New and already smoking(literally) - Printable Version
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New and already smoking(literally) - Fibber Mcgee - 02-03-2014
I am a complete novice with my only experience being recapping an Olympic Radio. Now I don't know what I've got into. I've got a Philco 40-190 that my Uncle's parents bought new. When he gave it to me he had plugged it in and said it smoked so I (being a novice) thought I would recap it and see if it would work as he said it worked 20 years ago when he stopped using it. So I plug it in and yep it smokes. The smoke is coming from a wire wound resistor that comes from the transformer and leads to another resistor among other things. This is #60 on the schematic and is a 150 ohm 1 watt resistor. I did check the resistance and it was about 135 ohms. Where should I look for a cause? Is 135 ohm okay? Any help would be appreciated but you might have to keep it simple as I am trying to learn as I go. Thank you.
RE: New and already smoking(literally) - morzh - 02-03-2014
All I could tell you is this:
1. Always give a link to the schematic.
2. Never plug in anything you don't know to work.
3. Powering up a device like this after a THOROUGH check is done via a Variac and preferably an isolation transformer also.
It also helps understanding what you are doing.
Let's start from the schematic link.
PS #60 smoking might mean your RF 1232 tube's bad (S to P short).
RE: New and already smoking(literally) - skyscraper - 02-03-2014
Schematic is here, in case you don't know where to look. http://www.nostalgiaair.org/Resources/339/M0013339.htm
Are you saying you have or have not recapped it yet? That resistor, I believe, creates the B+ negative bias, so several shorted caps could cause it to overload.
RE: New and already smoking(literally) - morzh - 02-03-2014
From what I understand he implied he recapped it.
RE: New and already smoking(literally) - jerryhawthorne - 02-03-2014
Attached is a link to the schematic. Always nice to put in with your problems. One question Fibber, did you replace at least the electrolytic caps yet? Uncertain from your post.
Jerry
http://www.nostalgiaair.org/PagesByModel/339/M0013339.pdf
edit: Others posted the schematic while I was offering it. Sorry. Still no clear if your have replaced the e-caps.
RE: New and already smoking(literally) - klondike98 - 02-03-2014
Fibber, here's some reading that might be helpful: http://www.antiqueradio.org/begin.htm . Hang in there, this group can help you through this.
RE: New and already smoking(literally) - Fibber Mcgee - 02-03-2014
I did replace all the capacitors. I knew not to plug it in without at least replacing caps. Sorry about the lack of a link. I didn't know where to find one online. I ordered one from a guy recommended on here and he mailed it to me. I know some basics of electricity but like I said I'm trying to learn. I know I don't know what I'm doing exactly but then again I didn't know exactly what I was doing when I rebuilt the transmission on my 41 Ford and it now works great. I learn by doing and that's why I need your help.
RE: New and already smoking(literally) - morzh - 02-03-2014
Have you tested the tubes?
Look at the one I mentioned, the very first one.
Check it for shorts.
RE: New and already smoking(literally) - jerryhawthorne - 02-03-2014
Fibber as Mike suggest it could be a bad tube. Might be instructive if you don't have a tube tester to pull the tube out and try the radio, you won't get any stations but see if that resistor gets hot.
Best, Jerry
RE: New and already smoking(literally) - Fibber Mcgee - 02-03-2014
Thank you morzh. I will check the RF 1232 tube in the morning ( I'm at work now). I will also check the wires at the base as I know some were bad and maybe I missed something. It sounds like it is doing the same thing as before he gave it to me as he said it was smoking when he plugged it in. I smelled it when I got it and it smelled burnt in that area but I thought it was the transformer. The transformer was not hot but it did have some old hard wax on the bottom. This is a family heirloom and I really want it working for him to hear. He said he remembers listening to the old radio shows as a kid on this set. Thanks again.
RE: New and already smoking(literally) - morzh - 02-03-2014
Basically the resistor will smoke if its right end is connected to high voltage.
Of course check the wiring and the panel.
Here's how I would do that:
1. Power OFF, radio is UNPLUGGED !!!!
2. Measure across the cap #58. See if there is a suspiciously low resistance.
3. If not, Check the cap for reversal.
4. If yes, trace the short.
PS. FOr a time being forget about the tube, the path is also protected by the anode resistor, so first do that above, then we will think of other venues.
RE: New and already smoking(literally) - Fibber Mcgee - 02-04-2014
Measured across 58 and got infinite resistance so I checked for reversal and the capacitor is - to ground. Where to next. And thanks for the help.
RE: New and already smoking(literally) - morzh - 02-04-2014
1. <<and the capacitor is - to ground.>>
What is to Ground?
2. When you say "infinite" do you truly mean infinite or very large?
Did you also see the charge when measuring (starts with low resistance and then grows to high)?
3. Have you check your tubes yet? Start with the rectifier tube. Check for shorts. Shorts is the most important check here.
RE: New and already smoking(literally) - TV MAN - 02-04-2014
Just some thoughts... when you did the recap, did you disconnect and replace the existing electrolytics, esp 61, or did you bridge them (put a new cap across the terminals)? I agree with pulling the rf tube to try. Could be shorted. It'd be a quick, simple test. The diagram shows 105 v on the grid of that tube. Also, does this radio use the cloth covered wire or the rubber wire that deteriorates? The wire could be shorted to ground where you cant see. Sometimes a short or overload wont show up until power is applied, as in, it may check ok with the meter cold, but when the voltage hits it, or the tube warms up (and starts to conduct), it pulls things down.
At least back in the day, they put way more smoke in these things than they do now!
RE: New and already smoking(literally) - morzh - 02-04-2014
I wonder if we should have a "magic smoke trap" - when it escapes, we trap it and then put it back.