I’m Back! Pilot TV37

[Chris K]

Originally Posted by Electronic M

I plan on doing the same next time I order. In addition to the Pilot I've got at least 7 other electrostatic sets I can think of...Make that 8...So I could definitely use some protection diodes.

So I can use one on the Motorola VT-71 I just obtained and plan to restore?

[Electronic M]

Originally Posted by Chris K

So I can use one on the Motorola VT-71 I just obtained and plan to restore?

Yes you can. Granted on the Motorola if you have a good original ballast (2 of my 3 setsdo IIRC) it's not needed as the ballast should provide a soft start. On a set with a modern replacement ballast the TVS diodes and a thermistor are a good idea.


On my set IIRC the vertical linearity pot was bad. If there are any mica caps in the vertical (or outside of the tuner/IF system) change them. Micas in the sweep circuits tend to be under more stress and die young. If you haven't changed off tolerance resistors in the vertical yet that's definitely something to do. If those suggestions don't help voltage measurements against the schematic may reveal the point of failure.
I did run mine up to 115V on the variac without a bulb once I had it recapped and it was fine...Granted I would ramp it over the course of a minute for safety.

Also I haven't heard of this on Pilots before, but on the Motorola's where the HV is 2-3x that of the Pilot sometimes the octal sweep sockets arc through and create problems that are challenging to diagnose if you didn't expect that possibility.

[Chris K]

Originally Posted by Electronic M

Yes you can. Granted on the Motorola if you have a good original ballast (2 of my 3 setsdo IIRC) it's not needed as the ballast should provide a soft start. On a set with a modern replacement ballast the TVS diodes and a thermistor are a good idea.


On my set IIRC the vertical linearity pot was bad. If there are any mica caps in the vertical (or outside of the tuner/IF system) change them. Micas in the sweep circuits tend to be under more stress and die young. If you haven't changed off tolerance resistors in the vertical yet that's definitely something to do. If those suggestions don't help voltage measurements against the schematic may reveal the point of failure.
I did run mine up to 115V on the variac without a bulb once I had it recapped and it was fine...Granted I would ramp it over the course of a minute for safety. Also I haven't heard of this on Pilots before, but on the Motorola's where the HV is 2-3x that of the Pilot sometimes the octal sweep sockets arc through and create problems that are challenging to diagnose if you didn't expect that possibility.

Thank you Tom. I've changed all of the caps in the set except for the little "pea pod" ones that are all over the place and a couple of HV ceramic caps. I've changed about 20% of the resistors but there are more out of tolerance resistors all over the place. There are a couple of 3kV 300 pf ceramics in and around the HV and vertical circuit that look burned and they'll have to go I guess. I don't see any mica dominos but, that's the only kind of mica capacitor I know how to identify. Are the pea pods micas? I've seen other restoration vids on these sets where these were replaced with modern mica capacitors.

[Chris K]

Originally Posted by Electronic M

Yes you can. Granted on the Motorola if you have a good original ballast (2 of my 3 setsdo IIRC) it's not needed as the ballast should provide a soft start. On a set with a modern replacement ballast the TVS diodes and a thermistor are a good idea.


On my set IIRC the vertical linearity pot was bad. If there are any mica caps in the vertical (or outside of the tuner/IF system) change them. Micas in the sweep circuits tend to be under more stress and die young. If you haven't changed off tolerance resistors in the vertical yet that's definitely something to do. If those suggestions don't help voltage measurements against the schematic may reveal the point of failure.
I did run mine up to 115V on the variac without a bulb once I had it recapped and it was fine...Granted I would ramp it over the course of a minute for safety.

Also I haven't heard of this on Pilots before, but on the Motorola's where the HV is 2-3x that of the Pilot sometimes the octal sweep sockets arc through and create problems that are challenging to diagnose if you didn't expect that possibility.

Here's what it looks like at this point. Tom, these little capacitors I described as pea pods, do you know if they're mica?

[jr_tech]

Could you post a photo of a “pea pod” cap, please?

jr

[Electronic M]

Originally Posted by jr_tech

Could you post a photo of a “pea pod” cap, please?

jr

Yeah. I don't remember anything of that description. A pic might fire some neurons.

[Chris K]

Originally Posted by jr_tech

Could you post a photo of a “pea pod” cap, please?

jr

Here you go

[jr_tech]

Ah! the “dogbone” caps are ceramic, and mostly last forever.

jr

[Chris K]

Originally Posted by jr_tech

Ah! the “dogbone” caps are ceramic, and mostly last forever.

jr

Good to know. Just ordered a complete complement of resistors. Will replace every one of them regardless of measured value. I’m going to get a full set of new tubes as well…just to be sure.