Recently Acquired 1969 Motorola Color Tube Tv

[old_tv_nut]

It's more likely that the meter is not measuring it properly than the capacitance is 10 times larger. Can you post the schematic?

[old_tv_nut]

Found these 15 uF NP caps, you could use two in parallel if you can't find 30uF.

https://www.amazon.com/15uF-100V-Cap...s%2C141&sr=8-6

[old_tv_nut]

You are not likely to find 30 uF these days, but standard value 33 uF is readily available:

https://www.parts-express.com/33uF-1...350?quantity=1

[old_tv_nut]

Note the 33 uF cap I found is 10% tolerance, so will satisfy the 30 uF 20% requirement.

[Dave A]

Wayne, I found these same 15mf and used one for a 25mf cap in a CTC3 convergence box for my 21CT55. I may now add one to get to 30mf to be above but closer to the RCA 25mf. Nice discussion on NP caps.

[Lain94]

Originally Posted by old_tv_nut

It's more likely that the meter is not measuring it properly than the capacitance is 10 times larger. Can you post the schematic?

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

Here is a snapshot of where the cap is on the schematic. I managed to find a cap that is nonpolar and is 33uf and 25V with the necessary tolerance. Digikey has a FEW nonpolar electrolytic but not a ton sadly.

Also another unrelated question, i noticed both light bulbs for the tuners are 6.3v incandescent. You can buy 6.3V LED bulbs that are supposed to be drop in replacements. They seem to be popular with pinball machine restorers. Would this be safe to do despite the LEDs likely drawing far less current than the old bulb? I would prefer to switch them to LED to eliminate frequent replacing and for more brightness on the tuner controls

[Electronic M]

In transformer sets you can. It's not really necessary for bulb longevity though....The incandescent bulbs in there probably lasted 15-20 years of heavy service before they failed. I've got a 71 Zenith that I ran daily for 10 years of heavy use and the dial bulb has yet to be changed during my ownership.

This last part is more personal preference, but I can't stand LEDs in vintage gear. The color temperature, brightness and light pattern are all wrong and it looks garishly unoriginal...The only times LEDs are an advantage are when the material around the lamp likes to melt from bulb heat or if a power transformer in a radio is overstressed and you're doing everything you can (like installing SS rectifiers where the tube rectifier was).

[Lain94]

Originally Posted by Electronic M

In transformer sets you can. It's not really necessary for bulb longevity though....The incandescent bulbs in there probably lasted 15-20 years of heavy service before they failed. I've got a 71 Zenith that I ran daily for 10 years of heavy use and the dial bulb has yet to be changed during my ownership.

This last part is more personal preference, but I can't stand LEDs in vintage gear. The color temperature, brightness and light pattern are all wrong and it looks garishly unoriginal...The only times LEDs are an advantage are when the material around the lamp likes to melt from bulb heat or if a power transformer in a radio is overstressed and you're doing everything you can (like installing SS rectifiers where the tube rectifier was).

Silly question but how will I know if my tv is a transformer set? I do know that the tv has a power transformer in it. But the chassis is ground. CRT aquadag discharges to the chassis as well.

[Electronic M]

Originally Posted by Lain94

Silly question but how will I know if my tv is a transformer set? I do know that the tv has a power transformer in it. But the chassis is ground. CRT aquadag discharges to the chassis as well.

Looking at the schematic is the best way. Some sets were hot chassis and had a transformer. One of Zenith's first FM stereo tube table radios had a heater transformer but directly rectified AC and tied one leg of the AC to chassis. Some TVs had a transformer for B+, but series heaters tied directly to incoming AC with one lead going to the chassis...

If B+ and heater are derived from a power transformer you've got a pure transformer set, otherwise you have a hot chassis set with or without a power transformer.

Also some transformer chassis sets can develop shorts that make the chassis hot...That's something to beware of too...I had a TV repair isolation transformer primary to secondary short on me....I didn't realize till I got shocked...the fun way to find out!

