ZENITH 7H820 FM BUZZ

ZENITH 7H820 FM BUZZ

Post by conferenceroo.. » Sun, 03 Feb 2013 14:03:18



Hello all,

I have question about a buzzy-hum on a Zenith 7H820 Chassis 7E01 AM-FM

It happens on the FM band mostly. You can hear it ever so slightly on the AM band.

The radio has been completely restored new caps resistors tubes--replaced the selenium rectifier with a diode and resistor.

The radio works great. But why the backround buzz on the FM band (sometimes its more noticeable than at other times)

The tubes are12BA6-12BE6-12BA6-12Ba6 12Au6-19T8 it uses a 35C5 power output tube (modified by the previous owner)

My tube tester is down. Could this caused by a weak tube like the 19T8 Disc-Limiter-AVC-AF?

I can live with the sound because the radio plays so well, and picks up everything.

Just curious.

Thanks! Barry F.

 
 
 

ZENITH 7H820 FM BUZZ

Post by Carte » Mon, 04 Feb 2013 02:41:58



Quote:
> Hello all,

> I have question about a buzzy-hum on a Zenith 7H820 Chassis 7E01 AM-FM

> It happens on the FM band mostly. You can hear it ever so slightly on the AM band.

Just an off the wall thought...

Do you have any compact fluorescent lights (CFLs) nearby?

My CFLs cause a buzz/hum on the FM band -- but not AM. Go figure...

 
 
 

ZENITH 7H820 FM BUZZ

Post by Tom Hoehle » Mon, 04 Feb 2013 02:50:47



Quote:
> Hello all,

> I have question about a buzzy-hum on a Zenith 7H820 Chassis 7E01 AM-FM

> It happens on the FM band mostly. You can hear it ever so slightly on the
> AM band.

> The radio has been completely restored new caps resistors tubes--replaced
> the selenium rectifier with a diode and resistor.

> The radio works great. But why the backround buzz on the FM band
> (sometimes its more noticeable than at other times)

> The tubes are12BA6-12BE6-12BA6-12Ba6 12Au6-19T8 it uses a 35C5 power
> output tube (modified by the previous owner)

> My tube tester is down. Could this caused by a weak tube like the 19T8
> Disc-Limiter-AVC-AF?

> I can live with the sound because the radio plays so well, and picks up
> everything.

> Just curious.

> Thanks! Barry F.

Maybe a little heater-cathode leakage in the first AF tube? Try swapping
with another.
Tom