Montgomery Wards Airline 94BR-2741B
 

I've finally gotten around to fixing this set. It's a Montgomery Ward Airline console combination AM/FM radio/phono. The chassis is model 94BR-2741B The set is a side by side combo, with a 12" speaker and a four speed record changer. The chassis is a small transformerless thing with a voltage doubler power supply.

I found this thing on the side of the road several years ago, and it was just the right size for a space in my bedroom. Where it sat dormant. The tubes were all missing when I got it, and this was a major stumbling block, because it uses a 12BA7 pentagrid tube - that I don't have, and hadn't been able to find (until a couple days ago). Once I had the tube, there wasn't anything stopping me from fixing it, so I charged ahead and recapped it - I didn't even bother to try it first, several caps showed physical signs of being bad, and the cord was brittle and broken in many places. I replaced all the paper caps, two of the electrolytics, the power cord, and the upgraded the selenium stacks to 1N4006's. Lacking any 300v electrolytics, I opted to leave the main 4-section filter alone for now. After an initial false start thanks to a simple wiring error (always power the set up the first time with a dim bulb tester!), it actually worked! It plays OK on AM (although not great, some squeals between stations hint at misalignment), but the FM is very garbled and distorted, with poor sensitivity. I was able to get one station in clear enough to understand some words, but everything was garbled. There is a small amount of background hum that I'm sure new filters would take care of.

Now, the problem. I don't have the schematic for this. Nostalgia Air doesn't have it. Thus, I don't have alignment instructions - I also need the dial cord stringing info too, since the dial cord is broken. I also haven't ever had to align an FM set, and I haven't worked on many - so I don't know if my garbled audio is caused by misalignment or by something else.

Any suggestions on where to go from here?

-Ian

It's in Sams 89-1 - I'll see if I have it.

Let me as an old fart preface this drivel of mine by saying that I am not meaning to ridicule here. In the art of restoring old radio gear there is no true pro, as a lot of the old knowledge may well be misplaced--if not altogether lost. I offer my knowledge to you with full respect as to your own knowledge as you have gathered it, and mean nothing else beyond this except to pass on what I have learned.

That said.....

If you know your tube basings you can actually do your alignment without benefit of Sams--and also w/o an RF sig generator for that matter. Provided you have a good knowledge about the principles of radio operation, and that of the superheterodyne radio operation above all. The process of getting one of these old sets to "listen" once again is not at all hard to do, once you have the basics down pat.

Did it many a time when I was a snot-nose kid, as I could afford neither Sams nor equipment.

For starters I'd start doing an injection scan of the IF chain in a broadcast radio--once I'd ascertained the IF stage frequency. Most were 455. I'd start from the 2nd detector and work my way back up the line, using the last IF output from a working radio receiver as a source of RF signal at the appropriate frequency.

That was back in the '60s....

I then became "spoiled" by having the proper test gear.

Then years later in the mid '90s I was in the cellar of some friends of mine whose kid had gotten interested in fixing old radio. The young man at that time was like me as a kid--and didn't have a sig-gen, and was dealing with an old console radio where it was obvious that other people in the past had fust with the "loose screws" on the IF cans by "tightening" the bahstids.

It took me a few minutes to remember my youth. Then I asked the kid to strip down a working table superhet. Bug-eyed he did as I asked. I tuned the working radio to a strong local station, and then used its IF output at the end of the chain to work the older misaligned chassis from the back end to the front. I had it working in about a half hour or perhaps less time in diddling.

In dealing with antique radio one's best resourse is one's imagination.....

Where have I heard this before....? :rolleyes:

I don't know if I would recommend aligning an FM set without a signal generator. I've tried it in a pinch but it usually ends up making the tuning too broad, where each station comes in over too large a position on the dial.

Garbled sound may be bad ratio detector diodes or a bad capacitor in the circuit.
Not sure if it uses a discriminator or ratio detector but if it is a discriminator it will have 3 if tubes and if ratio detector it will use 2 if tubes.
There is about a 5 to 10 mfd electrolytic in the circuit if it's a ratio detector and this may be bad if you have not replaced it. If it uses solid state detector diodes I would check those too (or check the 6AL5/12AL5 detector if it uses that). After these are ruled out you might try adjusting the ratio detector transformer carefully to see if any improvement is noted.

Also I would go ahead and replace filter caps to make sure you eliminate that as a problem. Sometimes there can be enough leakage to cause problems like low voltage to certain stages even though there is no obvious major hum.

Come to think of it we actually have this chassis at the shop though I don't remember what it uses other than the 12BA7. We haven't got around to fixing it yet, though. Also have another similar version but it is a transformer power supply chassis.

Yeah, there was a 5 microfarad (100v) electrolytic in there, and the audio was really garbled before I replaced it. I didn't have one, so I used a 10 microfarad electrolytic - it helped, but the audio was still garbled.

I did some careful tweaking, and was able to get FM to come in clearly on strong stations. AM is still a bit off. It still needs a proper alignment, I'll wait until I get a schematic or a Sam's - I'm having a bit of trouble determining what coils do what - this is the first time I've done any sort of adjustment to an FM set. Also, the broken dial cord is going to take a bit of figuring out without a manual.

I have an Eico 377 signal generator, but it won't go up high enough to do FM (as far as I know...).

This radio uses a really odd pilot lamp - at least, it seems odd that it would be on a radio. It was missing when I got the radio, so I don't know what it originally looked like. The socket looks a car tail light socket, with two contacts in the base (like for a brake light). Now, I haven't actually tried putting a tail light bulb in there yet, but it seems kind of odd that a radio would use such a bright (and heat producing) bulb for an indicator. And why a dual filament bulb? I honestly haven't traced the wiring for it (shame on me, I know). Also, the bulb is mounted on a bracket above the dial scale, so when the radio is in the cabinet, the bulb will be pressed directly into the wooden inside of the cabinet - not shining out. There is a woven pad, presumably asbestos or similar heat sheilding material in the front of the cabinet that lines up with this bulb. This would have likely lit up the glass dial scale from the edge. If I get a chance, I'll have to pick up a bulb at the auto parts store and see if it works, so I don't have to steal one from my car. (I know, officer, but I've got like six of 'em back there, and I needed one for my radio - one light out can't be that big of a deal, right?)

The record changer doesn't work either, it won't spin. It isn't badged, but it looks kinda like a Webster-Chicago. The three speed mechanism uses two little pulleys with drive shafts, coupled to the motor drive shaft with a now-crumbled rubber belt. The speed selector engages one of these at a time, at different positions, to set the speed. The idler wheel looks OK, but this belt is/was a small diameter, approx. 3/8" wide, red thing. Anyone know how big this is supposed to be, so I can find a replacement?

-Ian

It probably wouldn't be dual filament. Old sewing machines of years gone by had a 120v incandescant bulb with dual contacts like that. It looks like a c-7 christmas bulb, but with a dual contact bayonet base. Also used in vacuum cleaners I think. It would be probably a heat-producing bulb. I dont remember running across this in a radio. If you have 120v between the pins, this might be it. I have seen lots of radios with a similar bulb, but with a screw base.

Hmmm..... could it be neon?

John

I struck out on the Sams folder - I have Numbers 87 and 91, and none between...

I've run across several hot chassis radios which use a 120v filament type lightbulb for a dial lamp. In sets with a 35W4 rectifier tube there is a filament tap for a 6V dial bulb but in a set with selenium rect. the 120 volt bulb was often used. I'll check the one at the shop and see what the lamp looks like. I think it is still in the socket.