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 Post subject: Re: 1970s Magnavox console right channel not working?
PostPosted: Nov Tue 24, 2015 1:51 pm 
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Joined: Nov Sun 15, 2015 4:53 am
Posts: 96
Location: New Jersey
Hi Ed, thanks for the info. The 9 pin connector is for RCA jacks on the back of the cab and the input for the turntable. 2 are for playback (I can hook up a CD player to it and so on), 2 are for Record and the others are for the input from the turntable. With the chassis out and that connector disconnected,..the radio still works. There are speaker connectors for left, right and common shown above in a picture I posted. With the chassis out I hooked the speakers back up and still no right channel. I'm going to give the pots a good cleaning and see if that helps. I don't have any background in trouble shooting electronics or know how to test each component inside the chassis or even know what to set my multi-meter at to test the components. There is no headphone jack that I can test either.

I want to give the pots and switches a good cleaning to see if that helps. I would really like to get it to work again, but don't want to spend a lot repairing it either.

EDIT: I cleaned all the pots and switches today a few times working them each time and still the right channel is dead. I went as far as to try the RCA "play" inputs on the back of the console and used a good turntable I have. Same thing happens,.left side good, right side nothing. :(

John


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 Post subject: Re: 1970s Magnavox console right channel not working?
PostPosted: Nov Wed 25, 2015 5:57 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 6565
Location: Black Hills, SD 57745
You've given it the old college try! Maybe you missed seeing Darren's reply just after mine, perhaps he can help.
-Ed


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 Post subject: Re: 1970s Magnavox console right channel not working?
PostPosted: Nov Wed 25, 2015 7:46 pm 
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Joined: Nov Sun 15, 2015 4:53 am
Posts: 96
Location: New Jersey
Ed in SoDak wrote:
You've given it the old college try! Maybe you missed seeing Darren's reply just after mine, perhaps he can help.
-Ed


Yes I did give it a go. PM was sent to Darren and waiting on phone call. Thank you.


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 Post subject: Re: 1970s Magnavox console right channel not working?
PostPosted: Nov Thu 26, 2015 3:16 pm 
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Joined: Nov Sun 15, 2015 4:53 am
Posts: 96
Location: New Jersey
Update: talked to Darren on the phone yesterday and we will be meeting up after the Thanksgiving holiday. He is familiar with this chassis and has a good idea what the issue could be. He lives about 45 minutes from me. I'm very thankful that he is taking the time to look at this for us. My wife is looking forward to listening to her Christmas albums over the holiday. Thank you everyone for all the information and helping me get this old girl back playing music. I will update after the repair is complete.

Thank you Darren...!!!


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 Post subject: Re: 1970s Magnavox console right channel not working?
PostPosted: Nov Thu 26, 2015 7:48 pm 
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Joined: May Mon 02, 2011 4:54 pm
Posts: 160
Location: Cement City, Michigan
John, now that you are totally confused and have ten different opinions, here is opinion number 11. Just scrap that amp and by a known good one on Ebay. You might pay $25/$50 for one. BTW, the problem is in the audio output circuit, and unless you can trouble shoot, just scrap it.


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 Post subject: Re: 1970s Magnavox console right channel not working?
PostPosted: Nov Thu 26, 2015 9:26 pm 
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Joined: Feb Sun 24, 2008 4:21 am
Posts: 4662
Location: Sedona, AZ/ Placentia CA
Stick with Darren, it could be something as simple as a cap or two or perhaps a couple transistors. JMHO You never know what you buy on line is going to work.
Jerry

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A friend in need is a pest. Bill Slee ca 1972


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 Post subject: Re: 1970s Magnavox console right channel not working?
PostPosted: Nov Fri 27, 2015 1:21 am 
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Joined: Nov Sun 15, 2015 4:53 am
Posts: 96
Location: New Jersey
JerryHawthorne wrote:
Stick with Darren, it could be something as simple as a cap or two or perhaps a couple transistors. JMHO You never know what you buy on line is going to work.
Jerry


I hear ya and I'm going to wait on Darren. He knows his stuff and said he had 2 working chassis the same as mine. He knows these amps inside and out and has a good idea what the issue could be. Believe me, if the amp wasn't so clean, I wouldn't bother with it. Even the pots don't make noise when adjusting them and there's no static,.. plus it sounds really good with only one channel working. I can imagine with both working, it will sound great. I'm looking forward to getting it all together. I think it's worth the time and effort to get it going again. The cabinet is in almost perfect condition.


