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Blown fuse and its soldering to a PCB

I need competent advice:

I purchased a new amplifier (Dared MP-60, made in China). It is cheap and rather good sounding, but its left side got dead (left-side tubes stopped glowing) when I replaced the stock 5881 tubes with RFT EL-34 (everything was OK for 30 min. but next morning, when I was switching it on, the problem appeared), though it was permitted by the user manual and was authorized by the seller.

When I opened the cover, I saw four 125V 8A fuses covered with opaque plastic cases. The fuses have leads soldered to the PCB. We measured them and indeed one was blown.

What is strange that the seller says "you can use unsoldered fuse, but there is no place to place a unsoldered fuse on the PCB". I asked for explanations ("Does it mean that the whole PCB must be changed or that the unsoldered fuse should be replaced by another fuse which should be soldered to the PCB?, and she said "Yes, there is no place to place the unsoldered fuse on the PCB, it means the whole PCB must be changed".

Is this PCB a single-use dummy (if it is possible in principle)? How can it be that the blown fuse must be unsoldered but the new fuse cannot be soldered to the same place in the PCB?
transl
transl OP
156 posts
 
Thanks a lot!

I will contact Partsconnexion or Parts Express for that.
rodman99999
6,039 posts
 
If you can't locate a pigtail type fuse: Find a plastic inline fuse holder, ie:(http://cgi.ebay.com/FUSEHOLDER-INLINE-FUSE-HOLDER-WITH-14Ga-WIRE_W0QQitemZ270366963842QQcmdZViewItemQQptZLH_DefaultDomain_0?hash=item270366963842&_trksid=p3286.c0.m14&_trkparms=72%3A1234%7C66%3A2%7C65%3A12%7C39%3A1%7C240%3A1318%7C301%3A0%7C293%3A1%7C294%3A50) and solder the leads to the PCB. I can't understand what the problem would be with de-soldering and re-soldering to a PCB. We've been doing it for decades, in the electronics repair business. That's what solder suckers and solder-wick are for. Here's an inexpensive kit: (http://cgi.ebay.com/SOLDER-SUCKER-DESOLDERING-PUMP-HIGH-POWER-WICK-SOLDER_W0QQitemZ220376267737QQihZ012QQcategoryZ46413QQssPageNameZWDVWQQrdZ1QQcmdZViewItem)
markd51
762 posts
 
Here's a real stupid, but simple fix, and might work for you? I did this once to a Sansui Reciever, that had a similar type blown fuse on the power supply board, and did this to sidestep mucho headaches.

Go to Radio Shack, get yourself some Fuse Clips. Solder two pairs of Fuse Clips back to back. You can then clip one side of the Fuse Clips to the Blown Fuse, and then clip in the new fuse on top "piggyback" style.

The paired clips, will look like two "U's" back to back when soldered together.

As long as it's the same value fuse, all will work just fine, and this will permit you to do a quick fix, without ripping out boards, or the worry of damage to the board from heat. Hope this helps, Mark
magfan
1,583 posts
 
Not all circuit boards are created equal.
Glass/Epoxy boards that I have seen are kind of translucent light green will take more 'rework' than cheesy cheap boards. I have no idea what the cheapo boards are made of, but when cooked it charcoals nicely and eventually becomes low-level conductive. Traces of these boards lift more easily, but can sometimes be repaired by laying a piece of bare wire where the trace WAS and soldering it to what remains good of the trace at either end.
While you have the amp disassembled for repair, it may be a good thing if you make all 4 fuses replaceable.
Marks idea is pretty cool, and may make sense in this case of what sounds like limited clearance.
fluxus's avatar
fluxus
1 posts
 
Hi,
I have your same amplifier, branded Fatman iTube 252, and just the other day I turned it on and half of the tubes weren't glowing, with one channel being off.

I am using it with some RFT EL34, Melz russian 6sn7-ish, siemens 12ax7.

I suspect it may be your same problem, one of the fuses (or more) being blown.

How did you finally risolve your problem? Do you have any tip to give me? I haven't open my amp yet.

If you even have old pictures you want to share, feel free :))

After you fixed (hopefully) your amp, did it last long without problems, or you did you ran into blown fuses or other issues again?

Thank you!
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