rca ctc169CL5 - idiot me

[ratdude747]

Re: rca ctc169CL5 - idiot me

why are crt tvs such a PITA?

[PlainBill]

Re: rca ctc169CL5 - idiot me

why are crt tvs such a PITA?

Because they are the culmination of 60 years of design evolution, with the goal to reduce manufacturing cost to a minimum while adding features and improving reliability. Little consideration is given to REPAIRABILITY.

30 years ago a 25" color TV had a couple of dozen vacuum tubes, and a chassis about 12" x 20" x 6" high. In addition there was a tuner assembly about 4" x6" x 8" and the high voltage cage. It drew about 275 watts. And at that, many circuits did double duty. The audio was mono, the remote control was hollering at the kid to change the channel.

The last time I opened a CRT TV it was a 27" Mitsubishi. Other than the CRT, the entire electronics was on a 12" x 12" board. It drew about 90 watts, had stereo sound, remote control, and 'on-tube' display of channel number and volume.

PlainBill

[tmwalsh]

Re: rca ctc169CL5 - idiot me

PlainBill: 12"x12" .. and it had 6 components, each of which had 114 legs... and was surface mount. The only 'tuner' it has is a F-connector soldered to the mainboard which goes directly under a tin-can shield where there are maybe 2 more chips.
The dang things are so small, you'd have to be born with magnifying vision to work on them, and have the fingers of a baby. Additionally, the chips self-check them self and will refuse to do anything - much less tell you why they don't want to co-operate.

Yeah, this is exaggeration, but when you can pick up the chassis in one hand, it is mind boggling to compare it to the eleventeen boards in the Heath GR2000 of 1978, each with discrete components. The 'jungle' chips have more in one of them than half a dozen Heath boards.

I got my Blue ESR and am chugging away on the caps in the menagerie. It worked first time after I assembled it. Haven't adjusted the 'dead battery' thing yet. Some caps that I thought were good show 0 ohms when tested by the Blue ESR, but not when tested by an DMM. What's up with that?

tom

[PlainBill]

Re: rca ctc169CL5 - idiot me

PlainBill: 12"x12" .. and it had 6 components, each of which had 114 legs... and was surface mount. The only 'tuner' it has is a F-connector soldered to the mainboard which goes directly under a tin-can shield where there are maybe 2 more chips.
The dang things are so small, you'd have to be born with magnifying vision to work on them, and have the fingers of a baby. Additionally, the chips self-check them self and will refuse to do anything - much less tell you why they don't want to co-operate.

Yeah, this is exaggeration, but when you can pick up the chassis in one hand, it is mind boggling to compare it to the eleventeen boards in the Heath GR2000 of 1978, each with discrete components. The 'jungle' chips have more in one of them than half a dozen Heath boards.

I got my Blue ESR and am chugging away on the caps in the menagerie. It worked first time after I assembled it. Haven't adjusted the 'dead battery' thing yet. Some caps that I thought were good show 0 ohms when tested by the Blue ESR, but not when tested by an DMM. What's up with that?

tom

Yes, the circuit boards get smaller as the chips get more complex. If you want a 'throwback', take a look at the July 2009 Nuts and Volts magazine. It features a digital clock built entirely of discrete components (except the 7 segment displays). The board measures (roughly) 9" x 12" and holds 1228 components. And the kit costs $225

There seems to be some confusion on the ESR meter. A conventional DMM uses a DC voltage to measure resistance. The DC resistance of a capacitor should be very high. I have not found a DMM with a capacitance function that will measure power supply caps, the range doesn't go that high.

The ESR meter uses an AC voltage to determine the Effective Series Resistance of a capacitor. The ESR of a capacitor should be low, in the case of caps in an SMPS, the lower the better.

PlainBill

[tmwalsh]

Re: rca ctc169CL5 - idiot me

I guess the comment was in reference to having 'low' resistance and having zero resistance. Across a few I was testing, the reading was zero on the Blue. I have an old RS analog vom I put together in the late 70's that I used to use to test caps for the Heath. I 'expected' the ohms to go towards zero and then climb as the cap took a charge. If it was truly shorted, it would go to 0.
Now I iz confused. BTW, I gave the HK to my ma and pa back in 78. Their first real color tv. It still works decent, even showing SDTV converted back to RF on 3/4.
The instructions, assembly and trouble shooting guide for that are my TV knowledge basis. That along with sparks and smoke seem to be getting the job done ... slowly.

tom

[PlainBill]

Re: rca ctc169CL5 - idiot me

I guess the comment was in reference to having 'low' resistance and having zero resistance. Across a few I was testing, the reading was zero on the Blue. I have an old RS analog vom I put together in the late 70's that I used to use to test caps for the Heath. I 'expected' the ohms to go towards zero and then climb as the cap took a charge. If it was truly shorted, it would go to 0.
Now I iz confused. BTW, I gave the HK to my ma and pa back in 78. Their first real color tv. It still works decent, even showing SDTV converted back to RF on 3/4.
The instructions, assembly and trouble shooting guide for that are my TV knowledge basis. That along with sparks and smoke seem to be getting the job done ... slowly.

tom

I was very fond of Heathkit back in the 60's and 70's. I still have an oscilloscope and other test equipment I built. I found the technical portion of the manuals invaluable in learning how the circuits worked. Knowing how they work makes troubleshooting much easier.

