I’m Back! Pilot TV37

[Chris K]

Originally Posted by Electronic M

I did one earlier this year. I need to get a set of the ships wheel knobs, and add the CRT heater protection diode (been variacing it as a protection).

If yours is like mine you'll need to change about %90 of the resistors along with the caps to get good stable operation.

When you have the time, can you fill me in on your CRT protecting diode setup? I've been using the Variac as well.

[Electronic M]

Originally Posted by Chris K

When you have the time, can you fill me in on your CRT protecting diode setup? I've been using the Variac as well.

I can't take credit for the idea, but I do plan to take advantage of the idea next time I place a bulk order at mouser. The idea is basically that an 8.2V TVS diode (think 2 zeners in anti-series) clips AC peaks such that it regulates at 6.3V RMS. Read more here. antiqueradios.com/forums/viewtopic.php?f=3&t=409631&p=3499255&hilit=Pilot+T VS+diode#p3499255

[Chris K]

Originally Posted by Electronic M

I can't take credit for the idea, but I do plan to take advantage of the idea next time I place a bulk order at mouser. The idea is basically that an 8.2V TVS diode (think 2 zeners in anti-series) clips AC peaks such that it regulates at 6.3V RMS. Read more here. antiqueradios.com/forums/viewtopic.php?f=3&t=409631&p=3499255&hilit=Pilot+T VS+diode#p3499255

Just ordered 10 1.5KE8.2CA "fuse diodes" from Mouser. Figure I'll be able to find a stock useful.

[Electronic M]

Originally Posted by Chris K

Just ordered 10 1.5KE8.2CA "fuse diodes" from Mouser. Figure I'll be able to find a stock useful.

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.

[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?

[Chris K]

For any guru out there! I have a raster and I have full horizontal deflection but very little vertical deflection. I'm still a bit shy about running this on a straight 117V out of my Variac so I have it through a 300 watt bulb still. The vertical size adjustment has no effect on the 1 inch high vertical image. I need to do some troubleshooting on the vertical centering pot. I got what felt like a nasty 117V AC shock when I moved it. The pot is just below the AC male socket on the chassis. Don't know what's going on there. I'll need to look at the vertical deflection circuit in the schematic but does anyone have any off the top of the head ideas what might be wrong with this?...other than a lousy pot! I checked all of the pots for ohm values and they all seemed to be ok but maybe I missed something.

[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.

[jr_tech]

Originally Posted by Chris K

I need to do some troubleshooting on the vertical centering pot. I got what felt like a nasty 117V AC shock when I moved it. The pot is just below the AC male socket on the chassis. Don't know what's going on there. I'll need to look at the vertical deflection circuit in the schematic but does anyone have any off the top of the head ideas what might be wrong with this?...other than a lousy pot! I checked all of the pots for ohm values and they all seemed to be ok but maybe I missed something.

The centering pots are elevated to deflection plate potential (about 2 kV)...is the vertical centering pot missing its insulting “knob” ?

jr

[Chris K]

Originally Posted by jr_tech

The centering pots are elevated to deflection plate potential (about 2 kV)...is the vertical centering pot missing its insulting “knob” ?

jr

Here are some pictures of the "situation"! The knob does have 2 metal tabs on it that hold it to the sleve that mounts on the pot shaft. Touching that is how I got zapped but I doubt it was a 2kV shock. Felt like your typical 120v AC wall outlet shock.

[jr_tech]

Originally Posted by Chris K

Here are some pictures of the "situation"! The knob does have 2 metal tabs on it that hold it to the sleve that mounts on the pot shaft. Touching that is how I got zapped but I doubt it was a 2kV shock. Felt like your typical 120v AC wall outlet shock.

The 3 pots that are insulated from the chassis are likely elevated to HV...avoid the tabs on the insulated “knobs”.

jr

[Electronic M]

Originally Posted by jr_tech

The 3 pots that are insulated from the chassis are likely elevated to HV...avoid the tabs on the insulated “knobs”.

jr

+1. They're intended to be adjusted through holes in the back with a flat edge screwdriver... I'd use an insulated flat edge driver to adjust them.

[Chris K]

Originally Posted by Electronic M

+1. They're intended to be adjusted through holes in the back with a flat edge screwdriver... I'd use an insulated flat edge driver to adjust them.

I have been since the zap!

[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