Dead CTC169

[Eric H]

A guy at work has a 32"? RCA with a CTC169 chassis.
Dead as a doornail, fuse was blown, a new fuse was installed and it does nothing at all now.

Any easy fixes to try on this thing or should it got to the recycling center?

[kx250rider]

The AC fuse? That's usually a shorted B+ diode on those chassis. Measure all 4, and look for burnt traces under the diodes.

If the diodes are OK, then check the horizontal output transistor (Q4401, I think it was). If shorted, you have a bad Flyback.

Charles

[Geoff Bourquin]

I have seen the hot melt glue on the diodes do funny stuff to them. I like to scrape it off. I have seen some of those diodes short.
Another possibility is the power supply switching transistor may be shorted. If it is, you need to replace the power supply control IC, the transistor, a diode or two, and the electrolytics in the power supply; especially a 15/50 and 2.2/100 next to the IC. I replace those on EVERY CTC169 I work on. Iv'e seen a lot of those power supplies go *POOF* because a 25 cent cap fails. The horizontal output may be bad too, if the supply started running away. If the B+ goes up from the usual 140VDC the high voltage goes up too. Sometimes that killls the HOT, but the flyback survives. Check the big 15 watt resistor near the AC input. 2.2 ohm, I think. I've seen those open at the same time as the fuse, and even INSTEAD of the fuse.


I figured out how to use italics and BOLD. Cool!

[rca2000]

As I have pprobably fixed over a THOUSAND of these sets. And YES-- it is worth fixing!! The CRT is probably in great shape, as they nearly always are in these sets. The flyback, tuner and other expensive parts are likewise probably fine.

Now-- HERE is what you will need to get "er goin'

The reason that the fuse blew, and does NOT now-- the big resistor behind it, is most likely open. This is a 1.8 ohm -15watt resistor.

IT blew, because the chopper (switcher) transistor is bad. it is on a small heatsink, near the resistor and input cap. I GUARNTEE it is shorted. The RCA # is 200165. The generic # is SGSIF461. Do NOT use an NTE sub!!

Also-- the small chip, the switch-mode controller ic, will need to be replaced too. Is is right below the chopper transistor. A 16pin DIP. # 200419, or TEA2261

NOW-- there are 2 capacitors that MUST be replaced, or the parts WILL blow again, VERY soon!! There is a 2.2 uf cap, rated at 100volts or possibly 50 volts. (it is ok to use either, the voltage never goes over about 20 here.) It is next to the ic. REPLACE it!!

Also, right in front of the heatsink, will be another cap. it will either be a 39uf at 100v or a 47uf at 50 volt cap. REPLACE it with a 47uf at 50 volt cap.

Altogether-- the parts will most likely be less than $20 You WILL have a very nice set when you are done.

if, after you get the power supply running, you have a "chirp, chirp, chirp" and then nothing--The horiz. out is probably bad. In THIS chassis, it goes bad most often because of a bad yoke-return capaciror, or pincushion capacitor near the flyback. It is usually a blue or grey rectangular item, with a rating of ".48j250" or such. The pin cap is a smaller one, near the output sink and is labelled ".056j400" or such. If you have a bad h-out-- they are most likely bad.

Good luck, I own 2 ctc169's and would NOT trade them for a new RCA set!!

[dr.ido]

I have to wonder is there any relation between this RCA and any Toshiba?

I ask because what you just described above applies almost exactly (different chopper transistor, otherwise everything else is the same) to a Toshiba set (the model number escapes me at the moment) once common around these parts.

I will say that I learnt the hard way that those capacitors must always be changed.

[Eric H]

Thanks for the info guys, I will take a look at it today and see what's what.

[glen65]

Ahh yes,
The set with the tuner that doesn’t like to stay grounded.

[holmesuser01]

I never had big problems with the CTC 169's. It was the 175's that I worked on again and again that haunt my memories now.

I have a 169, and a 175 that see daily use. Working great, but didn't when I received them years ago.

[Eric H]

Originally Posted by rca2000

Now-- HERE is what you will need to get "er goin'

Yes, just as you said, the resistor is open, the transistor is shorted, the diodes seem to be OK but I may as well replace them, are they special or will regular 1A 600v diodes do the job.

Will generic Electrolytics be OK?

Where would I go to get the transistor and IC?

Thanks much for the help!

[rca2000]

Most likely, they are fine.

The caps can be replaced by normal ones, but try and get some with a 105 Degree rating on them(celsius). they will hold up longer than those cheap ones rated at 85degrees c.

The chopper transistor and controller can be gotten from a number of places. MCM electronics, andrews electronics, MAT electronics, fox, etc. NOT radio shack-- they have virtually nothing to fix this set(except if you are lucky-- the fuse!!)

[Eric H]

I will order them asap and let you know what happens.

Thanks much for all the help!

Originally Posted by rca2000

Most likely, they are fine.

The caps can be replaced by normal ones, but try and get some with a 105 Degree rating on them(celsius). they will hold up longer than those cheap ones rated at 85degrees c.

The chopper transistor and controller can be gotten from a number of places. MCM electronics, andrews electronics, MAT electronics, fox, etc. NOT radio shack-- they have virtually nothing to fix this set(except if you are lucky-- the fuse!!)

[Eric H]

The parts came today, I installed them and the set fired right up.
There was one heart stopping moment when the fuse I bought locally vaporized the first time I tried to power up, that was because the guy at the parts store gave me a 500ma fuse instead of a 5A one Put in the right amperage and away it went!

One more question, there is another small cap beside the IC, 1.5uf or 15uf @100v should I go ahead and replace that one too or is it usually OK?

[kx250rider]

Originally Posted by Eric H

The parts came today, I installed them and the set fired right up.
There was one heart stopping moment when the fuse I bought locally vaporized the first time I tried to power up, that was because the guy at the parts store gave me a 500ma fuse instead of a 5A one Put in the right amperage and away it went!

One more question, there is another small cap beside the IC, 1.5uf or 15uf @100v should I go ahead and replace that one too or is it usually OK?

One of those is a nonpolarized electrolytic, and I would replace it! Cheap insurance. That may often be the cause of the regulator blowing.

And as RCA2000 says, the diodes need not be replaced if they didn't burn or short. That's a different problem, not related to the stuff that went bad in yours.

Charles

[rca2000]

In your case, if you can get it, replace it.

However it does NOT go bad as often as the other two.

At this point, a standby and run b+ measurement is in order.

In standby, the B+ voltage(from COLD ground, the horiz. sink will do nicely) should be from 135-148volts or so. NEVER above 155. The diode near the flyback, from the big capacitor off of the SW. transformer, is the place to place the meter + probe. This is the 140v. diode, the supply on which regulation is referenced to.

In run or "on" mode--it should be between 141-144 volts and NO higher, and it MUST NOT vary from that by much!!

If all is ok, and the switching transistor(chopper) is not getting more than warm after about 5 minutes of running, then you are probably OK!!

Good luck!!

[captainmoody]

My neighbor gave me a 27" Proscan last week, it has the 169 chassis and still works perfect. However, remembering this post reminded me of all the cap related problems I dealt with before on these back in the 90's! (I forget things easily!) I am glad Jack posted about the 2.2 100v cap by the IC, because mine was open!! Boy, that was a close call! I changed all caps in that area to be sure, but when testing the ones that were replaced, only that 2.2 was bad.
Remember the late 80's Sylvania 27' and 31' sets that would be a no-start and have two open 2.2 caps in the switcher causing the problem? I can't remember, was it an "R" chassis or something like that?