PlainBill

[tmwalsh]

Re: rca ctc169CL5 - idiot me

ratdude747, are you a PU grad? or are you studying aero engineering in west laff?

I got out with a BSIM a long time ago
...
Back on topic, I get set #2 working by replacing the temperature sensitive resistor. I am going to order 4 new ones.

I got set #3 working. After replacing the 2.3uf with a donor from #1, I had 2 bad components - L702 and R701. The coil was mushed into a metal shield and was burned up, and the resistor was open. Stole them from another set, and bingo.

Set #4 am measuring resistance on all resistors in luminance ckt, trying to find if it is a resistor that is working better when warm. It takes about 4 minutes to get 'normal'. I was thinking that Q2906 might be weak, or the other luma buffer transistor.
Don't have enough room on the table to have two sets opened up and the gizzards out for scope connecting... one at a time.
Set #1 has been the donor so far, so it will have to wait until I send off for new parts. I plan to get all 4 caps in the power supply for all sets, the 4 temp resistors, coil (10h), resistor(10ohm), and the 15w 1.8ohm resistor in one order.
Once I figure out which component in #4 needs replacment, I will send for a pile of parts.
Saving the first, #1 (worst) for last...
tom

[tmwalsh]

Re: rca ctc169CL5 - idiot me

On to the last. C4311 was cooked, leaving a smoky spot on the board. Replace that, L702 and R701, the 15W cement 1.8ohm, and the usual suspect caps in the SMPS.
Back to where I was when the story started: Onscreen display works fine, audio works, but no video from the tuner or either of the video inputs.
No output on the jungle r-y, g-y, or b-y outputs, nor on the -Y from the chip. Have good chroma from the comb, selection voltage switch up and down as per notes based on tuner or RCA/S-video inputs.
Unless anyone has a better idea, I am going to replace the jungle, TA8680N. Hate to try to remove a 54 pin chip, but don't see what else to look at as it is not putting out what it should.
B+ standby max adjustable is 142.3, 7v is at 6.9, 13 is a 12.9. I replaced all the caps, and the B+ does not adjust as high as recommended, 143.5v. Used nichicon HE series for all but the 2.2uf which was a PW series.
The same limitation on the 140v B+ was noted on the other two chassis after replacing the capacitors. My theory was to replace them before they failed taking semiconductors along for the smoke release...

hasta la bye bye

tom

[Wizard]

Re: rca ctc169CL5 - idiot me

Change CR4118, use exact replacement, it is strange design diode used. This is for no color problem too. Yes, that can be strange for totally non-related "problem"!

Also, if you have PIP, by pass it for a test this causes no picture but good menu. Caused by bad caps in the PIP or module itself. Small or large PIP modules is interchangeable.

Cheers, Wizard

[Wizard]

Re: rca ctc169CL5 - idiot me

which pins that outputs r-y, g-y, or b-y?

Cheers, Wizard

[tmwalsh]

Re: rca ctc169CL5 - idiot me

R-Y PIN 15
-Y PIN 16
G-Y PIN 17
B-Y PIN 18

I will change cr4118. I had thought it would either fail completely or work perfectly.

adios
tom

[tmwalsh]

Re: rca ctc169CL5 - idiot me

The micro is supposed to put out a 'hi' on pin 21 to enable video from the jungle. I measure .62v, and tracing back through a resistor, get about 3.6 volts on pin 21.
This is the blanking signal for the OSD.

Can I apply voltage to pin 19 on the U1001 IC? It is labeled R OSD, and the word 'BLNK' with a bar over the top of the letters. [Active high?]
If the micro U3101 puts out a low voltage on 21, and sends it to jungle 19, would it have the same effect as what I am seeing? No activity on the R-, G-, B- pins, even when the setup menu is displayed on the screen. They are all 'high', as in the scope trace goes up when the probe is applied when watching for activity.

Per the words in the servicing manual:

"The literature also suggests you make certain pin 19 of U1001 is not stuck low. If it is low, it will account for the no-video symptom."

It is not 'low' as in 0, but measured at the jungle it is less than 1 volt.

Should I be watching for this signal on the oscilloscope rather than using a DMM?

thanks
tom

[Wizard]

Re: rca ctc169CL5 - idiot me

Scope. OSD is on screen text, outputs from micro to the jungle inputs, micro needs h and v pulses check these also.

Most of time they are green text. check the OSD G output first.

Cheers, Wizard

[tmwalsh]

Re: rca ctc169CL5 - idiot me

OSD on these CTC169s goes from the micro to a triplet of transistors that are connected to the emitters of the individual RGB driver transistors. It does not go to the jungle inputs.

