Mark IV No Sound / Not Working

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Tomarkiv

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Oct 15, 2020
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Hello,

I recently purchased a used Mark IV rack mount version. Before purchasing I asked the seller to verify it was working on all three channels via a YouTube video (due to distance) in the video all things checked out so I bought it. Get the amp delivered to my house, plug it in and no sound....verified all cables are functioning, verified recording out on the main volume was not pulled. All volumes are up...even removed tubes and reinstalled (except for the sheilded pre amp tube) even tried plugging my guitar into the effects return and still nothing...lights are on, tubes are glowing.

Amy help is greatly appreciated!!
 
Hello
Have you checked the connection into the HP amp ?
If the output transformer is ok and the lamps are on there is no reason do not to have sound if everything is correct ...
the guitar/amp jack is ok?
test with another guitar?

have a good day
dom
 
Can you verify what you mean about "into the HP amp" ? Thx

About cables etc I checked cables and guitar through my other amp and no issues.

Removed top of amp to verify input jack connection is still in tact and everything seems to be in tact.
 
Can you verify what you mean about "into the HP amp" ? Thx

About cables etc I checked cables and guitar through my other amp and no issues.

Removed top of amp to verify input jack connection is still in tact and everything seems to be in tact.
 
hello

just check the connections ...
jack to HP.


Otherwise, check TUBE V1 first.
Swap each preamp tube one by one and if that doesn't work swap the power tubes one by one.
dom
 
I didn't check the sheilded V1 tube. Will do that and check all connections and let you know. Looking at the schematic if the V1 tube is not functioning it appears nothing would work correct? That is the first tube in the chain to the pre amp right? Thanks
 
check V1 with another tube ..... or replace them( V1 to V2 and V2 to V1....)
it's very important to have a paire of 12ax7 in advance

for the connections look at the câble between black shadows hp and jack ( intern to the amp)
if it's ok certainly you need to look and remove the V1 tube and change to a new one.

look at the fuse too... but if you have a red light in each tube it's ok

after if you checked these all points, you need to check with a professionnal technician at Mesa brand and realize a serious repair ( transfo out, or bad alimentation)
dom
 
Hello.

Have you tried if it’s silent from all speaker outs? (4ohm and both 8ohms?)
 
Divide and conquer :) split the preamp from the power amp by just plugging a guitar into the fx return and see if you hear anything. That could assist in narrowing where to look.
 
I will try the slave out... didn't try that. But did try the recording out and still nothing.
 
Tomarkiv said:
I will try the slave out... didn't try that. But did try the recording out and still nothing.

It's a longshot since the Slave Out is just tapped off the output transformer. I do wonder about the standby, if that wasn't operating properly there'd be no output either.
 
Good point...I didn't think of that. I will take a look at the switch and wiring.. Fingers crossed.
 
Tomarkiv said:
Good point...I didn't think of that. I will take a look at the switch and wiring.. Fingers crossed.

Maybe perhaps try changing the Triode / Pentode and also the SIMUL-Class / Class A switch settings also, as they do effect the tube arrangements and power to them.
 

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