onward and forward with the magnifying glass.

Jerry

jerryp49
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Apr 22, 2005, 4:09 PM

Post #4 of 12 (1618 views)
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Re: [jerryp49] CTC169BJ2 from PS35652 no 5v Stnby [In reply to]	Can't Post

Gentlemen,
I've located a bad diode in the power supply of my CTC169.

It is CR4105 with marks of 352.ET on it. I'm unable to locate the RCA number or a cross over for this part. Can anyone help?

Thanks,
Jerry

mel
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Apr 22, 2005, 8:30 PM

Post #5 of 12 (1613 views)
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Re: [jerryp49] CTC169BJ2 from PS35652 no 5v Stnby [In reply to]	Can't Post

You can go to www.wehaveparts.com, plug in your model number and the Q4105 and it will take you to the RCA part number. Looks like they have it for about $4.

jerryp49
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Apr 22, 2005, 9:18 PM

Post #6 of 12 (1610 views)
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Re: [mel] CTC169BJ2 from PS35652 no 5v Stnby [In reply to]	Can't Post

Thanks for the help Mel. I just got back from the parts store and got the replacement for the Q4105 Zener (1N5365BP2 36v 5w). It was going weak but not shorted. I did get the 5vdc stand-by going earlier with your suggestions. It was the CR710 and CR606 that had shorted.

Now I'm trying to jump the next hurdle. If I bypass the the on off switch by cold grounding JW336 (like the computerized schematic suggest for testing) all I'm getting is a fast ticking of the relay but no start. All of the B+ voltages take a dive when this is done I already replaced the HOT again as a precation, but no change.

I've been going through all of the transistors, diodes, caps and resistors but haven't found anything else bad, other than the Q4105, which made no difference. The schematic tells me that I should have 5v ant the 'C' of Q4304 in the off setting but there is only 1vdc. I've tried to trace out this drop but can't locate it.

Any other thoughts? Jerry

mel
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Apr 22, 2005, 11:17 PM

Post #7 of 12 (1604 views)
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Re: [jerryp49] CTC169BJ2 from PS35652 no 5v Stnby [In reply to]	Can't Post

The collector voltage on Q304 comes from the 15v power supply across R127 which eans that you should have a 10v drop across R127 (15v on one side and 5v on the other). If the 15 volts isn't there, go back and check your 15v source. Q109, Q301, Q705 are in parallel to ground from this point so they are also likely suspects for loading down this voltage.

jerryp49
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May 2, 2005, 7:57 PM

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Hector read this...CTC169BJ2 from PS35652 Low 15v Stnby [In reply to]	Can't Post

Hector, I'm hoping you have checked in on this site. I have made multiple tests and still have not resolved the problem of a low (13v) +15vdc stand-by voltage. If I lift one end of JW324 the voltage will go over 15v but if I leave it in place and lift an end of JW320, no change. I've done this same type of search across other components and it seams to be leading me toward the regulator circuit.

I have several components on order now including U4101 and Q4111 and will be putting them in on Wednesday. I was wondering if it would be possible for you to email me a scan of your schematic for this chassis since the one that I'm using right now is not the exact model on the computer program? I would only need the regulator and HV sections to confirm all is well with my voltages etc. I noticed that this set has one additional transistor (Q4108) in the regulator circuit than the one I have on the computer.

Any help would be greatly appreciated, Jerry

(This post was edited by jerryp49 on May 3, 2005, 3:54 AM)

mel
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May 2, 2005, 10:16 PM

Post #9 of 12 (1580 views)
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Re: [jerryp49] Hector read this...CTC169BJ2 from PS35652 Low 15v Stnby [In reply to]	Can't Post

The results of lifting the two JWs narrows the problem down the 15B voltage source. Now you just need to start lifting individual component legs as I suggested earlier to further narrow it down.

jerryp49
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May 2, 2005, 10:40 PM

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Re: [mel] Hector read this...CTC169BJ2 from PS35652 Low 15v Stnby [In reply to]	Can't Post

Hi Mel, Yes I followed through with all the check points you suggested finding no fault on any of those items. I had just replaced the C145 cap before, thinking it was the problem as well. I continued up the circuit disconnecting components one at a time and re-checking with no change until I got to the connection at CR123 and C154. With that circuit open the B+ 143v and 15v stand-bys both dropped way down. I couldn't logically check much further because after the Q4111 is the Q4108 which doesn't show on the computer schematic I have.

Jerry

mel
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May 3, 2005, 10:02 PM

Post #11 of 12 (1570 views)
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Re: [jerryp49] Hector read this...CTC169BJ2 from PS35652 Low 15v Stnby [In reply to]	Can't Post

Apparently I'm looking at the same schematic as you are because mine doesn't show a Q108 either. Could it possibly be Q105 whose emitter is connected directly to the collector of Q111 and its collector is tied to the collector of Q109?

jerryp49
New User

May 3, 2005, 11:33 PM

Post #12 of 12 (1570 views)
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Re: [mel] Need Schematic...CTC169BJ2 from PS35652 Low 15v Stnby [In reply to]	Can't Post

No, it is definitely Q4108. The emitter is connected to the emitter of Q105 and the collector of Q111. Its collector is connected to the emitter of Q106 and Its base goes to JW331 which then goes to to R116V.

This set was built in 1994. Jerry

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