McCormack DNA-1 rear fuse won't stay in


I have a McCormack DNA-1 that I purchased new 20 some odd years ago. It is in my condo which I only live in during the week. Everything was fine when I left on Friday but today I come home to find that it won't power up. First I check the rear fuse and it seems fine but it won't latch back into place. I have looked at the fuse holder and don't see how it latches back in - usually you depress and turn it and something rotates under something else to hold it in place but I don't see anything like that on this fuse holder. Has anyone else experienced this issue? Does it need a new fuse holder?

Thanks in advance,

Bob Martin
wz4rfv
Seems like a good possibility.
Duct tape
The DNA-1 fuseholder is a "bayonet" type - push it in slightly with a blade screwdriver and rotate CCW 1/4 turn to release. Push in and rotate 1/4 turn CW to reinstall. It is possible that it might be damaged and not working properly so check it carefully for proper operation before plugging the AC cord back in. The fuse should be T8A - 8 Amp slow-blow. You can go up to T10A if need be but stick to T8A if possible. If the fuseholder is damaged and you are a DIY kinda guy, you can replace it with any similar holder that fits properly. ACME Audio Labs has a good one that has been silver-plated and cryo-treated for $6.

Good luck - I hope it goes well. Let me know if you need any help.

Best regards,

Steve McCormack
SMc Audio
Steve,

The problem is when I push in and rotate, the fuse pops right back out. So, new fuse holder it is. Thanks for the lead.

Bob Martin
Looks like we need a Plan B. I got the fuse holder and it's the wrong diameter! It's too big and won't go in the hole and filing the hole larger is a bit past what I want to do and a delicate electronic component. The nut from the fuse holder I received slides right over the threads of the fuse holder I removed. Any ideas?

Thanks,

Bob
Why not call Steve or Chris at SMcAudio. they are very helpful and patient folks. If the fuse holder that the amp designer himself recommended does not fit, then it's likely that the amp was further modified somewhere down the line. Regardless, Steve McCormack is a class act (witness his jumping in as usual when someone has a problem w one of his products) and I am sure he will be able to help you.
Sorry to hear you ran into a fit problem. I like the ACME fuseholder and I don't mind opening the hole size to fit it, but I understand this may not work for everyone. The fuseholder hole diameter on the DNA-1 is 1/2" with 2 flat sides to take advantage of the anti-rotation feature common to many holders. I often use a smaller fuseholder designed for 5x20mm fuses in other projects, and it has a 1/2" dia. body...but it does not have the flat sides so you would still have to file the hole out to fit. If you would like to try, you can get the part from Mouser.com - part no. 441-R3-12-GRX. Of course you will also have to get an 8A slow-blow fuse in the 5x20mm size. We don't have Radio Shack any more, but if you have any electronics parts store in your area you can take a look at what they have to offer.

I hope this helps - let me know if you have any trouble.

Best regards,

Steve McCormack
SMc Audio