Resistor question

[radio nut]

So far when restoring a set you replace caps and out of tolerance resistors, check tubes and fire it up and see how it goes.
Every time so far at least a couple of resistors that checked ok as far as tolerance will float out of tol. once power and load has been applied for a while.
As soon as it warms up here in Ohio....and stays warm I will be working on one of those big Rca projection sets model 9pc41 (if memory serves correct).
My Muntz tv had about 20 or so resistor change value after10 hours or so of running it.

So, Am I being stupid if I am thinking about shot gun replacing of the resistors in the projection set that has 4 chassis's and 41 tubes and assorted parts?
Yes it will already take a while to get this set close to running let alone stable.
Just wanting opinions....

[bob91343]

My usual attitude is not to fix anything that's not broken. Having said that, if you have the time and inclination, go ahead. Just realize all the chances for error and, on top of it all, most of that sort of gear was never such high grade as to merit a lot of effort to restore.

It's your call.

[Username1]

I have seen a number of tvs posted here after re-capping, and they still have problems. Some are traced to the caps, and some resistors I guess they went back and checked again..... I'm always in favor of fixing it first, restoring it second. If you fix it, it works, then you replace caps as you want, then if there was always some anomaly you were trying to fix by replacing caps, but it's still there, then maybe it's a resistor, or coil.... If you introduce an anomaly then it must be in your new part, or you may have put it back wrong.... But if you don't know if it works right, and just begin replacing caps, then when you fire it up, where are you going to look if it don't work right.... You actually have doubled the number of items that can be wrong....

With electrolytic caps being the most prone to cause loud explosions, those are really the only ones you need to change if you want to before a test fire up....

Really old resistors may not have been very stable to begin with.... Heat may have effected them over time even more than capacitors. I have seen here that people who really carefully go through their sets end up with something that looks quite nice, so you may end up changing a bunch of resistors too....

Just imagine would you know it if every part in your tv was 20% off....?

I don't know if we would.....

[Electronic M]

The thing about Muntzes is they have SO FEW parts to begin with that if they are not all pretty close to right you're going to have lots of problems. RCAs tend to be on the opposite end of the spectrum...They are so over engineered that they can preform rather well with significant component issues. My plan of attack if that RCA were mine would be to test the tubes, change the caps, see how it works, and then check resistors in any stage that is faulty.

Only resistors I sometimes hit first are PS resistors on sets that may have been powered up with shorted lytics (that can kill PS resistors pretty quick).

[N8NM]

I'm with some of the others in that I'll "shotgun" the caps and then troubleshoot and replace other parts as needed. About the only resistors I'll typically check before troubleshooting are wirewound bleeders, just because I've seen so many of those fail and odds are that I won't have replacements on-hand and have to order them.

[Phil Nelson]

Originally Posted by radio nut

thinking about shot gun replacing of the resistors in the projection set that has 4 chassis's and 41 tubes and assorted parts

With a set of that complexity I'd recap first (replace paper and electrolytic) and give it a controlled power-up to see where you stand. Shotgunning all resistors plus all of the caps means disturbing hundreds of connections. Many opportunities to miswire something or wreck a terminal, etc. For all you know, many those resistors don't need replacement and the TV won't play a bit differently if you change them. Once you have it up and running, you can do voltage checks, use an oscilloscope, inject signals, etc., to track down any remaining problems. Then you may decide to replace a few resistors, maybe a few mica caps, and so on.

Phil Nelson

[marty59]

After the normal restoration work, I've seen resistors drift too. On a Zenith I did a resistor would only drift when voltage was applied during operation, heat/cold did not affect it. Upon troubleshooting and locating the suspect, with my meter set to Ohms I immediatly checked that resistor right at power off and sure enough, drifted back to value.

You are not doing yourself any good replacing parts that will "most likely" be okay.

Gotta' have a little fun diagnosing and finding problems too you know!

[M3-SRT8]

Another problem with shotgunning resistors is that you can disturb alignment in the IF sections. Unless you can realign a set it's best to let them be until they rear their ugly head, if at all.

[Geist]

Hi All;
I would agree with most of the people here, that You do not need to replace any resistors, except for heavy or wire wound Power Supply resistors that are way out of tolerance.. Otherwise I would wait until they prove that they need to be changed.. I changed too much at a time between power ups on my RCA 630, and so now It would need to have each and ever part checked for value and for being connected correctly.. So, I would say that it is not worth it to change everything..
THANK YOU Marty

[ChrisW6ATV]

I definitely test every resistor and replace all out-of-tolerance ones as part of my "stage 1" restoration work (along with the paper and electrolytic capacitors and bad tubes).