Classic Hifi Care

This radio was my grandmother's. She got it brand new in 1936. It got struck by lightning sometime in the 1950's. The local radio repair shop told my grandparents it was not repairable, so it went into the back bedroom to become a plant stand for the next 30 years. Before she passed away, grandma gave me her old radio. My radio repair hobby was in its infancy in those days, but I recapped it and got it running somewhat dependably. It sat then for another 20 years or so not used hardly at all. Next time I decided to try it, all I got was static and noise. I removed the chassis from the cabinet, plugged it in on my bench, and it played. I did some tune up, let it play on the bench for a week or so, then put the chassis back into the cabinet. Nothing but static and noise, again. I pulled the chassis, put it back on the bench, and it played again. Back into the cabinet, nothing. It is like that to this very day.

I've come to the conclusion that my next avenue of investigation on this radio chassis should be to check the tube sockets. This fairly well-built radio chassis uses those cheap wafer tube sockets. Sometimes, when you plug a tube in, it pushes the terminal down out of the tube socket. I'll bet ten bucks tube sockets have something to do with it. I'm beginning to wonder if bolting the chassis down in the cabinet flexes the chassis just enough to break connection on the tube socket. Nothing else makes sense. I intend to replace the balance of the dogbone resistors that I haven't already done just to be sure. I have enough ceramic octal sockets to complete the job. Does this make sense to anybody else?

It makes perfect sense to me Greg. I went through something similar with my Silvertone table top record player. It too had the cheap tube sockets and after a week of trying to figure out why the voltages would change every time I ran tests I discovered the female connectors on the tube sockets were wonky. I ordered up new sockets and everything fell into place. It now works great and actually sounds better. Something else I discovered while working on the Silvertone. It was built for Sears by VM. The changer is a VM1200, and VM built the amp. I discovered this one day when I was checking eBay and found a VM/VM that looked similar. The photos on eBay actually showed the amp chassis and speakers and they were identical to the Silvertone. Go figure, that VM built stuff for Sears.

Bill

I'm glad you snitched on yourself without me having to!

I was going to give you credit for coming up with the solution to this 40 year dilemna. All you went thru with that Silvertone chassis got me to thinking. Grandma's old Grunow acts exactly like your record player chassis was acting. Maybe we can finally get this thing to perform like it should. Thanks for your help with this.

I have a floor model Grunow... not sure of the model Number but it has the tele-dial on it where a bunch of buttons rotate around the dial... one of the few radios I totally recapped... plays great... too bad the content for AM and SW is dying... at least in my area

My 1191 has been a head-scratcher for close to 70 years. They couldn't fix it in the 1950's, I tinkered with it in the late 1980's, got it going somewhat. Then I have tinkered with it off and on for thirty years or so. When Bill was troubleshooting his Silvertone record player, and discovered bad tube sockets, that got me to thinking about this old radio. I believe I'm going to start from scratch, completely recap it again, replace all the dogbone resistors I didn't replace before, and I might even replace all the micas just for grins. Then replace all the tube sockets with bakelite or ceramic units. I believe I have a complete set of tubes to sub if I need to. What else can I do? Every part in it will be new, so, with a good alignment, it should work. It's a beautiful old radio. I had it refinished probably 25 years ago by a professional here in town. Maybe someday, due to what Bill learned on his Solvertone record player amp, this thing will sing dependably, with the chassis in the cabinet once more.

