The PHILCO Phorum
Fairbanks Morse model 91 - Printable Version

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Fairbanks Morse model 91 - murf - 09-18-2013

Here is an interesting one that I brought home tonite.
It's a Fairbanks Morse model 91 console.
What a neat radio.
Has the most unusual looking dial, and it's a shutterdial to boot.
Brought it up on my variac after running a couple tests, and low and behold it works.
Seller claimed it had not worked for years.
Pulled the sheild off the chassis and found a 6F6 tube rolling around in there.
Put it back in and it worked well considering it needs to be re-capped.
I think this will be a beauty when done.
Has a real flowery print on the speaker cloth.
Can't imagine that it came with that.
But as well as it fits and the symetry of the print, almost makes me believe it could be original.
Anyone know where I could get a picture of the original?
I know there different versions of this cabinet then.
Great find for the money.
murf

RE: Faibanks Morse model 91 - jerryhawthorne - 09-18-2013

Murf, pictures please!!!!!!!!!
Jerry

RE: Faibanks Morse model 91 - Radioroslyn - 09-18-2013

Found two pics
http://www.radioatticarchives.com/radio.htm?radio=1044
http://www.radioatticarchives.com/radio.htm?radio=8310
Terry

RE: Faibanks Morse model 91 - Jayce - 09-18-2013

Oh my, definitely a neat looking dial! That's a make of radio I need to put on my bucket list since I own a few of the old Fairbanks-Morse one lunger engines.

RE: Faibanks Morse model 91 - murf - 09-19-2013

It's the second picture. The 91C.
Gonna be a fun project.
murf

RE: Faibanks Morse model 91 - morzh - 09-19-2013

If anything, it looks very cool!

RE: Faibanks Morse model 91 - murf - 09-21-2013

Looks like there is a 4mfd, a 100 mfd, and a cardboard can with a 16 and a 30 mfd in it.
Someone replaced the double one with a 16 and an 8 mfd.
Looks like they wired the positive ends of the 16 and the 8 together and connected them to the center tap of the 100 mfd.
Then both the negatives were connected to chassis ground.
This is not what the schematics say, as far as I can tell.
Can anyone draw me a readable diagram of where the pos. and neg. ends of these caps are supposed to be wired originally?
I am having trouble with the provided schematics.
They don't even give polarity on the electrolitic caps.
If I had your email address, I could supply you with a couple pics that might help.
I don't have much luck posting pictures on here.Guess I could have my kid teach me, but he is never home.
Anyone interested in helping out?
This is a rare radio, and I don't want to mess it up.
Thanks guy's and have a great weekend.
murf

RE: Faibanks Morse model 91 - jerryhawthorne - 09-21-2013

Murf, I am attaching a link for the schematic for others. This is one of three versions, not certain which one you have for the 91. I can't see that a 100mfd cap would be appropriate anywhere on a radio of this age.
As for posting, this has got a lot easier with Ron's effort. Download your pictures to your desk top from your camera. Label them so you know what they are. Type your thread and go to the bottom and look for the attaching information. I use photobucket and have learned how to use it but the Phorum has an easier method.
Regards, Jerry

http://www.nostalgiaair.org/PagesByModel/759/M0005759.pdf

Murf, this is an edit. I looked a little closer and you have items 30 and 31 as a 16mfd and 30 mfd negative going to the centertap of the transformer for the 30mfd and the negative for 31 going to chassis. You have cap 27 a 4mfd with negative to ground. Confusing me is item #4 on the schematic being listed as a 100 mfd. Just doesn't seem right to my limited understanding of radios. And no Murf, 30 and 31 should have separate grounds and go to different locations as indicated.

RE: Faibanks Morse model 91 - murf - 09-21-2013

Hi,
That's the same riders schematic I have.
If I had your email, I could send a couple pics.
Would explain alot more than my trying to explain it.
Up for it?
murf

RE: Faibanks Morse model 91 - BrendaAnnD - 09-21-2013

That parts list has at least one error in it. Capacitor 4 would NOT be 100uf. As you can see, it's in the antenna section of the bandswitch circuit, and connects the antenna directly to the input of the mixer tube, bypassing the RF amp. Can't tell for sure from the schematic, but this is probably for the AMBCB, and was a common practice in communications receivers, as they wanted to optimize SW reception but felt no need to further amplify strong BCB signals. That cap would then be a 100 uuf (pf)

RE: Faibanks Morse model 91 - BrendaAnnD - 09-21-2013

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.

RE: Faibanks Morse model 91 - jerryhawthorne - 09-21-2013

Here are Murf's pictures. Thanks BAD something was messed up about that 100mfd label. I don't think they even had caps that high back then. Jerry

[Image: http://i303.photobucket.com/albums/nn129/JerryHawthorne/fmchassistop.jpg]

[Image: http://i303.photobucket.com/albums/nn129/JerryHawthorne/fm91chassisbottom-1.jpg]

RE: Faibanks Morse model 91 - murf - 09-21-2013

See how they have both of the positive ends of the caps from the double cap can wired to the 100 center tap?
Both have neg leads to chassis ground.
Really hate it when repairmen do there own thing.
Makes it hard for us to figure out and put back where it belongs.
On the top side picture, you will see the black can marked 100.
This is the one in question as well as the wiring on the 16 and 30 can.
Are you as confused as I am?
Why do they still work after you totally change the original wiring?
Murf

RE: Faibanks Morse model 91 - murf - 09-21-2013

Also thought I would ask, why they put all those paper caps in metal sleeves?
Gives them a handy point to connect the neg. end of the cap.
Is there any reason I cannot just put new caps in there place and connect the neg. end to the sheild as they are now?
Thanks again

RE: Faibanks Morse model 91 - jerryhawthorne - 09-21-2013

Murf, a time to do a little tracing. It would be nice to have a component layout buy we don't. First, the labeled 4mfd cap on your chassis has no wires going to it. You have one labeled 100mfd, we know that was wrong and I wonder if that can is labeled with anything? The combo cap you have if I can read the red writing on it that you added I would guess seems to indicate two caps of the right value with different grounds? That would be appropriate for the circuit but probably old enough to replace and perhaps not original. If I had to make a SWAG, I would guess that originally that paper cap and the black one were separate and one was the 16mfd and one the 30mfd if I remember correctly the schematic. The one marked at 100mfd, was not. Hope this makes sense. Bear in mind this a SWAG.
Regards, Jerry

Murf, if your young a SWAG is a "Scientific Wildass Guess"