Motorola ts4j

[Electronic M]

Originally Posted by tom.j.fla

Best tool to find the fault will be a scope, with a isolation transformer to plug the set into. We do not want to do harm to any gear, tv, or tinkerer for that matter. Without the scope you are just making wild guesses as to what the fault is. All the best,Tom.J

Originally Posted by jr_tech

Not likely... I would recheck the wiring between the sync clipper and the vertical oscillator tube... it appears that the vertical sync pulses are not reaching the vertical oscillator. Perhaps a side by side comparison to your VT-73 would reveal an error or wrong part.
Of course, a scope would tell you in seconds if the vertical sync pulses are wrong or missing.

jr

Exactly. [starts chanting] Scope!.. Scope!.. Scope!...

One other thing you may be able to do is try injecting V sync from the VT-73 (or a B&K analyst or test pattern gen) into the VT-71. Make sure the hot chassis polarity matches before applying power or bad things could happen.

[Bill Cahill]

The high voltage caps coupling the circuits won't work right, either, if they are ceramic disc..
Those were originally .005 10 KV for vertical, and, .002 10 KV.
I may have my caps mixed up, but, I'm pretty sure on voltages on both. The cap on h. v. rectifier should be either .001, or, .005 at 10,000 volts.


I think they actually work at seven thousand volts.

[Electronic M]

Originally Posted by Bill Cahill

The high voltage caps coupling the circuits won't work right, either, if they are ceramic disc..
Those were originally .005 10 KV for vertical, and, .002 10 KV.
I may have my caps mixed up, but, I'm pretty sure on voltages on both. The cap on h. v. rectifier should be either .001, or, .005 at 10,000 volts.


I think they actually work at seven thousand volts.

Wrong. Every unrestored Moto VT-71 / VT-73 I've seen has 6KV rated HV caps, and the schematic linked above shows .001 on the H deflection plate couplings.

The HV coupling caps don't work well if ceramic (unless you increase the capacitance), but the only HV ceramics he says are in there are in the working Horizontal section....Add to that that it is a NO sync issue in the vertical (and not a sweep size/linearity issue, which is what HV cap issues would cause) and the HV caps should basically be irrelevant to the problem described.

[Bill Cahill]

Sorry. It's been a long time.