Marshall 2266 head - Buzz/errrrr/hum sound on HDR

[HF1600ie]

Dear all,
My lovely 2266 head owned since new is producing a noise, similar to a buzz or the typical "errrrrrrrrrrrrrrr" sound when turned on HDR.
The guitar doesnt need to be connected to have the noise. Just the amp. Or, even with guitar connected, if guitar volume is zero, the noise is already there.
On LDR this is not so noticeable.

It doesn´t seem guitar related and don´t remember if the amp always did this, but I think the only thing i used to hear in HDR was noise like "SSSSSSS", because we have more gain and I accept that.

Does anyone have or had the same problem?

Thanks everyone !

[surfnorthwest]

Could be a preamp tube gone microphonic. When you switch to HDR it engages another preamp tube (V2)

I would start by changing that tube with a known good one first.

[HF1600ie]

Good idea! Will try :-!

[HF1600ie]

Hi,
I tried another valve in V2 I had spare, a Tung-sul, and the same noise happened.

I wonder if this is a ground issue inside the amp? It´s like if the single coil noise is always there in HDR, but even without guitar connected !

[Dana,s blues]

It could be a power tube issue. How long have you had the amp? With my 2266c noise problems were due to defective power tubes.

Dana's Blues

[HF1600ie]

Hi,
My tubes are as old as the amp : 7 years. Only home used and 2 or 3 times at small jam sessions.

I used the KT66 in another amp and this noise didn´t come up !!

[HF1600ie]

Could this be a grounding issue? Capacitors? There´s really not much milleage in the amp...

[Dana,s blues]

If it is not tube related then you should have it serviced by a good technician. There are a number of possibilities and unless you know a lot about electronics it could be hard to find the problem. My 2266c is really quiet. No noise in HDR when nothing is plugged in. . The HDR is more sensitive to interference but the only thing that comes to mind is if you have an electrical problem in the room where the amp is plugged in. Improper voltage can cause the transformer to hum. I have seen this on stage when too much equipment was plugged in to an inefficient power supply. It partially bleu the mains fuse. After changing that everything was OK. Check your power supply. When the amp is on standby and it makes noise then it is possibly related to the impute transformer and it's circuitry. If you only hear the noise when the amp is on full power, defiantly get it checked by a technician. Good luck!

Dana's blues

[HF1600ie]

Hi,
The noise does not appear in standby.

It only appears when I put the amp working (both buttons - the black and the red are ON) and it becomes more obvious in HDR mode.

What I meant is that It doesnt come from the guitar, because with the guitar volume on Zero, the noise is there. So, it´s not a "single coil hum". It really comes from the amp and all that is needed is the amp to be ON...

I will try to connect it in another home room. But I suspect nothing will change, as my VOX doesn´t do this noise, and I remember hearing it in a Jam some months ago. I even thought my guitar wiring had a grounding issue...until I found the amp was doing that noise itself...