[Lain94]

Originally Posted by Electronic M

Looking at the schematic is the best way. Some sets were hot chassis and had a transformer. One of Zenith's first FM stereo tube table radios had a heater transformer but directly rectified AC and tied one leg of the AC to chassis. Some TVs had a transformer for B+, but series heaters tied directly to incoming AC with one lead going to the chassis...

If B+ and heater are derived from a power transformer you've got a pure transformer set, otherwise you have a hot chassis set with or without a power transformer.

Also some transformer chassis sets can develop shorts that make the chassis hot...That's something to beware of too...I had a TV repair isolation transformer primary to secondary short on me....I didn't realize till I got shocked...the fun way to find out!

After looking at the schematic and the tubes on the schematic. It looks like the B+ voltage comes from the transformer but the heater voltage does not. I guess that answers my question lol. Luckily I have not been shocked by anything yet, well other than a can cap early on.

[Yamamaya42]

Originally Posted by Lain94

After looking at the schematic and the tubes on the schematic. It looks like the B+ voltage comes from the transformer but the heater voltage does not. I guess that answers my question lol. Luckily I have not been shocked by anything yet, well other than a can cap early on.

If you have not been shocked yet, then you have not been working with tube stuff long enough!

My finger still has not fully healed from the last shock I got and the reaction pulling back! :O

[Lain94]

Status update:

All paper oil, wax paper, and electrolytic capacitors have successfully been replaced and correctly installed. The small exception being two low voltage electrolytic I overlooked on the pincushion circuit board, the third one I had replaced awhile back leading up to the horizontal oscillator frequency issue being solved.

I had taken the entire set apart and did a thorough examination of every wire and solder joint as I went along with the last major round of recapping. Performance has been improved notably with controls not causing bizarre things like effecting other things they should not be anymore.

Still fighting some minor pincushion issues notably with a bit of a curving in tendency on the left side of the image on the tv. Colors look amazing considering the emissions of the CRT and the brightness is more than ample for what I need. It does seem like a bit too bright in a sense because the dark parts of the screen that should be black are so bright that it is not making the contrast look good.

I decided to keep the NOS RCA 6GH8A tube in after using the original old motorola 6GH8A tube during my initial test run after the last recap. As I mention before the old tube had very poor emissions for the AGC part of the tube. The horizontal oscillator part of the old tube was better than AGC emissions but still very poor. The new tube makes the AGC control super sensitive compared to the old tube which necessitated me readjusting the other controls again.

Degausser still not working and no idea why, this tv does not use a thermistor or posistor but instead some sort of switch or relay.

https://imgur.com/a/9SmHDIM

[trinescope]

Motorola was good for using some sort of electromechanical thermal delay device for automatic degaussing in the tube era instead of the thermistor arrangement everyone else used.

[Lain94]

Originally Posted by trinescope

Motorola was good for using some sort of electromechanical thermal delay device for automatic degaussing in the tube era instead of the thermistor arrangement everyone else used.

Yeah and it turns out that Motorola actually invented their own unique way of degaussing their tv's using these special electromechanical switches back in the 60s. They were very innovative at the time. I am having a hard time though figuring out if it is basically a special relay and where I can order a NOS replacement. If they are a rare part I may opt for just wiring in my own little toggle switch that I can manually control at will. Anyone know anything about the degaussing switches that are on Motorola's? The degausser coil itself is fine and is not shorted or open from what I can see with my multimeter. It seems like the switch itself must have gotten stuck or failed.

[Lain94]

Found the thermal switch that is responsible for controlling the degaussing action. I removed it and measured it. Looks like it failed. It is supposed to be open when tv is off, but then when the tv heats up it is supposed to close up and short. I could hear a rattling sound inside and the ohm values seem to be all over the place. It is a "klixon" brand. It has some random numbers on it which I looked up on google but could find no info at all on this part. Not sure if it is safe to simply replace it with a manual toggle switch or button, or perhaps a generic thermistor?

The degausser is the last major thing on this tv to get working. The pincushion circuit seems to be having some minor issues with curving on the left side but that may have to do with the adjustments and controls not being properly done right.

https://imgur.com/a/EAcy3QL