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 Post subject: Re: 1970s Magnavox console right channel not working?
PostPosted: Dec Tue 01, 2015 9:29 am 
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Joined: Jan Mon 17, 2011 8:57 pm
Posts: 807
I hope you get this working again. Bad audio amp transistor in right channel would be my first guess for a totally dead channel. Also possibly bad caps. Caps are old enough that should probably be changed out anyhow.

I think I read online that the schematics are in Sams Photofact 1009-5. If you have the schematics, can you post a pic of it?

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 Post subject: Re: 1970s Magnavox console right channel not working?
PostPosted: Dec Tue 01, 2015 1:06 pm 
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Joined: May Tue 01, 2007 4:01 am
Posts: 1712
Location: Hamilton Square, New Jersey
Hi All,

She's working again. The last cap in the output chain was a goner. It blew out from the base. Impossible to see bet discovered through the multimeter signal tracing. Cap is replaced and both channels are working fine. A recap will be needed soon though.


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 Post subject: Re: 1970s Magnavox console right channel not working?
PostPosted: Dec Tue 01, 2015 2:39 pm 
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Joined: Nov Sun 15, 2015 4:53 am
Posts: 96
Location: New Jersey
Darren and I met at a local Wawa and he took the chassis last night around 7:00pm. I woke up this morning to a PM that said it was working again and it had one bad capacitor. Wow that was fast!! Darren also said,.."The unit sounds quite good and the stereo separation is really good". Darren is going to recap it in the spring for us. We are excited to get it back and put back in it's home. Christmas albums will be playing Thursday night!!. I'm going to pick up a blue tooth transmitter/receiver from Amazon to use my iPad through it.

Darren, again we can't thank you enough for taking the time and fixing this for us. It's an early Christmas gift..! :D


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 Post subject: Re: 1970s Magnavox console right channel not working?
PostPosted: Dec Tue 01, 2015 8:48 pm 
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Joined: Feb Sun 24, 2008 4:21 am
Posts: 4662
Location: Sedona, AZ/ Placentia CA
A happy ending!
Jerry

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A friend in need is a pest. Bill Slee ca 1972


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 Post subject: Re: 1970s Magnavox console right channel not working?
PostPosted: Dec Tue 01, 2015 9:34 pm 
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Joined: Jan Mon 17, 2011 8:57 pm
Posts: 807
That's awesome, glad to hear it!

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 Post subject: Re: 1970s Magnavox console right channel not working?
PostPosted: Dec Tue 01, 2015 10:25 pm 
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Joined: Nov Sun 15, 2015 4:53 am
Posts: 96
Location: New Jersey
Thank you everyone for all the great information. I'm grateful Darren was able to fix it and it didn't end up,..well you know!!


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 Post subject: Re: 1970s Magnavox console right channel not working?
PostPosted: Dec Wed 02, 2015 1:40 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 486
Location: Little Chute, WI
Hey that's great!
Glad to hear its going to be saved and not junked. Sounds like the same problem as the unit I worked on. We used to have this discussion with "antique" 1930s radios .... (do you replace all the caps or not), but now stuff from the 70's is old enough that there's a good chance they stop working from something as simple as a bad cap.

Good job Darren as well :D


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 Post subject: Re: 1970s Magnavox console right channel not working?
PostPosted: Dec Wed 02, 2015 1:53 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 6565
Location: Black Hills, SD 57745
Great outcome! Glad it was kept mostly original, replacing only what's needed. You could've shotgunned in all caps at once then never know how many or which one was the culprit.

