DSL Nosounditis

Nerine

Yeah, even when my 800 spewed a valve socket, it still made a noise. You could get it to loud TV/stereo volumes.
Just not much after that.

They're fairly simple to work on though!!

mike_l

Diagnosis

Needed

Bridge recifier BR102

Phase inverter valve

1x pre-amp valve

PCB track burnt from failed rectifier

Cleaned noisy pots and checked bias.

Total £96.

Can't complain at that.

Bidley

Who did you take it to, out of interest, @mike_l ?

mike_l

Chris Newman, as he is only about 10 mins from home.

Voxman

The bridge rect needed to be fixed on my DSL401 too - pretty much a design flaw so I'm told on 2003 and earlier versions.

ICBM

Voxman said:

The bridge rect needed to be fixed on my DSL401 too - pretty much a design flaw so I'm told on 2003 and earlier versions.

On all versions - they still haven't really fixed it. All they've done is raise it up a bit so it has (very marginally) more ventilation. I bolt a proper heatsink to them - that's what the hole in the middle is for! Why Marshall didn't, for the sake of a part which would only cost them a few pence in the quantities they buy, is beyond me. This is by far the most common fault on the DSL201 and 401 - to the point that I would guess they will all go eventually if used for enough hours.

The other main fault is the bias supply having to pass through the contacts of the MV pot as I mentioned earlier. Pure bad design - if the pot takes a knock or just gets old and scratchy and goes open circuit at any point on its turn, the power valve(s) on that side are left without bias voltage and blow. Easy to fix with a couple of 1M resistors to feed the bias past the pot. Cost of parts: about 2p.

I also increase the ventilation at the top of the cabinet as a matter of routine when servicing them - you just need to put a couple of standard electrician's grommets around the top rear screws to hold the chassis another 1/4" or so away from the cabinet. This is much more effective than fitting a fan blowing at the outside of the chassis as sometimes recommended, which does almost nothing except add noise!

Apart from those things - and blown output transformers on the 201, the 401 seems OK - they're actually quite reliable, better than the heads anyway.

mike_l

Voxman said:

The bridge rect needed to be fixed on my DSL401 too - pretty much a design flaw so I'm told on 2003 and earlier versions.

The guy who did mine has (like @ICBM ) seen a few DSLs.

He did put a 10amp* rectifier in as an upgraded part (at least that's what he telled me), which he seemed to think would help with reliability. 

*I think he said 10amp.