Maker Pro
Maker Pro

Marshall 6101 valve amp

N

N_Cook

Jan 1, 1970
0
In for a problem in heater wiring, corrected and working fine on the bench.
Reassemble in cab and no output now. I'm loathe to have to now take the main
board apart unnecessarily if I'm doing somrthing silly as there are a number
of awkward quirks about this model.
Feed signal in the "Return" and it outputs to the speaker. Normal signal to
the front input and output at "Send". There is 0R across all 4 un-inserted
"return" socket contacts as per schematic. ch select switches and status
LEDs work but pressing the muting switch does not mean the 3 LEDs come on
together now as a reminder indicator (this function not mentioned in the
user handbook). I've removed the digital board and nothing seems amiss with
that (secret lock within the XLR). Relay click at initialisation at power
up.
 
N

N_Cook

Jan 1, 1970
0
Something awry with the series/parallel sw. I noted the 3 LED on, if mute
on, function with another 6101 but it is not the case here, makes perfect
sense in the absence of a mute lamp on the front, anyone any knowledge? This
one wrong or the other one wrong or just variants? or does it require jacks
in place or something as well
 

shrtrnd

Jan 15, 2010
3,826
Joined
Jan 15, 2010
Messages
3,826
Not familiar with your equipment, but sounds like a grounding problem.
(ie: works fine on bench, but not when put back in 'cab').
Carefully check all your electrical contacts where they might touch the cab, grounding out your electronics. I'll bet something electrical is touching the cab when you put the chassis (or printed circuit board), back in the 'cab'.
 
D

dkxl5

Jan 1, 1970
0
dkxl5 had written this in response to
http://www.electrondepot.com/repair/Re-Marshall-6101-valve-amp-35906-.htm
:

N_Cook wrote:





-------------------------------------
dkxl5

The mute button between the pwr amp send/return jacks does not have any
indicator that I'm aware of.
The channel leds can be finicky sometimes. Sometimes when I turn mine on
all 3 leds come on and a quick
on/off of the power switch snaps it back to the proper channel led. There
are some awkward quirks with
the amp. Make sure the mute switch is not engaged. If the series loop
button is engaged you will not get
any sound from the amp, though the effects knob will vary the loop send
output and you can still send a
signal into the return and hear it in the speaker. When switched to
parallel you will have sound through
the amp from the input.

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N

N_Cook

Jan 1, 1970
0
dkxl5 said:
dkxl5 had written this in response to
http://www.electrondepot.com/repair/Re-Marshall-6101-valve-amp-35906-.htm
:

N_Cook wrote:





-------------------------------------
dkxl5

The mute button between the pwr amp send/return jacks does not have any
indicator that I'm aware of.
The channel leds can be finicky sometimes. Sometimes when I turn mine on
all 3 leds come on and a quick
on/off of the power switch snaps it back to the proper channel led. There
are some awkward quirks with
the amp. Make sure the mute switch is not engaged. If the series loop
button is engaged you will not get
any sound from the amp, though the effects knob will vary the loop send
output and you can still send a
signal into the return and hear it in the speaker. When switched to
parallel you will have sound through
the amp from the input.


##-----------------------------------------------##
Delivered via http://www.electrondepot.com/
Electronics Enthusiasts' Community of the Net
Web and RSS access to your favorite newsgroup -
sci.electronics.repair - 35126 messages and counting!
##-----------------------------------------------##


I'm wondering if the 3 LED lit thing is only at power up, I remember from
the other one it also locks out ch selection and maybe use at all via the
front input until de-muted. But maybe it was like your observation, poor
initialisation.reset at power up
 
N

N_Cook

Jan 1, 1970
0
Gareth Magennis said:
Bad Low voltage power supply (V mute switching).

Bad FET or switch.

Dry joint.

Definitely nothing to do with initialisation.



My guess is FET.

Amp not open at the moment, looking at schema if SW301 is the mute switch
then no logic connection to the 8031A / LEDs. The ch sw lines go through the
8031A to the HC574 to the LEDs so I suspect electro C301 of the p9 reset for
random power-up problems
 
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