Mark IVb Output and Speaker Problems

[fretout]

Hi everyone! I NEED SOME HELP!!!

I have a Mark IVb widebody combo and I am having 2 problems, these might seem kind of obvious, but I wanted to know if you guys had any advice on what caused these problems and how to correct them. Please help!!!

1. For some reason whenever I am playing, the signal seems to cut in and out. I wiggled the speaker cable on the back of the amp and determined that the speaker cable is the cause for the signal loss. My problem is that I can't tell if my speaker cable is shorting out at the speaker, or if the speaker ouput on the amp is the problem. Has anyone else had this problem? If my cable is shorting out, does this mean I am damaging my transformers (because there is no load connected due to the short), or is it just a signal issue?

2. The other problem I am having is that my Output control seems to be shorting as well. I can turn it to 4 and then all of a sudden it will cut off all sound to the amp, but then it seems to work from 5-10. Does this sound like a bad pot, or a bigger issue?

Has anyone had these problems before? I just don't want to damage my amp!!! Thanks in advance!

 

[Monsta-Tone]

I definitely would not run it long like this.

Here is where I would start:
Read this 1st, it could save your life: http://www.aikenamps.com/SafetyTips.html


Speaker Jack:
Try the amp with a different cable and cabinet. This will tell you if it's the amp.
Then, if it wasn't in the amp itself, try the old cable again, with the new cab. This will tell you if it's the cable.
Then, try the amp with the new cable and the old cabinet. (won't work if it's a combo)
Try the original cable and speaker in a different jack. This will tell you if it's the jack, maybe. It could be a loose solder connection that is shared with all of them.

When you wiggle the plug, it could be moving a number of things in the amp since it is attached by wires to the output transformer and these wires are sometimes tie-wrapped to other wires.


Output knob:
It sounds like the pot is dirty or damaged or there is a bad solder connection.
Discharge the capacitors:
Then remove the chassis and look at the pot. It should have 3 wires going to it. If any of the wires look loose or if any of the solder connections look weird, this could be the culprit.
Shoot some De-Oxit or another good brand of Contact Cleaner in the pot and turn the knob along it's full path several times. Repeat this at least twice. Usually this will clear up most issues if it is just a dirty pot.

While you have it open, look at the output jacks see if they are physically broken or if there is a bad solder connection or wire on them.

It could also be that the Output pot is cutting out and making the amp have the issue that looks like a bad speaker jack.

 

[Boogiebabies]

I remember a few people who had the pull silent switch on the Output knob short while playing as well.

 

[MrMarkIII]

And don't use a guitar cable instead of a speaker cable.

 

[fretout]

Thanks for the responses everyone!

The amp I am referring to is actually an amp that I wanted to buy, and I was testing it out when I noticed all the problems with it. I can tell you for a fact that there are 2 separate issues, the speaker cable and the output knob pot.

I will see if I can lug my 4 X 12 over to ther seller's house to determine whether the issue is the speaker cable, or the speaker output jack. Thanks for the recommendation.

Since the amp has been "cutting out" because of the speaker cable problem (which means there is NO LOAD connected to the amp), would the damage to the amp be immediate (amp would not work at all), or would the lack of a load gradually damage the amp? If there was any damage at all, would the amp still work? :shock:

And don't use a guitar cable instead of a speaker cable.

Uhhh, thanks. I'll try not to use my guitar cord as a speaker cable on the COMBO AMP.

 

[Monsta-Tone]

Uhhh, thanks. I'll try not to use my guitar cord as a speaker cable on the COMBO AMP.

:lol: You would be amazed at how many people actually do that!