Generic PCB question...

S

stain.

[H]ard|Gawd
Joined
Sep 17, 2006
Messages
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ok, this isn't computer related in the slightest, but I know there are some hella smart guys here (of which I'm not one :))

I've got a Marshall guitar head (MG100hdfx) and it's not working .. properly..

Here's what I did... probably stupid, or an easy fix.

When I got it, I dont' have a cabinet for it, and the volume of the fan was quite loud.. I changed it... also, because I don'thave a cabinet for it the amps that would be exiting it going to the speakers werent' getting put out? (idk?). It blew a fuse, and there is a tiny spot that is on the PCB that 'smokes'.. The fan I put on there was almost identical in size, and rating (actually it was a little lower).

Would I have done something terrible in doing so? can the wires on the fan be crossed and that create an issue?
 
So what you're saying is, immediately after you replaced the fan & powered it on, it blew a fuse? Did it blow a rail fuse or the mains/line fuse?

The smoking PCB...I assume this is a trace and not a SMD component? It is smoking even after whatever fuse blew, or does it only smoke after the fuse is replaced?

I have no idea what this is saying: 'don't have a cabinet for it the amps that would be exiting it going to the speakers weren't getting put out.'

Crossing the fan wires would, I imagine, either cause the fan not to work, or worst case, the fan electronics to be killed. I don't think the fan would short out, but I have never done this myself.

My guess is that you unknowingly damaged something with static electricity when you had it apart, but this is just a guess until you clarify what's happened here.
 
the cabinet is just the speakers for the amp.

I dont' think I damaged it with static electricity as I didnt' actually touch the PCB (to my knowledge) while I had the amp apart.

It only started smoking aftert he fan was replaced.

I'll take pics of the PCB when I get out of work.
 
Did it start smoking after some use or immediately after you powered it on, following the fan replacement?
 
Well, if not static electricity, then something was plugged in incorrectly or not at all - I seriously doubt a fan wired incorrectly would cause a fuse to blow (unless the fan wires are shorted).
Looking forward to some pics.
 
pics to follow.. I need to get a screwdriver :( lost my tools in a divorce.

I talked to a guy at guitar center and basically what he said is that if you power a head unit without an amp, it can do the aformentioned effects on an amp.
 
I'm a bit confused here...is this just a pre-amp/effects thing or a complete amp+preamp?
 
It's a head unit.

complete amp (not sure about the preamp) but it does have some effects on it. There are no speakers attached to it, which the more I talk to gear heads, the more I think that is the major malfunction.
 
2hgyb2u.jpg
 
Forgot about this thread for a bit....maybe post some pics of the internals? I assume this isn't tube gear from some google pics, so running it without speakers shouldn't damage the amp section.
 
Sorry, I haven't forgotten. i just don't have the tools to do what I needd to do.. damn divorces.

It's a solid state....
 
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