a real challange?

[Penthode]

I viewed the YouTube video and you either have an IF alignment problem or a problem in the video amplifier (open peaking coil). The black streaking suggests the phase response is very bad.

Stagger tuned stages are optimised for both correct phase and frequency response. It is essential that the manufacturers alignment instruction be followed to the letter.

But I must ask, do you understand the concept of the split sound design and vestigial sideband demodulation? Because unless you do, you will continue to go around in circles.

[Yamamaya42]

Originally Posted by Penthode

I viewed the YouTube video and you either have an IF alignment problem or a problem in the video amplifier (open peaking coil). The black streaking suggests the phase response is very bad.

Stagger tuned stages are optimised for both correct phase and frequency response. It is essential that the manufacturers alignment instruction be followed to the letter.

But I must ask, do you understand the concept of the split sound design and vestigial sideband demodulation? Because unless you do, you will continue to go around in circles.

There are 6 peaking coils after the video det, all check good resistance wise.

as was mentioned earlier the 1st IF coil L9 was broken and is new, and thus the hunt for a stable freq generator
have not had a chance to try to adjust it again.

Also, as someone said who has worked on these things, "the 4 720 pf coupling capacitors in the picture IF section can be troublesome."

if adjusting L9 does not help much, they are next

[Electronic M]

Originally Posted by Yamamaya42

There are 6 peaking coils after the video det, all check good resistance wise.

as was mentioned earlier the 1st IF coil L9 was broken and is new, and thus the hunt for a stable freq generator
have not had a chance to try to adjust it again.

Also, as someone said who has worked on these things, "the 4 720 pf coupling capacitors in the picture IF section can be troublesome."

if adjusting L9 does not help much, they are next

Those micas are known to be an issue in RCA sets and usually result in a totally dead or hopelessly oscillating IF. I suspect they are not the problem your looking for, but if you are aligning the IF anyway there's no harm in changing them.

[Kevin Kuehn]

Originally Posted by Yamamaya42

as was mentioned earlier the 1st IF coil L9 was broken and is new, and thus the hunt for a stable freq generator
have not had a chance to try to adjust it again.

Was that 43pf cap shown in parallel with the trap side of that 1st IF external to the old transformer? There is no dotted line shown around it on the Sams schematic, so I assume it was located outside the IF can. If by chance it was internal to the replacement you would now have twice the rated capacity. But you probably would have caught that.

[JohnCT]

Originally Posted by Yamamaya42

There are 6 peaking coils after the video det, all check good resistance wise.

Let me bore you with a story regarding peaking coils:

Back when I was just starting out in the family business, I had a Sylvania D series (hybrid) that had a color problem. I knew enough at that point to know the 3.58 osc wasn't running, but couldn't figure out why.

Dad put my older brother on it and within about 10 minutes he showed me a peaking coil and said to change it. I smirked and told him it wasn't the problem because the resistance was the same as the others just like it in the circuit. He explained that it probably had a shorted turn which would have little to no effect on the resistance, but a shorted turn would essentially turn it from a coil to a resistor.

Well, he was right. That was my first experience in magnetics. That was a good lesson, one I never forgot.

Probably not the problem here, but just to point out that normal resistance on coils only proves there's no broken wire inside.

John

[Yamamaya42]

Originally Posted by Kevin Kuehn

Was that 43pf cap shown in parallel with the trap side of that 1st IF external to the old transformer? There is no dotted line shown around it on the Sams schematic, so I assume it was located outside the IF can. If by chance it was internal to the replacement you would now have twice the rated capacity. But you probably would have caught that.

there was no can per-sey
it was all wax-paper
https://i.imgur.com/hRDLbIF.jpg
with the trap coil over the internal coil.

the new one is slightly different
both are in a metal can, with both coils on one central paper core, the trap wound above the RF one, both tuned the same way, and the trap coil did have a cap in parallel on it.

sort of like this
https://www.pirate-pete-electronics....dual-01_01.jpg
top coil having the cap

[Yamamaya42]

Originally Posted by JohnCT

Let me bore you with a story regarding peaking coils:

Back when I was just starting out in the family business, I had a Sylvania D series (hybrid) that had a color problem. I knew enough at that point to know the 3.58 osc wasn't running, but couldn't figure out why.

Dad put my older brother on it and within about 10 minutes he showed me a peaking coil and said to change it. I smirked and told him it wasn't the problem because the resistance was the same as the others just like it in the circuit. He explained that it probably had a shorted turn which would have little to no effect on the resistance, but a shorted turn would essentially turn it from a coil to a resistor.

Well, he was right. That was my first experience in magnetics. That was a good lesson, one I never forgot.

Probably not the problem here, but just to point out that normal resistance on coils only proves there's no broken wire inside.

John

well those coils a pretty much unobtainium,
you would be lucky to find 1, let alone all 6.

and the resistance does seem to check out with what is shown on the 630ts service guide. :O

[JohnCT]

Originally Posted by Yamamaya42

and the resistance does seem to check out with what is shown on the 630ts service guide. :O

Yes, but if one turn shorts out to an adjacent turn, it will have no measurable effect on the resistance you read with a meter. But what happens with a shorted turn is that one single shorted turn kills the Q of the coil. At that point, an 8 ohm peaking coil becomes an 8 ohm resistor.

