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Hello,

I have a DSL15 that is humming a 120 Hz tone, even with all controls down. This tells me the trouble is in the power section. I checked the bias voltage of both 6V6 tubes, and they are there. However, when I checked the voltage across the plate current sensing resistors, one is around 24 mV, and the other is virtually zero. I swapped the tubes, and the voltage values on the resistors went the other way round. It looks I have a bad 6V6 tube, but I'dlike to confirm before I go buying a new one. Any thoughts?

Thanks!

asked 12 Jun 2020 at 03:13 PM

Marcos Dossa
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Hi. I just bought Marshall 1959 HW and it's constantly humming when it's on. I have Wizard Modern Classic Amp and ENGL Powerball 2 and they don't hum like that when ON. Is it normal? Also when I strum a chord very loud mechanical noise going out of the back. Check the video I shot to hear how both issues sound:

asked 30 Jan 2020 at 04:15 AM

Andrew Zelenokhat
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Just received my new JCM 800 2203 head with a new vintage 1960 av cabinet. Hooked it up and turned the power on standby. Very noticeable humming sound coming from inside the head. Is this normal? I have a early 90's JCM 900 that never has made any sounds on standby or powered up fully. Can I get some advice before I decide to send it back and go with something else?

thanks much!

 

 

 

 

asked 14 Dec 2019 at 02:55 PM

Rory Lasee
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Hi My AS50D has developed a loud hum

It doesn't change if If connect different guitars or micsand changing the input levels has no effect

But it does get louder with the master volume

It sounds like a problem with the power supply is it an easy repair?

I live in the far north of Scotland so shipping is a problem

Here is a video of the hum 

https://drive.google.com/open?id=1TiVyTYxZsvzc8pF6fWeg_1OQyD2nKjuICw

asked 16 Jan 2019 at 10:10 AM

Stewart McCarroll
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Today I bought a brand new JVM 205H Amp and a 1936V Cab. I am soooo lucky :-) It sounds fantastic and I am really looking forward to learning how to get the best out of it. However, I made the mistake of unboxing everything and not paying attention as to which cable came from which box and the cables were not labelled.

There are 3 cables

* The long soft cable marked RJS ELEC - AWG18 - 41/0.16 - 0.824mm ...  I assumed is the speaker cable. Is that correct ?

* A short thinner cable marked Marshall PVC 0.34 SQmm X 2cores Wonderful VN (LF)... I assumed is for the 4 way footswitch. Is that correct?

* A long thinner hard PVC unmarked cable ..... I assumed is to connect the guitar. Is that correct ?

Using the cables connected as above, when I switched the amp to 'ON' I had an unpleasant buzz/hum. I discovered that the volume of hum was completely dependent on the volume control knob on the guitar. Turn it to zero and the hum disappears, turn it to 10 and the hum is very unpleasant.

I tried swapping the un-marked cable for a guitar cable that I already own (braded yellow) and the hum ALMOST disappeared even with the guitar at full volume.

1) Did I correctly guess the correct cables for the Amp, Footswitch and guitar ?

2) If I did guess correctly then why would using the cable supplied for the guitar create such a loud hum and is there anything I can do to resolve this issue completley?

Thanks in advance

Richard

asked 25 Oct 2018 at 09:42 PM

Richard Ward
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Hey Marshall Forum!

About a year ago I bought my first ever Marshall amplifier; the Silver Jubilee 100W head (with 4x12 cab).
Since I use it mostly at home, I haven't cranked the volume all that much. But when I do, I notice a loud humming noise.

Today I turned the amp on, without having the guitar cable attached to it, cranked up the Master volume (with 0 gain!) and it hummed like crazy. 
What could be the source of the humming?? And more importantly, how can I get rid of this awful humming? 

The only cables that were attached were the footswitch, FX in/out and the power cable. 

asked 24 Oct 2018 at 05:58 PM

Jarnick Hulzebos
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Getting a fair amount of hum in the FX loop with my DSL 50 head.

It's not the pedals. No problem in front.

Is this a common failure?

Tubes are good, and bias is at about 43mv, and even.

 

asked 13 Mar 2017 at 04:07 PM

Jeff Williams
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I've got a Valvestate S80 8240 which has developed a loud hum whether instrument plugged or not.

The hum disappears when it is tilted forward. Can anyone suggest a home fix?

I put up this question before but for some reason it seems to have been deleted!

asked 14 Jan 2017 at 01:21 AM

James McC
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