Garage sale find, DeWald AM=FM C800

[wa2ise]

An unusual score, a completely tube AM-FM hot chassis radio, no selenium rectifier or solid state diodes. I did the usual recap, and aside from a dirty band switch, and it might need a touchup on the alignment, it works. The dial cord string is undone, I'll deal with that later. And the knobs have that white powder disease.

[dieseljeep]

I had one of those sets about 50 years ago. It was ten years old then. I couldn't get the FM working very well. IIRC, I sold it the way it was.
Dewald made a lot of radios with that same cabinet.

[uxwbill]

I have one of those, with a badly broken cabinet. The chassis and knobs are good. I should really get around to electrically restoring it one of these days.

[ggregg]

I had one too many years ago. Mine was near perfect cosmetically. Sold it in ARC.

[Sandy G]

I have one. Decent on AM, not so good on FM.

[Jeffhs]

Originally Posted by Sandy G

I have one. Decent on AM, not so good on FM.

What are you using on that radio as an FM antenna? I don't know what stations you normally receive in your area, but the radio should get some stations on FM if it is working at all. If the FM antenna is OK, then I'd look at the FM RF amplifier tube; that might be the problem if it is weak or nearly dead (in a 50+-year old radio I wouldn't be surprised if the tube is very weak).

[Sandy G]

Nah, I had Terry go thru it, & he told me lots of times these old, old, old FM sets were kinda "Deef" on FM intentionally, unless you have a REALLY GOOD Antenny...That's one of the reasons why I keep askin' Santy Claws for a nice 30-40' tower to mount my Winegard on...That, & the ICOM R-7000, the 2 Nems-Clark Special Communications Receivers, the Hallicrafters SX-62A, the Yamaha RX-V1...

[dieseljeep]

Originally Posted by Sandy G

I have one. Decent on AM, not so good on FM.

The only early FM sets that were halfway decent were the eight tube Zenith sets. The sets that used a 6BE6/12BE6 as a convertor weren't as hot.
How about the FM sets that used the Fremodyne, Superregenerative FM tuner? They were kind of a joke.

[jr_tech]

Originally Posted by dieseljeep

The only early FM sets that were halfway decent were the eight tube Zenith sets. The sets that used a 6BE6/12BE6 as a convertor weren't as hot.
How about the FM sets that used the Fremodyne, Superregenerative FM tuner? They were kind of a joke.

IMHO, "halfway decent" was about as good as the early tubed table models* got. Sets using field effect RF transistors in the late 60s, or so, started the path toward decent performance.

jr

*however, some tubed component tuners such as the Marantz 10B were quite good performers.

[Jeffhs]

Originally Posted by jr_tech

IMHO, "halfway decent" was about as good as the early tubed table models* got. Sets using field effect RF transistors in the late 60s, or so, started the path toward decent performance.

jr

*however, some tubed component tuners such as the Marantz 10B were quite good performers.

As was noted, the eight-tube Zenith radios were good sets in their day, and still are today. My C-845 (the set in my avatar), an eight-tube set with a 6BJ6 RF amp for both AM and FM and two IF stages, consistently receives FM from 60+ miles distant just using the built-in line-cord antenna (given good propagation conditions in spring, summer and early fall). I live within one mile of Lake Erie and often hear stations from southwestern Ontario, Canada as well as Detroit, Michigan and Toledo, Ohio, as well as every major FM station in Cleveland. I also have a K731 Zenith atop my refrigerator that works just as well, with what amounts to three IFs on FM (the limiter stage is set up to act as a third IF stage on that band). Even my Zenith R-70 AM/FM nine-transistor portable has four IFs on FM (very unusual for a transistor portable), and can pull in stations from great distances with just its built-in FM whip antenna.

