The PHILCO Phorum
42 PT-7 - Printable Version

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+--- Thread: 42 PT-7 (/showthread.php?tid=20136)

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42 PT-7 - Arohn19 - 06-21-2019

im restoring a Philco 42 PT-7 radio for the first time and I’ve heard i could get shocked if I’m not careful.. What are my real dangers with it unplugged? I also heard on YouTube that paper capacitors should just be automatically replaced because they’ll likely go out soon if they’re not already. Can I just clip the wires on them (provided I take plenty of pics beforehand) without any dangers? My snips do have plastic handles so I should be good as far as that part goes… The guy who I bought it from on eBay said it did light up but no sound came out. Any guesses to what maybe wrong? I’m guessing likely a bad tube? But that’s only a guess, I have not attempted to plug it in myself I downloaded the schematic for it but I’m not sure how to read it. I don’t want any of my faults to keep me from trying to restore this thing though.

Any help would be nice!

Thanks,
Adam

RE: 42 PT-7 - Radioroslyn - 06-21-2019

Hi Adam,
>What are my real dangers with it unplugged?
Very little. Would be a freak sort of accident to get shocked.
>I’m guessing likely a bad tube? [Image: https://philcoradio.com/phorum/images/smilies/icon_lol.gif][Image: https://philcoradio.com/phorum/images/smilies/icon_evil.gif]
More than likely there will be several issues to correct. A tube or two may be part of the problem. Unless your set came from CA you are probably going to have decaying rubber wire which can be a bit of a pain to replace
> I downloaded the schematic for it but I’m not sure how to read it.
Not sure what you are saying. Is it just schematics w/vacuum tubes or you have no clue as to how to decipher what you are looking at on any schematic?
http://www.nostalgiaair.org/pagesbymodel/568/M0013568.pdf

GL

RE: 42 PT-7 - morzh - 06-21-2019

>>>>Can I just clip the wires on them (provided I take plenty of pics beforehand) without any dangers? My snips do have plastic handles so I should be good as far as that part goes

Not sure I got you right: are you implying snipping wires while plugged and powered? If yes, you are having some serious issues with understanding safety and should not attempt at repairs until familiarizing yourself with rules of it.
If not then why the plastic handles matter?

RE: 42 PT-7 - Arohn19 - 06-22-2019

Thanks for the info, Terry. The schematic i downloaded and printed off is the exact one you attached. I think I’m starting to understand it better

RE: 42 PT-7 - Arohn19 - 06-22-2019

No, I’m not that crazy.. Of course it’ll be unplugged before I even attempt to replace anything, I’m only 40.. I want to live longer! Lol

RE: 42 PT-7 - Arohn19 - 06-22-2019

I just know that some capacitors can hold a lethal charge even when the item they’re attached to isnt even plugged In,  that was main concern and that’s why I mentioned the rubber grips on my tools so I should be good I’m thinking as far as that goes. The table I’m working on isn’t metal either

RE: 42 PT-7 - sam - 06-22-2019

I would presume  you are not familiar with electronics ?
do you know how to solder  ? 
read  schematics  ? 
all round paper caps should be replaced  so should electrolytics
take lot of good pics  for reference
and ask a lot of questions

sam

RE: 42 PT-7 - NostalgiaRadioTime - 06-22-2019

While the little pre-war transitones are relatively simple in design, for a first attempt at restoring a radio it may not be the best choice due to the extremely cramped chassis and crumbling wire wrapped around everything. Be aware that any wire that gets disturbed will more than likely have its coating crumbling off, leaving you with a bare wire. Not good. Totally rewiring the radio to replace ALL of the crumbling wire would be preferred (see Ron's thread for a somewhat similar set up: https://philcoradio.com/phorum/showthread.php?tid=19779) but that would probably be above the skill level of someone just starting out. You may opt to just replace or sleeve the ones that are bare with shrink tubing, or at the very least use some liquid tape on a toothpick to coat the bare spots on the wire. Good luck!

RE: 42 PT-7 - Steve Davis - 06-22-2019

If your radio is unplugged, it is safe to work on. The tubes are still hot the moment the power is turned off and will continue to conduct for a second or two, this will discharge the capacitors. 

Steve

RE: 42 PT-7 - morzh - 06-22-2019

.....unless the radio was plugged in without the speaker, in which case the charge persists longer and we are all guilty of doing that every once in a while Icon_smile
Or the transformer is open.

Blue Compacitor - Arohn19 - 06-23-2019

Do I change the blue capacitor shown in the pic? And if so, with what? It says 20 + 20 MFD on it..

Thanks

RE: Blue Compacitor - Arohn19 - 06-23-2019

For some reason the pic isn’t posting

RE: Blue Compacitor - Radioroslyn - 06-23-2019

Check the size of the pic you may have to resize it (smaller) the Phorum doesn't do it automatically.

RE: Blue Compacitor - LarryFS - 06-23-2019

What radio are you working on?  What does the schematic or parts list show for electrolytic capacitors?  The 20 + 20 means there are two 20 MFD electrolytic capacitors present.  If the part is original or old, it would need to be replaced.  Easiest way to do that is with two separate 20 or 22 MFD electrolytic capacitors of an appropriate voltage rating.

RE: 42 PT-7 - Ron Ramirez - 06-23-2019

Two separate threads started by the OP have been merged into one.

Arohn19, separate threads on the same subject are not allowed per Phorum rules.

https://philcoradio.com/phorum/showthread.php?tid=4586

Please read and familiarize yourself with the Rules. Thanks.