Model 90 Tuning after cleaning tuning capacitor
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City: Maple Grove, MN
I'm working on a Philco 90 and had all the caps and resistors replaced and it sounded great. I was waiting for my bottom trim (see cabinet restoration) and i decided that what the heck i'm going to get that tuning capacitor clean inside and out. of course i took apart more than i should but i painfully learned to put it all back together. I knew it would need adjustment but now i can't even get a hint of a station. i followed the schematic tuning and it is very loud for the IF tuning but nothing when i try to tune at 1400. i checked my soldering and couldn't find a loose connection. I spent 2 hours on what should be a 15 minute task. Does any of this sound familiar? Nice and clean but doesn't work. Great. Thanks Rich
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Rich
So you are getting the signal from gen through? And no stations? See if all coils soldered properly, no wires going through the chassis short to it. How are your grommets? Do all basic checks. It's simple - you took it apart, now it does not work. Retrace the steps.
People who do not drink, do not smoke, do not eat red meat will one day feel really stupid lying there and dying from nothing.
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Morzh, great idea for the philco bakelite stuffing. you should get a prize for that one - made the job SO simple. I'm glad i found it.
I have re-traced my steps over and over. outwardly it looks ok. I think it has to do with alignment. My oscillation is screaming. However, i can't get any alignment when i try to tune at 1400. All i hear is hum. no wire connections are bad. the antenna is not detecting anything. I am so mad - i had a perfectly good radio til i decided to take apart and clear that tuning capacitor. i've checked over and over and the plates are not touching. I tried following the procedure in the schematic but the 1400 tuning is only hum. I had a great signal before so i believe the coils are fine.
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Maybe what you used to clean with,, left a film on the fins,,,,Deoxit maybe, or alcohol ,,,just saying
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ken, I will try that. I used window cleaner and dawn for the grease. Do you really think that would do it>
Ideas are what i need - i'm run out. thanks,Rich
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Ken did you try adjusting the trimmer/padders on the tuning cap? I had a philco 20 that after restoring and removing and cleaning the tuner was doing simular to what you describe. So with it on I started adjusting the trimmers and found that one was just way off and it started working. Just and idea. Good luck.
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I do not use spray cleaners, I either didhwash it or soak in dishwashing liquid and then rinse and dry.
Have you possibly shorted one of the rubber grommets?
Also see if your trimmers ar intact. The mica spacers might be damaged or not dry.
And ... The rotor (shaft) should be grounded, make sure it is.
People who do not drink, do not smoke, do not eat red meat will one day feel really stupid lying there and dying from nothing.
(This post was last modified: 01-25-2016, 03:35 PM by morzh.)
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City: Maple Grove, MN
I used a pipe cleaner with rubbing alcohol and cleaned the plates. is the rubber grommets supposed to keep the bottom separated (not in contact) with the chassis? mine is not. Also the rotor shaft grounded - i don't know whether mine is - it rotates and is held in place with metal springs at the ends. I don't know how it would be grounded but thru contact with the metal box it resides in? i'm checking my photos to see if i can detect something from those. Thanks for your help. Rich
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another thing i notice and it must have always been there but when i turn the rotor the back shaft floats a little left or right. This must be affecting the plates but i believe it was there before but not causing a problem?
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Just a couple of thoughts... first on the floating end of the shaft... is there a plate on the end? I made a similar folly to you with my 89B tuning cap and spent hours getting it back together. The end cap (on the far right) has a ball bearing under it and this is what tensions the entire shaft - at least on this model - it might be worth having a look at yours to see if whatever tensioner yours has is actually there - some later ones had a screw with a locknut to adjust the tension.
I know this because I forgot to tighten the two screws holding that plate down before aligning all the plates in all three gangs (spent ages doing this), and then I noticed it... tightened it up and suddenly realised all the plates were now solidly jammed against each other... so spent another ages doing it all again!...
[Image: http://i241.photobucket.com/albums/ff222...ii2cmw.jpg]
On the tuning problem - have you tried checking resistance / continuity between the chassis and each of the gangs? Make sure there isn't some kind of short - also do this for the trimmers (When I did this I took capacitance readings of all my trimmers and then when I reassembled it I reset them to what they were before I pulled it apart... too late for that now on yours - but if you have a capacitance meter that reads in pF then check your trimmers and tuning cap through their range as well.
You'll get there... you've got some of the best Philco people in the world helping out. I hope this doesn't put you off pulling things apart though - thats the best bit! 
Cheers
Steve
There are no personal problems that can't be overcome with the liberal application of high explosives
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Winston
What pipe cleaner? Like stiff steel brush type?
In my 90 (I think it is pushpull 45 output) the cap's box and the rotor are grounded; the stator plates should have some finite (6 ohm in my case) resistance to chassis.
People who do not drink, do not smoke, do not eat red meat will one day feel really stupid lying there and dying from nothing.
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I never had a end plate to hold down the rotor shaft to my knowledge. It worked fine before i did this "deconstruction". I notice when i touch the back of the gangs, only the high frequency set do not give a electric connection. I checked both wires from that gang to the coils and there is continuity so i don't know what that means. I can't tune the antenna but i can tune the oscillators. I am at a lost. I received Steve Davis's bottom trim but i want to get the radio working before i concentrate on the cabinet. I'm frustrated to say the least. Thanks for the ideas and encouragement. Rich
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Rich, Looking at the picture, it appears, the first plate toward the shaft is bent. If it was that way when it was assembled, it would cause a short.
On another note. Your condenser is a three gang. That indicates you have a late version 90. These are not very common.
Steve
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Steve
It's not his picture. And it is not a 90 cap.
People who do not drink, do not smoke, do not eat red meat will one day feel really stupid lying there and dying from nothing.
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Oops 
Steve
M R Radios C M Tubes
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