Marshall AVT50 super quiet unless FX Loop Jumped

SkidKid

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So as the title says, my AVT50 is SUPER quiet and extremely trebley unless the FX loop is jumped or used.

I have googled to find a solution however the only thing I could find is the R58 resistor problem. I bought the amp about a year ago and it had 0 issues when I tested it. Of course a day after I bring it home this happens but I've just jumped the FX loop and lived with its. I tried cleaning the jacks on the FX loop with electronics cleaner as well as the input jack but didn't have any luck.

Has anyone ever experienced this issue before or have any advice?

(FWIW - I am more than capable of soldering/unsoldering parts on a PC board)
 

fitz288

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or have any advice?
Sounds like the typical cliffjack problem to
me at the moment.

May i ask how exactly you tried to clean the jacks?
I'm guessing the same.
It might not be the contact with the cable, it might be the contact that gets lifted when the cable is inserted.
If you can access the jack from the inside, try some Deoxit right here.
1656037308589.png
 
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SkidKid

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Perfect, I was hoping thats what people would say. I'm thinking I cleaned them with some CRC electronics cleaner, I think I may have used some q tips as well. How exactly i did it, no idea.
 

Tatzmann

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Take a little piece of thick paper or thin
cardboard and soak it in electronics contact
cleaner.

Slide this back and forth between those metal tabs, which act as a switch in those jacks.

Takes a little patience, especially with big
hands, but thats the way to do it bassically.

You have to to do this thoroughly in the effects
loop jacks.
 

SkidKid

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@Tatzmann and @fitz288

Will do. Might I ask, what's the difference between Deoxit and all these other brands I see?
Does it actually do a better job or is it just popular?
 

fitz288

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Might I ask, what's the difference between Deoxit and all these other brands I see?
Does it actually do a better job or is it just popular?
It actually does a better job.
Not some kind of pyramid scheme that we are all getting kickbacks on for new recruits.
It does multiple things, and has been found to be the best thing on the market for general amp maintenance.
Cleaner, deoxidizer, and lubricant.
 

Tatzmann

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Doesnt have to be DeOxit, i dont even know
if this is available outside of the usa.

If the product is electronics contactcleaner
and states its usable for potentiometers,
switches and so on then it can be used.

I use teslanol oszillin for around 15 years
without any problem.

But DeOxit is the most known in the us for this task and probably very good also.
 

SkidKid

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Well I cleaned everything up, took my chances with the CRC Electronics Cleaner from Autozone. I'm patient what can I say. I'll get some DeOxit on order.

The fix worked for about 5-10 minutes then the issue returned. Upon inspection of the send jack, it looks like the ground contact on the jack has lost some tension and has a bit a spring to it. I inserted a cable and gently bent the contact down. Problem solved however we'll see how it lasts.

Thanks for the advice @Tatzmann and @fitz288
 

Tatzmann

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Good! Your a fast acting one:yesway:

Those jacksprings, once they are really "loose"
cant really be bent back into the right position/tension, atleast thats my experience
with trying to "straighten" them out.

Then its time to replace it. But most of the
time a thorough cleaning does the job.

Sorry for my bad english atm.:rofl:
 

SkidKid

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@Tatzmann No worries, no grammar police here! Lol.

I agree with what you said, I am definitely going to order a new jack for it. Has a weird one tho, a 4 pin jack with a grounding washer that is actually a pin or two into the board. 🤷‍♂️
 

Tatzmann

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Can you take a pic of this jack? Cant seem
to find any good pics of this on the net,
but from far away and blurry they look like
standard cliffjacks.
 

Tatzmann

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This rather angry looking toothwasher is separately soldered to the pcb. The jack itself
should be standard. You might have to desolder
the tootwasher to free the jack.

As bent as the tab looks yet i guess you have
to change the jack. Been there, done that.:p

Let us know how it goes!

Cheers
 


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