Restoration Commences on 1947 RCA Victor 721TCS

[stuben]

I just brought home a Crosley 9-408 tv that is all original with no repairs having been previously done. It looks nearly new especially the underside with it's numerous paper/wax capacitors. All the tubes are RCA with date codes ranging from the 11th-22nd week of 1948 with the exception of the two 5U4G's which are Sylvania.

I powered it up on a dimbulb tester with a 250 watt heat lamp and it passed that test. I also have an early RCA 630 TS that I electronically restored with the ever popular "shotgun" method of replacing all the Paper/wax caps and re-stuffing all the electrolytic caps. The set has been working quite well now for four years. While on the dimbulb tester I monitored the current draw with a kill a watt. The Crosley drew only a few watts less than the RCA.

The previous owner said the set worked and provided photographic proof. This mans father is a retired tv tech that fixed old tv's he is nearly 90.

I cautiously powered the set up on a power conditioner for a computer at a line voltage of 120 volts. I also hooked it up to a dvd player and applied a signal. After about 15 seconds I got a raster and after some fiddling with the brightness, horizontal, vertical and contrast I got horizontal and vertical sync and after a minute or so a fairly stable picture that looked quite good! Current draw was 295 watts, about 5 watts less than my RCA. I did not leave the set to run for more than a few minutes fearing that something might give out.

I was quite amazed that this was even possible! All the capacitors, resistors and even wiring looks nearly new. The resistors under the 1B3 have only a little dust and no carbon build up on them. I could even read the color bands easily after brushing the dust away. This set seems to have very few hours on it.

Unfortunately I don't have any tools for trouble shooting radio and tv other than a DMM which can measure resistance, capacitance, inductance, frequency and diode test. I do have a good digital soldering station.

The one job I enjoy the least is re-stuffing the electrolytic cans! After reading much of this thread I am convinced that it may not always be necessary.

Any suggestions? I will try to post some pictures of my set soon.

Thanks in advance!

Paul D.

[Penthode]

I want to emphasize that I never power up electronic equipment of this age without first doing a full electronic assessment. As with the RCA 721TS, I assessed each electrolytic individually by isolating each electrolytic and reforming the dielectric.

I apply a power supply current limited to 10mA maximum and wait until the full rated voltage is met with less than 1 mA leakage. I typically aim for less than 500 uA. If the leakage after a day or so is 1 mA or higher, the capacitor will be replaced/ restuffed.

The 721TS electrolytics all showed leakage well under 500 uA at full rated voltage and tested correct capacity within 10%. I will say that surprised me. But with my six RCA TVs from the late 40's, I have only had to restuff/ replace three electrolytic cans in total.

The problem is suddenly powering them up after a long dormant period without reforming will place undue stress. But I would be game to monitor current leakage over say a week of full rated voltage to see if they survive and if so, I would not hesitate in leaving them in place.

My 721TS has been running on the capacitors for two years now with no sign of failing despite warnings from others.