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 AWA 500m low volume
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 Return to top of page · Post #: 1 · Written at 9:25:40 AM on 13 March 2023.
Tallar Carl's avatar
 Location: Latham, ACT
 Member since 21 February 2015
 Member #: 1705
 Postcount: 2161

I have checked all caps ( recapped) and resistors. I found a mica ( black AWA ) cap coming off the antenna coil that reads as .05μF! Would this result in low volume. I think it's supposed to be 100pf . I will have to get a photo as I can't remember where the other end terminates ( not to ground ) there are two on the Antenna coil but only one goes to ground.


 
 Return to top of page · Post #: 2 · Written at 3:26:38 PM on 13 March 2023.
Tallar Carl's avatar
 Location: Latham, ACT
 Member since 21 February 2015
 Member #: 1705
 Postcount: 2161

Ok I just found out it is actually a .05 but I'm sure I saw uμF printed on it so what's the chance it's turned into a resistor?


 
 Return to top of page · Post #: 3 · Written at 7:07:07 PM on 13 March 2023.
BringBackTheValve's Gravatar
 Location: Linton, VIC
 Member since 30 December 2016
 Member #: 2028
 Postcount: 472

0.05μF seems too much capacitance for that end of town.


 
 Return to top of page · Post #: 4 · Written at 7:43:28 PM on 13 March 2023.
DangerousDave's Gravatar
 Location: Toongabbie, VIC
 Member since 1 September 2020
 Member #: 2438
 Postcount: 131

This sounds like C5. This is the AGC decoupling cap connected to the secondary side of the antenna coil. Leaking here would cause inoperative AGC and possible distortion on strong signals. How are circuit voltages? They perform ok these models but not hot performers by any means.


 
 Return to top of page · Post #: 5 · Written at 7:49:04 PM on 13 March 2023.
BringBackTheValve's Gravatar
 Location: Linton, VIC
 Member since 30 December 2016
 Member #: 2028
 Postcount: 472

If it is C5 it will not be a mica cap, probably wax. And it will not be hanging off the antenna coil but the coupling transformer from the antenna coil to the RF amp.


 
 Return to top of page · Post #: 6 · Written at 9:08:33 PM on 13 March 2023.
Tallar Carl's avatar
 Location: Latham, ACT
 Member since 21 February 2015
 Member #: 1705
 Postcount: 2161

Its actually C2. I pulled it out and photographed it . Blew it up and it reads 4pf but on the multimeter it read .05.

AWA condenser
AWA condenser


 
 Return to top of page · Post #: 7 · Written at 9:24:25 PM on 13 March 2023.
BringBackTheValve's Gravatar
 Location: Linton, VIC
 Member since 30 December 2016
 Member #: 2028
 Postcount: 472

Picofarads are more like it for that end of town.


 
 Return to top of page · Post #: 8 · Written at 9:44:47 PM on 13 March 2023.
DangerousDave's Gravatar
 Location: Toongabbie, VIC
 Member since 1 September 2020
 Member #: 2438
 Postcount: 131

C2 is unlikely to be faulty. You could just remove it and test the radio. It can be difficult testing caps that small.


 
 Return to top of page · Post #: 9 · Written at 2:02:53 PM on 18 March 2023.
Brad's avatar
 Administrator
 Location: Naremburn, NSW
 Member since 15 November 2005
 Member #: 1
 Postcount: 7342

Photos uploaded to Post 6.


‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾
A valve a day keeps the transistor away...

 
 Return to top of page · Post #: 10 · Written at 8:06:17 PM on 18 March 2023.
Fred Lever's Gravatar
 Location: Toongabbie, NSW
 Member since 19 November 2015
 Member #: 1828
 Postcount: 1267

Back in those days the standard units were F(arad), μF and uuF.
Reference Radiotron Designers Handbook 1944.

pF had not been invented!
To me thats a 4pF capacitor.

Am I right or has maths defeated me again?

Fred.


 
 Return to top of page · Post #: 11 · Written at 8:42:15 PM on 18 March 2023.
Brad's avatar
 Administrator
 Location: Naremburn, NSW
 Member since 15 November 2005
 Member #: 1
 Postcount: 7342

I think you are correct, Fred. The problem here stems from whoever set up the unit for capacitance in the first place and made the unit represent an unrealistic amount of capacitance, which is why the Farad is one of the few units in physics more commonly expressed in millionths (μF), billionths (nF) and trillionths (pF) of Farads instead of just Farads.


‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾
A valve a day keeps the transistor away...

 
 Return to top of page · Post #: 12 · Written at 10:40:03 PM on 18 March 2023.
Tallar Carl's avatar
 Location: Latham, ACT
 Member since 21 February 2015
 Member #: 1705
 Postcount: 2161

We found the actual problem today. It was a 40k resistor on the screen that had gone high. Its now a very healthy set Smile


 
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