1966 Magnavox astro-sonic console

T

taggart

New Member
1966 Magnavox astro-sonic console repair help needed

I have a 1966 Magnavox console unit with the astro-sonic stereo receiver and micromatic turntable. I recently took apart, cleaned, and lubed the turntable and it is working and sounding great. My problem now is the receiver, it is not working on am or fm, it powers on but no sound at all. I acquired the Sam's photofact folder on it and have replaced the majority of the electrolytic capacitors to no avail. This is where my knowledge of the subject runs out, as I have no testing equipment and am not sure how to test in circuit anyway. Any suggestions to try a fix of the problem before I spend too much money to have it repaired would be greatly appreciated. Also, if I do end up sending it out for repair, what would be a reasonable price for this sort of fix, so I don't get fleeced.

Thanks,

taggart
 
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Thank you loopstick,

I realize now that I jumped into something I should have got more advice on. I did clean all the controls with deoxit, while testing I hook up an FM antenna, and the AM antenna looks to be in good shape.
 
Is the amp working in phono or AUX?? If so you probably have a switching problem. If it has a speaker selector switch on the LEFT side of the cabinet, make sure it's connected correctly and working. If it's not working or broken, it can be bypassed and the speakers fed directly. IIRC it's in the FRONT LEFT Corner on that one.

Hit all the switches and pots again with DeOxit. 3-4 applications or treatments over a months time to clear a problem up is not unusual for older gear.Spray with D-5/EXERCISE the POTS and Switches. UP/DOWN; ROUNDY,ROUND; in/OUT 30-50 times each. You'll develip lower arm muscles you never though possible. The FUNCTION SELECTOR is the most notorious of the offenders on the ASTROSONICS.

The cabinet looks very much like my '67 Forest Hills. As does the turntable (which is the one I used for the "Micromatic teardown and rebuild" tutorial in the Phono Forum back in '09). The Bezel looks the same. but I can't vouch for the receiver as it's been 5 years since I've had it out of the cabinet.

Take a RCA Cable, and wrap one end of a .01uf//600V cap on the center lead (solder it on if you want). Plug the other end into a receiver AUX. Then power up and touch the various component legs in the signal path from the output back to the input.Keep the volume down to keep from blowing a speaker. Headphones would be ideal here. When you get a signal on the input side of a component and none on the output side, thats your bad part.
 
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Looks exactly like my 67 astrosonic:yes: let me know how things turn out, I actually have that exact receiver somewhere in my parts bin in good working order. :D
 
larryderouin said:
Is the amp working in phono or AUX?? If so you probably have a switching problem. If it has a speaker selector switch on the LEFT side of the cabinet, make sure it's connected correctly and working. If it's not working or broken, it can be bypassed and the speakers fed directly. IIRC it's in the FRONT LEFT Corner on that one.

Hit all the switches and pots again with DeOxit. 3-4 applications or treatments over a months time to clear a problem up is not unusual for older gear.Spray with D-5/EXERCISE the POTS and Switches. UP/DOWN; ROUNDY,ROUND; in/OUT 30-50 times each. You'll develip lower arm muscles you never though possible. The FUNCTION SELECTOR is the most notorious of the offenders on the ASTROSONICS.

The cabinet looks very much like my '67 Forest Hills. As does the turntable (which is the one I used for the "Micromatic teardown and rebuild" tutorial in the Phono Forum back in '09). The Bezel looks the same. but I can't vouch for the receiver as it's been 5 years since I've had it out of the cabinet.

Take a RCA Cable, and wrap one end of a .01uf//600V cap on the center lead (solder it on if you want). Plug the other end into a receiver AUX. Then power up and touch the various component legs in the signal path from the output back to the input.Keep the volume down to keep from blowing a speaker. Headphones would be ideal here. When you get a signal on the input side of a component and none on the output side, thats your bad part.
Click to expand...

