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RCA 6T - Printable Version

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RCA 6T - Paul Philco322 - 05-09-2023

Time to move on this one, either get it going or move it to a new home where it can get what love it needs. I should try for some better photos, these are a bit fuzzy. Has mostly metal tubes, I guess the "Radiotron" was being heavily marketed when this set came out. The far bottom right knob is a Range Switch, I am guessing like a local/dx switch. It is an impressive set size and weight wise. The speaker looks good though I did not pull it out, can't see the spot behind the audio trfr. I got it at I would say is a fair price, from a good radio guy, I had good luck with the Livingston 6 RF 9. So I hope to get in the hands of one better skilled than I this weekend. Anyone familiar with one of these sets?

https://www.flickr.com/photos/92577012@N02/albums/72177720308145020

Paul B

RE: RCA 6T - Chas - 05-09-2023

Paul,

I have had the occasion to work on similar RCA's. They are well documented in the RCA service notes.

I have experienced open power transformers and split open mica caps as well as IF transformers of which had internal opens to the litz windings. Individual strands, causing broad response. Replacement from salvage was the answer.

The wiring orientation must not change especially the bus wires from the oscillator coil to the band-switch. Even the slightest bend will shift sensitivity/calibration in the high HF bands. The magnetically tuned IF's have a very narrow peak if the windings and the resonating caps are in good condition.

The mica caps in the HF/OSC should be replaced only if the casing is split open and/or the HF/OSC bands do not calibrate properly. Be sure to use metal tubes where called for as capacitance changes will effect sensitivity and calibration.

FWIW, I do not stuff the electrolytics, there is plenty of room for axial or radial filter caps as well as terminal strips under chassis.

GL

Chas

RE: RCA 6T - Ron Ramirez - 05-09-2023

Paul

"Radiotron" was RCA's brand name for their tubes, dating back to 1920 and the first UV-200 and UV-201 tubes.

The far bottom right knob is the band switch, not local/DX.

Properly restored, it can be a good radio in spite of its low tube count. I owned one many years ago and was impressed with it. RCA produced some excellent radios in the 1936 and 37 seasons (this one is a 1937 model).

The biggest drawback to these is the rubber-covered wiring used.

I know a 6T probably isn't your cup of tea, considering your propensity for the small table model radios. And that's ok...but perhaps it is time to widen your horizons a bit and welcome the 6T into your permanent collection? Icon_smile

BTW, I agree with everything Chas said, save for the electrolytics - I'm a firm believer in restuffing the electrolytic cans whenever possible.

RE: RCA 6T - Paul Philco322 - 05-09-2023

Thanks guys, so I guess the way to interpret the "Range" knob is a tuning range meaning Broadcast or SW.
I have seen the old Ads in the magazines for Radiotron tubes, a way to be different, I like the lettering too.

Well will see how this thing comes along, I gave it a good cleanup today, somebody had an old decal, like a paper label an old store would put on stuck on top. Got most off, there is a little of the black border trim at the bottom front that is gone, but it is pretty presentable IMHO, so that may be it for the case.

So Ron my affinity for table sets is still there and that is most of my collection, I do find myself appreciating my larger sets, its the speakers, the better sound the better sensitivity, I even have snuck another console in, not a Scott but it's the speaker that makes the difference. Been listening to a Philco 38-93 as well and again only 5 tubes but the larger speaker makes it more listenable. It was also "restored" when I got it so much so that old Ray Bintliff the Condenser and More Author re restored it to perfect shape. Keep you posted on the RCA.

Paul

RE: RCA 6T - DaleHCook - 05-09-2023

Ron Ramirez Wrote:  The biggest drawback to these is the rubber-covered wiring used.

I've never worked on an RCA of that vintage, but I own a few Zeniths with rubber-insulated wiring. I have gotten pretty good at replacing it and getting the dress correct (I stock PVC insulated wire in all ten RMA colors, in solid and stranded, and in five gauges). Getting the dress is easier since I upgraded the workbench lighting and installed a bracket for my networked DSLR above the bench (it is remote controlled with a program on the shop laptop).

RE: RCA 6T - radiorich - 05-10-2023

Hello Dale,
That sounds great and bench lighting is really a great idea .
I have a half dozen sets that are waiting to be rewired and I find taking tons of photos really helps plus marking wires too .

Sincerely Richard

RE: RCA 6T - Ron Ramirez - 05-10-2023

Dale

Let me ask you a question - where do you purchase your PVC insulated wire from?

Make that two questions - is it rated at 600 volts?

RE: RCA 6T - DaleHCook - 05-10-2023

Ron -

Most of the time I use 300 volt rated NTE wire. My local parts jobber stocks most of the types that I use, and can order others for me because they send in NTE orders weekly. I stock 600 volt rated NTE wire in only a few types, which my parts jobber gets for me as needed.

For me a full stock of 300 volt wire would be 100 spools - 10 colors x 2 types (solid and stranded) x 5 gauges (18 to 26). I never have a full stock because I seldom need 26 gauge. The photo below is several years old and I have roughly doubled my stock since it was taken. One recent addition is that I now stock test lead wire in ten colors instead of just red and black.

[Image: https://plymouthcolony.net/starcity/radios/images/wirestorage.jpg]

Some types I have only in the Explorer wire case - if I need it in the field I don't want to drive as much as 75 miles back home to get it. If I need something in the shop that I don't have on my wire racks (repurposed pants racks) I can always get it from the Explorer. The stock in that case has been greatly expanded since that photo was taken - almost every gauge except 26 gauge is now full.

