Motorola ST-82A stereo AM-FM record player

Discussions about instruments in smaller cabinets. If they don't set on the floor, they belong here. Tube and solid state, stereo and mono.
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electra225
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Re: Motorola ST-82A stereo AM-FM record player

Post: # 10140Post electra225 »

One Admiral thingy...... ;)

Lawrence Welk on RCA. This is actually a pretty good compilation.
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Re: Motorola ST-82A stereo AM-FM record player

Post: # 10149Post William »

Thanks, Greg, now I know what an Admiral thingy is. :roll: ;) :lol:

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Re: Motorola ST-82A stereo AM-FM record player

Post: # 10150Post Hi-Fi-Mogul »

electra225 wrote: Wed Oct 05, 2022 3:22 am There is a little plastic bolt/screw under the tone arm that apparently adjusts how high the tone arm lifts. I gave it a quarter turn. It doesn't take much to make a lot of difference. It seems better the more records that get stacked on the spindle. I don't know how many the limit is, but I stacked six and didn't have any trouble. I have the service instructions for VM changers that I consulted to see what I needed to do. Taking the mechanism apart is out of my wheelhouse at this point. Maybe sometime down the road. I'm learning in baby steps how to work on changers. There was a time in the not-too-distant past I wouldn't have attempted even this much. I appreciate everybody giving me the benefit of their knowledge on changers. :)

I gave the mechanism a "shower with your socks on" kind of clean and re-lube.
That's good you found an easy answer to the tonearm problem.

The service lit says 1/2 inch high stack of albums is
load limit for these V-M models with the short record spindle.

I adjusted the contrast on the photo, and I see your
V-M is a B1267. If you post the numbers after "857",
we can tell you the date it was made.

It's in Sams 748-11 from 4/65.
I've got that file if you want it later.
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Re: Motorola ST-82A stereo AM-FM record player

Post: # 10151Post electra225 »

I need to buy a tripod. When I try to take a close-up photo, it comes out all shaky. Old age, Mr. Mogul. Sorry........ :oops:

And thank you for your kind offer. I have a fairly comprehensive text on VM here that I consulted to get me that far. ;)

You are welcome, Bill. I'll store the Admiral thingy on my Motorola platter until somebody needs it....
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Re: Motorola ST-82A stereo AM-FM record player

Post: # 12797Post electra225 »

I thought this thing was fixed..... :oops: :roll: :oops:

When it is cold, I have no AM at all, FM is all drifty and comes in and out, with very little volume. After it runs for five minutes or so, AM may work and may not, FM works okay, but no stereo. Another couple minutes, stereo starts working. I suspect a tube, but which one?
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Re: Motorola ST-82A stereo AM-FM record player

Post: # 21704Post electra225 »

This thing is still causing me fits almost a year and a half after I posted. I've had the guts in and out of this thing so much I've got the screw holes worn out. I'm about ready to remove the changer and speakers then "round file" the rest. Nothing I do seems to work. When I have the guts out, they work. Back into the cabinet, they don't. The worst issue is on AM. FM still has an issue, but it seems to be a little better. AM will work about 20 minutes, then is slowly fades away. Sometimes moving the function switch to another position then back "fixes" it. Sometimes that doesn't work. I have subbed all the tubes in the front end. The record player is no problem. It seems to me like maybe all it needs is a good alignment. I believe the oscillator quits running. The next thing I'm going to try is to fire up about six VTVM's, then connect them to certain places in the chassis. I want to see if the oscillator quits. I want to make sure I don't lose B+, or that B+ doesn't "droop" or slowly fade away for some reason. The tubes stay lit. I want to spritz the function switch with De-Oxit to see if that helps. I'd think if B+ faded away, the record player would quit as well. I don't know anymore. I know I'm sick of this thing. I used this stereo in my restoration shop. It ran a LOT back then. In recent years, it is just not dependable. This is the one I found in the back of a station wagon I bought for parts. I should have left it where it was....... ;) :roll: :cry:
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Re: Motorola ST-82A stereo AM-FM record player

Post: # 21724Post electra225 »

Okay, since I decided to quit feeling sorry for myself...... ;)
The FM side of the tuner will run sometimes all day without quitting. "The Ride" comes in strongly at 94.1, the stereo light comes on, fidelity seems good. AM is another story. It will play from 15 minutes to two hours, then it just fades away over a period of about two minutes. I don't have the chassis out yet, but I had subbed all the tubes from a Motorola table radio with no change. The tubes from the stereo work well in the table radio, so I think I can eliminate tubes as an issue. I was under the assumption that perhaps a tube filament was opening when it got really warm, but apparently that is not the case. The record player will work seemingly forever with no issue.

I believe the first avenue of investigation will be to determine whether the AM oscillator is quitting after a time. I also want to check B+ to see if it's going away for some reason. I think it's fair to say the issue is in the front end somewhere. The function switch is not above suspicion, either. I'll get the chassis out, sub in some test speakers, then connect two or three VTVM's and see what they tell me.
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Re: Motorola ST-82A stereo AM-FM record player

Post: # 21735Post electra225 »

For those of you who might care to follow along, the chassis on this stereo is HS 1323 D. 8 tubes plus solid state rectifier and SS Multiplex section. I have a "sort of" drawing that was supplied with the stereo. This thing has factory documentation. I need a drawing that has alignment instructions and voltage readings more than just a few. What I found today is this.

