McCormack DNA-0.5 Protection Circuit problem?


Hi Folks ~ My problem is regarding a McCormack Deluxe Edition Power Drive DNA-0.5 Amp. I bought this unit new in '98 and it performed flawlessly for me from that time until I moved in 2005. At that time I put it into a local storage facility - in it's original box, foam padding and plastic bag. A week ago I took it out of storage, unpacked it and left it out inside my home for a week. Yesterday for the first time since 2005 I tried hooking it up and using it. I should also say for the first time since 2005 I am also using my McCormack Micro Line Drive, in combination with the DNA-0.5 - which I think is working as it should. But, something is wrong with the amp. When I power up my cd player, dac, and Micro Line Drive, then the amp, the amp stays in protect circuit mode. The illuminated light in front stays orange/yellow (instead of turning green), and it does not "click" like it used too, after the light turned green, signaling no protection circuit problem.

I probably should not have done this, but one thing I did do while trying different options was to have a source running into the rest of the system - a disc playing in the cd player, and then turned the amp on while that was playing. When this was done, music did come out of the speakers for a split second, before shutting the sound off. I read another thread on this forum - http://forum.audiogon.com/cgi-bin/fr.pl?aamps&1332879246 where that person used a multi meter on both channel outputs with the unit powered on, but with nothing connected to either the outputs or the input. I have a digital multi meter, but I am not too familiar with how to use it - what setting it should be on. When I use the multi meter on the outputs (with nothing connected to the outputs or input and powered on) I do not get any readings. Is this the way it should be or not? I think this is correct, since I do not want to pick up a DC current. If it did pick up a DC current at the output, I think this unit is designed to shut down the amp, and shorts the input to ground.

I have not removed the top cover yet. I tried to d/l the manual/schematics from hifiengine.com, but all I got after the d/l was blank pages...I guess I do not have the latest adobe upgrade. My Firefox browser should have been adequate. This unit has never been serviced. I guess one of the rail fuses could be blown, or some of the capacitors? Any thoughts and or suggestions would be most welcome. I live in a small town, and would likely have to drive a couple hours to find a reputable service business. Also, if it may matter, my home is off-the-grid. I get 100% of my home electrical power from a PV Solar Array. I had plenty of power when I was trying to using this amp. Previously before hooking up the 0.5 and micro line drive, I was having no problem with the cd player, dac, and a NAD integrated amp, along with the same speakers.
Ag insider logo xs@2xharold_may
Hello Harold,

In all likelihood you have blown one or more of your 4 internal power supply (rail) fuses. These are 6A or 6.3A fast-blow types (5 x 20mm size) that you can hopefully find locally. Replace the blown fuses and you should be back in business.

This probably happened because the amp has not been used in a long time. Now that you are using it again it shouldn't be a problem.

Best regards,

Steve McCormack
SMc Audio
Hi Steve,

I did not expect a response from you. Thanks a lot for your reply and for telling me what to replace. And thanks for designing such nice equipment.

peace,
Harold
I had a similar issue about ten years ago and Steve gave me the same advice and all was well. I'd just recommend getting some additional replacement fuses while you're at it just in case. Shortly after I replaced the first fuse another one blew probably for the same reason as the first, and I haven't had a single problem since. Nice to have a couple extras around.