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Marshall JCM 2000, DSL 50W, year 2005

Whether red or green channel , on rare occassions the output will go clean, ie not distorted. Of course I cannot induce that at will. As the LED stays on ok unlikely a sw problem, often seen with those yellow shaft push push switches. An FET or relay contact problem ? but which one would be common to both red and green channels? Valves all test out fine for gain and CH/R but again which section would be common to red and green, a problem in the splitter driver would increase distortion

Reply to
N_Cook
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looks as though SW1b switches ok but not SW1a between clean and crunch

Reply to
N_Cook

Is this when using the footswitch?

I had a TSL that would intermittently switch the FX loop in and out, but the LED status would not change to follow suit. Eventually tracked it down to a dirty footswitch switch, that somehow was dirty enough to flip the loop in and out, but not dirty enough to change the LED status. Very strange, but true.

Gareth.

Reply to
Gareth Magennis

stays

push

common

down

loop

Could well be that, Jalco white and black isolated sw 1/4 in sockets, problems with those switches I've seen plenty of times before. I sent myself on a bum steer with Sw1 and the wrong proxy probe points for the inaccessible sw points, SW1 actions are ok.

Reply to
N_Cook

stays

push

common

down

loop

Putting a pot over the open ch change footswitch socket then around 55 to 59 ohms you can get tone change with no change of LED and slightly different resistance to dim LED and then a bit more change then both LED on situation is just possible. With very light touching of a rod in the enclosed Jalco Return socket ,of the effects loop, I can easily get 2 or 3 ohms remaining on either of the switches, 0.1 and 0.6ohm as found,so with amp heat that could easily upset things but I've not worked out whether all or any of those 3 situations could lead to the observed symptom of dirty channels becoming clean

Reply to
N_Cook

I'm waiting on reply from owner wrt footswitch and/or S/R sockets use. Exploring the Jalco switches, the one nearest the send so. if non grounded would only induce stray pick up from the Return opamp (assuming bare amp with no use of S/R). The one furthest from the Send so. cleanly switches Relay 3 with a transistion point of about 280 ohms. Despite being able to get about 7Kohm by slightly pushing the switch, and holding there, all it would do would mute the amp, not attenuate the throughput to the PA. I cannot get an intermediary ohmage on the other switch above a few ohms

Reply to
N_Cook

I don't know what I call my tool - engraver with nylon bolt in place of steel point and bashing hell out of the pcb on max oomph, but looks as though Relay 2 has a dodgey contact. Initial whanging finds approximate area of pcb then turn down the oomph dial and bash components. Not had time to check /substitute yet. But as in ultra gain area would make more sense than footsw S/R area

Reply to
N_Cook

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