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 Radio goes dead in a certain location.
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 Return to top of page · Post #: 1 · Written at 2:46:36 AM on 18 April 2024.
Frequencyman's Gravatar
 Location: Brisbane, QLD
 Member since 18 April 2024
 Member #: 2633
 Postcount: 5

Hey folks, thanks for having me

I have a question. I have an old Hotpoint valve radio. It often goes dead on a certain station, the same one every time and when I tap the unit softly it comes back. it also comes back when I turn the tuner to the other side of the dial. When it goes dead there is no sound whatsoever, but the light stays on, I took it to my tech and hes had it on his bench for 2 days straight, he has had zero issues with the radio so is there a possibility that my actually location somehow makes it go dead?

Thanks guys! Any help would be fantastic.!


 
 Return to top of page · Post #: 2 · Written at 5:38:59 AM on 18 April 2024.
Brad's avatar
 Administrator
 Location: Naremburn, NSW
 Member since 15 November 2005
 Member #: 1
 Postcount: 7342

Have you played the radio since taking it in to be looked at? Does the problem still occur.

Yes, this can happen but it is rare and usually caused by a stronger signal in the same frequency range flooding the signal you want to receive. When I drive past the ABN TV transmission tower in Gore Hill every morning its transmissions drown out 2GB on my car radio briefly. The ATN tower up the road at Artarmon has never had the same effect.


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

 
 Return to top of page · Post #: 3 · Written at 7:18:40 AM on 18 April 2024.
STC830's Gravatar
 Location: NSW
 Member since 10 June 2010
 Member #: 681
 Postcount: 1284

"When I drive past the ABN TV transmission tower in Gore Hill every morning its transmissions drown out 2GB on my car radio briefly."

I notice that when driving past the 1431 transmitter at Windang, the AM station you happen to be tuned to goes silent. I assume that the AGC is overwhelmed by 1431 and cuts the sensitivity across the dial. So perhaps there is an issue with another strong station (or other interfering signal) that works through the AGC. Not consistent with being reversed by tapping though - that sounds like a crook connection.


 
 Return to top of page · Post #: 4 · Written at 7:57:18 AM on 18 April 2024.
STC830's Gravatar
 Location: NSW
 Member since 10 June 2010
 Member #: 681
 Postcount: 1284

Might be worth checking the contactors for the rotating part of the tuning gang - maybe a dead spot right on the station.


 
 Return to top of page · Post #: 5 · Written at 8:57:33 PM on 18 April 2024.
Tallar Carl's avatar
 Location: Latham, ACT
 Member since 21 February 2015
 Member #: 1705
 Postcount: 2161

Shorting tuning gang. Easy fix. Run your fingers along the top of the vanes and beend the outer ones out a tad.


 
 Return to top of page · Post #: 6 · Written at 9:40:14 PM on 18 April 2024.
Marcc's avatar
 Location: Wangaratta, VIC
 Member since 21 February 2009
 Member #: 438
 Postcount: 5303

Tuning gangs can develop corrosive mounds and if not serviced with the rotor fully closed the outer ones can get bent. Normally you can find a bit of card that will slide between the stator & rotor to get gunk out an help space the outer ones.

You can disconnect the stator & check for shorting, as you rotate it, with an ohm meter. The oscillator section is the most vulnerable to flashover from burrs on the vanes & corrosion. They take a bit more aggression to clear.

I will, sometimes with the usual precautions, Insulation test the nasty ones with an insulation tester at 500V, in dim light.

There could be a problem with the IF alignment or its actual frequency and decoupling on the AGC like a wrong cap.. The object with the IF is to have it on a frequency such that any heterodyne does not fall on the frequency of a radio station. That is why HMV have a seemingly odd ball IF frequency of 457.5kHz in many of their sets.


 
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