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I’ve recapped this radio and it works GREAT except for one thing. The two local stations at the high end of the dial come in too well. By this I mean with the volume turned down all the way the volume is too loud. When I tried to neutralize the radio following the procedure in the Philco Library I got all the way to the last step. I can’t get the 1st RF stage neutralized, 2 and 3 adjusted just like they were supposed to. The trimmer doesn’t seem to do anything. I’m using a plastic wrench and did replace the capacitors connected to the trimmers.
Any thoughts?
Thanks in advance.
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When I couldn't neutralize a stage with the respective trimmer, I found out I was trying to trim a wrong trimmer.
As long as the trimmer and the coils are good it should neutralize.
PS. I think I used a dud instead of a socket with a disconnected heater pin.
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 think the trimmer is good, but should I swap it for another one to see if the problem moves? Number 2 for number 1? I’m 99.44% sure I’m adjusting the correct trimmer. I had to rewind the primaries of the other three coils but this one was good. One thing I wondered about at the time was that the primary of this coil has probably twice as many turns as the other three. Might this have something to do with my problem?
Thanks again.
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Make sure the trimmer is connected on both sides (output and input coils). Also make sure the coils are OK and have continuity on all contacts (including the one where thr trimmer goes to).
If you have a modern trimmer cap you could install it in parallel (or with the original disconnected) and see if it works. Easier than moving the trimmer.
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: 10-29-2019, 07:41 AM by
morzh.)
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The coil is fine and the trimmer is connected. I tried switching two of the trimmers, no change.
I’m starting to wonder if I have some kind of fluke problem. Our station at 1490 comes in way too loud with the volume turned down all the way with no antenna connected.
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Another observation. I had to rewind the primary windings on the three other RF coils. The two stations that are way too strong now were the only stations I could get before I repaired the coils.
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Another observation. When I’m tuning the radio I frequently get a sound kind of like an A-10 airplane firing its cannon. Is this motor boating? If so, is it related to my problem?
Thanks again.
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Kirbyc
When you first tried it, you said the radio worked great. Then you said the trimmer was good, then you said you had to rewind three coils.
Why don't you make sure the coils are all OK and are exactly as they were before they went bad, including the tap location etc.
Then make sure you follow the actual procedure and not what you think the procedure is. Like what if instead of trying to achieve the minimum signal the maximum is being achieved.
Your trimmer not working is suspicious.
Check all the tubes.
Make sure the tube used for neutralizing the stages is what it says it should be. Same tube that is either a dud with all structure OK except the filament is open, or a good tube mounted in a transition socket with one filament pin disconnected.
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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Let me reset the timetable. I recapped the radio. When I first fired it up after the recap I could only receive the stations at 1440 and 1490. That’s when I rewound three of the RF coils following the instructions in The Philco Repair Bench. After I rewound them was when the radio worked very well everywhere except it worked too well at the 1440-1490 end. By too well I mean that with the volume turned all the way down the volume is too loud. It is motorboating so I guess isn’t really working well.
I’ve checked the tubes, but I’ll check them again.
I used the procedure from the Philco Library to align and neutralize the set. I used a transition socket and the tube for each stage and a plastic wrench.
I also swapped trimmer 4 and 5 as shown on the Philco procedure with no difference in the outcome.
One other thing. The grid leak resistor should be 750k ohms but is 880k ohms. Could this be a problem?
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No I do not think GL resistor would result in this.
In fact I think it is not the gread leak detector but is the plate detector.
Also: you did replace the 0.1uF caps inside the resistors? (co-axial parts 7, 12 and 17)?
And, keep in mind: this is a simple TRF set with no AVC, so strong stations will come very loud and you cannot do much about it.
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: 11-06-2019, 09:12 AM by
morzh.)
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I did replace the capacitors by cutting the wires that went to ground. Should I maybe replace the resistors too?
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No, as long as the resistors are OK (being wirewound they are not likely to drift) you don't have to.
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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