Motorola roundie

[timmy]

Can a 3.58 xtal be paralleled temporarily with the old to see if the old one is bad ?

[Yamamaya42]

Originally Posted by timmy

Can a 3.58 xtal be paralleled temporarily with the old to see if the old one is bad ?

https://img.freepik.com/premium-vect...544.jpg?w=2000


The chances of this being related to the crystal are pretty much none whatsoever.

It works or or does not, you can not put 2 in place that won't work.

You are looking for something that changes state from cold vs warm/ hot.

[timmy]

Then obviously that would be a possible tube or probably a resistor for sure I just wish I can find it because all the resistors are checking perfect or less then the rating. It’s frustrating

[Yamamaya42]

Originally Posted by timmy

Then obviously that would be a possible tube or probably a resistor for sure I just wish I can find it because all the resistors are checking perfect or less then the rating. It’s frustrating

less? that may also be a sign.

I would use this...

https://www.allaboutcircuits.com/too...de-calculator/

and test on the 5% scale and be suspect of anything that does not fall within that 5% range.

[old_tv_nut]

Originally Posted by timmy

Then obviously that would be a possible tube or probably a resistor for sure I just wish I can find it because all the resistors are checking perfect or less then the rating. It’s frustrating

Are you checkig the resistors while they are still connected in the circuit? This will generally result in a lower reading because of parallel current paths.

[timmy]

Some I checked in circuit but the ones that showed less I mean 100k showing 97k so it’s not much.

[bhegges]

I fought an issue with high HOT current, I had checked all of the resistors and they measured good. Finally I started shotgun replacing resistors in the horizonal circuit, each pulled resistor measured good until ultimately had a resistor break apart as soon as I clipped the first lead. The resistor either failed after I measured it or the fact that it easily broke maybe it only was failing under load and somehow measured good.

You could go back and re-measure resistors paying extra attention to visually suspect resistors. Also as others noted pay attention to parallel resistors; with the way some of the B+ is feed to multiple circuits there could be a lot of resistors in parallel. Worst case you can pull a lead to measure, of course then you are 50% towards just replacing the resistor.

[Alex KL-1]

Indeed some faults are frustrating to find.

Just now, I'm fighting (I will, when I have proper time) with a issue with vertical of my Telefunken delta-gun TV. Very irritating, since this occurs only sometimes, and is heat related: this not occurs when TV is cold, and most times not occurs when is hot. Most time only occurs with thermal transition (when warming) so I donb't have much time window to play with
Then, I need some clear time to try to find the culprit, but certainly has a culprit. I need to study well the schematic, for not shotgunning every related part, but the bhegges idea sounds very good now...

Is curious that this defect ocurred 6 months ago, vanished, and returned now, go figure...

[Electronic M]

Back in the day TV techs used to find thermally dependent faults with freeze spray. Get some canned air or that old radio shack tuner cleaner that is basically oil that comes out of the can frozen and with the set on and the chassis jigged so you can access everything in the circuit with it running hit every component in the offending circuit a few at a time once warm and see which component when chilled puts it back to the cold operation state, once you find a region of the circuit that effects it narrow your chilling until you isolate the exact part that's causing it.

[old_coot88]

We used to keep a movers blanket to throw over a set to hasten warm-up (not unattended of course), then go in with the targeted Freez Spray. You could probably use a hair dryer for a quick warm-up too. Don't any of the supply houses still carry the spray?

[Yamamaya42]

yop, you can still find it, we use it all the time @ work.
https://www.amazon.com/Vaxxen-Labs-I...s%2C123&sr=8-2

[timmy]

Well I can’t use freez spray because it’s at the point that the color don’t sync at all now

[old_tv_nut]

I'm not going to reread the whole thread, but did you replace tubes or not?

[timmy]

Originally Posted by old_tv_nut

I'm not going to reread the whole thread, but did you replace tubes or not?

Originally I did when the set was done and I since checked the tubes for the section for the color

[Yamamaya42]

Once again, you will be likely finding yourself up the creek without a paddle here (an oscilloscope), with very little to guide you in the right direction, for all you know, the IF could be acting up again, and annihilating the color sync information before it can be processed.

A good start that is IF you had a scope, would be to check the beat pattern going into V22, chroma phase detector, fed from the burst amp, this is what locks in the ref osc.