I took the chassis out of the old Grunow this afternoon. I put it on the bench and did a good "visual" as Shango always likes to say. It looks to me like maybe my stepdad changed a handful of the dogbone resistors out for (probably used, salvaged) more modern resistors. Most of these have drifted way high in value. I checked a 220K that measured almost 285K. I 47K measured 68 K, on and on. So probably new resistors, this time NEW ones at the correct value might be in order. I saw one tube socket that the layers of the wafer have come apart. One of the output tubes has part of a tube pin connection missing. That can't be good. So probably some replacement tube sockets would be in order. The 5Z3 rectifier has been changed to a 5U4 sometime in the past. I connected the chassis to the Variac, dimbulb and KAW and found I have a short in B+. It lights the dimbulb to full brightness at about 85 volts on the line. It also pulls almost 100 watts at that voltage, so something is wrong. The filter caps were replaced probably close to 40 years ago now. The chassis and cabinet are nice, but it is a mess electronically. My stepdad said this radio was not worth messing with, since it has been stuck by lightning. My plan at this point is to get the power supply squared away, then to get a baseline on the chassis to see what I have. Then as I replace the various components, I can test periodically to make sure I don't introduce a new fault. I'd really like to figure out for once and for all what is wrong with this radio.

It sounds like you are having fun in the "SHOP", which is long over do. You must be thrilled to finally have some place to work and enjoy all of your toys?

Bill

I have run into a bit of a sticky wicket with the old Grunow radio. The drawing does not list values of components, only part numbers. There are three dogbone resistors that are still there. My guess is that I couldn't identify them 40 years ago when I recapped this radio. One has a green body with a black dot on one end and an unidentifiable color dot on the other. One has a white or tan body with an orange dot and an unidentifiable color dot on the other. I have alignment instructions, but I don't have a parts list. Now what do I do?

I found the drawing that lists component values. I had filed it with General Electric for some odd reason. The drawing probably fell out of the folder, I found it, picked it up off the floor then put it with whatever I had open at the time. "I'll fix that later" was my reasoning. At my age, there may not be a "later".

I narrowed the short in the B+ line to the front end of the radio. Somewhere. That's all I know for now. I have the short run down to ahead of the first IF transformer. Somebody has done a lot of hack work on this radio chassis. There are components suspended by the leads. "Mystery" soldering. I can't believe Cousin Calvin did work like that. I CAN believe my stepdad would. If he was "hunting" something, he may have chopped then stuck things together just enough they would not fall apart. LOTS of bad solder joints. LOTS. There is a totally bare wire going up into the 3rd IF can. It's about the size of bell wire, which may make a good substitute. There is a dogbone resistor going to ground that I need to check. That might pull B+ down as well. This thing needs lots of work. I can understand why Sam said this radio was not worth fixing. I'll forge ahead.

electra225 wrote: ↑Wed Jun 15, 2022 2:27 pm One has a green body with a black dot on one end and an unidentifiable color dot on the other. One has a white or tan body with an orange dot and an unidentifiable color dot on the other. I have alignment instructions, but I don't have a parts list. Now what do I do?

The body color is one digit in the value, right? And the first dot another digit, and the last dot a multiplier? I've got a notebook that gives the code. But the colors are not always true or verifiable if they've been cooked, or if they have flaked off. Good news that you found a values list. And there's much to be said for rescuing an unlovable radio.

Chris Campbell

This one would probably be on the burn pile if it hadn't belonged to my grandmother. It will take more work than I typically like to put into one. Of, course, I don't remember what work was done to this radio in its lifetime, but I'd think that if it had truly been "lightnin' strick" there would be blackening and burning of various components, mainly those connected to the antenna, in the front end of the radio. Other than some hack work, the underside of the chassis looks pretty good. What little rubber wiring there is has no insulation anymore. Mostly going up into the IF cans. The mess with the dangling components may have been due to my stepdad "snipping and tacking" trying to find the exact trouble I am. A lot of that mess is in an area I am currently working in trying to find the short in B+. I have almost the entire B+ rail disconnected, but still have the short. I'm down to just a few components. I don't see how a coil, such as an IF coil or oscillator coil could cause a short to B+. The wires are so fine, they would just smoke and then they would be open. I believe I remember a dogbone resistor connected to ground that I haven't gotten to yet. The other two dogbones still left have drifted low. The short I'm chasing is not a "dead" short, but a low-resistance path to ground, in the order of 50K ohms. My stepdad was my first elmer. He either did not know about, or was too cheap to buy, an ESR meter. He taught me to measure the resistance from the rectifier cathode to ground. This give an indication of what load the rectifier is "seeing". If the resistance is about, say, one megohm, then it is generally safe to power up, using safety equipment. Lower than about 500K ohms for a transformer set, you need to see why the resistance is so low. That's how I was taught and it works well for me, regardless of being pooh-poohed by the "experts".

