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 Post subject: 1970s Magnavox console right channel not working?
PostPosted: Nov Sun 15, 2015 5:04 am 
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Joined: Nov Sun 15, 2015 4:53 am
Posts: 96
Location: New Jersey
Hi, I'm new here and have a question. We have an early 70s Magnavox console am/fm with turntable that was given to us by a family member. The right channel is not working. Speakers are good. Wires are good and hooked up correctly. Everything seems ok with the wiring. What can I look for to get it working again, trouble shooting? It's a solid state unit.
Thank you,

John


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 Post subject: Re: 1970s Magnavox console right channel not working?
PostPosted: Nov Sun 15, 2015 6:14 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 486
Location: Little Chute, WI
Hi John,

First, check to see if the balance control is set all the way to the left.

I recently fixed a similar unit for a friend that had 0 volume. I ended up totally recapping the unit, and it played and sounded like new. Not saying that's whats wrong with yours, but by this time the capacitors have outlived their lifespan, and would need to be replaced before further troubleshooting.


Take care,
jerry


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 Post subject: Re: 1970s Magnavox console right channel not working?
PostPosted: Nov Sun 15, 2015 3:57 pm 
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Joined: Nov Sun 15, 2015 4:53 am
Posts: 96
Location: New Jersey
Thank you Jerry, I will pull the unit out to see if there's anything noticeably burnt. The balance is up the middle. I check the balance control and turned all left, and there's no issue. Turn it all right and I get nothing even at full volume. Like I said, the speakers are good as I checked them on the working channel. Another question, if I get the unit to work again are there replacement speakers available for these that will sound the same as the originals? I know I can get speakers anywhere, but I'm sure they won't have the same sound as the originals. I'm sure the cones are dry rotted,.but they look good. Honestly, it sounds really good with just the left channel working, so I could imagine it will sound even better with the other channel working. We have around 300 albums we would like to start listening to. Do you have a site to get parts if needed? Caps and so forth. It's been a while, but when recapping (If needed) and since it's solid state, there's no need to bring the voltage up slowly like a tube amp,...correct? I attached a picture of it when we picked it up from our family member. It is in really nice shape. Just need to get it working and then detailed. What do you think?
Thanks again for you help,

John


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Magnavox.jpg
Magnavox.jpg [ 115.46 KiB | Viewed 4191 times ]
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 Post subject: Re: 1970s Magnavox console right channel not working?
PostPosted: Nov Sun 15, 2015 6:24 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 486
Location: Little Chute, WI
Hi John,

I usually order caps from http://www.digikey.com/en

The speakers in this unit are good, and don't need replacing. They do not have foam surrounds that deteriorate.

The most likely culprit (from a quick remote assessment via the web :) ) would be defective capacitors. There could be some other problem but that would be a good place to start. BUT FIRST - I'd double check the wires going to the crossover network and speakers, to make SURE there is not a loose connection or broken wire etc. on the right channel.

Have you ever done any electronic / cap replacement work before? Do you have a soldering station? If not, let me know, and I'll try and talk you through it. Not that hard, but it takes a little patience and attention to detail.

Take care,
jerry


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 Post subject: Re: 1970s Magnavox console right channel not working?
PostPosted: Nov Sun 15, 2015 9:08 pm 
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Joined: Nov Sun 15, 2015 4:53 am
Posts: 96
Location: New Jersey
Thanks Jerry. I'm pretty good with a soldering gun, but never replaced caps before. Once I make sure the speakers and crossover are ok, I'll move on to the chassis. Any way to tell if the caps are bad in the first place if this is the case? Can I measure voltage across them. Or how should I test them? I will take some picture of it and post. If it's ok with you, I'll shoot you a PM when I post them. I'm very bus this coming week and should have pictures posted next weekend. I've always liked these consoles. I grew up in the 60s and remember these consoles well. The one my parents had was tubes. I remember that thing was loud.


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 Post subject: Re: 1970s Magnavox console right channel not working?
PostPosted: Nov Mon 16, 2015 12:33 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 1667
Location: Illinois
Since you've never recapped a set before, a word of warning. It's very easy to make a wiring error. Best to disconnect one leg of the old cap and connect one leg of the new cap, then the other leg. If you make a wiring error, then you have two problems, which much complicates troubleshooting.

