Zenith H2447R 19" Porthole TV

[Crist Rigott]

Thanks Bob. Good thought. After I get it running and with the can off I'll do a temp measurement and report back. I just might need to be reminded. Then again with the can on might be a good idea. We'll see together how this method works out.

[init4fun]

This is why whenever I restuff cans I always make sure to go with 105 C rated caps rather than the 85 C rated ones , and haven't had any failures of my restuffs yet .

[Crist Rigott]

Originally Posted by init4fun

This is why whenever I restuff cans I always make sure to go with 105 C rated caps rather than the 85 C rated ones , and haven't had any failures of my restuffs yet .

Yep!

[Crist Rigott]

I did some chassis work this afternoon. I looked for a section that could complete and saw this section. R116 was a 2 part resistor of 200 ohms each rated at 3W. Also the Candohm resistor is 15K rated at 10W. It was open. Didn't really matter, it was going to get replaced anyway.
I replaced the 200 ohm 3W with 200 ohm 7W resistors and the Candohm was replaced with a 15K 50W chassis mount resistor. I used some heat sink compound between the resistor and chassis.

[Crist Rigott]

Originally Posted by bandersen

Beautiful job but one thought occurs to me. Capacitors can get warm from self heating due to internal ESR plus ripple current. Especially the main B+ filter caps. Sealing them up with hot glue and PVC isn't going to allow them to breathe much and may hasten their demise.

Originally Posted by Crist Rigott

Thanks Bob. Good thought. After I get it running and with the can off I'll do a temp measurement and report back. I just might need to be reminded. Then again with the can on might be a good idea. We'll see together how this method works out.

I checked the temps today using my HF infrared thermometer. I took a measurement when I started, then 2 hours later. Here are the results:

E-Cap - Start - 2 Hours later with Can - 2 Hours later without the can
C1 - 22C - 46.1C - 39.3C
C2 - 22C - 63.1C - 43.9C
C3 - 23C - 45.7C - 40.4C
C4 - 22C - 38.0C - 32.9C

C2 is located on the power supply chassis next to V11 6BF5 audio output tube. This tube glows brightly under normal operation and gets very hot. IIRC it measured @268 F.

It looks like the can and sleeve actually acts as a barrier to the surrounding heat of the chassis as shown by about a 3 to 5 degree difference between the can being on or off. The exception is C2 due to being close to the 6BF5.

This test wasn't very scientific but does demonstrate that enclosing them in the PVC and their cans actually proves to reduce the heat of the E-Caps. In any case, all of these E-Caps are 105C and are no where near their rated temperature.

I did a life span estimate from the Nichicon website of C2 22uf 500V E-Caps at 45C, and their life span was 131,400 hours. That's about 45 years at 8 hours a day, every day!

[Kevin Kuehn]

Originally Posted by Crist Rigott

E-Cap - Start - 2 Hours later with Can - 2 Hours later without the can
C1 - 22C - 46.1C - 49.3C
C2 - 22C - 63.1C - 43.9C
C3 - 23C - 45.7C - 40.4C
C4 - 22C - 38.0C - 32.9C

C2 is located on the power supply chassis next to V11 6BF5 audio output tube. This tube glows brightly under normal operation and gets very hot. IIRC it measured @268 F.

It looks like the can and sleeve actually acts as a barrier to the surrounding heat of the chassis as shown by about a 3 to 5 degree difference between the can being on or off. The exception is C2 due to being close to the 6BF5.

To me it looks like they all ran cooler without the can except for C1?

[Crist Rigott]

Originally Posted by Kevin Kuehn

To me it looks like they all ran cooler without the can except for C1?

Yeah, a typo. I'll correct it. It should be 39.3C.

[Kevin Kuehn]

Originally Posted by Crist Rigott

Yeah, a typo. I'll correct it. It should be 39.3C.

So I'm still not understanding why you said:

"the can and sleeve actually acts as a barrier to the surrounding heat of the chassis as shown by about a 3 to 5 degree difference between the can being on or off."

Looks like in each case they ran cooler without the can, but not by a long shot?

[tom.j.fla]

Nice! When I do a full restore I try to go the route you do. Once again nice, very nice. All the best, Tom.J

[Crist Rigott]

Originally Posted by tom.j.fla

Nice! When I do a full restore I try to go the route you do. Once again nice, very nice. All the best, Tom.J

Thank you Tom. Much appreciated.

[Crist Rigott]

I did a terminal strip located near the front of the chassis. It was pretty much self contained and consisted of just a few parts.



During the removal of the old parts, I noticed that there was that yellow CAD plating residue on parts of the terminal strip.





What I do to clean off that residue is I use CLR cut 50/50 with water. I brushed on a little with a cut down acid brush to about 1/2 inch long. I then "scrub" the area with the acid brush. Then I mop up the area with paper towels, Q-Tips, and alcohol. The residue comes off very easy this way.



I then replaced the components and cleaned off the flux, and I'm done.



Since this picture was taken, I added some more solder to the lower ground terminal.

[Crist Rigott]

Moving to the upper part of the chassis I decided to do the terminal strip near T3.
Pretty routine and nothing special to report except I had to lengthen a lead on R84 a 100 Ohm resistor. What I do is trim the one side to about 1/4 inch length. I then use some 22awg bus wire and attach it to the trimmed lead using the coil method. I then figure out how long the lead needs to be and slide a piece of 1/16 inch heat shrink tubing down to the coil. I then shrink the tubing and then use a 1/4 inch long piece of 1/8 heat shrink tubing to cover up the coil.

[Crist Rigott]

Did some work around V9. Here are the before and after pictures.





And some around V14.





And an over all picture of my progress.

[Electronic M]

UHF channel strips were available for these tuners and IIRC were more common than UHF converters/outboard tuners with these sets. Watch a youtube video of an old Zenith film 'Fog Over Portland' for an interesting look at Zenith's UHF preparations.

[Crist Rigott]

Originally Posted by Electronic M

UHF channel strips were available for these tuners and IIRC were more common than UHF converters/outboard tuners with these sets. Watch a youtube video of an old Zenith film 'Fog Over Portland' for an interesting look at Zenith's UHF preparations.

Good video.