I really, really wish I hadn't done that...

EC8010 · 30th September 2005, 03:02 PM

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.

Geek · 30th September 2005, 03:13 PM

Oh, man!

I ran across a Normende like that - salvaged the FM module, sockets and OPT and filed the rest.

SY · 30th September 2005, 04:43 PM

Do the British recognize the term "All-American Five"?

EC8010 · 30th September 2005, 04:54 PM

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.

SY · 30th September 2005, 05:01 PM

Yes, but which five tubes?

anatech · 30th September 2005, 05:26 PM

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

wa4htz · 1st October 2005, 12:42 AM

SY:

7A8, 12BA6, 14B6, 35Z5GT, 50L6GT

Make? Year sold?

Ken

SY · 1st October 2005, 12:52 AM

Loctal is a clue- they weren't around for long. Early '40s? Sylvania?

wa4htz · 1st October 2005, 01:03 AM

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

wa4htz · 1st October 2005, 01:17 AM

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

30th September 2005, 03:02 PM	#1
EC8010 diyAudio Moderator Join Date: Jan 2003 Location: Near London. UK	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. __________________ The loudspeaker: The only commercial Hi-Fi item where a disproportionate part of the budget isn't spent on the box. And the one where it would make a difference...

30th September 2005, 04:43 PM	#3
SY diyAudio Moderator Join Date: Oct 2002 Location: Austin, TX Blog Entries: 1	Do the British recognize the term "All-American Five"? __________________ “Listening to records is like ****ing a picture of Brigitte Bardot.” - Sergiu Celibidache

30th September 2005, 04:54 PM	#4
EC8010 diyAudio Moderator Join Date: Jan 2003 Location: Near London. UK	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. __________________ The loudspeaker: The only commercial Hi-Fi item where a disproportionate part of the budget isn't spent on the box. And the one where it would make a difference...

30th September 2005, 05:01 PM	#5
SY diyAudio Moderator Join Date: Oct 2002 Location: Austin, TX Blog Entries: 1	Yes, but which five tubes? __________________ “Listening to records is like ****ing a picture of Brigitte Bardot.” - Sergiu Celibidache

1st October 2005, 12:42 AM	#7
wa4htz diyAudio Member Join Date: Dec 2002 Location: The West Coast of Sunny Florida	SY: 7A8, 12BA6, 14B6, 35Z5GT, 50L6GT Make? Year sold? Ken __________________ Remember, one hobby is not enough!

30th September 2005, 03:13 PM	#2
Geek diyAudio Member Join Date: Sep 2004	Oh, man! I ran across a Normende like that - salvaged the FM module, sockets and OPT and filed the rest.

30th September 2005, 05:26 PM	#6
anatech diyAudio Moderator Join Date: Jun 2004 Location: Georgetown, On	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

1st October 2005, 12:52 AM	#8
SY diyAudio Moderator Join Date: Oct 2002 Location: Austin, TX Blog Entries: 1	Loctal is a clue- they weren't around for long. Early '40s? Sylvania? __________________ “Listening to records is like ****ing a picture of Brigitte Bardot.” - Sergiu Celibidache

1st October 2005, 01:03 AM	#9
wa4htz diyAudio Member Join Date: Dec 2002 Location: The West Coast of Sunny Florida	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 __________________ Remember, one hobby is not enough!

1st October 2005, 01:17 AM	#10
wa4htz diyAudio Member Join Date: Dec 2002 Location: The West Coast of Sunny Florida	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 __________________ Remember, one hobby is not enough!

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