Personally, I sort of doubt the problem is with a cap. That usually doesn't cause a channel to go dead. Could be a transistor in the audio section of the dead channel. Best to troubleshoot in a systematic manner with a multimeter. Try to get a schematic, but otherwise, you have one channel that is working that can be used for comparison purposes. The problem will be in the circuitry unique to the dead channel, not components, such as the power supply, that are shared by both channels.

If the one dead channel is dead for AM, FM, and phonograph, all three, then suspect the problem is in the audio stage of that channel. Compare voltages between the two channels. If you have never done such step-by-step troubleshooting before, this set is probably not the place to start. You may need help beyond what you can get from a website like this one.

I have a feeling that if you start wholesale replacement of caps, this project may not end well. Systematic troubleshooting is called for, which takes some experience.

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Doug


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 Post subject: Re: 1970s Magnavox console right channel not working?
PostPosted: Nov Mon 16, 2015 2:29 pm 
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Joined: Nov Sun 15, 2015 4:53 am
Posts: 96
Location: New Jersey
Thank you. Yes, I will go over everything before replacing anything. There is a schematic inside the console. Once I look at the speaker connections, I'll move on from there. I don't want to spend a lot of money on it either. So if it's not something that is simple to fix, I will convert it over with updated components I have already. BUT, I'd like to see it working again if possible.


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 Post subject: Re: 1970s Magnavox console right channel not working?
PostPosted: Nov Mon 16, 2015 2:34 pm 
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Joined: Nov Sun 15, 2015 4:53 am
Posts: 96
Location: New Jersey
If I post the schematic, can someone walk me through testing? What to test and so forth? I will also post closeup pictures of the chassis. It's a shame, because the cabinet is in almost perfect shape.


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 Post subject: Re: 1970s Magnavox console right channel not working?
PostPosted: Nov Mon 16, 2015 4:08 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 4541
Location: Charleston, W.Va.
Hi Thesmanman,
Good advice above from Jerry and Doug.

Yes, by all means post the schematic if you can. If not, it is likely that a SAMS Photofact can be found for your Magnavox which will have complete service data.

You mention you don't want to spend a lot on this one. If we can help you figure out the problem and you are able to fix it yourself, its is likely that cost for parts/components required (if any) will be very minimal.

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Poston


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 Post subject: Re: 1970s Magnavox console right channel not working?
PostPosted: Nov Mon 16, 2015 4:11 pm 
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Joined: Nov Sun 15, 2015 4:53 am
Posts: 96
Location: New Jersey
Thank you. I will post a few pics once I have it apart. Should be soon.


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 Post subject: Re: 1970s Magnavox console right channel not working?
PostPosted: Nov Sun 22, 2015 8:37 pm 
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Joined: Nov Sun 15, 2015 4:53 am
Posts: 96
Location: New Jersey
Hi everyone, I looked at all the speaker connections and they are all good. There are 3 wires coming out of the chassis for the speakers, 2 C 1. The # 1 connector is not outputting signal. I can take the speaker wire off number 2 and connect number one wire to it and the right speaker comes on. I would imagine it's something that has gone bad on the chassis on that right side. With that said,..how in the world do I remove the chassis from the cabinet? It looks to me that the chassis slides out but for the life of me, it won't move and I can't figure out how to get it out. Please see pictures. I also have no idea once I remove it what to look for. Of course if something is obviously burnt I'll see it. I also tried to look for a schematic diagram, but can't find that either. The only schematic inside the cabinet is the speaker wiring diagram. Any help would be appreciated to get it up and running again. If not, I'll toss it. The chassis a 1970 R22276 DE if this helps,.but not sure of that because I saw the same one on ebay and figured it was the same.
Thank you,

John


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image(2).jpeg
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Last edited by Thesmanman on Nov Sun 22, 2015 11:41 pm, edited 1 time in total.
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 Post subject: Re: 1970s Magnavox console right channel not working?
PostPosted: Nov Sun 22, 2015 10:37 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 4541
Location: Charleston, W.Va.
Hi John,
Don't give up this Magnavox just yet, it's a good piece of equipment. From your chassis #, service data was published in SAMS Photofact #1009-5. You need to get this Photofact which contains complete service data. It is available from the SAMS Technical Publishing, Inc. official website, but before paying them a high price place a WTB here in the Classified section of the ARF. One of our members may sell you an original cheap or maybe even send you one for free.

