Recently Acquired 1969 Motorola Color Tube Tv

[Electronic M]

Originally Posted by Lain94

Ok that is a relief, and makes things way easier knowing that. Another question though. It it OK to replace an electrolytic cap in the tv with a ceramic cap as long as it has the correct mF as mentioned and same voltage or higher. Or will the ceramic cap bother the tv? For example replacing 10uf 15V electrolytic with a new small ceramic one which is 10uf and has a voltage rating of 50v?

I am asking because I have a ton of ceramic caps laying around and it so happens SOME of them seem to fit the values needed for the lower volt/low uf caps.

Based on the values it sounds like the 'ceramic' caps you have ar ceramic encased Tantalum dielectric caps.
I believe modern tantalums will sub fine for lytics, but haven't tried those in tube gear to be sure.
Ceramic dielectric caps are usually disc caps and typically aren't seen in values above 0.1uF. The old school ones that look like 30s era dog bone resistors are typically pF (aka mmf in old speak).

Paper caps shouldn't be replaced by ceramic dielectric caps as ceramics are not temperature stable and exhibit piezo electric dimensional changes in dielectric thickness and thus capacitance as voltage is applied so in some applications where they get high voltage AC waveforms they will pass them in a non-linear fashion.

[old_tv_nut]

Tantalum caps can be useful for their small size, BUT they degrade permanently and fail if they are EVER reverse biased. So, typically used only for bypassing power to ground, not as interstage coupling or waveform generating components, where the voltages on either end can rise at different rates during turn on.

Safest thing in restoring old gear is to replace electrolytics with electrolytics.

[Lain94]

I just pulled this capacitor out of the tv and I am not sure what type it is. It is definitely not an electrolytic. I can not identify it but it resembles the "black beauty" or "black cat" capacitors. Can anyone identify it?

https://imgur.com/a/KWQtDRu

[Notimetolooz]

That is a Motorola brand cap and I don't know whether it is paper of plastic film. It is a molded plastic case.
There were some caps by Sprague that looked similar. The ones with white printing were paper, the ones with red printing were plastic film.
That was a situation that was not very common where it was hard to tell from the general look.
Those could actually be made by Sprague but branded by Motorola, that kind of thing happened many times.
If you have a capacitance leakage tester that tested using hundreds of volts it would tell if the capacitor is good.
I'm pretty sure someone else may know how they are constructed.
I have cut similar caps apart but it can be hard to tell, the paper can be extremely thin and look transparent like plastic. They also can be very tightly wound.
Also from the time the TV is from they could be either one. Sometimes the SAMS parts list states if it is paper or plastic. SAMS also lists electrolytic caps separately.
With out knowing for sure, I would not replace those unless they were suspected to cause a problem.

[Electronic M]

Originally Posted by Notimetolooz

That is a Motorola brand cap and I don't know whether it is paper of plastic film. It is a molded plastic case.
There were some caps by Sprague that looked similar. The ones with white printing were paper, the ones with red printing were plastic film.
That was a situation that was not very common where it was hard to tell from the general look.
Those could actually be made by Sprague but branded by Motorola, that kind of thing happened many times.
If you have a capacitance leakage tester that tested using hundreds of volts it would tell if the capacitor is good.
I'm pretty sure someone else may know how they are constructed.
I have cut similar caps apart but it can be hard to tell, the paper can be extremely thin and look transparent like plastic. They also can be very tightly wound.
Also from the time the TV is from they could be either one. Sometimes the SAMS parts list states if it is paper or plastic. SAMS also lists electrolytic caps separately.
With out knowing for sure, I would not replace those unless they were suspected to cause a problem.

If I couldn't prove it's not paper I'd change it...$0.50 and a minute of soldering is easier than having more things to doubt after a recap when it doesn't work.

[old_tv_nut]

Originally Posted by Electronic M

If I couldn't prove it's not paper I'd change it...$0.50 and a minute of soldering is easier than having more things to doubt after a recap when it doesn't work.

Ditto.

Where was this in the circuit?

[Lain94]

Originally Posted by old_tv_nut

Ditto.

Where was this in the circuit?

The capacitor was physically on the top part of the chassis near the high voltage box. As far as the schematic goes it looks to be in the general area where the vertical output tube is and the other stuff related to the vertical.

