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Fisher KM-60 problem

75.130.151.82
Posted on June 17, 2024 at 13:27:07
posaune32foot@gmail.com
Audiophile

Posts: 96
Joined: March 8, 2023
 I have a KM 60 that has worked perfectly for years. Last week it blew the main fuse. I replaced it and now still no lights/power. Is the large can capacitor next to the transformer a part of the power supply? If it failed would there be any visible signs of the failure? I haven't removed the bottom cover and looked, yet I'm OK with a soldering iron. A few months ago the 6DJ8 needed to be replaced. Any thoughts or advice would be appreciated.

 

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RE: Fisher KM-60 problem, posted on June 18, 2024 at 13:44:26
fredtr
Audiophile

Posts: 2197
Location: Phoenix
Joined: January 4, 2005
Contributor
  Since: August 16, 2024
 Sure, take off bottom panel and look around. Large capacitor, yes part of power supply, if electrolytics haven't been replaced they should be. Check the diodes with an ohm meter.

 

RE: Fisher KM-60 problem, posted on June 18, 2024 at 14:57:44
6bq5
Audiophile

Posts: 4674
Location: SF Bay
Joined: August 16, 2001
 as fredtr said-

Electrolytic capacitors are the most likely to fail, and for a KM-60, that is a highly likely proposition!

you could also leave it in place, disconnect it and put the new caps as you find space-
usually the large cans were multi-caps with 3-5 lugs and 2-4 elements (caps) so a little homework to figure it out...
Happy Listening

 

RE: Fisher KM-60 problem, posted on June 19, 2024 at 13:35:10
BFitz
Audiophile

Posts: 548
Joined: July 21, 2000
 That one uses a selenium rectifier full wave bridge.

Shown on the schematic as SR. They are known to go bad whan old, and usually smell bad on the way out. You can replace a SR with normal 1200V rated silicon diodes, but they will have significantly less voltage drop. To match the old B+ voltage you can insert a power resistor in series after the diodes.
That's a great tuner, mostly a kit version of the FM100B with different metering. I like the KM-60 horizontal tube for tuning, like certain Sherwood S3000 models meters...

 

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