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Old 30th September 2005, 04:02 PM   #1
EC8010 is offline EC8010  United Kingdom
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Default I really, really wish I hadn't done that...

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.
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Old 30th September 2005, 04:13 PM   #2
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Oh, man!

I ran across a Normende like that - salvaged the FM module, sockets and OPT and filed the rest.
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Old 30th September 2005, 05:43 PM   #3
SY is offline SY  United States
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Do the British recognize the term "All-American Five"?
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Old 30th September 2005, 05:54 PM   #4
EC8010 is offline EC8010  United Kingdom
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This Brit is aware that it isn't something to do with slapping your hand against someone else's in a ritual form of greeting, and that it's actually a five-toob radio.
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Old 30th September 2005, 06:01 PM   #5
SY is offline SY  United States
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Yes, but which five tubes?
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Old 30th September 2005, 06:26 PM   #6
anatech is offline anatech  Canada
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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
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Old 1st October 2005, 01:42 AM   #7
wa4htz is offline wa4htz  United States
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SY:

7A8, 12BA6, 14B6, 35Z5GT, 50L6GT Make? Year sold?


Ken
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Old 1st October 2005, 01:52 AM   #8
SY is offline SY  United States
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Loctal is a clue- they weren't around for long. Early '40s? Sylvania?
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Old 1st October 2005, 02:03 AM   #9
wa4htz is offline wa4htz  United States
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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
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Old 1st October 2005, 02:17 AM   #10
wa4htz is offline wa4htz  United States
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SY,

In all fairness, I actually skipped the all-minature tube All-American-Five era. Neither my parents or I ever owned one. I was exixting on donated radios with real power transformers and 6-volt tubes with only one letter in the middle and they were watching TV.

Ken
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