The PHILCO Phorum
Fisher 800B Restoration - Printable Version

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+--- Thread: Fisher 800B Restoration (/showthread.php?tid=16225)

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RE: Fisher 800B Restoration - TV MAN - 02-12-2017

Mike, I bought it that way. I originally bought it so I could repair it using parts from mine that got "moused", but I don't have the heart to knock any of those in the head, esp one that I know worked, so I am looking for a tranny for this one. It is a 500c. I may put an ad in the wanted section one of these days.

RE: Fisher 800B Restoration - Ron Ramirez - 02-12-2017

You know, seeing this thread is making me start to think about setting aside all of that solid-state stuff for awhile and maybe get started on something I've put off for too long...restoring my Fisher TA-600 receiver. Tubes and lots and lots of caps.

RE: Fisher 800B Restoration - KCMike - 02-12-2017

Go for it Ron. Bet it will be a great thread. Icon_thumbup

RE: Fisher 800B Restoration - sam - 02-13-2017

come on  this is a PHILCO phorum
put that modern junk away
restore some thing nice and relaxing with warm bright glowing tubes Icon_thumbup




sam

RE: Fisher 800B Restoration - Ron Ramirez - 02-13-2017

uh, Sam...

Fisher 800, 500, 400, and TA-600 receivers do use warm, bright, glowing tubes...

RE: Fisher 800B Restoration - TV MAN - 02-13-2017

Aaahh, Sam, Sam, Sam ... No haven't your ever seen a nice, healthy quad of 7591a's glowing in a sweet sounding Fisher 500 or so series? Icon_rolleyes I used to have a little mirror behind my 500c. Icon_mrgreen Icon_lol Icon_thumbup There is something about the "hi-fi" era of the late 1950's through the mid 1960's. Beware tho, it can be addictive! Just ask Ron, Icon_cool !

RE: Fisher 800B Restoration - KCMike - 02-18-2017

Well finally got the parts and time to revisit the rectifier in the 800B.
Here is the old one.
[Image: http://i1336.photobucket.com/albums/o654/220kohms/Fisher%20800B/DSC02147_zpsayuck1gt.jpg]  [Image: http://i1336.photobucket.com/albums/o654/220kohms/Fisher%20800B/DSC02155_zps2zjxdkgu.jpg]
   And the new one that will be going in.
[Image: http://i1336.photobucket.com/albums/o654/220kohms/Fisher%20800B/DSC02160_zpstjxexsyw.jpg] 
  I hooked it up with jumper wire to see how it would perform and it looks like it will do the job.
[Image: http://i1336.photobucket.com/albums/o654/220kohms/Fisher%20800B/DSC02158_zps9tmxxm3b.jpg]
  -22.23v calls for -22.25v
[Image: http://i1336.photobucket.com/albums/o654/220kohms/Fisher%20800B/DSC02159_zpsv853naiv.jpg]

 Now to figure out a neat installation.
Thanks Mondial you probably saved my tubes and transformers from destruction. Icon_smile

RE: Fisher 800B Restoration - Mondial - 02-19-2017

Looks good. Check your AC line current draw with the new rectifier. I'll bet its a lot lower now due to the decreased output plate current

Yes, the bias on the output tubes is very important. With low bias the tubes overheat, liberating gas inside the tube. This causes the plate current to increase further resulting in a runaway condition. The final result is a meltdown of the power supply and/or the output transformers. 

The line fuse should provide some protection, but make sure it is the correct current value (or lower!). Sometimes people replace the fuse with a higher amp rating which is a recipe for disaster.

You probably should replace the green molded line bypass cap with a safety rated type. There is another identical cap across the power transformer secondary.

RE: Fisher 800B Restoration - KCMike - 02-19-2017

Just checked the fuse that was in it. A 10 amp! Icon_thumbdown 

 Should I use safety caps on both of the .01uF - C-103 & C-106? Thanks.

RE: Fisher 800B Restoration - Mondial - 02-19-2017

Yes the safety rated Y cap should be fine in both locations. Its not really needed across the transformer for safety but they are usually rated for 240VAC so its a good choice.

I would go with a 2.5A slo blo fuse, or maybe even a 2A if your measured draw is less than that. Its better that the fuse blows before anything else expensive. In any case the fuse is easy to replace and if you find it blows under normal operating conditions you can up the rating slightly.

RE: Fisher 800B Restoration - KCMike - 02-19-2017

I forgot to mention the amperage draw. It was little over 2 amps and dropped down to 1.5amps.
with the new rectifier.

RE: Fisher 800B Restoration - KCMike - 02-21-2017

Just a quick update on progress of the receiver.
 Got the rectifier installed. This pic. is in the trial stage. I wanted to locate it away from the 15 ohm 5 watt resistor so I used a terminal strip.
[Image: http://i1336.photobucket.com/albums/o654/220kohms/Fisher%20800B/DSC02162_zps0avirhco.jpg]  Also installed a line safety cap and a inrush current limiter.
[Image: http://i1336.photobucket.com/albums/o654/220kohms/Fisher%20800B/DSC02167_zpsyl0tpetj.jpg] 
 Changed out the coupling capacitors and added the 4-10 ohm 1/4 watt resistors to the output tubes.
[Image: http://i1336.photobucket.com/albums/o654/220kohms/Fisher%20800B/DSC02171_zpsfoxmfhe7.jpg]  So far so good. I did run into a problem on one of the 12at7 tubes in the MPX section.
 tube V100 called for 95v on the plate and 7v on cathode. On 1/2 of tube.  I was getting .855v on cathode and 129v on the plate.
 I changed the tube and still not correct but better. Now getting 5v on cathode and 112v on plate.
 Checked the resistors in that part of circuit and they are all very close or spot on.
The second half of tube the voltages are correct.
  It's playing very well on the bench but does have some scratching while tuning .
I'll be addressing that tomorrow with a good cleaning of the tuner.
 If anyone has ideas about the V100, tube voltage please let me know.

RE: Fisher 800B Restoration - Mondial - 02-22-2017

Don't be concerned about the exact voltages on the first half of V100. They are very much affected by the individual characteristics of the 12AT7 installed. 

If you have 5V on the cathode and 112V on the plate that is in the range of normal operation. You can try another 12AT7 and see if the voltages get closer to those on the schematic.

RE: Fisher 800B Restoration - TV MAN - 02-22-2017

I am curious as to how it sounds in 'stereo'. I always had to run my 'old' 500c in mono because the stereo had an echo or ringing sound. Probably alignment, but I didn't have anything to set it up with at that time or any help doing it. If I can find a power transformer I am going to start a resto on my 'replacement' 500c. I am following your thread with a lot of interest. Keep posting Icon_biggrin

RE: Fisher 800B Restoration - KCMike - 02-23-2017

I won't worry about the tube voltage on V100 Thanks Mondial.
Tim I don't have any ringing on stereo setting. It does sound little better and louder when set to stereo.
I don't think I will have to align this one.
I did find something that I don't know if its a problem or not.
While checking the channel separation of the left and right speaker. Its quiet on either speaker when balance is turned all the way left or right. But with the loud switch on I can hear audio in both speakers when balance pot is turned full right or left. I would say maybe 20% sound out of the side that should be off.
Hope I'm being clear on this.
All pots and switches have been cleaned with deoxit and lubed.