RCA 8CP41 Recent Find
 

Just bought home a 8CP41 projection set. Thought it was neat enough to justify the size/weight. A few questions.

The 5TP4 tests really well, I guess it wasn't used much. It's got an external coating that's flaking. The datasheet calls for dag down to the base of the neck, but a non conductive coating on the rest of the bell. What's should be used for the non conductive coating? Regular spray paint?


For the HV doorknob capacitors, what's an acceptable modern day substitute? Ceramic? I'm somehow missing one of five.

Contact the tv museum to see if someone can give tech advice. The guy that works on a lot of zenith tvs in Midwest I would try to ask questions. That guy works on all types of stuff..

Not long ago I seen NOS doorknobs for sale, and there was a nice selection. I don't remember where it was though. Ebay perhaps.

Does anyone happen to have the RCA service literature? I believe it should be in volume 4 of the red book. The SAMS has some discrepancies and error/typos. I didn't see anything avaliable online, but may have missed it

I was able to get the mirror recoated. Intresting in that it was an aluminum mirror, not silver. Not sure if it was recoated previously or if it was the original coating.

The set looks largely untouched underneath and I've started to work though it.

Sams is available on the ETF website. You can download entire RCA service manuals by the year on World Radio History.com

https://www.earlytelevision.org/pdf/..._sams_90-9.pdf

I looked but couldn't find it.
https://www.worldradiohistory.com/BO...kshelf-RCA.htm

It should also be in Riders

I think its in volume IV.

https://www.worldradiohistory.com/AR...948-Vol-IV.pdf

They're still out there.

What does that have to do with an RCA projection TV?

You can probably scavenge a doorknob cap from any early B&W TV. They all seem to use 20kV 500pF doorknob caps.

Been a year since I had to, but I was able to buy new production doorknobs off mouser. All are spendy and some are metric and you may need to use coupling nuts or 1/4" metal tubing and a long screw down the middle to make everything mount properly. Not something I do unless the original is shot or I'm working on an early color where the flyback is worth more than the caps and about 1000x harder to find.

Doorknob caps are still being made, but they are pretty expensive. Here is a 500 pf/30 kV unit from DigiKey:

https://www.digikey.com/en/products/...0DKT50/2687057

Thanks all for pointing me to the online service data, volume 4 does indeed have both chassis revisions. That'll be helpful for some of the larger resistors

As for the doorknob caps, I can probably scrounge at least 1 off of another chassis, but not sure on the condition of the rest of them. (Choosing to believe that they're all good for now) Still not sure why one was pulled/missing.

A few other questions:
The "lid" mirror probably needs to be resurfaced/replaced. I was talking with a few mirror places, and no one locally has first surface mirrors. I've been debating on whether a normal mirror might suffice, if anyone has any input. (Obviously there are drawbacks, but not sure how much impact they have)

I assume water/soap is ok to use to clean the screen? The backside is filthy.

Also, any special caution with this set's HV unit? I noticed the tripler, and am assuming it's about the same as getting bit by a color set? (Plus a few kV) Just want to make sure I'm not missing anything

You really do need a front surface mirror. Get it working and evaluate the results with what you have.


Are you referring to the fresnel lens screen? Yes, you can clean that with water and soap.

It's around 28,000 volts so be careful.

One thing you could do is if you can find a parts 80s-2000s rear projection TV those usually had front surface mirrors... Might need to be cut down by a glass shop.