Maybe you'll be able to participate in the eventual recap or even take some or all of that job on yourself.

Have a Very Maggie Christmas!
-Ed


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 Post subject: Re: 1970s Magnavox console right channel not working?
PostPosted: Dec Wed 02, 2015 2:35 am 
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Posts: 2077
Location: Long Beach, CA 90808
Kudos to Darren! Huzzah!

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 Post subject: Re: 1970s Magnavox console right channel not working?
PostPosted: Dec Wed 02, 2015 5:55 am 
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Joined: May Tue 01, 2007 4:01 am
Posts: 1712
Location: Hamilton Square, New Jersey
Thanks all. Challenges are fun. This model is in the 1970 Magnavox catalog as the Old World Meditteranean model 3653. My initial guess was 1969. I was off by one year. That chassis continued into 1972 for the stereorama/continental and hexagonal end table models but this record changer was a transitional model setting the stage for the more modern sleeker design of 1971.


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 Post subject: Re: 1970s Magnavox console right channel not working?
PostPosted: Dec Wed 02, 2015 3:35 pm 
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Joined: Nov Sun 15, 2015 4:53 am
Posts: 96
Location: New Jersey
Ed in SoDak wrote:
Great outcome! Glad it was kept mostly original, replacing only what's needed. You could've shotgunned in all caps at once then never know how many or which one was the culprit.

Maybe you'll be able to participate in the eventual recap or even take some or all of that job on yourself.

Have a Very Maggie Christmas!
-Ed


I would like to participate in the recap as I don't have the knowledge to do it myself. I've never done something like this before and honestly I'd be afraid of destroying the unit if I tried. I would like to learn, but right now I have no clue of even how to trouble shoot electronics.


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 Post subject: Re: 1970s Magnavox console right channel not working?
PostPosted: Dec Thu 03, 2015 6:21 am 
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Joined: May Tue 01, 2007 4:01 am
Posts: 1712
Location: Hamilton Square, New Jersey
Recapping is actually quite easy. When it's time to recap this one, you can definitely participate. There are two quirks with this particular chassis: 1. Magnavox decided that the chassis have a positive potential; to this end the main filter cap has a positive can ( Chassi are negative 99% of the time); 2. There is a misprint on the chassis layout-the polarity of one of the preamp caps is etched backwards on the circuit board so one has to rely on the polarity of the actual cap and not what's printed on the circuit board. Replacement caps ensure ongoing reliability, better supply of B+ voltage, less power droop during loud musical passages, a tighter transient response and improved treble response. Additionally, the often unobtainable semiconductors are protected from failure. Sometimes the difference in performance with a recap is dramatic, sometimes not so, but the security of knowing that failure has been prevented is a great thing.


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 Post subject: Re: 1970s Magnavox console right channel not working?
PostPosted: Dec Thu 03, 2015 9:46 pm 
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Joined: Nov Sun 15, 2015 4:53 am
Posts: 96
Location: New Jersey
DarrenWGaransi wrote:
Recapping is actually quite easy. When it's time to recap this one, you can definitely participate. There are two quirks with this particular chassis: 1. Magnavox decided that the chassis have a positive potential; to this end the main filter cap has a positive can ( Chassi are negative 99% of the time); 2. There is a misprint on the chassis layout-the polarity of one of the preamp caps is etched backwards on the circuit board so one has to rely on the polarity of the actual cap and not what's printed on the circuit board. Replacement caps ensure ongoing reliability, better supply of B+ voltage, less power droop during loud musical passages, a tighter transient response and improved treble response. Additionally, the often unobtainable semiconductors are protected from failure. Sometimes the difference in performance with a recap is dramatic, sometimes not so, but the security of knowing that failure has been prevented is a great thing.


Thanks again Darren. I'm looking forward to doing this with you. When the time comes, let me know what we need for the re-cap. I'll purchase everything ahead of time and have it ready to go. Do certain caps sound better than others, brand and so forth?


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