D-60 Blowing Fuses

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#1 George-Costanza

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Posted 03 April 2014 - 02:59 PM

I have an old Crown D-60 power amp that was working fine until a couple of days ago.  I turned it on and it blew the fuse (one of those small 2 amp glass fuses).  I went out and bought an indentical replacement but it also blew as soon as I turned the amp on.

The amp has been mounted in a rack in my studio for almost 5 years and hasn't been moved during that time.  What would cause this?  I'm assuming that some component somewhere has failed due to age?

#2 joust


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Posted 03 April 2014 - 03:16 PM

Hello George,

Welcome! There is not too many things that can cause an amplifier's main fuse to blow.
The first thing that comes to mind, is probably the power supply : Verify for shorted diodes, maybe a faulty filter cap (replace both, if necessary).
The other issue could be serious : an output device may have died, and probably took a few more devices with it. Troubleshooting time!
If it should be an output device, the usual suspicious cause is heat transfer and its evacuation. Make sure that 'all' devices are thermally secure (use thermal compound).
Note : I have seen 'mica' isolators (looks metallic, greyish, between output device and heat sink) in some amps being intermittent.
If you have this type of isolator, I recommend the replacement of all of them for transistor (TO-3) silpads (silicon pads).

Hope this helps!