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 Post subject: fisher 400 tuner 7868 tube question
PostPosted: Aug Fri 04, 2006 7:55 am 
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Location: barre, vt usa
i got a Fisher 400 tuner it all works fine right now but i tested all the tubes they all test great except the 4 7868. they all test low. on my tester where 60 is minumum acceptable 2 of these test right in the range of 60 and one test about 40 and the other test about 50. should these tubes all be replaced or will they still work fine being weaker.


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PostPosted: Aug Fri 04, 2006 9:32 am 
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Location: Albuquerque, NM 87123
I had a Fisher 400 years ago and the outputs tested low on 2 checkers I had (don't remember which ones), but mine also worked just fine. Keep using them until you notice a problem like distortion or low output.


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PostPosted: Aug Fri 04, 2006 2:51 pm 
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Location: Detroit, MI USA
Exactly, if they still sound OK and most important if the bias on the tubes is correct, then there could be lots of use left in those tubes.

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Dennis

Experience is what you gain when the results aren't what you were expecting.


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PostPosted: Aug Sat 05, 2006 12:32 am 
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Location: barre, vt usa
i did notice after using it for a while when i turn the volume up it cuts in and out and volume goes low and then goes back up high but if i use it on low to medium loudness it works fine.

also i am using it on FM mono whne i try FM stereo it does not work at all . anyone know why this is. all the other inputs work fine the aux tape and phono.


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 Post subject:
PostPosted: Aug Sat 05, 2006 12:50 am 
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Location: San Jose, CA USA
It's possible that all you need to do to fix the volume problem is squirt a little contact cleaner into the back of the volume control. Radio Shack Electronics Cleaner spray works well for me, as does silicone lubricant spray (although some people recommend against that). Various "sliding contact cleaner" sprays also work fine.

Also try wiggling tubes in their sockets when it's running. If you get a scratchy sound, wiggle it some more, or use contact cleaner on the socket. Another thing to do is spray contact cleaner on the contacts of any rotary switches or slide switches in the equipment.

The problem with the stereo demodulator may require more detailed troubleshooting. Is the stereo demodulator included on all Fisher 400s, or is it an option? (Make sure it is supposed to be able to work in stereo...)

If this unit has original paper and/or electrolytic capacitors in it, you may need to replace many or all of them.

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 Post subject:
PostPosted: Aug Mon 07, 2006 2:33 pm 
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Location: Rochester NY USA
I have scans of the early and late 400 service info - email for a copy - let me know the serial number or what the front end tubes are. As mentioned, the caps may be bad - leaky caps can cook the output tubes, even take out a power or output transformer.

Electro Harmonix makes new 7868s - but I hear the pins are a little oversize - if you use them you can't go back to NOS tubes.


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 Post subject:
PostPosted: Aug Wed 23, 2006 1:05 am 
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Location: barre, vt usa
does anyone know where to get the front panel replacment light bulbs for the fisher 400 one of mine does not work.


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PostPosted: Aug Wed 23, 2006 1:13 am 
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Location: Detroit, MI USA
If they are the ones which look more like fuses, they are almost always available on eBay in small lots for very reasonable prices. Search for "fuse lamp" and you should find them.

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Dennis

Experience is what you gain when the results aren't what you were expecting.


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 Post subject:
PostPosted: Aug Wed 23, 2006 1:14 am 
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Location: Fernandina Beach, FL
jaso109 wrote:
does anyone know where to get the front panel replacment light bulbs for the fisher 400 one of mine does not work.


Does the bulb have a number? If not, could you post a scan or picture please?

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Don


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 Post subject:
PostPosted: Aug Wed 23, 2006 1:15 am 
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Location: Fernandina Beach, FL
Mr. Detrola wrote:
If they are the ones which look more like fuses, they are almost always available on eBay in small lots for very reasonable prices. Search for "fuse lamp" and you should find them.


Believe it or now, I can get the fuse type lamps at Baynesville Electronics in Baltimore, the only electronics store left to my knowledge. Also, there is a guy in Colorado Springs, Colorado that sells the fuse lamps...

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 Post subject:
PostPosted: Oct Sun 08, 2006 9:53 pm 
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Location: Lewiston, ID
Original fuse lamps for Fisher receivers are getting quite pricey, often going for well over $10 each.

This is an auction for a replacement that isn't original, but looks like it should work fine. No involvement with the seller...

http://cgi.ebay.com/FESTOON-FUSE-LAMPS- ... dZViewItem


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