Marshall JCM 2000, DSL 50W, year 2005

N

N_Cook

Guest
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
 
looks as though SW1b switches ok but not SW1a between clean and crunch
 
"N_Cook" <diverse@tcp.co.uk> wrote in message
news:j714j6$898$1@dont-email.me...
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
Click to expand...

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.
 
Gareth Magennis <sound.service@btconnect.com> wrote in message
news:_MGdnT8fI7GhsAnTnZ2dnUVZ8jmdnZ2d@bt.com...
"N_Cook" <diverse@tcp.co.uk> wrote in message
news:j714j6$898$1@dont-email.me...
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




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.
Click to expand...
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.
 
Gareth Magennis <sound.service@btconnect.com> wrote in message
news:_MGdnT8fI7GhsAnTnZ2dnUVZ8jmdnZ2d@bt.com...
"N_Cook" <diverse@tcp.co.uk> wrote in message
news:j714j6$898$1@dont-email.me...
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




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.
Click to expand...
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
 
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
 
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
 
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