View Full Version : Rca 8t241


DavGoodlin
06-05-2012, 08:46 AM
Picked this up last week.
174761
The model has a KCS28 (sams 74-8) chassis. Similar to my 721TS (KCS26 sams 70-7) , cost me alot more but is much better condition.:thmbsp:

The main difference seems to be the tuner does not have channel 1 like the 721, but it does have a 4th IF amp:D and the sound IF is taken off at the 2nd IF amp rather than the tuner. Probably this alone made it a great DX set. It has a sticker on the chassis from a shop no closer than 60 miles to Philadelphia or Baltimore, that each had three channels by 1948. The only "local" station, 15 miles away, came in 1949.

The 721TS's AGC circuit contrasts sharply with the 8T241 (pun totally intended here). Where the 721's contrast control simply varies the bias on the 1&2 IF amps, 8T246 has 2 additional 6SN7s as 2 AGC rectifiers and sync separators plus an AGC control. :tresbon:I can only speculate that the 721TS (found in suburban Baltimore) would generally suck in a fringe area that the 8T241 seemed to be designed for.

Both classic sets are missing the classic items, back covers and HV cages:sigh: The 721 TS needs channel knobs also.

I don't plan on powering anything up until all Electrolytic caps and some select paper caps are replaced; damper cathode bypass, two at the vertical output grid are prime suspects.

I save all the old stuff yet have little time or motivation to re-stuff caps as some artisans here do quite well.:drool:

Penthode
06-05-2012, 11:50 AM
The 8-T-241 is a well designed set. During the "nightlight" analog broadcasts in late June 2009, just prior to the total cessation of high power over-the-air analog TV broadcast, I used the KCS28 chassis to pull in a number of stations from Canada, Mexico and as far west as Phoenix and east from Boston and Miami from Southern Illinois! (I'l post some pictures later to prove this!)

As far as the electrolytics are concerned, I have restored four of these chassis and never have had to replace an electrolytic. Al I do is to reform them with a DC supply and monitor the leakage current. As the dielectric reforms, you will find the leakage should diminish to less than 100uA and the capacitor is fine. I give the reforming a few days.

I have not found an electrolytic capacitor from late 40's RCAs which do not reform. And the sets are used daily for extended periods.

Zenith26kc20
06-05-2012, 01:01 PM
I'd have loved to have seen that critter on my Jerrold (Wade) VIP-307 antenna when analog was still around! a lot of old black and whites were great DXR's!

Boobtubeman
06-05-2012, 02:39 PM
I used to get up early and align my tvs to the sighn on patterns and just loved the DX signals ide get, nice array of patterns that way :D

DavGoodlin
06-06-2012, 08:01 AM
Thanks for the electro-advice, Penthode. That means I will focus on replacing wax-paper caps and the set will be working sooner. I suppose, with all the tubes out, I can apply operating voltage without disconnecting anything and possibly do several caps together?

A Wade antenna is the best you can get since channel master "crossfires" are GONE.

Zenith26kc20
06-06-2012, 08:44 AM
early AGC circuits are sometimes "entertaining!" I have to pull the schematic on that set. Early RCA's had plenty of parts, just like the DuMont's! RCA had some really strange tuners on the early sets if memory serves me right.... I wonder how they compare to the DuMont Inductuner from Mallory.
Sorry to say, I think Wade no longer makes the VIP series antennas anymore. I got mine directly from Wade a few years ago to replace one Katrina destroyed.
I want to see a picture of that little guy running when you get it up and going!

Boobtubeman
06-06-2012, 02:41 PM
I got a T100 with a burned up e-cap and a BAAAD AC HUMM.. Wouldnt reccomend runnin on old caps.. Especialy E-caps... May hurt an unobtainable part..

Better safe than sorry or SMOKED.... :D

SR