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February 18, 2008
For a long time now I've wanted one of the magnificent 1935 RCA tombstone radios, either the 6-tube 128 or
the 8-tube 143. But they tend to cost several hundred dollars in decent shape and I can't
see spending that kind of money on a radio most of the time. So I keep looking out for a
bargain.
Last week eBay yielded a surprise - the Westinghouse equivalent of the RCA 143. Same chassis but in a more angular, art-deco styled cabinet. I found it good looking, unlike GE's blocky, squarish version of the same radio (their model M-81.) The Westinghouse started at $22.00, and didn't seem to be attracting much attention. There was a reason for that; it had issues. Nothing I thought was a show-stopper though. I kept an eye on it. With a half hour to go there were still no bids, so I placed a small bid and waited to see what would happen. Unbelievably nobody else put in a bid, and for $58 (including shipping) the radio was mine.
It came with a story. The seller had been a missionary with HCJB Global in Quito, Ecuador, back in the '80s, and received it as a gift from a fellow missionary. The seller had just recently gotten it working. The steps he had taken to make this happen were, shall we say, unorthodox. Check out the list of "fixes" he had done, as described in the eBay listing here.
Anyway, it arrived today and unsurprisingly came damaged. A bit of wood was torn at the bottom of the grille and the face was separating from the rest of the cabinet. Annoying, but solvable.
I took it out and put it on the bench. It's........interesting. :-)
The radio, pre-disassembly. Incorrect refinish, wood damage at bottom of grille, missing speaker screws, missing dial, wrong knobs.
Rear view. Serious chassis rust at right hand corner. Extra output transformer on the inside. And see that big square box where the speaker belongs?
The speaker. Yes, really. This is the speaker he used. I have no further comment.
Inside looking at the new output transformer and new speaker cardboard. Note the lovely burlap grillecloth.
Inside. At least the dial glass is still whole.
Chassis underside, after having removed all the knobs. Note the mix of caps, and the new choke in the middle of the left leg.
The rectifier tube was broken. Oddly enough that tube was a 5R4GY. Odd, as the expected tube here was a 5Z3, a 4-pin tube instead of an octal. The rectifier socket had been replaced with a plastic octal socket. I note that the screws holding the new socket in place were very rusty; obviously a very old (wartime?) repair. Because of this provenance I'll keep it as an octal and use a 5U4 here.
I put in a 5U4 and tried the radio. It was advertised as working, but it didn't when it got here. Complete silence. Probably a bad connection somewhere. I hope....
Next step is to get the radio to play again, one way or other. So far I have also inquired about repro knobs to replace the ugly new plastic test-equipment knobs it came with, looked for photos of this set with an original finish (I may have found a couple) looked for a new dial (Mark Oppat has it) and checked the correct speaker size (8"). We'll leave it here for now.
February 19
With the chassis out on the bench and the speaker safely in the trash where it belongs, I decided to try the set again
to see why it didn't make any sound. I don't have an 8" field coil speaker handy to use right now. I'll keep my eyes open for an original, but to get this set done now I'll just
have to pick up some random 8" field coil speaker with reasonable specs to use in the set.
I set the bandswitch to band B (the BC band), turned on the radio, waited for the tubes to heat, and put my scope on the output transformer wires. The scope showed a happy little speech-sound graph. Hmmmm. Seems like this thing should play.
I grabbed a random permanent-magnet speaker off the shelf and attached it. It made noise. Shortly I was able to tune in a station. Tuning around found many more stations. Good. I switched to band C and found a couple more stations. It was hard to know where I was tuning without a dial, but the point right now was to hear something. Bands A and D found no stations. I hooked up the signal generator to see if I could receive on those bands. That worked on both bands. They received but were too weak to grab anything out of the air, probably due to weak components. The restoration process will do something about that.
Well, good. Since we know all the major components are in good shape, I'm confident to plow ahead with the full electronic restoration this set needs for maximum performance. More next time.
February 23
After soliciting some advice and surviving a bout of stomach flu, I have determined to go ahead and use the electrolytic process to
derust the chassis. An explanation of the process can be found
here.
Unfortunately this means doing a great deal of disassembly. I have to take off all the coils and the tuning cap, along with the can caps. Removing the coils is absurdly difficult work, and the worst part is remembering what I'm taking apart so I can put it back together. I've been taking a zillion digital pictures of everything before I take it apart so I can reassemble it when I'm done. Also, there are a billion connections to each one, and some of them are hard-to-handle bus wire. I did the two antenna cans tonight, and now I'm worn out for the night. I'll finish them up some other day.