No need to worry about how to get chassis out until you have service data/knowledge to repair it. Problem may be something relatively simple.

It might be wise to post your location in your profile. Maybe one of our members in your area could help? Or know someone who can?

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Poston


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 Post subject: Re: 1970s Magnavox console right channel not working?
PostPosted: Nov Sun 22, 2015 11:23 pm 
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Joined: Nov Sun 15, 2015 4:53 am
Posts: 96
Location: New Jersey
Hi Poston, thank you. I'll look into seeing if I can get the service data. As of knowledge about fixing this, I'm really not sure about it. I'm good with fixing things, but I never tried to fix a bad channel on a stereo before. I don't even know how to trouble shoot it.


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 Post subject: Re: 1970s Magnavox console right channel not working?
PostPosted: Nov Mon 23, 2015 12:44 am 
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Joined: Nov Sun 15, 2015 4:53 am
Posts: 96
Location: New Jersey
Inside there is a paper glued to the cab that has instructions that tells you how to remove the chassis,.but it has reverted nuts on the pots. How do you get those off if you don't have the proper tool?


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 Post subject: Re: 1970s Magnavox console right channel not working?
PostPosted: Nov Mon 23, 2015 4:58 am 
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Joined: May Tue 01, 2007 4:01 am
Posts: 1712
Location: Hamilton Square, New Jersey
Hold the outer volume ring where one channel is making sound and the turn the inner ring without the outer one moving. Both controls most likely move together by friction one might be turned to minimum. Work the mode selector a few times to see if there are dirty connections. You should do the same with the speaker selector switch. Spray the speaker selector, mode selector and volume/balance contro wit deoxit or contact cleaner. This might bring back the other channel.
I would not be concerned about the speakers. Replacements will not improve the sound. This unit was actually made in 1968-69 and these speakers do not deteriorate they were designed for that amplifier and cabinet. That amp is about 30 watts. At some point you might want to replace the electrolytic capacitors for better sound; I've never seen one of these with one channel out due to a bad transistor or bad capacitors. The most common problem is dirty contacts on the selector switches or the audio controls.


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 Post subject: Re: 1970s Magnavox console right channel not working?
PostPosted: Nov Mon 23, 2015 2:07 pm 
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Joined: Nov Sun 15, 2015 4:53 am
Posts: 96
Location: New Jersey
Darren thank for the information. It's not the balance control as I've checked that and was hoping it was. I can take the balance control turn it to the left and the left speaker has signal,.turn to all right and I get nothing from the right channel. I also traced the speaker wires (see picture) from the chassis to the selector switch. I unscrewed the selector switch mounting plate from the cabinet and jumped the right side wires directly to the speaker and still get nothing. I'm going to try to jump the direct output connectors from the chassis to the speakers and see if that gives me the right channel back. If that doesn't work,..I don't know where to go from there?

Would any of you electronic wizard be able to walk me through testing the electronic components so I can find what is wrong? I've attached a picture of inside the chassis and not sure if that helps?

EDIT: I jumped directly from the speakers outs on the chassis (see picture below),.left channel ok,.right channel nothing. Where do I go from here?

Thank you,

John


Attachments:
Speaker outs.jpg
Speaker outs.jpg [ 116.17 KiB | Viewed 3947 times ]


Last edited by Thesmanman on Nov Mon 23, 2015 6:00 pm, edited 1 time in total.
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 Post subject: Re: 1970s Magnavox console right channel not working?
PostPosted: Nov Mon 23, 2015 3:50 pm 
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Joined: May Tue 01, 2007 4:01 am
Posts: 1712
Location: Hamilton Square, New Jersey
Does the problem occur in AM, FM and the phono modes? If so check all the traces on the circuit board, check for loose caps and any other loose components that may need to be resoldered.


