Are These Circuit Traces Bad

[Findm-Keepm]

What are the original part numbers? 121-868's are TO-202, not what you have installed in the set (TO-5's, probably 121-775 or 121-777s, IIRC). Zenith made a mod kit that modded the video outputs to the 868's. You seem to have received the replacements for the 868s, but without going through the mod. Were 868's what you ordered? With the original number, I can look up the mod kit for you. The mod kit has the 121-868 transistor, the proper heatsink and that gooey heat sink compound. The sams I have lists the 868s, but not the original part numbers, you have to get that directly off the transistors.

If your set is operating ok, there is no need to do the mod.

Cheers,

[TinCanAlley]

Originally Posted by Findm-Keepm

What are the original part numbers? 121-868's are TO-202, not what you have installed in the set (TO-5's, probably 121-775 or 121-777s, IIRC). Zenith made a mod kit that modded the video outputs to the 868's. You seem to have received the replacements for the 868s, but without going through the mod. Were 868's what you ordered? With the original number, I can look up the mod kit for you. The mod kit has the 121-868 transistor, the proper heatsink and that gooey heat sink compound. The sams I have lists the 868s, but not the original part numbers, you have to get that directly off the transistors.

If your set is operating ok, there is no need to do the mod.

Cheers,

Oh yeah, she working fine. I've just been trying to stock up on some parts so in the future I can handle anything that comes my way. I've been trying to get my hands of this TV for years and now that I finally have one, she's staying with me for a long time.

I'll be opening her up on Monday or Wednesday and I'll pull the sink off of one and get the number.

Now I could use a little assistance. Do you know how to increase the brightness range? I've done the adjustment of the brightness limiter and it's dead on. Only thing is, I have to crank the brightness almost all the way up to get it to where it's enough. I've never had a set where there was so little headroom to go higher and I don't think the limiter I set is the issue. I'm thinking I may need to crank up the G2s a little more?

Anyway, thanks for the input. I figure if the transistors for the outputs are working, and the replacements aren't actually going to make an improvement worth the effort, I'll just be patient and find OEMs of the current ones.

[TinCanAlley]

Originally Posted by Findm-Keepm

What are the original part numbers? 121-868's are TO-202, not what you have installed in the set (TO-5's, probably 121-775 or 121-777s, IIRC). Zenith made a mod kit that modded the video outputs to the 868's. You seem to have received the replacements for the 868s, but without going through the mod. Were 868's what you ordered? With the original number, I can look up the mod kit for you. The mod kit has the 121-868 transistor, the proper heatsink and that gooey heat sink compound. The sams I have lists the 868s, but not the original part numbers, you have to get that directly off the transistors.

If your set is operating ok, there is no need to do the mod.

Cheers,

Looks like what's installed are the 121-743 transistors. Do you know which are newer/better?

[Findm-Keepm]

Originally Posted by TinCanAlley

Looks like what's installed are the 121-743 transistors. Do you know which are newer/better?

Are the installed ones bad? If so, then you'll need the kit - I'll have to look them up in my looseleaf Zenith parts guide from 1980.

If they are good, and you want spares for the future, you'll also need the kit.

How did you get 121-868 from 121-743? Sams? A bit of advice - Sams is pretty broad with part numbers vs actual parts. I've got a Sams for a Packard Bell 19" Solid State set that has the same part number for every transistor in the sweep circuits - Wrong! The lesson is this - if it works, let it be. If you need parts, always quote the original part number, and never from Sams. If you had the Zenith CM (service manual), maybe, but never quote part numbers from Sams. Also, post the part numbers here in the forum (classifieds are best) to see what can be had for postage. As Sandy says, we may have a screw loose for wanting to preserve these old TVs, but we have each other's back nonetheless.

I'll report back tomorrow with the replacement info from Zenith.

Cheers,

[TinCanAlley]

Originally Posted by Findm-Keepm

Are the installed ones bad? If so, then you'll need the kit - I'll have to look them up in my looseleaf Zenith parts guide from 1980.

If they are good, and you want spares for the future, you'll also need the kit.

How did you get 121-868 from 121-743? Sams? A bit of advice - Sams is pretty broad with part numbers vs actual parts. I've got a Sams for a Packard Bell 19" Solid State set that has the same part number for every transistor in the sweep circuits - Wrong! The lesson is this - if it works, let it be. If you need parts, always quote the original part number, and never from Sams. If you had the Zenith CM (service manual), maybe, but never quote part numbers from Sams. Also, post the part numbers here in the forum (classifieds are best) to see what can be had for postage. As Sandy says, we may have a screw loose for wanting to preserve these old TVs, but we have each other's back nonetheless.

I'll report back tomorrow with the replacement info from Zenith.

Cheers,

Just wanted spares. And yes, I went by Sams. So far it hasn't been wrong except for the three video output transistors. So I have three of the 868s, but no sinks, etc. Not a huge deal as the current ones seem to be fine.