[Image: https://plymouthcolony.net/starcityeng/images/wirecase.jpg]

RE: RCA 6T - DaleHCook - 05-10-2023

radiorich Wrote:I have a half dozen sets that are waiting to be rewired and I find taking tons of photos really helps plus marking wires too.

I have a set of ScotchCode wire marker numeral tapes in the ten numerals in the shop. I seldom use them on antique radios because, when rewiring a chassis, I replace one wire at a time (just as I replace one cap or other component at a time). Replacing one wire at a time makes it easier to get the dress correct.

I use the ScotchCode numeral tapes a lot more in the field, and carry three sets in the Explorer for field use. If I have to replace a wire in a broadcast transmitter those are always numbered (generally with three digits). Some of those transmitters are nearly 6 feet wide in three cabinets. Tracing a wire without a number is insane in a large transmitter that has hundreds of numbered wires, so I always number the replacements. I also use them when building new studios and create documentation to match. There I am mostly installing cables, but in a facility like the one I built last year with five studios, a rack room, and a utility room, numbering cables (with three digits) with documentation is critical.

RE: RCA 6T - Ron Ramirez - 05-10-2023

Interesting.

Having no local jobber in my area, I have purchased from Remington Industries in the recent past but they only stock 20 gauge wire in 300V insulation. 600V insulated wire in 20 gauge, with its thicker insulation, more closely resembles old rubber-covered wire of the type used in old Philco, RCA and Zenith radios. However, I have found that 20 gauge wire with 600V rated insulation is next to impossible to find - for some reason.

Yes, I could use, and have used, 300V rated wire instead in these sets, but I don't like how thin the insulation is - it seems that it would be very easy to accidentally nick and potentially cause a short.

Paul, sorry for hijacking your thread.

RE: RCA 6T - Ron Ramirez - 05-10-2023

Richard

Taking lots of photos does indeed help.

However, RCA sets of 1937 and earlier are so well documented, complete with pictorial wiring diagrams showing where each wire goes (not the proper routing, but the wiring itself), which makes servicing these radios so much easier.

Take heed, Paul - you have one of the best documented sets there is, should you choose to restore it. Other manufacturers could have taken lessons from RCA when it came to documentation. Unfortunately, RCA started cutting back on their documentation about midway through the 1937 season, as they began to leave out pictorial wiring diagrams that could be a real help in difficult sets.

RE: RCA 6T - Paul Philco322 - 05-10-2023

Np on the wire, topic, all related. Oddly one of the wires leading to the grid cap on a tube is rubber and crumbly, the other 2 are cloth and in very good shape, so this could be a mixed bag, will see. You never know whats up until you evaluate more thoroughly, my RCA 28X, which I thought would be straightforward turned out to be maddening. As Roseanne Roseannadana sez, always something....

Paul B.

RE: RCA 6T - DaleHCook - 05-10-2023

Ron Ramirez Wrote:I have found that 20 gauge wire with 600V rated insulation is next to impossible to find - for some reason.

I suspect it is because electronic equipment nowadays seldom has voltages that high, and if it does it doesn't need anything that large. None of the solid state radio transmitters that I work on have anything over 300 volts. They use combined power MOSFETs in class E mode in their power amps. I do carry some 600 volt wire in the Explorer, along with red and black 5 kv working voltage (20 kv breakdown) test lead wire for higher voltages in vacuum tube transmitters. I even carry a spool of color TV CRT anode wire for a few transmitters with 15 kv plate supplies (but not a lot of current).

NTE does have 600 volt Teflon insulated wire in all 10 colors in gauges from 18 to 26 in 25' packages and 100' spools. See their site.

RE: RCA 6T - Chas - 05-10-2023

I use Alpha 600 volt 20ga solid PVC covered hookup wire as well as a few colors of same in strand. I had gotten 10, 100' spools years ago nearly all gone now, it was very expensive then. It was the same O.D as the rubber covered RCA chassis wiring of the 30's. It seems to resit the "splaying" of the insulation when a connection is made and a close right angle bend made in the wire. Try as I might, I occasionally forget and arrange a connection that causes that retraction, splitting of the PVC when soldering the connection Icon_sad

I have found that disconnecting the bad wire at one end, soldering that end to a new wire, then pulling out the old wire from the far end, taking the new wire with it, saves threading of the wire and the adding lots of bumps to the to the new wire. All, while estimating as best as possible the length of the old wire to the new.

Replacing grid leads can get "iffy" as the grid cap connector is often crimped and soldered to the wire. making de-soldering and prying open the grid connector difficult. Sometimes grid leads are shielded, this too, can be awkward as the capacitance of the shield does have an effect... I keep tinned braid for the purpose and heat shrink to create a new assembly.

I used Newark for a vendor of the hookup wire. Seems they subcontract to have the wire re-spooled but in doing so, often wrap the completed spool in sticky clear packing tape. That, gets adhesive all over the first layer of wire on the spool... Requiring solvent to remove, another extra step...

RE: RCA 6T - Ron Ramirez - 05-10-2023

> It seems to resit the "splaying" of the insulation

Good point, Chas. The Remington wire will "splay" badly if you aren't careful with it.