February 24
The RF coils are out. They're laid out just like the antenna coils, and since I had some experience
now these went a little easier. I'll do the rest (oscillator coils, IF cans, power transformer, driver
transformer and electrolytic caps) another time.
February 26
God help me, the thing is done. Here's what's left.
I'm going to do the derusting tomorrow. I have my plastic tub and battery charger at the ready, but I don't have any steel to use as an anode and we need baking soda. I'll pick those up tomorrow and let the derusting run tomorrow night.
I sure hope I can get this thing back together. I have a million photos and RCA's wiring diagram, but it's a challenging set. I also hope I didn't damage anything removing it. Hoping for luck. :)
February 27
Okay, this is nasty.
I filled a plastic tub with 8 gallons of water, threw in a half a box of baking soda, dropped the chassis in (good grief, I have never intentionally wet a chassis before.....this is scary) and took a shovel out of my garage and put it in the tub too. Hooked up the battery charger and turned it on. I quickly got three amps of current flow at 12 volts.
Four hours later this is what I came back to.
Disgusting.
I'm letting it run until tomorrow night. We'll see what happens then.
February 28
This is better?
It took a lot of scrubbing to get as much of the black oxide off as possible. This is where I got sick of the work, and really nothing more was coming off anyway. I took it back down and sprayed it with WD-40 to forestall further rusting. It'll have to be painted. I don't have any stainless steel paint, so I'll pick some up soon. Anyway, there won't be any more updates for a week. It'll take that long for the chassis to thoroughly dry.
February 29, 2008
Picked up a can of Rustoleum Metallic silver paint. I might paint tonight or tomorrow
depending on how well the WD-40 holds up.
In the meantime, tonight I finished off a Zenith.
March 10
Well, I finally started spray painting the chassis. I would have done this a bit sooner except for a couple
things - (a) I've been busy framing up walls in the basement, and (b) I couldn't figure out how
to spray the chassis without painting all the underchassis wires and whatnot. My masking tape wasn't
sticking well to the chassis. Tonight it occurred to me that I am stupid, because all I needed
to do was stuff paper towels in the holes. So I did that and sprayed a coat. No pictures yet because
it'll need another coat. There will be pictures then when that's done and dry.
(later)
Well, it was dry so I put another coat on. I think this will be enough. I snapped a photo.
Okay then. I guess this will have to do. The top looks coarser than the back panel because the
paint is sparkly, and with the camera angle that shows more on top
than on the side. I'll have to clean up a little more of the overspray, but either way
it at least looks much better than the rustbucket it was.
I'll wait a couple days and then start reassembling it,
and with any luck there will still be a radio in here somewhere.
March 27
Long break. We took a vacation this week, and that (and preparing for it) stopped work here for
a long time. I got back this morning. Tonight I took the end bells off the power transformer
(a job that would have been very easy, but one of the screws was rusted so tight I couldn't break
it, stripped out the screw head, and ended up having to hacksaw it off.) Then I painted them.
They're drying now. When they dry and I get back to this set I'll buff the paint, put it back
together and see if I can rebuild the radio's power supply.
March 31
Went to make sure the power transformer was ready for reinstallation. The blue leads (6V heaters)
were pretty worn out. I wanted to resleeve them and lengthen one lead that was cut way short, but
I have no hookup wire, no blue heatshrink, and no caps in a number of important values. And payday
is four days off. :-/ Can't work without supplies. I guess I'll pick this up again next week.
April 7
Reinstalled the power transformer. Straightforward, just time consuming to get it right.
It worked fine and will light the tubes,
high voltage is perfect. I haven't reinstalled the power switch/tone control
yet, so I just jumpered across the terminal board where its leads are. Soon I'll put filter caps in and see if I get DC out. This is the easiest
part of the reassembly.
April 8
This radio is supposed to have five electrolytic caps up top. There are the two filter caps,
C53 and C54, both 10uF. Originally each of these had its own little can in the right rear corner
of the chassis near the fuse and the rectifier. At some point years ago, someone had pulled these
out, put an FP can in one hole and put a plate over the other. The FP can had corroded at
the bottom, though, so I planned to set this back to something like original.
