I hope someone is familiar with this problem ( I made a short post in Solid State a few months ago w/o answers).
This radio's tuning started acting up. Turn the tuning knob and the digital display/received frequency might or might not change. Then turning the knob had no effect. Now the display doesn't change and the frequency doesn't change. The radio still works stuck on one freq.
This radio uses string, spring, pulleys and a variable capacitor to change frequency. I suspected a mechanical problem with these parts but all is intact, except . . .There's a large string driven wheel on the variable capacitor shaft. It turns the shaft but the capacitor does not rotate. There's some sort of micro gear reduction (?) box between between those two parts. It's hard to see with the radio intact. Too inaccessible for foto. Any help??
The Repair Guide has a mechanical diagram of the radio and it shows the tuning cap as a single device to which the large wheel attaches. No detail about a "gear box" if that's the term. The Guide also says the tuner section can be removed as an assembly. Removal would probably afford a better view but I'm seeking advice before I dig in. For other owners, there is a useful diagram of string/spring/pulley system
These radios sound quite good, they weigh a ton but are very cramped inside.
Thx for any advice/experience.
dizmayed
This radio's tuning started acting up. Turn the tuning knob and the digital display/received frequency might or might not change. Then turning the knob had no effect. Now the display doesn't change and the frequency doesn't change. The radio still works stuck on one freq.
This radio uses string, spring, pulleys and a variable capacitor to change frequency. I suspected a mechanical problem with these parts but all is intact, except . . .There's a large string driven wheel on the variable capacitor shaft. It turns the shaft but the capacitor does not rotate. There's some sort of micro gear reduction (?) box between between those two parts. It's hard to see with the radio intact. Too inaccessible for foto. Any help??
The Repair Guide has a mechanical diagram of the radio and it shows the tuning cap as a single device to which the large wheel attaches. No detail about a "gear box" if that's the term. The Guide also says the tuner section can be removed as an assembly. Removal would probably afford a better view but I'm seeking advice before I dig in. For other owners, there is a useful diagram of string/spring/pulley system
These radios sound quite good, they weigh a ton but are very cramped inside.
Thx for any advice/experience.
dizmayed
Some of the reduction gears I've seen in the past rely on rolling balls in a cage within the front plate of the assembly. It could be that these have become gummed up. I'd try staying that point with a little solvent spray, being careful not to spray anywhere else.
If you do have to take it apart, keep a detailed drawing of the cord lacing plan, including direction and number of turns. Use tape to keep as much as the lacing in place.
If you do have to take it apart, keep a detailed drawing of the cord lacing plan, including direction and number of turns. Use tape to keep as much as the lacing in place.
<. . . try spraying that point with a little solvent spray, being careful not to spray anywhere else. . . If you do have to take it apart, keep a detailed drawing of the cord lacing plan . . .>
Thx for that suggestion but no effect. I'm obviously missing something here, but what?
Still hoping a member knows these radios and can clue me in. I do not look fwd to disassembly.
dizmayed
Thx for that suggestion but no effect. I'm obviously missing something here, but what?
Still hoping a member knows these radios and can clue me in. I do not look fwd to disassembly.
dizmayed
I appreciate your efforts to help. I know w/o a foto or direct experience it's hard to picture what I'm looking at.
Yes, the capacitor rotates with some delicate poking. So does the large, string driven pulley outboard of the variable. That leaves the "gearbox" in between as the culprit. With a mirror I can see tiny plastic gears there and with more delicate poking I can get the cap to rotate when the tuning knob turns. For a short while.
I know. Terribly amateurish troubleshooting on my part.
The tuner <can> be removed as an assembly, as I mentioned above, per the Manual. Okay . .
Rumination: is all this worth the trouble? I can buy a working Proton 300 for ~$100USD. Well, I think these radios are worthy . . .
We still play iPod, CD, bluetooth rcvr thru this thing's aux input. I don't have golden ears or audiophile creds but the 300 seems unusual, very pleasing. Modestly designed, boat-anchor heavy, >20W@<.03 THD (it says) to the woofer thru its own power supply and amplifier. Tweeter gets its own discrete parts too. Maybe that's how table radios are built?
