1966 Magnavox Astro-Sonic Radio

hello. i'm in the process of refurbishing a 1966 Astro-Sonic. I've recapped the chassis and it appears to receive all bands. however, when i choose the FM Stereo, the indicator light does not work. i've traced the wiring back as best i can, and re-soldered the connections, but it still does not work. any suggestions?

also, i seem to be able to receive all bands, but only the FM Stereo actually produces sound thru the "test" speaker i've set up. any thoughts on why AM, FM AFC, FM standard do not produce sound? Aux and Phono appear to be ok as well as the FM Stereo.

please note, i openly admit to being a novice with these things. i'm taking my time and learning as much as i can. any help is greatly appreciated.

Tony.

PS. Merry Christmas!

Hi Tony,
Obvious, first question(s)---is the lamp good--is it in a socket, and if so, is the socket good, and is it the correct size, and type lamp ?
I have no idea, as to how you have hooked up, a test speaker, and also, I know nothing about that product, but if it's not correctly hooked up, the mono/stereo functions may not work as such ?
Ron Rich

Thanks for the reply Ron. yes, it has a socket and it appears in good shape. i've replaced the original bulb with the same bulb (mfr, model, size, etc.) so assumed it would work. going to check the actually socket itself, but i did re-solder the wiring. all the other bulbs are working, so it appears to be limited to just the stereo. i've attached a single speaker to the speaker connections on the chassis. but may have to consider a different approach. didn't know if the non stereo bands worked off a separate speaker connection.

Just because it had a lamp installed, it may, or may not be the correct type. You need to check that "someone" did not install an incorrect type. The Service Manual, or information manual, should indicate the correct number. Ron Rich

The stereo multiplex indicator lamp on those Astrosonic chassis are a low voltage low current specialty bulb, and require proper replacement.
Additionally, the lamp triggering transistor can be damaged by installing an improper lamp.
On other issues, the multiplex circuitry itself may be malfunctioning due to aged, defective, or damaged components.
This would require replacement of defective parts and a proper multiplex re-alignment - with a multiplex signal generator, oscilloscope, and other test equipment.

Thanks MattTech, this is very helpful. i've verified the bulb is correct, but upon further inspection, i noticed the print board where the wiring for the indicator light is connected is damaged. do you know where i can find a replacement board?

for the other issues, i inspected the multiplex switch as well and noticed the mechanical switch/power connection was also damaged. i've attached a picture. i'd rather not have to replace the entire switch if i don't have to. Any ideas on where to find a replacement part?

thanks again for all the help on this guys.

tjurek51 wrote:Thanks MattTech, this is very helpful. i've verified the bulb is correct, but upon further inspection, i noticed the print board where the wiring for the indicator light is connected is damaged. do you know where i can find a replacement board?

for the other issues, i inspected the multiplex switch as well and noticed the mechanical switch/power connection was also damaged. i've attached a picture. i'd rather not have to replace the entire switch if i don't have to. Any ideas on where to find a replacement part?

thanks again for all the help on this guys.

multiplex switch for maggie.jpg

Nothing was mentioned about what R-chassis it is.
There are different series, with different configurations.
That switch has nothing to do with stereo multiplex, it's a power switch.
And after 50 years, boards and switches are certainly not stocked by magnavox anymore.

Best bet is scour the 'net for another matching chassis and hope for the best.

Sorry. Chassis is R210401-AA

hello all. i was able to find an old chassis online and have salvaged some parts. i now seem to be able to receive all bands and the stereo indicator light now works!

however, still having the issue with sound only coming from the FM Stereo, Aux and phono. any thoughts on why AM, FM AFC, FM standard do not produce sound? again, Aux and Phono appear to be ok as well as the FM Stereo.

Chassis is R210401-AA

hello, it's been awhile since i've posted. still working this refurbish. replaced the function switch but still having problems with FM Mono, FM AFC and AM working. i've tested the voltage on the paths as documented in the schematic and it appears i'm getting power thru the switch to the FM Mono and FM AFC sections on the board, but still no signal or sound. same with the AM, get power thru the switch, but no sound or signal.

are there adjustments to be made on the signal board receiving the antenna signals that i need to adjust? other ideas on how to fix this is appreciated. again, all other functions work. FM Stereo actually sounds great even on the test speaker. i see the other signals come thru a different part of the same circuit board, but i don't see any damage or issues visually.

any help is appreciated. thanks.

Chassis: RC210401-AA

I know nothing about this unit--never saw one, but if you "see" the other signals, I would think you could follow them to, and through, the function switch-It would be my GUESS, that they do not make it to that switch ?? Ron Rich

Putzing with ANY alignment on these sets will surely ruin things, even for a service pro to re-align.
They do not require "adjustments" to perform properly, and I've never had to do any, unless they've been previously putzed with.
Proper troubleshooting procedures by an experienced tech is what is required here.

sorry, i don't actually "see the signals" (bad use of words here). i can trace the circuit and see where it goes. what i can't seem to determine is why only those functions do not work. the only thing i see in common is they are on the same part of antenna board. i just don't know where to go from there.

tjurek51 wrote:sorry, i don't actually "see the signals" (bad use of words here). i can trace the circuit and see where it goes. what i can't seem to determine is why only those functions do not work. the only thing i see in common is they are on the same part of antenna board. i just don't know where to go from there.

Audio signal tracer handy?

"tjurek51" The mono section of the FM ckt is working if you now have FM stereo. It comes before the multiplex demod section. Which then leads to the input switch as possible culprit.

As Matt suggested, if you have an audio signal tracer it will be easy to test for the presence of audio at the selector switch. Bear in-mind that other things are switched by sections on that switch stack, so it isn't just audio you need to look for, but also any DC power switching done there.

An audio signal tracer is just a simple audio amp-speaker with extra features (that are not needed here). A regular audio amp can be used -but be careful not to connect it's input to a DC source on the unit under test. If you go this route use a capacitor of at least 1mfd @100 volts in series with the "high" lead to protect the test amp from possible damage. Make sure the input selector is set to the input you are testing for.

Rob-NYC