The PHILCO Phorum
42 PT-7 - Printable Version

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RE: 42 PT-7 - Arohn19 - 08-02-2019

I got a few questions, two of which I think I know the answers too. 1) Is it ok to replace a 5.2K resistor with a 5.6K? 2) is it ok to replace a 430K with a 470K. Also, do tube sockets have to be installed a certain way? I’m thinking on replacing the tube socket that has a loose pin rather than wait and find out when I’m done that it should be replaced. I think I that sockets have a numbering system and I’m not sure if installing it wrong would affect that and then obviously the wires and resistors that go in those spots.

RE: 42 PT-7 - Radioroslyn - 08-02-2019

Yes
Yes
And which socket are you replacing?

RE: 42 PT-7 - Arohn19 - 08-03-2019

Thanks Terry! I thought question 1 and 2 were gonna be both yes but, I wanted to check. And according to the schematic, it the rectifier socket. It’s the pin that I just got done soldering the 3.3Meg too. Do I have to replace the entire socket or are the pins easy to change? It’s got a lot of front to back “play” in it. It’s almost like the slot it goes in got longer with age.

RE: 42 PT-7 - Radioroslyn - 08-03-2019

Go here: http://www.jollinger.com/radio/tubes/tube_basing.html
Look under OCTAL and use this diagram to discover how to count the pins on the bottom the the tube or socket. Your rectifier tube is a LOCTAL but you count the pin in the same way. So which pin has this resistor and such connected to it??

RE: 42 PT-7 - Arohn19 - 08-03-2019

It looks to me like the 3.3 Meg is located on pin 2 and 3 with the problem pin being pin 3

RE: 42 PT-7 - Arohn19 - 08-03-2019

I was hoping installing the resistor would’ve tightened things up but it didn’t

RE: 42 PT-7 - Radioroslyn - 08-04-2019

Don't see a 3.3M resistor connected to the 35Z3 socket so double check the pin numbers and what socket you are working on. There is a 3.3M resistor on the 7C6 but in wouldn't be connected the the pins you mentioned.

RE: 42 PT-7 - Arohn19 - 08-04-2019

Yeah, that’s my bad, Terry. I think it’s actually pin 4 and 5, if I’m counting correctly

RE: 42 PT-7 - Arohn19 - 08-04-2019

Why are PIN numbers so important? The tubes don’t seem to mind which direction they go into the socket so, that tells me that a certain wire doesn’t need to go onto a certain pin. Just curious

RE: 42 PT-7 - Arohn19 - 08-04-2019

I think it’s socket 7C6, Terry and I’ve got the 3.3 Meg there

RE: 42 PT-7 - Radioroslyn - 08-04-2019

<Why are PIN numbers so important?
Because each pin connects to different internal element inside of the tube. These different elements do a separate job. With the wrong wires or parts connected to the wrong pins bad things can happen. It would similar taking the ignition wires on a car engine disconnecting them from distributor cap and reconnecting them willy-nilly with no regard to the order they came off.

RE: 42 PT-7 - Arohn19 - 08-04-2019

I just realized my error. I installed the 3.3 Meg where a 52K or a 5200K should go, I don’t which one. Luckily I took a pic of the old one so I could rerun it on my app. If I read it right (the 1st band closest to the end) should be orange. Does that sound right? If not then it’s a 52K because the first band would be green

RE: 42 PT-7 - Arohn19 - 08-04-2019

I-think I had 3.3M in my head

RE: 42 PT-7 - mikethedruid - 08-04-2019

If you are serious that "tubes don't seem to mind which direction they go into the socket," then you have a problem. All tubes are keyed in some way. In old types they either had 2 larger pins that allowed the tube to be inserted only in the correct way, or they had a peculiar pin layout that also only allows one way. Later types, octal and locktal have a thick post in the center of the base with a ridge down one side of it. This keys into a little cut out on the side of the center hole in the socket that the post fits into. Later 7 and 9 pin miniature tubes have a wide gap between two of the pins, which matches a gap in the holes in the socket, so they can only go in one way. If your tubes can go into the socket in more than the correct way, then you have a problem. Perhaps it is a damaged socket from someone forcing a tube in the wrong way. In that case you will have to replace the socket.

RE: 42 PT-7 - Arohn19 - 08-04-2019

I just checked all the sockets and the tubes DO go in only 1 way like you said, Mike.. My bad. Is it possible for someone to put a tube in the wrong socket? I’m starting to think that’s what’s going on because the tubes in the pictures I took before taking them out show them in different sockets than what the schematic saids they should be. I checked all the resistors and the 3.3 MEG that Terry and the schematic both said should be in socket 7C6 isn’t a 3.3 MEG and it’s the only one on that socket. I double checked it with a 3.3 MEG I got in the kit I recently bought. That 3.3 MEG on the 35Z3 socket. And according to my pics, the old resistor that I replaced was a 
3300K and if that’s true.. There was never a 3.3MEG in the radio and there should’ve been one (that’s not there) on 7C6. The guy I bought it from on eBay did plug it in and showed a pic of the tubes glowing but he said there wasn’t any sound.