Thanks again larryderouin, I am working the pots more now.
 
kydog said:
Looks exactly like my 67 astrosonic:yes: let me know how things turn out, I actually have that exact receiver somewhere in my parts bin in good working order. :D
Click to expand...

wow kydog, It would be much easier for me to just swap out the receiver, i'm quite a novice when it comes to electronics. How much $ would you want for the replacement?
 
larryderouin said:
Is the amp working in phono or AUX??
Click to expand...

I don't see that you've answered this question; it is a very important one if you plan on continuing to troubleshoot here, as it could indciate where the problem is.

For instance, if "yes" then it means the preamp and power amp are both working. But since neither AM nor FM is working, then that tells me the problem is probably at or near the function selector switch. Maybe you bumped or shorted to ground a signal wire en route to the selector. Or maybe it just needs more cleaning.

It could be that both AM and FM have issues, separate from one another. Some of the Astrosonic tuners have gain pots on the chassis for MPX stereo balance. You could try adjusting those, or test in the mono setting only, if there is one.

Also many of those receiver function switches incorporate a power switch into the Phono setting so that when the changer shuts off, the power to the receiver does too. All the other functions should be unaffected, power-wise, but you want to make sure that the faceplate lamps are on when you are testing the tuner settings.

Post the schematic if you can, or give us the chassis number. In my opinion you'll get a lot of satisfaction in fixing this one, and I bet you are closer than you realize.

RWood
 
RWood said:
I don't see that you've answered this question; it is a very important one if you plan on continuing to troubleshoot here, as it could indciate where the problem is.

For instance, if "yes" then it means the preamp and power amp are both working. But since neither AM nor FM is working, then that tells me the problem is probably at or near the function selector switch. Maybe you bumped or shorted to ground a signal wire en route to the selector. Or maybe it just needs more cleaning.

It could be that both AM and FM have issues, separate from one another. Some of the Astrosonic tuners have gain pots on the chassis for MPX stereo balance. You could try adjusting those, or test in the mono setting only, if there is one.

Also many of those receiver function switches incorporate a power switch into the Phono setting so that when the changer shuts off, the power to the receiver does too. All the other functions should be unaffected, power-wise, but you want to make sure that the faceplate lamps are on when you are testing the tuner settings.

Post the schematic if you can, or give us the chassis number. In my opinion you'll get a lot of satisfaction in fixing this one, and I bet you are closer than you realize.

RWood
Click to expand...

Yes, I would prefer to fix this one, so I will tell you all I can.
when the record player is hooked up to the phono out, and the selector switch is in the phono position, there is sound through the speakers, and it functions great in phono mode, which leads me to belive that the preamp and power amp are working. When switched away from phono, the phono powers off. Also, you are right about the power shutting off when the record player cycles off.
When switched to any other function the faceplate lamps are on.
The speaker switch is turned to internal, and they work fine in phono.
I will post the schematic soon.
 
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schematics

RWood said:
I don't see that you've answered this question; it is a very important one if you plan on continuing to troubleshoot here, as it could indciate where the problem is.

For instance, if "yes" then it means the preamp and power amp are both working. But since neither AM nor FM is working, then that tells me the problem is probably at or near the function selector switch. Maybe you bumped or shorted to ground a signal wire en route to the selector. Or maybe it just needs more cleaning.

It could be that both AM and FM have issues, separate from one another. Some of the Astrosonic tuners have gain pots on the chassis for MPX stereo balance. You could try adjusting those, or test in the mono setting only, if there is one.

Also many of those receiver function switches incorporate a power switch into the Phono setting so that when the changer shuts off, the power to the receiver does too. All the other functions should be unaffected, power-wise, but you want to make sure that the faceplate lamps are on when you are testing the tuner settings.

Post the schematic if you can, or give us the chassis number. In my opinion you'll get a lot of satisfaction in fixing this one, and I bet you are closer than you realize.

RWood
Click to expand...

The chassis # is R21406 AA
Here are some pics of the schematic, I can't figure out how to attach the photofact folder, too large?
sch 1.jpg

sch 2.jpg
I really appreciate all the help.
 
