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 - 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, 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.
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.

Cool...well done Mr. McCormack.
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.
I recently finally got around to replacing these fuses, and apparently I messed up. Hopefully Steve McCormack will again see this post, and suggest something. I got a couple sets of fuses from Radio Shack - 6.3 Amp/250 Volt Slow-Blow fuses (270-1068), and 6 Amp/125 Volt Fast-Acting fuses (270-0145).

I first found and removed just the one blown fuse, and replaced it with one slow-blow 6.3A/250v fuse (even though Steve said to use fast-blow...). Reconnected electrical wires, put a load on the amp, connected pwr and turned on amp. Sound of blown fuse resulted. Powered off, removed pwr cable, removed amp cover, found same fuse re-blown and another blown fuse. Again used 6.3A/250v fuses but replaced all 4 this time - 2 on each side rail/circuit board. But this time I forgot to reconnect electrical spade wires on one side rail that I had to remove in order to get my hands on the lower fuse. I connected pwr cable,put amp cover on, powered on, and again heard sound of blown fuse, although maybe worse(?) this time... Removed cover and immediately noticed that I did not reconnect electrical spade connector on one side.

I removed all these fuses, installed the fast acting 6 amp/125 volt fuses, correctly connected all the elec. spade wires, connected pwr cable, powered on, and now I get absolutely nothing out of the amp. Meaning it does not seem to get any pwr going through it at all. Pwr light does nothing, no sound at all.

I still have the original foam padding and box. Was wondering if I could ship it to Steve for a repair?

Did you check the fuse in the IEC receptical, where the power cord plugs in?
Hi Harold,

Apparently your amplifier has some internal damage and will need service. The AC Mains fuse (attached to the AC inlet) has now blown as well, but you should not attempt to use the amp again at this point - the fact that the internal fuse blew immediately tells me that some transistors have failed and will need to be replaced.

Here is the name of a good service shop that can repair your amp properly. Please contact Stephen Pappin at Clifton Audio - (760) 487-8951 or Steve is a good tech and should have your amp back in service quickly.

Best regards,

Steve McCormack
SMc Audio