Fairbanks Morse model 91 - Printable Version
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+--- Thread: Fairbanks Morse model 91 (/showthread.php?tid=7502)
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RE: Faibanks Morse model 91 - murf - 09-21-2013
Hi Jerry,
If you look at the pics, you will notice that the black can in question on the top side marked 100, has a single lead on the bottom side with many things connected to it.
Would that not look like a 100 mfd cap could be housed inside?
Kind of lost as far where to go with this, specially seeing as the double cap can appears to be wired different than the schematics.
murf
RE: Faibanks Morse model 91 - Ron Ramirez - 09-21-2013
BrendaAnnD Wrote:Ron, is there some problem with the quick reply? When I try to post using it, I'm getting an error message saying the thread doesn't exist. I can post using the New Reply, but this does take longer.
Works for me, and I normally use the Quick Reply box. In fact I composed and posted this reply using the Quick Reply box. Maybe a problem with your browser? Try clearing its cache.
RE: Faibanks Morse model 91 - jerryhawthorne - 09-21-2013
Murf, sorry I was thinking and writing while you were. It is time to look at what you have and wire it to the schematic. The two positives together on the cardboard (replacement) is wrong. Why will it work,well these old radios could handle a lot of variations in values in certain areas. Not right but workable. What I would do would be to restuff or cut off the leads and add the necessary caps. For me I would find from someone a metal cap for the cardboard one and restuff it. I don't believe it is original but that is the hard road to travel. Many will install caps underneath on terminal strips. Just fine.
We all do things differently and all are OK for how the radio works. This one is just messed up a bit. You also need to find what and where the 4mfd can cap with no wire has had something put in to replace it. This is what makes undoing someone else's work a bit fun and frustrating. As you can see that cardboard cap is just not wired properly, needs to be replaced with proper wiring as indicated several threads above and the schematic. You also need to search and find out where that "100mfd" cap is wired in. We know it is not a 100. Perhaps you "100" is the other cap, the 16 or the other?
Jerry
RE: Faibanks Morse model 91 - murf - 09-22-2013
Your right Jerry, there is nothing hooked up to the 4 cap, because I replaced it already.
You will see it over on the left side of the chassis.
I wrote the correct values on the cans.
The double can actually is marked as having an 8 and a 16 in it.
Appreciate all the help you guy's and gals are providing.
How can I determine which wire is the center tap of the tranny?
Have a great day.
murf
RE: Fairbanks Morse model 91 - murf - 09-22-2013
Ok ,You got me to thinking.
I think Jerry is on to something here.
Looking to me like the double was originally a single 30 mfd cap.
Someone replaced it with a double 16 and an 8 mfd wired together pos to pos.
What would be the end result if wired together like this.
Those are wired neg. side to chassis ground.
The black can next to it probably has the single 16 mfd in it. It is wired neg. side to transformer center tap like it should be.
What do you guy's think?
Is this possible?
That would make the 100 mfd in the parts list a typo like you guy's said.
Should I try it?
murf
RE: Fairbanks Morse model 91 - BrendaAnnD - 09-22-2013
If you parallel capacitors, the values add directly: 16+8= 24
RE: Fairbanks Morse model 91 - murf - 09-22-2013
Ok people,
Put them in and it works fine.
Really appreciate your help.
You really made me have to think. Kinda hurts to have to think once in a while.
Guess I can now proceed with replacing the rest of the caps and a few resistors.
That is quite a typo in the parts list.
Anyway,
I'll Be Back!!!!!!!!!
murf
RE: Fairbanks Morse model 91 - jerryhawthorne - 09-22-2013
Good job Murf
Jerry
RE: Fairbanks Morse model 91 - murf - 09-22-2013
Gonna figure out how to post pics on here so I can send a picture of the completed re-finished radio.
Gonna be a classic for sure.
murf