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tubes for 1954 fisher 101 help

J

jerrysgarcia

New Member
Have a 1954 fisher 101 console. Im going to attempt to restore myself! Never messed with tube gear. Yanked out amp and ready to order parts.
Tubes- 5y3 , el84 x 2, 12ax7, 6sc7..havnt checked out capacitors yet. 85 watts with three 8" speakers and a garrard tt. Need advice on brand and where to buy parts. Is it even worth it? Thanks in advance
 
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First, it is not 85 watts speaker output. If it says 85 watts near the power cord, that just means what it draws from the wall socket. It is more like 10 to 12 watts speaker output that a pair of EL84's will do in push/pull.

No need to buy tubes. They are more than likely still good but you will need to replace the power filter capacitor(s).

Tubes and more dot com should have all the parts you will need.
 
Since this thread is about a specific model of Fisher equipment, and not a general question about tube gear, moved to the Fisher Forum, where you'll find great information.

And welcome to AK! :D
 
I'd also go with testing the tubes before replacing them. The tubes generally out-live most of the other parts. They also don't really age when not in use, unlike the rest of the components.
 
Well worth it! The service manual here......
http://www.fisherconsoles.com/service manuals/fisher series 101 sm.pdf

Last page has Parts List, Voltage and Resistance charts. Resistance chart is done with the unit UNPLUGGED! This will give you a general feel for the health of the resistors.

With a unit that is 60 years old, shotgun the electrolytics. 47uf/25v, 47uf 450V, and the 3 section CAN. 47uf-47uf-22uf /450V. www.Tubesandmore.com will have all of them.

If any of the tubes have a WHITE getter, it is shot. File 13 it and get a new tube. Any other color means the vacuum is still there. The best test is with the actual amp. So just go easy the 1st power up and bring it up slow.

Film caps....up to you. The one's that look like brown jelly beans (I call them Dogturds) should be replaced. Leave the ceramics as they are generally stable.

Test the resistors. They all have a 10% variance so 5% off is ok. Carbon Composition resistors tend to go high due to moisture absorbtion over the years. Replace any over 10% out with carbon or Metal Film (your preference).

1st power up use a variac AND a dim bulb tester. 85W consumption a 60W bulb should be sufficient (INCANDESCENT ONLY!!! NO CFL, LED, or Halogens.)
DO NOT POWER ANY TUBE GEAR UP WITHOUT A SPEAKER OR DUMMY LOAD (8ohm/50W resistor) connected.

Replace the capacitor on the speaker x-over.

And that's it, Other than the Turntable cleanup/rebuild.
 
Very interesting that this unit has a fixed constant power circuit installed: Instead of the usual Negative "Voltage" Feedback, it employs Negative "Current" Feedback. Such circuits work to basically do the opposite of traditional negative voltage feedback systems -- which in this case, is primarily to LOWER the damping factor of the amplifier (that is, to raise its source impedance), no doubt to accentuate the bass frequencies.

All such circuits are rather speaker specific, so you will want to make sure you maintain the original speaker system to use with the unit.

Good luck with it!

Dave
 
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