Again, unlikely that's your problem, but I was just pointing out that a single shorted turn can't be read with an ohmmeter.

That's why ringers were so popular with TV techs. A shorted turn in a flyback, yoke, vertical output transformer, etc. won't show up in a resistance check, but will in a ringing test.

I bought an LC75 Sencore Z Meter brand new back in 1985 and still use the crap out of it. It will perform both ringing tests and test the value of any inductor as well. Smaller inductors that don't ring well on ringers can be tested for their value.

I paid $1000 for the Z-Meter back in '85, but today, we can buy these handy multi-testers for pocket change:



I know these are toys, but I couldn't resist and bought one. Just put any two or three lead part into the socket in any direction, and this toy will identify what it is, what the lead configuration is, and give you things like transistor gain, resistance in ohms, capacitance and ESR, and inductor values. These will check inductors for value but no ring test. But a shorted turn in an inductor will throw off the value. If your TV has more than one of the same part, you can compare them if the schematic doesn't identify the value of the inductor.


John

[Yamamaya42]

Originally Posted by JohnCT

Yes, but if one turn shorts out to an adjacent turn, it will have no measurable effect on the resistance you read with a meter. But what happens with a shorted turn is that one single shorted turn kills the Q of the coil. At that point, an 8 ohm peaking coil becomes an 8 ohm resistor.

Again, unlikely that's your problem, but I was just pointing out that a single shorted turn can't be read with an ohmmeter.

That's why ringers were so popular with TV techs. A shorted turn in a flyback, yoke, vertical output transformer, etc. won't show up in a resistance check, but will in a ringing test.

I bought an LC75 Sencore Z Meter brand new back in 1985 and still use the crap out of it. It will perform both ringing tests and test the value of any inductor as well. Smaller inductors that don't ring well on ringers can be tested for their value.

I paid $1000 for the Z-Meter back in '85, but today, we can buy these handy multi-testers for pocket change:



I know these are toys, but I couldn't resist and bought one. Just put any two or three lead part into the socket in any direction, and this toy will identify what it is, what the lead configuration is, and give you things like transistor gain, resistance in ohms, capacitance and ESR, and inductor values. These will check inductors for value but no ring test. But a shorted turn in an inductor will throw off the value. If your TV has more than one of the same part, you can compare them if the schematic doesn't identify the value of the inductor.


John

$1000 in 1986 money?
but that is the problem, something to really test them are VERY costly.

[JohnCT]

Originally Posted by Yamamaya42

$1000 in 1986 money?
but that is the problem, something to really test them are VERY costly.

In terms of the time it saved me in the past 35 years, it not only cost nothing but made me a small fortune. It's been in continuous use since I bought it.

But the cheap tester I linked is like $15, and will read inductors like your peaking coils for values between .01mh and 20h. It's likely not as accurate as the Z-Meter but it doesn't have to be either.

Next week I'll run some small inductors through the cheap tester and compare them to the Z-Meter and see how accurate it is. I did compare it to the Z-Meter for value and ESR on capacitors, and it was close.

John

[Yamamaya42]

OK, I attempted again to tune the 1st IF coil and this is what I found.

Following the instructions, and adjusting the “ contrast control point stated to -3v as mentioned caused NO readable voltage at point A, no matter what I did , no deflection was seen, and when a video was fed in, it was cut off completely.

Turning contrast back up to the point the picture came back, the voltage was about -1.4
Point A would then react to the RF input and I adjusted the coil.

This did not seem to help the picture much as after I was done, there seemed to be more RF noise than when I started.

So obviously there are other things wrong with the IF, most likely more bad resistors, and perhaps the bypass caps, setting it to -3v like it says in setup should not cause nothing to pass though.


Also, the black streaking seen on bright objects on the screen is NOT from the IF, as I bypassed it and fed direct video in and it was still there, but as Kevin Kuehn mentioned, it could be caused by the old test CRT and not the video circuits.

but now I must go over the IF section and look for more bad resistors, it's that ot just go direct video input :/

[Yamamaya42]

definitely more bad resistors

example, the 39 ohm cathode resistor R24 for 1st IF checked at 53 ohms, and the one for 2nd is 48 ohms.
no wonder the gain is all messed up

[JohnCT]

Originally Posted by Yamamaya42

definitely more bad resistors

example, the 39 ohm cathode resistor R24 for 1st IF checked at 53 ohms, and the one for 2nd is 48 ohms.
no wonder the gain is all messed up

In the 20% to 30% area. Don't be surprised if that has little to no effect.

John

[Yamamaya42]

I just went over the IF checking resistors , and 50% of them are over the %20 tolerance rating, by quite a lot, not sure if i should replace the coupling caps now yet or not... :/

[Yamamaya42]

Originally Posted by JohnCT

In the 20% to 30% area. Don't be surprised if that has little to no effect.

John

and I would think that the effect would be additive, if half of the resistors are %20-%40 or more out of spec, it has to have an effect on how well it works.