75 Tube - Printable Version
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75 Tube - dconant - 05-16-2024
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
RE: 75 Tube - David - 05-16-2024
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
RE: 75 Tube - Steve Davis - 05-16-2024
Also, try resoldering the pins.
Steve
RE: 75 Tube - Arran - 05-16-2024
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
RE: 75 Tube - radiorich - 05-17-2024
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
RE: 75 Tube - dconant - 05-17-2024
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.
RE: 75 Tube - David - 05-17-2024
Something to add to the tool kit is the cleaning tips used with a torch. The cost will be under ten at horrible freight.
RE: 75 Tube - DaleHCook - 05-17-2024
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.
RE: 75 Tube - tym - 05-26-2024
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.
RE: 75 Tube - morzh - 05-26-2024
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.
RE: 75 Tube - dconant - 06-06-2024
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