Very respectable sound for a box the size of a bread loaf.
yr friend,
dizmayed
Yes, the capacitor rotates with some delicate poking. So does the large, string driven pulley outboard of the variable. That leaves the "gearbox" in between as the culprit. With a mirror I can see tiny plastic gears there and with more delicate poking I can get the cap to rotate when the tuning knob turns. For a short while.
I know. Terribly amateurish troubleshooting on my part.
The tuner <can> be removed as an assembly, as I mentioned above, per the Manual. Okay . .
Rumination: is all this worth the trouble? I can buy a working Proton 300 for ~$100USD. Well, I think these radios are worthy . . .
We still play iPod, CD, bluetooth rcvr thru this thing's aux input. I don't have golden ears or audiophile creds but the 300 seems unusual, very pleasing. Modestly designed, boat-anchor heavy, >20W@<.03 THD (it says) to the woofer thru its own power supply and amplifier. Tweeter gets its own discrete parts too. Maybe that's how table radios are built?
Very respectable sound for a box the size of a bread loaf.
yr friend,
dizmayed
If the tuner is mechanically worn out, you can remove the tuner module from the side of the box,
and convert the 300 to a 301 powered speaker. Use it with another Proton 300 for stereo.
The powered speaker won't turn on with signal like a real 301, but you could switch both units
with an powered outlet instead.
Some people will spend hours keeping these table radios alive. The radios must be really, really good.
This radio had a tuning problem: the tuning knob would only intermittently cause the variable capacitor to rotate. After simply removing a cover it was easy to see that the dial string was OK, that the big dial string pulley attached to the capacitor was turning, that there was a little cast metal gearbox behind the big pulley and that the capacitor moved only sluggishly in response to turning the tuning knob.
Something was wrong between the capacitor and dial string pulley. Sounds simple to diagnose but parts are really packed into this radio.
The repair manual explains how to remove the tuner section. Good luck. I had success disconnecting the display board and several push connectors and disassembling dial string parts, etc.
Then you can remove the parts that turn the vari-cap. Two set screws secure the dial string pulley and 2 tiny screws secure the gearbox. The gearbox has a small plastic gear. No problem found so far.
Between the gearbox and vari-cap is a larger plastic gear that engages the small plastic gear and turns the capacitor.
That's the problem. The capacitor has a small diameter round shaft. The larger plastic gear is merely press fit, no set screws. It slips on the shaft causing the problem. Careful dabs of crazy glue secured the gear and all is well. Just re-assemble and get the dial string system working again.
Self-test: why would I spend hours repairing a useful table radio when I can readily buy a nice one for $75-$100?
dizmayed
This radio had a tuning problem: the tuning knob would only intermittently cause the variable capacitor to rotate. After simply removing a cover it was easy to see that the dial string was OK, that the big dial string pulley attached to the capacitor was turning, that there was a little cast metal gearbox behind the big pulley and that the capacitor moved only sluggishly in response to turning the tuning knob.
Something was wrong between the capacitor and dial string pulley. Sounds simple to diagnose but parts are really packed into this radio.
The repair manual explains how to remove the tuner section. Good luck. I had success disconnecting the display board and several push connectors and disassembling dial string parts, etc.
Then you can remove the parts that turn the vari-cap. Two set screws secure the dial string pulley and 2 tiny screws secure the gearbox. The gearbox has a small plastic gear. No problem found so far.
Between the gearbox and vari-cap is a larger plastic gear that engages the small plastic gear and turns the capacitor.
That's the problem. The capacitor has a small diameter round shaft. The larger plastic gear is merely press fit, no set screws. It slips on the shaft causing the problem. Careful dabs of crazy glue secured the gear and all is well. Just re-assemble and get the dial string system working again.
Self-test: why would I spend hours repairing a useful table radio when I can readily buy a nice one for $75-$100?
dizmayed
