Are These Circuit Traces Bad

[DaveWM]

did you ever get anywhere on this problem? the main things to look at and check if you did not scope would be that diode and those two voltage divider resistors )100k each, think they were banded 5%

[TinCanAlley]

Originally Posted by DaveWM

did you ever get anywhere on this problem? the main things to look at and check if you did not scope would be that diode and those two voltage divider resistors )100k each, think they were banded 5%

Well getting my brother over with his scope is proving to be a major task. I don't know when he'll have the time or desire.

I did manage to find NOS OEM transistors and the blanking diode. I also got my hands on the 1K, 33K and some 100K resistors, but I have a question about the 100Ks. The original 33K is a carbon composite (I believe from its shape and brown color case). The 100Ks look like standard film. I got my hands on the 33K replacement in the composite form. My question is about the 100Ks. I was given a few that are also composite, not film. Is it okay to use the composites as replacements? The wattage is the same. In the attached pics you can see the diode, 33K and two 100Ks in one and the 1K connected to the transistor in the other pic). Those are the ones I'm looking at changing.

So with the new transistor, diode and resistors I might just go ahead and replace them all. Of course this is after I replace the blue convergence coil that seized up. I managed to find an NOS replacement and it should be here Monday at the latest.

[DaveWM]

I don't see any problem with using metal films in that location. Be aware that even new carbon comps can be way off spec, always best to test. Tube sets are a bit more tolerance specs. if its marked 5% you should check before it goes in.

Just a warning, changing those parts may have NO effect on the problem, but its the only thing that comes to mind when you talk about vert bars commonly described as jail bars. The scope would let you see it before and after (the blanking) and may be enough to tell if its the problem at all, but even that is not assured since the waveforms may not be very reliable.

If I were in your shoes I would just change it and see. keep the old parts if by some chance the replacements make things worse (I don't see it happening but never hurts).

good luck with it.

[TinCanAlley]

Originally Posted by DaveWM

I don't see any problem with using metal films in that location. Be aware that even new carbon comps can be way off spec, always best to test. Tube sets are a bit more tolerance specs. if its marked 5% you should check before it goes in.

Just a warning, changing those parts may have NO effect on the problem, but its the only thing that comes to mind when you talk about vert bars commonly described as jail bars. The scope would let you see it before and after (the blanking) and may be enough to tell if its the problem at all, but even that is not assured since the waveforms may not be very reliable.

If I were in your shoes I would just change it and see. keep the old parts if by some chance the replacements make things worse (I don't see it happening but never hurts).

good luck with it.

Okay, the diode arrived today as well as some 33Ks. The 100Ks should be here on Monday.

Since I was ordering NOS parts, I went down the list of transistors and ordered what they had so I could keep them on hand. I ordered some of the red, green and blue output transistors, but what I got doesn't match what's installed. What I have are what looks like round metal canisters with aluminum heat sinks and a plastic piece over the top to hold them and warn about the voltage. What I got as replacements are TO-202 types. These replacements might be functional replacements, but not physically. They obviously generate enough heat to need a sink, so these can't be installed or they'll overheat.

I'm attaching a pic and if you look to the right of the RGB outputs, you'll see the type of transistor they are.

[Findm-Keepm]

Originally Posted by TinCanAlley

Okay, the diode arrived today as well as some 33Ks. The 100Ks should be here on Monday.

Since I was ordering NOS parts, I went down the list of transistors and ordered what they had so I could keep them on hand. I ordered some of the red, green and blue output transistors, but what I got doesn't match what's installed. What I have are what looks like round metal canisters with aluminum heat sinks and a plastic piece over the top to hold them and warn about the voltage. What I got as replacements are TO-202 types. These replacements might be functional replacements, but not physically. They obviously generate enough heat to need a sink, so these can't be installed or they'll overheat.

I'm attaching a pic and if you look to the right of the RGB outputs, you'll see the type of transistor they are.

Aw geez, here we go again - part numbers, please? Original vs replacements.

And "replacements" - do you mean ECG/NTE or Zenith? You have to be a bit more specific to help some of us help you.

Cheers,

[TinCanAlley]

Originally Posted by Findm-Keepm

Aw geez, here we go again - part numbers, please? Original vs replacements.

And "replacements" - do you mean ECG/NTE or Zenith? You have to be a bit more specific to help some of us help you.

Cheers,

They are 121-868 and NOS Zenith parts. I was more telling DaveWM about it than asking anyone to fix something for me.

[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,