Magnavox Astro Sonic 1968 - schematic & receiver bearings
Posted: Sun Dec 27, 2015 8:56 pm
Hi Folks,
I am in the middle of repairing & refurbishing a 1968 astro sonic, chassis # R21203 BB (paper id tag) also id'd as R212 03-11 on the ink stamp. I have a few questions. If anybody can help, I'd be grateful.
1) Any tips on finding a schematic? Sams lists schematics for R21203AA and R2120300. Would these be similar/useable? The unit seems to have good volume and power, not too much noise, but as a precaution, I thought I would replace the capacitors. The nichicon caps are all legible for identifying the replacement values, but I would like to have a schematic just the same.
2) Help resolving a tuner issue: The tuner had good, smooth action for the first few weeks I used it, but then the dial got stuck in the 94-95 FM range while ascending the dial. I assumed it would be a bound up dial cord, but upon removal, I found the dial cord fine. Removing the dial cord entirely from the cord spool/condensor plates, I find the same bind-up/sticking issue always occurring about the same place in the rotation of the reciever shaft, and always in the direction ascending in frequency. I cleaned and re-lubricated the bearings at the top end of the shaft, and movement is improving (the dial cord is now able to pull through the rough spot), but it does seem like one of the ball bearings is out of line, or not spaced properly. Movement always gets difficult at the same location in the rotation, and I have to back up direction before dialing up again. Descending the dial, there is a similar problem, though not as pronounced. My question is this -- Does this sound like it could be a bearing issue? If so, is it worth/possible to fix? It doesn't seem that there is a way to replace the bearings without ruining the receiver, or at least its calibration... or ever getting it back together. No?
Thanks in advance,
Greg
Tucson, AZ
I am in the middle of repairing & refurbishing a 1968 astro sonic, chassis # R21203 BB (paper id tag) also id'd as R212 03-11 on the ink stamp. I have a few questions. If anybody can help, I'd be grateful.
1) Any tips on finding a schematic? Sams lists schematics for R21203AA and R2120300. Would these be similar/useable? The unit seems to have good volume and power, not too much noise, but as a precaution, I thought I would replace the capacitors. The nichicon caps are all legible for identifying the replacement values, but I would like to have a schematic just the same.
2) Help resolving a tuner issue: The tuner had good, smooth action for the first few weeks I used it, but then the dial got stuck in the 94-95 FM range while ascending the dial. I assumed it would be a bound up dial cord, but upon removal, I found the dial cord fine. Removing the dial cord entirely from the cord spool/condensor plates, I find the same bind-up/sticking issue always occurring about the same place in the rotation of the reciever shaft, and always in the direction ascending in frequency. I cleaned and re-lubricated the bearings at the top end of the shaft, and movement is improving (the dial cord is now able to pull through the rough spot), but it does seem like one of the ball bearings is out of line, or not spaced properly. Movement always gets difficult at the same location in the rotation, and I have to back up direction before dialing up again. Descending the dial, there is a similar problem, though not as pronounced. My question is this -- Does this sound like it could be a bearing issue? If so, is it worth/possible to fix? It doesn't seem that there is a way to replace the bearings without ruining the receiver, or at least its calibration... or ever getting it back together. No?
Thanks in advance,
Greg
Tucson, AZ