CTC169 Dead Set HELP!!!

When you say chopper transistor, do you mean the switching power supply transistor ? I will assume this for now. Did you also check the horizontal out put (HOT) transistor. ? Also, did you check the irradiation detector circuit ? I'm sure there is something you have over looked.

Does the start up appear to attempt an on cycle ? If not, I would first look there, also, you may want to look at the degaussing circuit..

Make sure you don't have any low voltage taps from the flyback that has bad caps and diodes on it.. Also check the yoke for bad connections to the circuit board.. I've found cracks many times in these area's due to the fly back vibration and heat combined..

CRT units are so great././. :)

P.S. Place a scope on the base drive of the HOT, if you don't see a short attempt of horizontal drive then you have a power supply start up problem. If you do see a short burst then you have a problem in the HV section.

Sounds like your power supplies are working and you have no horiz drive. Look for two brown 330uF capacitors leaking electrolyte onto the board in the vicinity of the T-chip. It will ooze under the Horiz. oscillator (Blue plastic case, near T-chip) and stop horizontal drive. As these sets get older, this is becoming a VERY common problem. Replace the caps (to stop them from leaking electrolyte), clean up the board (with the oscillator removed) - you can try to reinstall the oscillator, but I have had some that actually soaked it up inside, and it was necessary to replace. If the Horiz. output was shorted, the power supply would not be able to develop

"Marc" wrote in message news:2f6dnTbNo55USDXVnZ2dnUVZ_s snipped-for-privacy@comcast.com...

Haywire,

I looked all over the board and even in the parts list (sam's photofacts) and there are no 330ufd caps on my chassis. I do see the small blue oscilator. There is some residue around the the end of the chip and there are 2 caps, but they are not brown and nowhere near 330's. Any chance you can share the part symbols for the caps?

drive.

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that

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Hmmm, I'll have to look at the schematic to be sure, but there are two identical in value - my memory may have failed me on the values (150uf, maybe?) one filters Defl B+ (To the T-chip) and the other filters a seperate B+ pin on the same IC. Both can make a mess on the board - it is the conductivity of the leaked electrolyte that causes the problems, and can usually be seen by a wet spot eminating from around the culprit capacitor(s). Most of the ones I have seen leaking had dark brown heat shrink on their case, but since RCA used different suppliers of discrete components during manufacturing, it is possible they may be dark blue, or whatever... Try removing the oscillator by desoldering, and clean up the board. It is not even necessary to replace the caps for a test run, but I would after deciding whether this is your prob. or not - for the longevity of the repair. Another tell-tale sign that this may be your problem, is that it may smell like rotten fish during the desoldering process (of the oscillator, or the suspect cap's) due to the boiling/burning off of the electrolyte from the heat of your soldering iron. If that happens, you're probably on the right track, and it may be necessary to replace that little blue oscillator if it cannot be adequately cleaned, or if the acid-based electrolyte has wicked up inside the "unsealed case".

Also, my scratch-and-sniff approach may be off-target. Do you have any horizontal drive pulses coming out ot the T-chip?

"Marc" wrote in message news:ucydnRKaXNLFXjHVnZ2dnUVZ snipped-for-privacy@comcast.com...

Haywire,

seperate

little

photofacts)

there

you

in

get

stop

develop

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O.k. - (I hope) you may have given me a big clue when you said that the run supplies are not "getting on their feet". I will assume for now that the standby's are NOT dropping significantly when you attempt power on, which will lead me to what I am about to suggest...

(Once again, I type from home in the evening, and have no schematic or old boards in front of me, but here goes...)

On the underside of the board, on the secondary side of the switching transformer to the left of your rectifiers, such as CR4118, etc. (viewed from bottom)look for another, larger filter capacitor that leaks. It will wick down to the UNDERSIDE (foil) of the board, and have the green coating blistered, or lifted in places all over several fine PC traces that if you scrape and clean them (the ones with black-looking blisters and bubbles) you will find they are quite oxidized, and black. I think you may find at least one of these eaten completely through, and causing lack of Run B+, therefore no supply from which to generate horiz. drive pulses... I have been also seeing this more and more often lately, too as these sets get some age on them... I hope this gets it for ya, as I am running out of ideas, and you sound like you know these chassis pretty well, too. Oh, yeah, and replace that cap when you are done patching trace(s). It should be pretty evident on close inspection which one is a leaker - and it will smell like fish when you heat the leads! I wish I has a cap' number for you but as I said, I type from home (and I pretty much I just know which one physically to look for from memory when one is in front of me...)