1960 TV repair

[Tazman1966]

If you've got almost two pictures squashed one above another divided by a black bar and flickering, your vertical frequency is running at half speed. Check the resistors near the vertical hold control. The caps in the vertical oscillator may need to be very close to the correct value.

Good luck and well done so far.

[Mitch-W]

Thanks!
I also did some quick checkups yesterday of the carbon composites in the vertical section, and they were a bit high, but still in the 10-15% margin. Could the problem be somewhere downstream (B12/ECH81 or B2/PCF80)?

As I don't currently have the exact values, I did some cap value substitution. For the two 56Ks, so I wired 47K and 68K caps in parallel, so I got a 57nF cap (47+68)/2, which is an almost correct value, but it didn't solve the problem. Perhaps I also need to get the C114 and C111 spot on the value, as I used about 80% higher value ones?

I'll do more tomorrow, and of course I'll keep you posted.

[Mitch-W]

Today I checked every single resistor in the vertical section, and they are all within 10% margin. Of course I desoldered one leg every time, so I didn't got false readings. I only found a R115 that drifted about 25% above, so I replaced it.

I also got all the capacitors the exact values now, I hoped that would help. But the situation remains the same.
If I am correct, isn't the vertical frequency derived from the mains frequency?
Well, I came this far, but now I am in a dead end.

[Nicklyons2]

Is the +2 HT rail voltage correct?

What are the voltages on the Frame Output pentode screen grid and Cathode?

[Mitch-W]

I found two more resistors that drifted away, R87 (1M, got open) and R71 (120K, measured 400K). Despite replacing them, I still have the same problem.

The +2 Rail is 230V, so it is a bit high. However, this set is originally for a 220V mains, but now we have here 230V mains, so I expect a bit higher voltages.

Here are the voltages on the PCL82 frame output:
p1: 25V
p2 (cathode): 14V
p3 (grid): 5.6V (18V if measured on AC setting)
p6: 210V
p7: 137V
p8: 140V
p9: 18V if on AC setting

[Heatercathodeshort]

I think you need to check your capacitor values. It is a simple circuit but I note that you are coupling two capacitors in parallel to obtain a lower value? This will produce the total capacitance 1.15uf causing very bad problems in the frame circuit. Any chance of a off screen picture rather than a raster? John.

[Focus Diode]

Agree John, also double check the replacement values are correct.

Many years ago I was puzzled by one ended frame locking on a set. It turned out I'd fitted a 47000pF (0.047uF) replacement capacitor in place of the correct 4700pF (0.0047uF)!

Cheers,
Brian

[Mitch-W]

I triple and quadruple checked all the capacitors. I made a mistake before by parallel wiring two capacitors, so I got a 28K instead of 56K. This time I used one 47K and one 6.8K in parallel, so I got around 55K (also measured by cap. meter). I also got the 18K to exact value, and also the 27K.

But still no avail. Then I decided to check front panel, and found a broken ground wire leading to Vertical hold pot (R120). Resoldering the wire did the trick, and now I don't have annoying flicker anymore and the raster is centered. But now I have a new problem.

The image is shrunk to a letterbox format, and I can adjust it using the Vertical Height Control and Vertical Linearity (R123 and R125), but I can't do much. See the photo below.

[Heatercathodeshort]

You need to get a test card/picture on the screen before you can progress further. The display will give up it's secrets once we can see the results. Take the picture face on, level with the front of the screen. J.

[Mitch-W]

I did that. I tuned into a channel via coax. I can actually get the picture in sync, but then it's even narrower.

See the picture:

[Nicklyons2]

Check all the linearity controls actually do something?, does the height control work (even if it makes the height less. Do the controls 'meter' OK? - that is - can you measure the track across the ends as well as each end to slider? double check the values of any capacitor you've replaced (we've all had a mental block and replaced one by a factor of 10 out). Check the HT voltage on the triode section.

[Mitch-W]

Yup, the capacitors are the right values. I checked them with a capacitance meter to be sure. The linearity controls do work, but I can only make height less. The controls go from 0 ohms up to about 0.8M, so I guess they're fine.

I'll do some check-ups tomorrow, I am also planning to replace all the carbon composites in the vertical section, there are three of them, and they all drifted about 10%. HT triode check also coming up.

