1. Home
  2. Electronics Repair
  3. Marshall 6101 valve amp

Marshall 6101 valve amp

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.

Reply to
N_Cook
Loading thread data ...

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

Reply to
N_Cook

------------------------------------- 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

formatting link
Electronics Enthusiasts' Community of the Net Web and RSS access to your favorite newsgroup - sci.electronics.repair - 35126 messages and counting! ##-----------------------------------------------##

Reply to
dkxl5

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

Reply to
N_Cook

Bad Low voltage power supply (V mute switching).

Bad FET or switch.

Dry joint.

Definitely nothing to do with initialisation.

My guess is FET.

Reply to
Gareth Magennis

formatting link

on

from

the

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
Reply to
N_Cook

ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.