I thought I'd fix the hum on the radio in the workshop. I got it into the lab and whipped the back off. Oh dear, no mains transformer. Live chassis. So that means half-wave rectification. I start taking out the HT capacitor (a three-in-one job) out. It has solder tags with holes, but that didn't stop the manufacturer from bending the tags and hardwiring it into the circuit. Without a clamp.
In fact, everything is horrible. Then I start wondering about the hum, and whether it's really the capacitor I've just struggled to remove. Perhaps it's heater/cathode insulation. Or maybe it's supposed to hum? Then I find the resistor on stand-offs that has broken its pads on the PCB (oh, didn't I mention? It's all on a nasty 44-year-old PCB). And you can't get to those soldered pads because someone has left an output transformer in the way. The output transformer is held in place with weird hex head screws. But none of my nutdrivers can get in there to undo them.
I have a feeling this radio is going in the skip. (Once it's given up its variable capacitor and loudspeaker.)
Just in case you need to avoid one, it's a PYE model 1107. Plain Yucky Engineering.
In fact, everything is horrible. Then I start wondering about the hum, and whether it's really the capacitor I've just struggled to remove. Perhaps it's heater/cathode insulation. Or maybe it's supposed to hum? Then I find the resistor on stand-offs that has broken its pads on the PCB (oh, didn't I mention? It's all on a nasty 44-year-old PCB). And you can't get to those soldered pads because someone has left an output transformer in the way. The output transformer is held in place with weird hex head screws. But none of my nutdrivers can get in there to undo them.
I have a feeling this radio is going in the skip. (Once it's given up its variable capacitor and loudspeaker.)
Just in case you need to avoid one, it's a PYE model 1107. Plain Yucky Engineering.
Hi EC8010,
Are you sure it hasn't been serviced before?
Normally they don't audibly hum, they would have been hard to sell. They will hum or buzz if they pick up interference from flouresent lamps or SCR / Triac controlled devices. It is very possible that the main filter cap is bad, that's an easy fix as you know.
I guess the general condition has you wanting to pitch it. In that case, strip and throw.
-Chris
Are you sure it hasn't been serviced before?
Normally they don't audibly hum, they would have been hard to sell. They will hum or buzz if they pick up interference from flouresent lamps or SCR / Triac controlled devices. It is very possible that the main filter cap is bad, that's an easy fix as you know.
I guess the general condition has you wanting to pitch it. In that case, strip and throw.
-Chris
SY,
I really don't know when it was designed, but my parents bought it in 1939 when they got married. "It" is a Philco Transitone AM "table model" radio. It sat on top of our refiridgerator for many years. Both parents are deceased but I still have it and am hoping to some day restore it. It was working the last time I turned it on many years ago. I don't think I'll subject it to Rush, though.
Ken
I really don't know when it was designed, but my parents bought it in 1939 when they got married. "It" is a Philco Transitone AM "table model" radio. It sat on top of our refiridgerator for many years. Both parents are deceased but I still have it and am hoping to some day restore it. It was working the last time I turned it on many years ago. I don't think I'll subject it to Rush, though.
Ken
Geek said:
Yes.
The Isophons head off to eBay, leaving me with a free chassis to use as i like. I've got iron stashed away for a pair of EL84 (or 6V6) monoblocs using the big OPTs and a couple of the ECLL800 amps to play with (the idea of a 3 tube stereo push-pull amp i find immensly appealling).
dave
Sy and Everyone,
Not Loctals but...
If my memory serves me the 7pin all-minature All-American-Five Table Radio included:
50C5 (AF output)
35W4 (half-wave rectumfrier)
12BE6 (pentagrid converter)
12BA6 (Remote cut-off RF pentode)
6AV6 or 6AT6 (Detector, AF-Amp)
= 115VAC @150mA heater current
(A) suffix on all types = controlled heater warm-up times.
Wayne
I'm back after a long honeymoon, she's out of town, hehe!
Not Loctals but...
If my memory serves me the 7pin all-minature All-American-Five Table Radio included:
50C5 (AF output)
35W4 (half-wave rectumfrier)
12BE6 (pentagrid converter)
12BA6 (Remote cut-off RF pentode)
6AV6 or 6AT6 (Detector, AF-Amp)
= 115VAC @150mA heater current
(A) suffix on all types = controlled heater warm-up times.
Wayne
I'm back after a long honeymoon, she's out of town, hehe!
anatech,
My Philco is cream colored but I believe it's just painted. The inside of the case is brown. I believe the material is bakealite (sp?) or something like it. The center of the knobs and the backing for the dial are really tacky-looking gold paint.
In the all-minature tube line-up, I believe the detector-AF amp could also be a 12 volt tube. My RC-20 RCA Tube Manual shows a 12AV6 in that spot for the AC-DC radio in the Circuits section. I guess it came down to how brightly the manufacturer wanted the tubes to glow (Or how fast they wanted them to burn out! I can't believe RCA didn't want them to burn out as fast as possible.).
BTW, just to remind everyone, as SY and others have said, the triode in that 6AV6 (or 12AV6) is the same as one half of a 12AX7.
Ken
My Philco is cream colored but I believe it's just painted. The inside of the case is brown. I believe the material is bakealite (sp?) or something like it. The center of the knobs and the backing for the dial are really tacky-looking gold paint.
In the all-minature tube line-up, I believe the detector-AF amp could also be a 12 volt tube. My RC-20 RCA Tube Manual shows a 12AV6 in that spot for the AC-DC radio in the Circuits section. I guess it came down to how brightly the manufacturer wanted the tubes to glow (Or how fast they wanted them to burn out! I can't believe RCA didn't want them to burn out as fast as possible.).
BTW, just to remind everyone, as SY and others have said, the triode in that 6AV6 (or 12AV6) is the same as one half of a 12AX7.
Ken
Hi Ken,
Yes, normally the 6AV6 would be a 12AV6. A 12AT6 will work as well with lower gain. The triode section amplification factor is around 70 as opposed to 100 for the *AV6. Since the 6V versions have a 300mA heater, they won't even drop the 6V or light up.
I haven't found mine yet. I remember the dial is near the bottom, unusual looking radio for sure. I'll let you know when I find it.
-Chris
Yes, normally the 6AV6 would be a 12AV6. A 12AT6 will work as well with lower gain. The triode section amplification factor is around 70 as opposed to 100 for the *AV6. Since the 6V versions have a 300mA heater, they won't even drop the 6V or light up.
I haven't found mine yet. I remember the dial is near the bottom, unusual looking radio for sure. I'll let you know when I find it.
-Chris
It has been done. The PYE has been scrapped. The more I took it apart, the more horrible stuff I found. Pulleys held on their shafts with the popper studs more commonly found on clothing! The 7" x 4" loudspeaker was a tour de force - the diaphragm was so flimsy it barely needed any corrugations to form a "suspension".
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