[Electronic M]

Or just buy some 31guage wire and use the same approximate length as the original #31 fusible wire link....

[Lain94]

I just realized there were two standards SWG and AWG. Apparantly AWG is the now more commonly used one. It does not specify whether is AWG or SWG. But SWG was a british made standard and AWG is American so I am guessing AWG. I will post an update on results after replacing the burnt fuse and bad capacitors. If I am lucky the tv will fire up without issues after appropriate repairs are made.

[Lain94]

This wax paper safety cap. that blew appears to be on the AC side of the circuit. From what I read online electrolytic caps are not supposed to be put in for AC voltage. Also AC and DC voltage ratings for caps. are often different. Finally this wax paper cap. only shows the DC value and not AC value. This cap appears on the schematic as polarized but wax paper caps are not polarized caps. I am very confused yet again.

https://imgur.com/a/xBRTFcF

[Lain94]

Also for replacing that wax paper safety cap I mentioned: Would this be an acceptable replacement?

https://www.mouser.com/ProductDetail...EmAOx7Mg%3D%3D

https://media.discordapp.net/attachm...687&height=478

[Electronic M]

The original appears to be a ceramic bodied paper cap....Prior to the 80s those were common in across the line RF filter duty.

You could get away with the cap you've found (I often use normal 630V film caps), but modern standards call for a X or Y rated across the line safety cap.

AC voltage is rated in RMS which is basically set up so if you had a 120V light bulb it would reciever the same energy from 120VAC RMS as it would from 120VDC which was useful a century ago when some regions had DC power and others had AC. Peak AC voltage is the square root of 2 (or 1.414) times the RMS. Peak AC voltage (about 170V) is the max instantaneous DC voltage that the cap should normally see, but usually at least double that is used as a DC rating to provide a safety margin and help the cap run cool.
It's important to know that RMS should only be applied to sine waves...Non-sinusoidal waveforms need more complex math to get RMS values, and often don't measure accurately on most AC meters since most lack a true RMS measuring circuit.

[Lain94]

An update on the Motorola tv. I have replaced the wax paper safety cap that had blown along with the blown wire fuse. In addition I have recapped 2 additional electrolytics and what was later discovered to be a paper-oil cap. I still am going to recap any remaining paper and electrolytic caps in the tv. I have managed to get the tv back to working condition, but it appears to still need adjustments, likely convergence, color purity, and perhaps also tuning. I am suspecting perhaps a weak horizonal output tube as well since the right side of the picture is wavy sometimes.

I attached some photos to show the current status now after making the basic repairs.

https://imgur.com/a/4AimE3e

[Electronic M]

If the side is wavy that's usually AC hum on the DC rails indicating filter capacitor (or sometimes B+ doubler diode) failure.

The raster not filling the screen horizontally is potentially a sign of a weak horizontal output/damper, but could also be a sign of B+ being below spec (which could be a result of the items from the previous paragraph).

B+ voltages and tubes should be checked.

Purity and convergence aren't hard to adjust if you have the right test patterns and sufficient patience... Dynamic convergence typically requires adjusting coils. Make sure you have a plastic hex diddle stick (AKA alignment tool). Do NOT use a metal hex key. Metal keys crack the adjustible slugs easily (which is very bad), and even if you have the godlike finesse/luck not to crack them the metal tool will it's self skew the adjustment such that if you have it perfect then it will be slightly off the moment you remove the tool. These are lessons I learned the hard way on convergence don't repeat my mistakes.

[Lain94]

A bit of a minor update. I recently acquired my first CRT tester. It is a Sencore CR 161. From what I have heard online, Sencore is a trustworthy brand. After reading the instructions and manual, I quickly learned how to use the tester and began using it to test all the CRT's I have.

The one in this motorola tv is supposed to be 6.3 volts and hi bias mode. At this voltage red and green color guns were good. Blue however was on the weak side. However at 7.3 volts which would simulate what a tube brightener would do to the emissions, emissions improved for all three guns notably, and blue went solidly into the good territory.

No shorts were found for this CRT which is good to know.

While this CRT has many hours on it, I am a bit surprised that emissions seemed higher than I would have guessed based on the alleged history and heavy use of this tv over the decades (barber shop tv). I was fairly impressed.