[Heatercathodeshort]

Almost there! The voltage on pin 9 of the PCL82 should be 60V [DC] Check R127 1.2M and C115 C116 if you have not already done so.
I know it's boring but Nick's comments are very valid. We all make mistakes and sometimes it can be due to the brain working overtime. I have been caught out a good number of times but I think your problem lies with the supply to the oscillator section pin 9 PCL82. Looks good so far. John.

[Mitch-W]

I am returning to this TV after 3 months. In this time I did a full restore of a 1965 Iskra Triglav De Luxe radio, a very nice and big radio (bigger than this 1960 TV). In that time I also obtained around 150 valves from a retired TV serviceman, that were just gathering dust. So if a valve goes, I can swap them to check.

I fixed the vertical, so it now opens up completely. It was a PEBKAC, just as Nick commented. I soldered the C118 to the wrong contact. Also, the capacitors are now all in 10% tolerances, except for the C119 which is 22n instead of 18k. I also changed the rectifiers from PY80 to proper PY82, just because I had them.

But the vertical still isn't 100%, as the bottom half of the picture is stretched down, so the people have short bodies with very long legs, and so on. It looks like there is some spacing between scanlines. Swapping the PCL82 with a new one did nothing.

[Hunts smoothing bomb]

Good work, well done!

I'm glad you got to the bottom of this, I also find that when you start pulling your hair out because you can't get to the bottom of a fault, it often pays to take a break from the set and do something else for a while, I always make sure I document what I have done in case it is a long period before I return to the restoration

As for introducing faults by making wiring errors it can happen to us all, I did exactly the same only this week while restoring a Bush PB53!

Keep up the good work

Cheers

[Mitch-W]

I got it now fixed 100%ish. The 18K capacitor had intermittent contact, so I resoldered it correctly, and now the vertical is correct. The vertical is quite solid, however I can get it to roll if I change channels.

It receives nicely, only it looks like it has alignment slightly off, as if I tune in for the best picture, the audio is a bit off then and vice versa if I tune for the best audio. But when I tune for the best audio, I also get annoying hum (hum control needs adjustment perhaps?). Also there is a very loud hum when there are scenes with a lot of white colour showing. I have it plugged in directly to a cable TV coax without any balun, even without it, I receive very clear picture - but perhaps this causes the hum issues?

Thanks

[Nicklyons2]

The 'hum' is intercarrier buzz perhaps. I would reduce the signal fed to the set until the picture just becomes slightly noisy though before I began to adjust the intercarrier area, just in case signal overload is making it worse. (thoughts of BRC 1400 here)

[Mitch-W]

I am returning to this TV after some time. I ran it for few hours few days ago, and next day the TV played well, but the signal clarity was a bit lower than the day before. The picture is a bit snowy, also there is some additional noise present, so audio isn't clear. This happens on the all channels, the signal was fed from a local cable coax (we still have some analogue CATV broadcasting) and I used a 75 to 300 ohm balun. The set has all the paper caps replaced, but I've kept all the elecrolytics since they were all good.

I've replaced the tuner valves (PCC88 and PCF80) but there was no improvement. Also I replaced the EF85 valve immediately after tuner, also no change. Any ideas?

The intercarrier buzz is still present, and I guess there is even some more. I wanted to sort this in these days, but I am not too sure which coils should I adjust.. I really don't want to throw this set even more out of alignment.

[Heatercathodeshort]

The grain shows either problems in the RF amplifier stage PCC88 or a fault on your cable supply. [unlikely] Check the aerial input socket and the isolating capacitors that may have become disconnected or damaged due to a lightning surge. Check the operation of any AGC preset control you may have [It may be O/C] and the components in the AGC line particularly any high value rsistors and decoupling capacitors. The IF amplifier looks OK by the vision noise that is usually generated in the first stage. Hope this helps. John.

[Mitch-W]

I tried it then in a few days and the picture was good. This set doesn't have an AGC adjustment, so I don't really know what was wrong.

I pulled the set out today and there was again a bit noisy picture. I measured around and found another problem. The resistors R3 and R4 (47R) were replaced at one time with a 5R1 resistors, but when I did initial measurement, I made a tenfold error and marked them as good, as they were almost exactly 10x lower resistance. They're before the PY82s rectifiers, I guess they are surge current limiters.

This is probably why I get so high B+ voltages, as they are all about 30-35V higher than specified. I am going to replace these two resistors with proper values, but I am not sure about the wattage rating of these resistors?