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Joined: Jun 2022
City: Marion
State, Province, Country: NY
Hello, I seem to run into bad time with the 75 tube. I have four of these that seem to be somewhat finicky in that they cause noise and fading or no reception even though they test good in my tube tester. My Philco 60 has been the test bed for these. I was beginning to think the problem was elsewhere but I am convinced it is the tubes. Has anyone else run into issues with the 75 tube. I have another radio where I had a problem with the 75 tube and got a good one working in it.
Thanks,
Dan
Posts: 1,262
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Joined: Jan 2014
City: Wellborn Florida
Try cleaning the tube socket Q tips etoh WD 40 deoxit are your friends. Clean the pins on the tubes 0000 steel wool and etoh . Good luck David
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City: Linn Creek, MO
Also, try resoldering the pins.
Steve
M R Radios C M Tubes
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Joined: Sep 2008
City: Sandwick, BC, CA
The grid cap is also another weak point with double ended tubes like these, especially the glass ones. Don't forget about the grid cap lead either, I would resolder or replace all of those whilst you are at it.
Regards
Arran
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City: Omak
State, Province, Country: WA
hello Dan
I agree with the others I am restoring my Philco model 38-10T and the tube pins has green corrosion on the pins that it made it hard to remove some of the tubes .
Plus the grid cap leads were stiff and brittle.
Sincerely Richard
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City: Marion
State, Province, Country: NY
All of the 75 tubes in question have nice clean pins. I have replaced the grid cap wire and cleaned the connector but have not done the pins or resoldered. I'll give that a go today or tomorrow.
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City: Wellborn Florida
Something to add to the tool kit is the cleaning tips used with a torch. The cost will be under ten at horrible freight.
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Joined: Apr 2023
City: Roanoke
State, Province, Country: Virginia
dconant Wrote:... even though they test good in my tube tester.
That, of course, does not mean that they are good - it only means tha they are not definitively bad.
Dale H. Cook, GR/HP/Tek Collector, Roanoke/Lynchburg, VA
https://plymouthcolony.net/starcity/radios/
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Joined: Dec 2023
City: Greater Boston
State, Province, Country: MA
Flaky grid cap connections have definitely been a problem for me with 75 tubes, among others. After many decades, the solder joint to the grid lead can become intermittent. Agree with others it's a good idea to resolder them.
I even bought several spare 75s "just in case" and now have more than I'll ever need, so let me know if you want an extra.
(This post was last modified: 05-26-2024, 03:17 PM by tym.)
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Dan
What Steve suggested makes sense: resoldering pins and the cap mean just that, resoldering the pins and the cap, not their wires.
Solder over time, under certain conditions, may develop "cold spot". If it is not that infamous "beta tin", which cannot be melted or soldered with an iron, then you simply need to re-flow the pins and especially the grid cap. Often times you will, upon melting the solder on top of the grid cap, will find out un-wetted oxidized copper wire. At which pont you need to clean it, tin it and reflow with tin-led solder.
No guarantee this is it, but I've seen that too.
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.
Posts: 243
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City: Marion
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Well resoldering the caps and pins saved my 75 tubes. All working good. so now I have some good spares for the future radios that may need one. Thank you.
Dan
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