They don't make them like that anymore. Too bad, because these radios represent, IMO, darn near the top of the line in Zenith's product line from the 1960s through the early '80s (the R-70, so I have been told, was the last "good" transistor portable Zenith ever made before the company went out of the radio business for good later in the decade). I also had a 4-mode Zenith integrated stereo system in the early '80s that had an excellent FM tuner, but the AM tuner was not much better than a crystal set and received short wave in the middle of the AM broadcast band (no foolin') at night. I never did figure out why, unless the AM front end was so poorly designed it wasn't funny.

[Sandy G]

...Add to that list of my poor, poor radios that want a tower to be fed from, a Zenith MJ-1035. Mine is the 12 tube version, a SILLY number of tubes for a set which was produced c.1965, more or less at the tail end of the Tooob era...

[Jeffhs]

Originally Posted by Sandy G

...Add to that list of my poor, poor radios that want a tower to be fed from, a Zenith MJ-1035. Mine is the 12 tube version, a SILLY number of tubes for a set which was produced c.1965, more or less at the tail end of the Tooob era...

I have an MJ1035 also, Sandy, but it's not working at the moment -- however, it worked and sounded great when it was working. It suffered a few indignities, such as being thrown around at the UPS terminal and generally manhandled, while in shipment to my apartment from Arizona (I got the set from a VK member who doesn't post here much anymore). The radio arrived here with two loose potentiometers, but miraculously it still worked right out of the shipping box -- go figure.

Four years later the volume control is shot, however, and I made the mistake some months ago of taking some of the tubes out and putting them in a little red box. This may not seem like a mistake, but the mistake actually was when I put the red box somewhere and hid it from myself! Now I can't find the box no matter where I look, although I'm sure it must be around here somewhere.

I swear, my apartment must have a Bermuda Triangle somewhere in the bedroom, as things often get misplaced or downright lost around here and I can't find them for days, weeks, months, even years (! ! !) afterwards; in fact, I think that's what must have happened to the box I put my radio's tubes in. Right now, I'm thinking the box is under my bed, in a place I cannot reach without poking a broom handle around in there. I'm half thinking of giving up and looking for replacements online. I used to know the URL of a surplus electronics parts dealer somewhere out West, IIRC, but it escapes me as I write this. Just wait -- as soon as I post this the address will come to me. I've had that happen to me more times than I can count.

[Sandy G]

Tell me about it, Jeff-I hope, when I die, to get to go at least temporarily, to that Majical Place where Things Go When They Get Lost...

[dieseljeep]

Originally Posted by Sandy G

...Add to that list of my poor, poor radios that want a tower to be fed from, a Zenith MJ-1035. Mine is the 12 tube version, a SILLY number of tubes for a set which was produced c.1965, more or less at the tail end of the Tooob era...

I had one of those sets in the late 60's. I don't remember which chassis version it was. All I know is, it didn't impress me at all. Very poor performance. The set was only a few years old at the time and in excellent condition. I sold it for what I had in it.

[wa2ise]

Did some more work on this radio. Unusual for today it turned out to have a bad tube, the 12AL5 twin diode for the FM demodulator. One diode was weak to dead, thus the ratio detector didn't work right. At first I thought someone mucked with the alignment, so I added additional mucking But as I couldn't get the demod to zero out, I started checking the circuit. And found the bad tube. Of course I can't find any 12AL5s, and a 6AL5 won't light up on 150ma string current. But this tube is at the bottom end of the string, and I decided to get more current for the 6AL5 heater by having it pass the "plate" current of all the set's B+ load currents. Just like how we have a #47 pilot light in parallel with a 35Z5 heater tap and have enough current to make the voltage across that 6V. So one side of the 6AL5 heater gets the powerline "ground" side, and the other side of that 6AL5 heater becomes the set's system ground. It works, but it does take twice as long for the 6AL5 heater to get fully warmed up as the other tubes in the set.

As this radio's chassis is very hot (a hard wire, not just thru a cap), I rewired the power switch to switch the powerline feed to the top of the heater string and rectifier tube, instead of switching the chassis ground feed side of the powerline. And used a polarized plug to have the chassis be close to real ground. Actually, with the 6AL5 kludge the chassis is about 6VAC above earth ground.