How do I test for a faulty electrolytic capacitor in the power supply of my Crate guitar amplifier????
Sep 09, 5188 by Jackoff | Posted in Engineering
This can be rather easy, in many cases.
Electrolytic capacitors have a PVC shrink-tube plastic cover to shield the aluminum case from other devices, as the case is tied to the negative terminal. When many electrolytics start to fail they heat up. The heating causes the shrink tube to shrink even more, and instead of covering much of the end, it pulls away and can even leave the end of the capacitor exposed totally. Replace any that have this indicator whether or not they have failed yet.
But the easiest way to solve the problem is the shotgun approach- replace them all! They are cheap (mouser.com) and there are only a few big ones, anyway. Since they are the weak point of any circuit board, as they are the workhorse of a circuit, it is good to replace them anyway on an old system. It will give the circuit board new life. They will fail over time...
Warren W- a Mormon engineer | Sep 09, 5638
Just take it to Dr. Brown, Marty
Darma B | Sep 09, 8081
If the capacitor has failed it may just be because of a bad connection. Have a look at all the solder cnnections on all the capacitors and look for a dull looking solder, one which is not shiney like the rest. If you find one this may need re-soldering.
As this is a power supply capacitor and you are not sure what you are doing I suggest leaving it to a professional as capacitors even when not connected to the power can contain dangerous stored electricity which might be several thousand volts.
Mike | Sep 09, 2625
Where can I find a replacement power transformer for my crate gt80 guitar amplifier?
Sep 09, 8172 by Mike | Posted in Other - Electronics
I have contacted Crate and they gave me a list of parts dealers but all insist that they do repairs and not sell just power transformers. I am looking for a part #94-029-01. Thank you for any help!!
First, what you need to know is the secondary voltages of the
transformer you wish to replace. A part number is nice, but
tells you very little, unless you have a book on hand, and
usually, these numbers are only for that product line (in house)
part numbers. I can tell you where to go to find a power x-fmr.
but will need to know: How many watts will said amplifire send
to the speakers, how many wires come off of the secondary,
and how big is it? If you can get a schematic drawing of your
amplifire with power transformer output voltages, I can tell you
exactly where to get a transformer from. Feel free to e-me.
Why did it fail? Are you sure that the power transformer is bad?
There may be other issues, here. I rarely see a transformer go
bad under normal use. If the fuse blows, replace it with a 1/2
amp larger than it calls for. If it calls for a 2 amp fuse, try a 2.5
amp fuse. If it still blows, try a 3. if it still blows, you may have
a short in the power output section of your amp. I don't normally
recommend that higher fuse ratings should be used, but that
is what I would do if I was working on it. You may find other
issues besides the power transformer. If you have voltage going
into (the primary) and no voltage on the secondary at all, then
you might have a transformer that has a thermal cutoff unit that
is hooked up in series with the primary windings protecting
the transformer from over heating. This has been known to
happen, and can be easily repaired, if you have the right tools,
a soldering iron, and a lot of patience. I can walk you through it.
| Oct 27, 2009
