RCA G27221WK (CTC169 chassis) dead Vreg w/Schematics

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RCA G27221WK (CTC169 chassis) dead Vreg w/Schematics

I've spent the past 2 days & nights working on and thinking about this thing, and the issue lies somewhere in a tiny section of about 20 components. The problem is, I don't know where to point the finger, because, well, I just don't have the experience to tell exactly how each component interacts with the rest.

The set, a huge wood console TV from 1992 that looks on the inside like the whole design was a huge afterthought, died three days ago from an otherwise flawless existence. It had perfect video, extraordinary sound, and only had a broken power button on the front. It could only be turned on/off via the remote - a remote with a flaky power button, no less. So, that morning three days ag, I was in a major hurry. The computer (which I have attached to the S-Video of the TV) was taking too long to copy a file, I was running late for work, so I grabbed the USB hard drive and went to shut off the TV. Batteries fell out of the remote. The power cord was easier to reach than the batteries. I yanked the cord, and plugged it back in, hoping it'd stay off. Turned back on. So, screw it, I left it unplugged. Got back home about 11 hours later, roommate was wondering why the TV won't turn on. "Oh, I unplugged it (insert recap of story above). Plug it back in". "I did", he says. Enter chaos. I spent the rest of that night tearing apart the TV and poking around with a multimeter and my shiny new digital oscilloscope.

I've narrowed it almost entirely down to one component, U4101, the control ("regulator") IC, TEA2261 (RCA P/N 200419). But I just want to know if that's even a reasonable assumption, given the circumstances.

First and foremost, here's the schematic, as promised (click for the full image):

ctc169 high side PSU schematic

The problem is somewhere in there. No voltage is getting past the transformer or even to the IC itself. When it's plugged in, everything but B+ (right off the rectifiers and filter cap) shows about 0.04v. Yeah - 0.04v. It's a mystery to me how the voltage can drop that low!

Here's a list of the things I've checked so far:

  1. Prior to my poking around, voltage on the other side of R4003 varied like a sine wave. It seemed to reach a point (about 7 volts) then drop back to 6 volts where it started to ramp up again. It was like the resistor wasn't providing enough power, so the control IC would cycle on at 7v, drain the power to 6v, kick off, recharge to 7v, etc. If I unplug AC, the recharge time increases in a logarithmic scale (getting significantly longer over time) but the discharge rate always stays the same sharp drop. Always the same voltage - at around 6 and 7 volt points. After poking around (particularly around the time I played with C4110 below), it no longer cycles - it always stays at 0.04v max when plugged in.
  2. R4003, tested OK but replaced anyway, 2w/33K. Seems to be the only way power gets into the circuit.
  3. C4110, removed and it's not shorted, and tests at about 450uF with a digital capacitence meter. I bought a replacement but made the dip-idiot-amateur mistake of installing it backwards. While I was testing with a small (2a) regulated +12v supply, it drew about 3.2 amps, promptly bulged and almost popped, but I caught it in time and removed it, reinstalling the original in the proper polarity. D'oh.
  4. R4126, tested OK, 8.8 ohm/3 watt.
  5. R4149, tested OK, 1.2 ohm/1 watt.
  6. CR4101, tested OK, removed and powered a 12v/0.3a fan in only one direction, no power when installed backwards (so it must not be shorted). Only way I could think of to test it!
  7. CR4106, tested OK, same as CR4101
  8. Q4101, not sure how to test, but none of the leads are shorted (0 ohm). I think only two pins showed conductivity, about 100 ohms on my meter, but still not enough to cause this issue...
  9. C4153, not sure how to test that either, but in the schematic it connects directly to ground, so I popped that off to see if it helped. Showed zero conductivity even at the highest ohm range. Is that normal? I'm not sure what purpose a capacitor that small can serve, but I sure see a lot of them in the schematic...
  10. Tested the raw B+ voltage in both AC and DC mode - DC showed about 164 volts at the capacitor, and AC mode showed absolute 0 volts. I'm not sure how else to test AC leakage, since my oscilloscope only goes up to 50 volts...
  11. The B+ voltage drops to near zero relatively quickly, in the order of about 3 volts a second all the way down, when it's unplugged. The 33k/2w resistor also gets slightly warm to the touch within about 30 seconds - just barely noticable, but the power's going somewhere.

So, basically, I've got ~164vdc on the raw B+ side and 0.04vdc on the opposite side of a 33k resistor attached to it. Something must be shorted here. But is it the IC? I've got it queued up in a shopping cart ready to buy, but I really, really, really need to know if this is what should fix it after testing all these other components.

I'd hoped that more than 8

I'd hoped that more than 8 people would be interested in helping someone that took the effort to post schematics for crying out loud...

I'd really like to know if anyone has experience with this sort of thing - that is, a chip itself going bad. Anyone? Please? Something?


C4104 115uf
C4102 2.2uf
C4108 39uf (some are 47 - 39 is better)
C4118 470uf
all Low ESR 105C
CR4118 is also a suspect. It cannot be reliably tested in circuit or out.

Likely, if you have any luck other than bad, the standby will come up after you replace the caps & diode.

cathodes of:
cr4116 (140v) to COLD ground sb >50k
cr4118 (15v) to cold ground sb 500ohms or better
cr4117 (7v)

Oh, jeez... this is an oldie.

Oh, jeez... this is an oldie. I got the TV fixed (or rather, another forum member helped me get it fixed) a few months ago. Now it works beautifully once again. It was C4104 that tested off the chart (I think that's bad?), but I also replaced C4102 and C4108. The full thread (with a lot more replies ;) ) is at http://forum.eserviceinfo.com/viewtopic.php?t=64742

Thanks for the advice, though!

It's me again ... with my

It's me again ... with my original id...

Obvious mistype of the cap farads, but wanted to mention that you need 105C temp capable caps. If you put in 85's they won't last as long by far.
The comment box cut off some of the K values from the cathodes to ground, but it was just a generic check to see if the chassis had obvious grounds when voltages read low.

Where did you get the schematic?


I have one of these that runs

I have one of these that runs if you're still wanting one...


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