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I'm not looking to gain anything for the receiver. I've given parts to other members before. I rather them to be put too use than to just sit:yes: just pay it forward to this site or other members. The satisfaction of getting yours repaired with the great help from Larry is a worthwhile endeavor :D

Good luck :music::thmbsp:
 
loopstick said:
You could take a few closeups and post as separate attachments. Here's what looks like what could be a "stereo" light. Is there any action meter or light wise when you tune around a known strong station with antenna attached?

attachment.php


Also, to get you in the mood, here's a shot of my favorite (only) Maggie:


attachment.php
Click to expand...

Beautiful receiver loopstick!

I was actually paying very close attention to the stereo light while tuning. No response at all.
 
kydog said:
I'm not looking to gain anything for the receiver. I've given parts to other members before. I rather them to be put too use than to just sit:yes: just pay it forward to this site or other members. The satisfaction of getting yours repaired with the great help from Larry is a worthwhile endeavor :D

Good luck :music::thmbsp:
Click to expand...

You are awesome kydog!
Hopefully I can get this one working with all the great help on this forum. I'm glad I found you guys, I was about to give up.
 
larryderouin said:
Is the amp working in phono or AUX?? If so you probably have a switching problem. If it has a speaker selector switch on the LEFT side of the cabinet, make sure it's connected correctly and working. If it's not working or broken, it can be bypassed and the speakers fed directly. IIRC it's in the FRONT LEFT Corner on that one.

Hit all the switches and pots again with DeOxit. 3-4 applications or treatments over a months time to clear a problem up is not unusual for older gear.Spray with D-5/EXERCISE the POTS and Switches. UP/DOWN; ROUNDY,ROUND; in/OUT 30-50 times each. You'll develip lower arm muscles you never though possible. The FUNCTION SELECTOR is the most notorious of the offenders on the ASTROSONICS.

The cabinet looks very much like my '67 Forest Hills. As does the turntable (which is the one I used for the "Micromatic teardown and rebuild" tutorial in the Phono Forum back in '09). The Bezel looks the same. but I can't vouch for the receiver as it's been 5 years since I've had it out of the cabinet.

Take a RCA Cable, and wrap one end of a .01uf//600V cap on the center lead (solder it on if you want). Plug the other end into a receiver AUX. Then power up and touch the various component legs in the signal path from the output back to the input.Keep the volume down to keep from blowing a speaker. Headphones would be ideal here. When you get a signal on the input side of a component and none on the output side, thats your bad part.
Click to expand...

I haven't tried the signal tracing yet, I don't have a capacitor with that low uF, or that high voltage. I actually don't feel super confident doing the signal trace. Is there a resource that would walk me through the process step by step? I really am a novice when it comes to electronics, and would like to err on the side of caution here.
 
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Well, I made a signal tracer, and it works when I test it on a little mp3 player output, but using it on this receiver is just way beyond me. I think it's time for me to call it quits on this one. I was hoping it would be a visually obvious issue that I could figure out. :tears:
 
loopstick said:
This will give you an idea of how limited the problem is. Here's the full common audio path, left and right:

attachment.php


Here's the part that's just downstream from the function switches:

attachment.php


Here's the final part that drives the speakers:

attachment.php


So, if the turntable works in both channels then that's a good sign that the common audio section is healthy.
Click to expand...
Looking at the schematic I can start to make sense of the big picture, but looking at the components in the actual receiver is the part that gets my head spinning.
I found this course at my local community college:
"EET101 Intro to Elect. Test Equip
Introduces the operation and use of various types of equipment and tools used in electronic technology including; oscilloscope, function generator, DMM, and voltage source, calculator, and EXCEL. Uses software controls to obtain and analyze data available on this equipment, and Spice to perform simulation."
I am hoping to take this course in the spring, I think it will help. This astro-sonic has really peaked my interest in vintage audio equipment.
 
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