I found some appropriately sized aluminum can caps in the junkbox. I'll work on these later,
though, because I can't find my Dremel to cut them open and I need a new heat gun to help slide the
guts out.
Right now I'm working on the other can cap, a multisection thing which contains C45, C46 (both around the cathode of the 76 tube) and C55 (bypasses the screen grids of the 6D6s and 6A7.) I don't know if the can I got with the set is original; it doesn't have the right part number on it and the leads are wrong but the values are all the same. The can is a cardboard tube painted silver to match the rest of the chassis. I decided to gut and restuff this with new caps. So I unrolled the cardboard tube at both ends, lifted the round cardboard covers out of the top and bottom, grabbed the leads and the tube and pulled the guts out of the tube. Then I dug out and cut off the leads for re-use. Next was to get the new caps, connected them together appropriately, soldered the leads on and hot-glued the caps into the can. Reattached the covers, rolled up the ends and done. There'll be a picture when I get around to it; unfortunately I didn't take a picture when I had everything open but it wasn't anything special to look at, just three caps wired together and glued into the tube. I should probably repaint the rolled up part of the can too, the paint wore off and it looks rather shabby.
April 9
Thinking I would simplify the wiring by doing so, I had tried last night to restuff the
aluminum can caps I found to install. The stuffed caps didn't work
as well as I hoped, so tonight I just threw in a rectifier tube, tacked new caps underchassis and put
a resistor across the field coil leads of the speaker cord to see what would happen when
power was applied to this thing.
What happened is that we have B voltage. I also smoked a dogbone resistor near the screen of one of the 42 tubes, likely due to a wiring issue (there are loose ends from removed components all over the chassis. No real loss.) There's no load so the voltage is way too high. I guess I'll set these new caps up permanently on a terminal strip when I get around to it, mount the cans up top just for show, and call the power supply good. I had no plans to restuff the rest of the caps in the set anyway; all the paper ones were ruined in the derusting tank and the originality of this set is shot anyway, so we're aiming for a reasonably well done functional restoration here.
August 27
Set this aside while working around the house this summer. I'm thinking about getting back to it now because I'm
tired of the chassis lying around the basement.
I'm abandoning the restuffing of the filter caps. I pulled the new electrolytic caps out of the old cans, taped them shut and mounted them on the chassis temporarily. Then I grabbed the documentation and went through it to identify all the new caps and resistors I'd need to complete the restoration. Say what you want about RCA, but their documentation was absolutely first rate. The only reason I'm able to get away with disassembling the chassis is because I have access to a complete underchassis layout and wiring diagram, so I can put everything back together the way it was and not screw it up. I also still have all the pictures I took a couple months ago.
I'm going to need 17 paper caps and 25 carbon resistors, along with three power resistors. The original candohm is long gone, and whoever worked on it previously used a couple of 12K power resistors that are much too large for this application (should be 6500 and 4500 ohms, and a 450.) I'll have to order those and refresh my stock of caps and resistors, since I'm out of some of the values.
I only had an 8x11 sheet with the wiring diagram, so I printed a new copy off my CD onto the wife's 18x24" DesignJet. Even at that size it was still a bit illegible, so I marked it up to clearly identify all the parts to be changed out. With this and the schematic, I should be all set to go.
Next order of business is to buy the parts and remove all of the motley collection of old caps and resistors from the chassis. I'll start on the ASAP.
August 28
Desoldered all the resistors and paper caps out of the chassis. The micas all test good so I left them alone.
I started installing new parts in the neighborhood of the IF stages, so far about four resistors and six caps. The plan for now is to finish the power supply, audio and IF stages up to and including the first IF transformer. Then I'll put power to it and see if I can get modulated 455kc out of it.
I contacted Mark Oppat for a dial, caps and the power resistors necessary to replace the candohm. I'll order them once he gets me a price and with any luck they'll be here soon.
September 6
The parts arrived today. I installed the power resistors. Managed the break the lead clean off
of the 470 ohm one, which was annoying. I found two 225 ohm units in my box and connected them
in series between the cathode of one of the 42s and ground. Less pretty but it worked.
I tried installing the dial. The pointer is held on by a small screw that I couldn't remove with any screwdriver I own. I'm going to have to get a jeweler-size screwdriver with a big handle so I can make enough torque to remove it.
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