RCA Victor 8T241 (?) scored--Pics

[N2IXK]

Just picked up an RCA Victor set off eBay. Looks like an 8T241, but there is some discussion in the auction thread that it may actually be the 1949 model, with slight changes to the CRT mask. The set is in pretty rough shape with a lot of rust, but for $15 and a few gallons of gas, I decided to go for it.

Got it home and did the initial disassembly out on the deck, to give it a once-over for mice, roaches, termites, or other critters I wouldn't want to bring into the shop. Nothing found but a long dead spider, and some fluff/leaves indicating that this thing spent at least some time outside.

Got the CRT out, and the chassis out of the cabinet. Cabinet is complete, but needs a thorough refinishing. Chassis is pretty rusty, but looks complete and unmolested. A quick glance didn't show any obviously replaced parts under the chassis, and all the tubes I checked were RCA branded. The CRT is a 10BP4, with some aquadag flaking off. Branded RCA Victor, so I am thinking it is probably original to the set (Replacements were only branded RCA AFAIK). Getter looks good, but will have to get my hands on a CRT tester to really investigate its condition.

Tossed the chassis onto the bench, and will do some further investigating tonight to see if this set is restorable, or a parts donor.

[N2IXK]

More pics:

[Username1]

Ain't bad.... I got one like it.
So this one ain't perfect, so turn it into your daily use set...
One day you'll get one a lot better, and keep it as your low hour perfect set....
Looks like you'll be on that one with a wire wheel.....

Good Luck ! Keep us posted !

[Kevin Kuehn]

Funny how mice like to mark their territory, like every square inch they crawl over.

[N2IXK]

Not sure if this one actually saw any mice. No telltale smell or nesting material found. Think it was just in a damp location for many years.

Already wire brushed a couple spots by hand, and it seems to clean up reasonably well. Before getting too aggressive over a larger area, I will want to figure out some kind of dust collection system, as I suspect there is cadmium plating in and under that rust.

All but 3 of the tubes were original RCA Victor, including the 6BG6. Flyback looks good, as does the yoke. Underside of chassis looks completely original, with no signs of a soldering iron touching it since it rolled off the assembly line.

Set is starting to look like a keeper, and "daily driver" is pretty much where I want to go with it. It is never going to merit a "concours grade restoration", but it certainly looks like it could be made to work again.

Time to start making up a list of caps to be replaced, and make some ohmmeter checks of the flyback, yoke, and that big ugly "candohm" resistor on the back of the chassis.

[Kevin Kuehn]

Originally Posted by N2IXK

Not sure if this one actually saw any mice. No telltale smell or nesting material found. Think it was just in a damp location for many years.

Interesting. You're lucky there's no smell. strange how the cabinet doesn't appear that moisture damaged. Looks like a lot of cleanup work ahead. Best of luck with restoration.

[Nuke]

If there were mice in that set, they would have chewed the cardboard of the electrolytics. That just was in a really damp place or it got rained on once and never dried off.

I'm glad you won it. I just don't have the time or desire anymore for that sort of extensive restoration. At least right now. That said, I will follow your restoration process as I have one of those also. Right now it is a shelf queen.

[N2IXK]

Spent a few hours this afternoon poking around. Decided to get the set at least somewhat electrically working before tackling the cosmetics and rust. That way if a showstopper crops up, all the time wire wheeling and cleaning won't go to waste.

The set certainly appears to be a 9T241, not an 8T241. Have found several differences in chassis layout and component values between my set and the Sams 74-8 which covers 8T241. Does anyone out there have a copy of the 9T241 schematic/service data? A few minutes Googling turns nothing up, and I cant seem to find a Sams listing either.

Ran a quick ohmmeter check on the power transformer, and found that the transformer is good, but the on-off switch isn't. It feels fine, clicks nicely, but is stuck open. Will put that one on the back burner for now, and just jump with a cliplead for initial powerup. Ohmmeter checks on the flyback, focus coil, and yoke are also encouraging. The power supply bleeder/voltage divider string is hard to say, as the circuitry is quite different from my schematic.

Started compiling a capacitor order list, to get the caps I don't have in stock. Am not even going to apply power to the set until at least the power supply filters are replaced. Will probably replace a few of the crummier looking paper caps before then, including the micamold line bypass caps which test incredibly leaky even on a simple DMM test.

[Kevin Kuehn]

I don't see a 9T241 listed in Sams or Riders. Is there a KCS number on the back of the chassis?