Is there supposed to be a pic?

No pictures. Let me get done making a mess. Nobody wants to see that......

I am down to the last branch of the B+ line. I am down to basically from the first IF transformer to the front end, toward the oscillator coil. I'm not buying a shorted coil. I have never heard of an oscillator coil shorting out B+. There are a couple of bypass caps from IF amplifier plates to ground. Both are .05 mfd @630 volt units. They were replaced close to 40 years ago, the typical little cheap yellow caps everybody uses. IF one of those has shorted or became extremely leaky, that will be a first for me. I have this poor old chassis so "unwired" I may never get it back together. I've never had to take one apart this far before.

The power supply is back to normal. B+ is almost dead on the 355 volts at the rectifier cathode specified on the diagram. Element voltages are spot on as well. I have no idea, really, what I actually did to fix it. I replaced those two .05 mfd caps that bypassed plates to ground on the IF amplifiers. I still had relatively low resistance to ground, but it was more than 50K ohms. More in the area of 150K ohms. Still too low, but better, so I powered up with the dimbulb and KAW. The dimbulb came on brightly at first, then got dim. It is drawing between 110 and 114 watts. With eleven tubes, that is pretty close. The eye tube does nothing. It is always open. And I have lots of noise like SMD if these IF cans could have SMD. I don't see any arcing, don't hear any, voltage never wavers. Only on the broadcast band. I still have a long ways to go. I'll leave it off for a while, then power up again to verify correct power supply operation. I need to make a list of things I need, one of almost every part in the radio. I sure don't see any evidence this radio has been struck by lightning. I'm beginning to believe it has a bug in it that nobody can find, then just got tired of messing with it. Grandma may have complained about how it worked until Cousin Calvin got tired of hearing about it. Then Sam got the same treatment. It definitely has some wonky tube sockets. And four dog bone resistors nobody thought to change.

Didn't a lot of those eye-tube sets have a resistor inside the tube socket? Maybe there's one in yours and it has gone way hgh.

Chris Campbell

I thought of that and I'll check it. That is way down the list at this point. My next chore is to use the signal tracer to try and find what component is making the noise. I suspected a tube element such as a cathode to heater short, but why would that not appear on every band? You would think that if something was arching I'd see it. Some of the tubes are in shields, so if fireworks were going on in one of those tubes, I might not be able to see it. I also should check to see if I'm getting positive voltage on a grid in the IF section. Reception is fairly weak at this point. I'm sure an alignment wouldn't hurt it. No use to do that before I'm satisfied the electronics are squared away. I found out a minute ago that the tone gets really tinny when the volume is turned down. The volume control is center-tapped to allow for bass reproduction at low volume. This will be a step-at-a-time restoration. IF I throw enough parts at it, surely whatever ails it will be eliminated.

I can kill the noise, but I can't isolate it. It is basically everywhere in the radio between the grid of the converter to the volume control. The volume control affects the noise. I am suspecting a short in a tube, but why does it just make noise on the broadcast band? A shorted tube should affect all bands.

Any possibility that your new shop or a neighbor has an AM band noise source? Or maybe a trimmer cap with some conductive dust in it?

Chris Campbell

I just looked at Nostalgia Air--they have schematics for 1181 and 1291. Both have lots of audio amp tubes, tuned RF, 2 IF amps, discriminators and AFC(must have one of those mechanical search-tune systems that needed AFC).

Is yours similar to those?

Chris Campbell

The noise is only in this radio, and only on the broadcast band. Mine has chassis 11G, quite similar to the 1291. Mine does not have the telephone dial. It has three stages of IF, with a tuned RF stage.