Marshall 8200 Bi-Chorus Head - Oh poop!!! Its NAD:

Noise Update:

Last night, the local radio station (95.1 Kountry KFRG Kfrog FM) was playing loudly through this amp. Kfrog's tower is about 1.5 miles east of us and about 1 mile higher up the hillside in elevation.

The transmitter is located at
34° 11' 51" N, 117° 17' 13" W and operayes at 50,000 Watts. The transmitter elevation is 3419 feet asl the transmitter is 236 feet above ground and 489 feet above the average terrain in this area.

You could clearly make out commercials and station IT'S. When I pushed the dB boost for the FX loop, the white noise and RFI increased. I sent @syscokid and @DonO videos.

20211230_071505.jpg

Ok...

This morning, I switch the amp back on. It was still plugged into the sam wall ug and still sitting (unmoved) in the same location by the fireplace.

This morning, no hiss, no radio station bleeder, nothing...

Interesting...
 
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Atmospheric conditions could be affecting the FM signal power. It’s much cloudier today than yesterday. Also, a long shot, but are you using the original power cord? Next time you can hear the radio, try a new cord, at least 18 gauge.
 
I had literally 5 minutes of an empty house. I videoed the first road test...

Note: the cell phone video sounds much darker than it is in person.

 
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old rocker said:
So Robert, is your best sound out of this Amp(without Chorus), better than your best sound for the HF ORI ?
Click to expand...

The cell phone audio isn't a faithful reproduction of what I'm hearing. The video sounds darker than it does in person.

The 8200 has more gain on tap than the HF/Ivanberg Modded ORI50 produces, even with a tube screamer. It's unbelievable how much gain you can get from these Valvestates.

I'd say the quality of the tone is about equal.

I really need to find the time to get this amp properly recorded.
 
Robert Herndon said:
Noise Update:

Last night, the local radio station (95.1 Kountry KFRG Kfrog FM) was playing loudly through this amp. Kfrog's tower is about 1.5 miles east of us and about 1 mile higher up the hillside in elevation.

The transmitter is located at
34° 11' 51" N, 117° 17' 13" W and operayes at 50,000 Watts. The transmitter elevation is 3419 feet asl the transmitter is 236 feet above ground and 489 feet above the average terrain in this area.

You could clearly make out commercials and station IT'S. When I pushed the dB boost for the FX loop, the white noise and RFI increased. I sent @syscokid and @DonO videos.

View attachment 78114

Ok...

This morning, I switch the amp back on. It was still plugged into the sam wall ug and still sitting (unmoved) in the same location by the fireplace.

This morning, no hiss, no radio station bleeder, nothing...

Interesting...
Click to expand...
There for about 2 weeks this summer, my JCM2000 was doing the same damn thing. Picking up radio signals, the intercom at Tractor Supply about 1/8th a mile away and even some cordless phones. Had never done that before and i even have 2 other amps plugged into the same quad-duplex, that didnt do it. I ended up using a wrap- around ferrite magnet at both ends of the plug and never heard it again.

Oddly enough, the JCM900 SLX actually has a small capacitor and 22ohm resistor series paralleled, thats grounded from the board to chassis that is labeled " RF Interference" from the factory
 
syscokid said:
You wouldn't happen to have a pic of this part of the circuit, do ya?
Click to expand...
Yes sir, took me a while to find it but this was from the old Marshall Forums, it was none other than @Amp Mad Scientist who helped me with some stuff on this amp before it blew up again a while later ( not related to this by the way lol). On the back of the board its listed as "RF"rps20200417_183916.jpgSLX preamp ground.png
 
Robert Herndon said:
Noise Update:

Last night, the local radio station (95.1 Kountry KFRG Kfrog FM) was playing loudly through this amp. Kfrog's tower is about 1.5 miles east of us and about 1 mile higher up the hillside in elevation.

The transmitter is located at
34° 11' 51" N, 117° 17' 13" W and operayes at 50,000 Watts. The transmitter elevation is 3419 feet asl the transmitter is 236 feet above ground and 489 feet above the average terrain in this area.

You could clearly make out commercials and station IT'S. When I pushed the dB boost for the FX loop, the white noise and RFI increased. I sent @syscokid and @DonO videos.

View attachment 78114

Ok...

This morning, I switch the amp back on. It was still plugged into the sam wall ug and still sitting (unmoved) in the same location by the fireplace.

This morning, no hiss, no radio station bleeder, nothing...

Interesting...
Click to expand...
The input jack is supposed to ground the input tip when the guitar cable is removed.
But this switch contact on the jack can get oxidized.
Which is why I often just change the jacks.
You can clean the switch contacts but the problem might come back later. It often will when the jacks get old and crusty.
The jacks also shrink when they get really old, and sometimes you can't plug in anymore.
 
Amp Mad Scientist said:
The input jack is supposed to ground the input tip when the guitar cable is removed.
But this switch contact on the jack can get oxidized.
Which is why I often just change the jacks.
You can clean the switch contacts but the problem might come back later. It often will when the jacks get old and crusty.
The jacks also shrink when they get really old, and sometimes you can't plug in anymore.
Click to expand...

Played the 95.1Mhz frequency wether or not the guitar was plugged in.
 
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