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 Post subject: Re: 1970s Magnavox console right channel not working?
PostPosted: Nov Mon 23, 2015 3:57 pm 
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Joined: Nov Sun 15, 2015 4:53 am
Posts: 96
Location: New Jersey
Darren, I checked all,..AM, FM, Turntable and nothing from the right channel. I will need to pull the chassis at this point. This is going to give me an issue as well. It has inverted pal-nuts that hold the bezel on. I have no idea how to loosen these nuts. A standard socket won't work!! :?

EDIT: I made a nut to fit inside the pal-nuts and was able to remove the chassis. I don't see anything that looks burnt. The chassis # is R22206 DE. I'm trying to find a local TV repair shop to fix it, but is it worth having it fixed is the question? I'm not experienced enough to fix it myself.

Would anyone know what year this console is? The chassis is a R22206 DE and model # is 1P 3653.
Thank you,

John


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image(4).jpeg
image(4).jpeg [ 159.28 KiB | Viewed 3900 times ]
image(5).jpeg
image(5).jpeg [ 198.51 KiB | Viewed 3900 times ]
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 Post subject: Re: 1970s Magnavox console right channel not working?
PostPosted: Nov Tue 24, 2015 8:34 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 6565
Location: Black Hills, SD 57745
Just about dead center in the first pic of the insides, there's a square with 9 pins like a Domino pattern. Its labeled Ch1 and Ch2, so it must be a connector from the amp to something left/right related, and you should find a mating connector and wires on the outside of the chassis at that spot. Just another spot to check for weak wiring. You wouldn't think it would be the turntable audio and power in one connection, but that's possible I guess. Easy enough to track the thing that plugs in there.

Now you can get at the insides of the controls and switches from the front panel. Openings in these and visible wipers/fingers in the switches are where you should aim the cleaning spray, then work that control back and forth a bit and move to the next control. Spray and work, repeat... I use CRC electronics cleaner which you can probably find in many stores. Deoxit is the favorite on ARF, but not the only choice. You should try a cleaner spray first before worrying about tearing into it. No matter which, a little can go a long ways, no need to flood it, but it may take more than one application to do the job.

It's all doable with patience, persistance and simple tests and intuition, which you've already shown you possess. I kinda doubt it's a cap myself, but that is possible just the same. There's a bunch of them in there! The fact one channel works is a plus. A power supply problem would most likely affect both channels equally. By inference, for a cap to be the problem, there would need to be two caps of the same value, one serving each channel, but only one is bad.

Since it's stereo, you will spot many identical pairs of parts, left and right versions. They may be adjacent or tend to wander a bit to follow the circuit traces and chassis layout more efficiently or seemingly by an engineer's whim. ;) But with practice, you'll be able to sort out the left and right halves of the circuit by eye, although a schematic or full service manual will certainly help immensely.

So armed, you can begin to compare the working side to the failed one and possibly detect a different reading or see a visible indication. It's not at all unusual for old factory errors to surface, such as skipped solder connections or failed joints. Don't over look inspecting the traces for breaks or burned spots, dark-looking or crispy parts, but I don't think this one was a smoker when it failed. But, like a light bulb, a part can just pop open when the unit is turned on, no real other reason except age and it's time was up. As suggested, a dirty control or weak connection if the first line of attack. A DMM can help find open or shorted parts or verify "good" if it reads similar to its opposite channel's mate.

Is there a headphone jack? Try it there yet? Sometimes it's dirty or worn and does not switch back properly to the speakers when the headphones are unplugged.

Dig in, take your time and have fun learning!

-Ed


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 Post subject: Re: 1970s Magnavox console right channel not working?
PostPosted: Nov Tue 24, 2015 1:27 pm 
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Joined: May Tue 01, 2007 4:01 am
Posts: 1712
Location: Hamilton Square, New Jersey
John, I noticed that you are in NJ, send me a PM. I might be able to take a crack at this.


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