[bandersen]

I'm pretty sure it's 9T240. Check out this website: http://tjcjr.homeip.net/RCA9T240.htm

I'm not sure how he could possibly have put $400 of parts into it

[N2IXK]

If there was a KCS- number, it is long gone with the rust. My best guess on model number would also be 9T240, if the double-D mask actually places it as a 1949 model. It looks just like the one linked above.

Struggling with the crummy Sams .PDF from the ETF website, I think I have the differences sorted out. The chassis shown in the Sams is from the console unit with the AM/FM/Phono and PP 6V6 amp on a separate chassis. So my Chassis has a single 6V6 added, and uses a spare section of 6AV6 as an AF amp.

[Tubejunke]

WOW! This is what I WISH that my very similar 8T-243 looked like! Mine was given to me several years ago and I did a little work on it, then other things came into play and I have never gone back to install a pile of caps that I bought for it.

I have always complained that the set is too plain, if not downright ugly, and the main reason is that mine has the rectangular mask. I think that the double-D style is much more interesting looking and if you don't have a rectangular tube, then why have a rectangular mask?

I have dealt with two of these style chassis, one being a restoration (TC-127). They are all about the same and fairly complex, but not a DuMont or anything like that. I will say to just go ahead and change out the power supply filters before doing much of anything unless you have a pile of 5U4s that you want to burn off or maybe an extra power transformer. Good luck!

[N2IXK]

OK, got the caps ordered from Digi-Key today. Will hopefully get here for next weekend.

Checks of the 3 section "Candohm" resistor (R117) were showing a couple open sections, so I desoldered and removed it. Sure enough, both the 850 ohm and one of the 650 ohm sections were intermittently open, coming and going when I pressed on a couple of the lugs. But strangely enough, after wiggling all the lugs, the connections now seem rock solid, and all sections test OK, even when pressing and prying at it. Does anyone have an opinion as to whether this thing should be reinstalled? Was considering hooking it up to a power supply to heat things up to see if the fix is permanent or not.

If I do replace it, what would be the recommended modern equivalent, and how to mount it? The unit consists of a separate 850 ohm 12W section, and 2 650 ohm 6W units with a center tap between them. I immediately thought of the standard square wirewounds, but presumably the candohm was used to get the heat dissipation onto the outside of the chassis, rather than underneath. Maybe some of those fancy aluminum cased screw mount jobs?

There was a thin layer of fiber insulation board (almost certainly asbestos-based) that was between the chassis and the aluminum resistor mounting plate, presumably to keep some of the heat from soaking into the chassis wall. It was very carefully removed (soaked down with water/detergent to prevent dust), and will be replaced with a modern fiberglass based material.

[bandersen]

I just ran into a bad candohm section in a Dumont RA-113. I've found bad ones in a few other sets too so I like to replace them entirely whenever possible. Sure, those fancy (and expensive) aluminum housed ones would work well. Another option is to use over sized (2x wattage) vitreous or enamel coated power resistors and mount them on terminal strips. They'll handle the heat no problem.

[N2IXK]

OK, it's been a couple weeks, and things are progressing slowly.

Spent several sessions at the bench replacing ALL the paper caps, restuffing the 4 multi-section electrolytic cans, and replacing the flaky candohm resistor. Used a 820 ohm/50W aluminum cased unit to replace the 850 ohm/12W section, and a pair of 20W axial ceramic units to replace the original 650 ohm/6W sections. Also disassembled the volume control, and got the power switch working again (really dirty contacts).

Now it was finally time to apply power to this beast, for the first time in who knows how long.

Hooked my DMM across the 5U4 socket plate pins, and plugged into a dim-bulb tester and a variac. Turned the switch on, and brought the variac up while watching the DMM reading. Brought the applied voltage up in slow increments until the applied line voltage was 117V, and the 5U4 plates were seeing about 800Vrms. The series lamp was dark, so no shorts in the power tranny. Let the unit sit for about 30 minutes with no drama, so powered down, removed the dim bulb, and repowered the set. Again, no drama, and let it sit for a while to see if anything was going to fail.

While the set was cooking, I gave the tubes a quick cleaning to remove the grime, then powered down and reinstalled them all, except for the 5U4, 1B3, and the CRT. Then powered the set up again, and found 2 tubes that wouldn't light. The 6K6 vertical output tube, and one of the 6AG5s in the IF strip. Wiggling the 6K6 in the socket found a loose socket contact, which will need tightening or replacement. The 6AG5 is just plain open (maybe why the set was retired years ago?). Let the set cook with the filaments on for about an hour, and the transformer barely gets warm. So far, so good.

So over the weekend, I need to fish around in the junkbox for a 6AG5, and look into the 6K6 socket issue. Next up will be pulling the HOT back out, putting in the 5U4, and bringing the B+ up slowly to see what happens....