OSD for menus is light blue text , or white text, or yellow text on a darker blue background which highlights the selected adjustment. There are blue hashmarks and white,green or red "-/+" signs at either end of the scale.

CR4118 replaced with a MUR460RLG [600V 4a Ultrafast] to no discernable effect.

Pin 21 on the micro [labeled BLNK] is at about 4.62V, but drops to .27 volts immediately after a surface mount cap. Pin 19 on the jungle measures 1.2volts. This makes no sense as the micro should be the 'driver' of the jungle.

caio
tom

[Wizard]

Re: rca ctc169CL5 - idiot me

Blnk, is not RCA correct term. I recall it is blanking. You really need a real RCA schematics. There are out there somewhere to get.

Cheers, Wizard

[tmwalsh]

Re: rca ctc169CL5 - idiot me

Wizard:
"Blnk, is not RCA correct term."

BLNK with an overscore is the label on the input to pin 19 of the jungle as referenced in the H W Sams book:
'Tips and "Trade Secrets" From the ctc130 to the CTC195/197 Series'

It is a signal sent from the micro, U3101-21, System Control/OSD Micro, labeled on the callout:
"BLNK" [with overscore], Description: "OSD black surround out. Low = Black"

I am beginning to suspect the Jungle - TA8680N - for which I cannot find a readable description of the innards. Either the Jungle has failed, or there is a signal being applied to the Jungle which is turning off the R, G, and B outputs, along with the -Y output on pin 16. All of these are developed, amplified, or processed subsequent to the input, processing and output of luma on pin 38, which appears to happen.
In other words, the chip is creating luma out, and then failing to produce the RGBY output. It is being disabled by blanking or the chip is defective.
My question:
Am I looking at the inputs & outputs in a logical manner, or have I missed something by a wide margin.

I had thought previously that the grounding of the CRT to the Q4101 shield would have blown a small electrolytic, as my shorting the Hot ground to Cold ground through the oscilloscope caused, but the lack of outputs from the jungle do not support that.
thanks again

tom

[Wizard]

Re: rca ctc169CL5 - idiot me

Open that blanking pin and see? Otherwise, either pull or down with a resistor to either VCC or ground.

Cheers, Wizard

[tmwalsh]

Re: rca ctc169CL5 - idiot me

It may be fixed, or at least functional:

I put a scope on the output from micro-21, {ovserscored}BLNK for OSD, which was supposed to have lots of activity at ~4 volts, and a little at ~1(?) representing the 'setup menu' information, I suppose.
It had lots of signal at both higher and lower voltage on the scope screen, I thought possibly enough to blank the screen all the time.

I pulled up one end of a resistor in the circuit, turned the set on, and had snowy video. Tried the character displays for audio, video, and general setup, and all displayed. Tried the fake NTSC rainbow DVD I had recorded, and it displayed fine. The menus displayed while DVD was playing.


In the schematic, this blanking signal is fed into the Red OSD input on the jungle, and the Green OSD input is left unconnected. The actual OSD information is fed from the micro directly to the driver transistors.
I suspect that the signal is used internally to the jungle to turn off the normal picture information while the OSD is being fed into the driver transistors. I did notice that the menu displays were not as deep a color, the blue was more washed out, for example.

Now what? As far as I can tell, leaving the resistor disconnected will hurt nothing, and the set works. Am I mistaken?

I was just about ready to drive 50 miles and get a replacement jungle, but suspect that the problem is actually the micro, which I suspect is NLA...
The standby B+ is still in the 141-142 range, and the 15v(?) is at 13 after changing the capacitors in the SMPS.
tom

[Wizard]

Re: rca ctc169CL5 - idiot me

The pin 21 should be quiet when OSD is not displayed. Purpose is to "cut out" the video and let anything else that needed to be displayed in the "holes" without looking washed out. That's "overlay" method.

Think of a someone cut a outline of characters and it look black because no signal for OSD is applied.

Obtain a blank eeprom and try I think the original eeprom is corrupt. It is only for customer settings. Not for TV settings.

Cheers, Wizard

[tmwalsh]

Re: rca ctc169CL5 - idiot me

Okay, I am a little confused. The eeprom only carries the labels and such for the channels. Nothing for the setup of the set.
Are you saying get a blank eeprom and solder it in place?

I looked at another set, and realized that the letters of the menu or setup screens have a very narrow black border around them. The set where I disconnected the BLNK signal have no black border. The blue is a little more pastel rather than a rich deep blue on the set with the disconnected BLNK signal. Totally functional other than that.
The picture is fine, but the tuner hesitates to tune (I have an Radio Shack box to distribute NTSC on channel 15 and 66) with a bit of horizontal twist for a second or two, and then it pops into place.
The S-video and composite signals work fine. I have an ATSC CECB box that I plan on using for the majority of usage, so the NTSC signals are of low impact. It will be S-video or composite input for the most part.

I don't care about the display being bordered by a bit of black. Will I damage stuff by just leaving the BLNK signal interrupted?

Thanks

via con dios
tom