First, nothing I did helped it one iota. It has a two-part function switch. One part is mounted tight to the front with a shield around it. Makes it very hard to get a good cleaning job on the switch. I found a broken AVC wire off the antenna, which makes no difference connected or disconnected. It will play better on FM than AM. When it quits completely on AM, FM is really weak, but you can still hear it. I don't have the changer connected, but I need to so I can see if the audio section is affected. I thought at first it wasn't, but now I won't swear to that. When AM quits, if you move the function switch to FM then back to AM, usually that will get AM working again. After the set runs for a couple hours, nothing will make AM work. You have to shut the set off and let it cool. After cooling for about an hour, the process starts over again. It acts like something is getting warm. I'm supposed to have minus 11.5 volts on the oscillator. IT has been running about 12 to 14 volts negative, this measured by an analog VTVM. If I touch one end of the loopstick antenna, the volume will get higher, which leads me to wonder if it is just out of alignment. I'm going to have to find a more-complete drawing. This thing is full of Carbonneau-built speakers. The tone arm weight is set at 2.8 grams.
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Re: Motorola ST-82A stereo AM-FM record player

Post: # 21764Post electra225 »

I'm not sure yet what this means. The function switch controls B+ to both radio bands. B+ for the AM band goes to Pin 5 of the 12BE6 converter tube, the plate. I have about 85 VDC there. When the AM band gets weak or quits entirely, B+ rises to about 115 volts. That would indicate to me that the function switch is still working and making contact. IT would also indicate to me that something is opening, lowering the load on B+. I need to measure B+ at the cathode of the rectifier to see what it is and what happens when the radio acts up. There are several carbon resistors and several sand resistors that I need to check the values on. This set may be in need of a component by component rehabilitation. This is a strange one..... :roll:
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Re: Motorola ST-82A stereo AM-FM record player

Post: # 21765Post electra225 »

i pulled the substitute tubes out, put the original tubes back in. In the exchange, I put some PB BLaster on a Q-Tip, then mopped the tube pins before I put them back in. After they were in, I wiggled them really well. Now I can't get the thing to quit..... ;)

I'm not confident that this fixed anything.... :oops:
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Re: Motorola ST-82A stereo AM-FM record player

Post: # 21766Post electra225 »

This set has run all afternoon and hasn't skipped a beat since I repopulated the original tubes. I went thru the changer. I'm going to hook it up then check it out that way. I have no idea what I did to fix this stereo, and still don't have a lot of confidence that I fixed it. I believe I'll order the Sams for this, do a good alignment, as well as check the resistors and that. It pulls 51.64 watts without the changer motor on.
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Re: Motorola ST-82A stereo AM-FM record player

Post: # 21770Post electra225 »

Neither the instrument model number nor the chassis number are listed in Sams. Is there a secret to ordering service literature for a Motorola?
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Re: Motorola ST-82A stereo AM-FM record player

Post: # 21783Post electra225 »

I fired this set up this afternoon and it wouldn't play on AM or FM. I decided to work on the changer, play some records, then see what it did. After I played a stack of records, both AM and FM would work just fine, thank you.....

I took the VM model 1267 changer apart to clean and lube. The process went fine, no problems. I put it all back together, put on a stack of 45's. This short-spindle VM changer will drop stereo 45's for some reason. After the first record played, the changer cycled like it should. I noticed that the tone arm operated a bit too jerky for my taste, the swing back to the tone arm rest was not smooth. The next record did the same. The third record, when the tone arm came to the cycling grooves, the tone arm went in toward the spindle, moved back about a 1/4 inch, then came back about an inch and up at the same time. It bounced down and hit the record grooves. Not good.

I asked Mr. VM for his input and he said what I was thinking: I messed up. :oops: :roll:

I pulled it all back apart to check my work. All the parts were there, all in the right spot. I got to looking and found the ramp on the slide that pushes up on the tone arm shaft was dry as a popcorn fart. No grease at all. So I redid all the lube, made sure everything was free, put it all back together, put on a stack of 45's. Worked like a charm. I read that you should not over-grease. Well, that might be true, but you have to at least "somewhat" grease. Lesson learned.

I still haven't found service information for this set. I sure need some. ;) ;)
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Re: Motorola ST-82A stereo AM-FM record player

Post: # 21797Post electra225 »

I decided to try something different. I tested the tubes stone cold, after setting overnight. I tested them after I had run the set for a time last time. The 17C9 in the tuner is an RF amp. My initial thinking was that it was for FM only. Apparently, not so. Half of this tube is the RF amp for AM and FM, the other half is the mixer/oscillator for FM. Half of the tube tests totally dead, with no output at all, the other half barely moves the needle. Of course, in phono operation this tube is unimportant, as long as the filament lights, since this is a hot chassis. I left this tube in the tube tester to let it get warm. I'll see if we have emission after it's good and warm. This would explain why the radio fades after a time, yet takes several minutes to come on when cold. Why moving the function switch from AM to FM and back has any effect, I haven't figured out yet. Maybe coincidence? Maybe still a dirty function switch? The 17C9, Sylvania-sourced, is the only original tube left in the chassis. I don't have a 17C9 in my tube stash, but may have one in an Admiral chassis upstairs. Stand by..... ;)
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