BY-PASS Capacitor model 47-1230 - Printable Version
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+--- Thread: BY-PASS Capacitor model 47-1230 (/showthread.php?tid=459)
BY-PASS Capacitor model 47-1230 - bill T - 11-01-2006
Hi, I do not really have a big question here , just some thing to pass along to others rebuilding Philcos... Working on 47-1230 found a "funny"
capacitor with two leads on one side. It was marked .01mfd 400vdc.
I assumed it was a dual package of caps. Wrong! One lead is just a wire through the package. Caused me to get my meter out when nothing worked. Putting a cap where the wire is blocks bias voltage to grid or screens on tubes where this wire was going . Once I replaced it with a wire things started working ! Thought I would pass this along as it is weird device. Maybe I am missing something here ? Why not just use a wire ? There isn't a space problem. All I can think is this cap was special for some other purpose and they had some left over ? Strange component !
- Ron Ramirez - 11-01-2006
It's a feedthrough capacitor, and you really should replace it following the guidelines shown here:
http://www.philcoradio.com/tech/ftcap.htm
This page also explains its use in the circuit.
- bill T - 11-01-2006
Ron , I missed that on your web site . It would have saved me some time to read it. But I am confident that the circuit is right now. The diagram is of my model ! I will shorten the lead on the capacitor as shown . Looks like that is what Philco should have done to begin with. I hate to think that there wasn't some reason behind this type of component . Must be a fine point I am still missing . Does'nt matter problem resolved ! Thanks again !
Bill
P.S Enjoying this model ! Phono Works ! Spare speaker with phono works.
Makes it easy to bench test . AM ...Couple stations right now .
Needs some bandswitch and PB cleaning before checking alginment .
- Ron Ramirez - 11-03-2006
How well does the FM work on your set? That feedthrough cap is only in the circuit when the band switch is in FM position.
- Poston Drake - 11-03-2006
Hi Bill and Ron,
In the recent past I have done two electronic restorations of model 47-1230 for others, and I have a nice original one of my own still awaiting restoration. (As they say, the cobbler's own shoes always get repaired last!)
But in answer to your question Ron, I have found FM reception to be outstanding on the models 47-1230 I have worked on, once properly aligned.
Bill, in regard to that feedthrough cap, I have always used the method of replacing it as Ron describes on his website, and have never had any problem with it.
Poston
- Ron Ramirez - 11-04-2006
I too have found FM reception to be quite well indeed on the 47-1230 sets I have had occasion to work on, Poston.
I was a bit curious about how Bill's set was working on FM, though, if he didn't replace the capacitor or left it out of the circuit in favor of the wire he used?
- bill T - 11-05-2006
Hi Ron , Poston and All ...
Had a little problem . Everything was working great .
Only had to roll trimmers back and forth and basically
put them back where they started. Got the M4 phono changer
to drop records, amazing ! Then hooked in a modern turntable
directly to the banana jack on input side of phono transformer .
And that worked (mono)!I am going for more original changer but
was curious. I was ready to put the chassis back in and call
it done. Switched back to AM nothing ! FM , Short wave ,PB no
stations .Tap antenna lead with screw driver got a pop type noise.
Put phono back it worked. Shutdown looked carefully at wiring. I
have forgotten to solder things before.Found white wire from terminal
board to band switch tinned and wrapped around lug but not soldered .
A place I did not work on ! That wire was must have been fine until
I moved the other end of it putting in caps. Actually the person that
did that made a great mechanical connection that lasted until I moved
the wire. Anyway everything works again .I aligned the set by ear.
AM and short wave are better than any older 41-42 models I have (or as good).
FM sounds excellent! Very happy with that ! I had to redo the Am alignment and FM by ear again. Tried to do alignment with meter/scope/signal generator but could not get it to work.To late at night to continue .So I did it by ear.Now I recall that if using a VTVM and not an output meter you have to get on the AVC line.I Kind of remember the last one I did I swore that I would make a loctal adapter for this .Never did though. Even though the Fm sounds great I am not sure it is best it can be. Put Cap wire back as prescribed. Seemed to work equal both ways. But as I said do not think it is 100% yet. Seems to be a lack of FM channels on low end of dial.sound quality is there .So I am leaning toward full alginment with meter .May need help on this alignment . Never did FM . What is special about the "output audio meter " that a VTVM can't be used on terminal 3 to chassis ? Or am I wrong in recalling this ?
To recap on the wire and capacitor and be clear about what I found. I would have to say it did not matter. The leads are in a wide open area of the chassis where there is little for high freq to jump to or interfere with .
Even so I go with the recommended repair.That is because I felt under certian reception conditions it could matter . Plus it is a neater way to wire.
The general rule I follow is do not move these type of wires or change thier lead length. I think you can adjust out lead length to some extend .But if you place wire in wrong area it may cause problem that can't be adjusted out.Once this is done I am not going back in to move a wire .
Therefore I go with the way it is on Ron's site.
Thanks for all the interest and help ... Bill !
- bill T - 11-06-2006
Back again , Done and happy ! Found that Fm missing on lower end of dial was not what I thought . Stations had shifted about 6 mc up dial ! Lower stations way up dial higher station gone . Realigned Bc with scope on AVC . Peaked out about the same as it was , and worked well.
Fm alignment . Put fluke digital across c321 per instruction for 10 vdc .Had to go to ground rather than across cap which also should be ground.Did not understand that . May be problem . When ohm'ed terminal board side is ground ,tube side 51,000 k to ground .Anyway got ten volts when injecting 9.1mc .Followed procedure . Was'nt hard at all.Ended up with good sounding stationway up the dial again
Backed out all fm trimmers ,did it by ear .Got a station in correct spot on low end of dial and tweaked it in . Works great all kinds of stations sounds good and are where they belong! Only dfference is three antenna padders. With meter alignment they were about half way down . By ear about 3/4 of the way up .They are slug type padders . Never saw those before.Touched one and it appears to have light coat of some sort of grease on it.Did not clean it off but thought about it .Everything is working now so why mess it up.I do not want to spin the trimmers till they strip. So I put the Chassis in the radio and consider it done .I am happy with it ! Will see how well it runs without adjustment. All I can think of with this Fm alignment is I have a bad connection again. Over time it may act up . Thanks !
Bill