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Blown fuses on a Cyrus One but phono still works: stick or twist?

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Posted on December 21, 2016 at 09:48:00
goomer
Audiophile

Posts: 191
Location: Norwich
Joined: May 1, 2003
I am soon to receive a Cyrus One (the old mid/late 1980s version) amplifier which has one or both of its fast blow fuses blown and apparently no sound through the speaker outputs, though the moving magnet phono stage still works fine through the tape outputs to another amplifier's line input. I have a use for it just for its phono input so I could use it as is (connected to a phono input-less amp), though I also have some 3.15A/250V fast blow fuses available so I could pop some in when it arrives and try it out beyond the phono stage. My question is though, do I risk doing further damage to it - which could damage the presently working phono input- by trying it out again with fresh fast blow fuses installed?

edited to add: I should say that any further testing if I do install fresh fuses would be to test for DC at the speaker outputs first, then, assuming no DC present, via a pair of cheap/sacrificial speakers to test the audio.

 

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RE: Blown fuses on a Cyrus One but phono still works: stick or twist?, posted on December 21, 2016 at 23:17:39
goomer
Audiophile

Posts: 191
Location: Norwich
Joined: May 1, 2003
Have been thinking about this further and I think that I will just stick. Who knows what caused the fuses to blow in the first instance, and it may have been luck that no damage has been done to the phono stage which is what I actually want to use.

 

RE: Blown fuses on a Cyrus One but phono still works: stick or twist?, posted on December 22, 2016 at 07:44:06
Jonesy
Audiophile

Posts: 1054
Location: Winnipeg, Manitoba
Joined: September 1, 2005
That might be best.

I started to post you a couple of times but wasn't sure if I had the answer. If you google Cyrus One or Cyrus 1 blown fuses, you will see that it comes up a lot.

Different reasons for the fuses blowing. Shorted wires, op amps, even type of speaker wire itself.

So you might put the fuses in and it could work or blow right away. Some cases I read where the fuses were okay after the first speaker was wired up, but then blew when the second speaker was wired up. Go figure. Others had the unit working fine for a while and then out came smoke. Could it damage the pre-amp section? Possibly.

For consideration, it looks like there is enough info on the net to get the whole unit up and running. First place I would start with giving it a good visual and checking and measuring anything you can on the inside with the tools you have and are accustomed to using. I remember it being a pretty good amp at the time, being able to drive some pretty tough loads.

Or, just use the phono section until you get an urge to explore further.

Cheers!

Ed

"I know just enough to get into trouble. But not enough to get out of it."

 

RE: Blown fuses on a Cyrus One but phono still works: stick or twist?, posted on December 23, 2016 at 01:19:47
goomer
Audiophile

Posts: 191
Location: Norwich
Joined: May 1, 2003
Thanks for the reply, in the longer term I think that that is what I'll do: do a step by step investigation to find out the issue before hopefully repairing to full function again. I have received it now and have had the lid off to look, though - not unsurprisingly - there is nothing visually apparent other than the one blown fast blow fuse. I have now removed both of the internal fuses so that the amp isn't trying to drive a speaker-less load, and have been enjoying the phono stage via the tape out of the Cyrus into my other amp. Sounds great with my Rega Planar 3/AT 440mlB cartridge, hum free and barely a hiss even at quite high volume so I am happy to use it as is for the foreseeable future.

Thanks again for the reply.

 

RE: Blown fuses on a Cyrus One but phono still works: stick or twist?, posted on December 23, 2016 at 07:32:49
Jonesy
Audiophile

Posts: 1054
Location: Winnipeg, Manitoba
Joined: September 1, 2005
Good idea taking the other fuse out!

Cheers!

Jonesy

"I know just enough to get into trouble. But not enough to get out of it."

 

RE: Blown fuses on a Cyrus One but phono still works: stick or twist?, posted on December 23, 2016 at 20:33:22
Awe-d-o-file
Manufacturer

Posts: 16489
Location: 100 miles west of DC
Joined: January 10, 2004
Contributor
  Since:
October 31, 2005
Blowing a 3.15 A fuse has the highest chance of being related to the amp section, not the line or phono stage. I think you are quite safe to try new fuses.
ET

"If at first you don't succeed, keep on sucking till you do suck seed" - Curly Howard 1936

 

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