Welcome Guest! Be sure you know and follow the Phorum Rules before posting. Thank you and Enjoy! (January 12, 2025) x

Thread Closed

Fisher 800B Restoration
#23

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.


Messages In This Thread
Fisher 800B Restoration - by KCMike - 02-10-2017, 09:26 PM
RE: Fisher 800B Restoration - by Mondial - 02-11-2017, 12:19 AM
RE: Fisher 800B Restoration - by TV MAN - 02-11-2017, 10:48 AM
RE: Fisher 800B Restoration - by KCMike - 02-11-2017, 11:19 AM
RE: Fisher 800B Restoration - by Mondial - 02-11-2017, 12:05 PM
RE: Fisher 800B Restoration - by morzh - 02-11-2017, 12:29 PM
RE: Fisher 800B Restoration - by KCMike - 02-11-2017, 12:30 PM
RE: Fisher 800B Restoration - by Mondial - 02-11-2017, 12:43 PM
RE: Fisher 800B Restoration - by KCMike - 02-11-2017, 01:21 PM
RE: Fisher 800B Restoration - by Mondial - 02-11-2017, 01:29 PM
RE: Fisher 800B Restoration - by KCMike - 02-11-2017, 04:58 PM
RE: Fisher 800B Restoration - by Mondial - 02-11-2017, 05:49 PM
RE: Fisher 800B Restoration - by TV MAN - 02-12-2017, 03:34 PM
RE: Fisher 800B Restoration - by KCMike - 02-12-2017, 05:03 PM
RE: Fisher 800B Restoration - by Ron Ramirez - 02-12-2017, 05:31 PM
RE: Fisher 800B Restoration - by TV MAN - 02-12-2017, 09:14 PM
RE: Fisher 800B Restoration - by Ron Ramirez - 02-12-2017, 10:54 PM
RE: Fisher 800B Restoration - by KCMike - 02-12-2017, 11:02 PM
RE: Fisher 800B Restoration - by sam - 02-13-2017, 01:10 PM
RE: Fisher 800B Restoration - by Ron Ramirez - 02-13-2017, 01:27 PM
RE: Fisher 800B Restoration - by TV MAN - 02-13-2017, 01:29 PM
RE: Fisher 800B Restoration - by KCMike - 02-18-2017, 10:11 PM
RE: Fisher 800B Restoration - by Mondial - 02-19-2017, 09:26 AM
RE: Fisher 800B Restoration - by KCMike - 02-19-2017, 07:52 PM
RE: Fisher 800B Restoration - by Mondial - 02-19-2017, 08:34 PM
RE: Fisher 800B Restoration - by KCMike - 02-19-2017, 08:46 PM
RE: Fisher 800B Restoration - by KCMike - 02-21-2017, 11:04 PM
RE: Fisher 800B Restoration - by Mondial - 02-22-2017, 10:05 AM
RE: Fisher 800B Restoration - by TV MAN - 02-22-2017, 12:49 PM
RE: Fisher 800B Restoration - by KCMike - 02-23-2017, 05:36 PM
RE: Fisher 800B Restoration - by KCMike - 02-28-2017, 05:08 PM
RE: Fisher 800B Restoration - by KCMike - 03-02-2017, 11:35 PM
RE: Fisher 800B Restoration - by Clayvu - 04-12-2019, 10:36 PM



Users browsing this thread: 1 Guest(s)
[-]
Recent Posts
Philco 71 Code 125
Hello,  I am in need of a schematic for this radio. Mine has the three separate circular tube shields and a shadow me...dconant — 08:06 AM
Stromberg Carlson 1500 Squeal
And life just keeps getting more complicated.dconant — 07:57 AM
54C Complete Teardown/Rebuild
Hello Roy, here is this one sincerely Richardradiorich — 12:45 AM
54C Complete Teardown/Rebuild
Richard, Had grabbed it already but thank you just the same.  I find myself wanting to find some way to block out the...glyphmon — 12:03 AM
54C Complete Teardown/Rebuild
Hello roy, here is a link to the schematic . Sincerely Richardradiorich — 11:54 PM
54C Complete Teardown/Rebuild
Richard, The Silvertone 2014 also is a transformerless set, so I am incorporating a 1:1 600 ohm audio isolation transfo...glyphmon — 11:37 PM
Preliminary work on wife's Silvertone 2014
Did an alignment today which was interesting.  IF alignment went great, almost all was already spot-on.  Adjusting on th...glyphmon — 11:35 PM
54C Complete Teardown/Rebuild
The main problem with adding a Bluetooth input is that this set lacks a traditional power transformer to isolate it from...radiorich — 11:19 PM
54C Cabinet Refinish
I started stripping this cabinet before it got super chilly out because I knew I wasn't going to be able to work on ...glyphmon — 11:18 PM
54C Complete Teardown/Rebuild
While I'm waiting to wrap up the final steps on my wife's Silvertone 2014, I started disassembly on the next project.  O...glyphmon — 11:07 PM

[-]
Who's Online
There are currently 1630 online users. [Complete List]
» 1 Member(s) | 1629 Guest(s)
Avatar

>