New and already smoking(literally) - Printable Version
+- The PHILCO Phorum (https://philcoradio.com/phorum)
+-- Forum: Philco Radio Discussions (https://philcoradio.com/phorum/forumdisplay.php?fid=5)
+--- Forum: Philco Electronic Restoration (https://philcoradio.com/phorum/forumdisplay.php?fid=8)
+--- Thread: New and already smoking(literally) (/showthread.php?tid=8678)
+- The PHILCO Phorum (https://philcoradio.com/phorum)
+-- Forum: Philco Radio Discussions (https://philcoradio.com/phorum/forumdisplay.php?fid=5)
+--- Forum: Philco Electronic Restoration (https://philcoradio.com/phorum/forumdisplay.php?fid=8)
+--- Thread: New and already smoking(literally) (/showthread.php?tid=8678)
RE: New and already smoking(literally) - TA Forbes - 02-04-2014
Pull the 84 tube and turn it on. If there is no smoke it is possible that the previous issues caused your power xfrmr to go bad. This often happens when the filter electrolytics in the B+ circuit go bad.
Test the 84 tube also. Although rare, sometimes the tube goes bad due to the above problem.
If tube is good measure the resistance between the two plate pins of the 84 tube socket with the tube removed. Tell us what it is.
RE: New and already smoking(literally) - Fibber Mcgee - 02-04-2014
I pulled 1232 this morning and it still smoked. When I checked resistance on #58 the meter never moved as if the it was off. When I say the - is to ground. I mean the - side of the electrolytic(#58 ) is wired to a terminal that connects directly to the chassis ( sorry about the terminology but I'm used to working on cars electrical system). When I recapped I removed and replaced each one. The wires are rubber covered and I replaced a lot of them but could have missed something. I am at work again so in the morning I will try some of your other suggestions.
RE: New and already smoking(literally) - Mondial - 02-04-2014
Resistor 60 is the main bias resistor, so all of the B+ supply return current passes through it. Any overload on the B+ supply will cause that resistor to overheat.
Does the resistor get hot immediately on turn on or does it only happen after the tubes warm up?
As someone mentioned previously, remove the 84 tube and check the resistor. Then replace the 84 and remove the two 41 tubes and see if it overheats. The 41's draw the majority of the B+ current in the radio and would be my prime suspects if everything is otherwise wired correctly.
RE: New and already smoking(literally) - morzh - 02-04-2014
OK, its been now suggested trice. Remove the rectifier tube.
RE: New and already smoking(literally) - jerryhawthorne - 02-05-2014
Morzh, pulling the rectifier will certainly not cause the resistor in question to overheat, no B+. But the OP can try that. Pulling the output tubes should help us to figure out what is going on. As indicated, they are the major source of pull on the B+ line. Of course a nice resistance measurement from the B+ line to ground could also be instructive.
Jerry
RE: New and already smoking(literally) - Mondial - 02-05-2014
Jerry, If the 84 has a heater to cathode short ( actually quite a common failure), it will provide a path for B+
to ground, which will have to return to the transformer through the bias resistor.
Removing the 84 just eliminates that possibility as the cause of overheating.
RE: New and already smoking(literally) - jerryhawthorne - 02-05-2014
And indeed that is why you guys are smarter than me! Never thought of that. Correct me if I'm wrong but removing it and no heating of the resistor would not really tell you anything as it could be the tube but could also be some short in the B+ line? Perhaps testing that tube or a replacement might eliminate the possibility of the tube being bad?
Best, Jerry
RE: New and already smoking(literally) - Fibber Mcgee - 02-05-2014
Okay in the morning I will start by pulling 84 and then go from there. It take about 5 or ten seconds to smoke and increases as time passes. I could see where it would be as the tubes warm up.
RE: New and already smoking(literally) - Fibber Mcgee - 02-05-2014
Okay I removed 84 and no smoke so I replaced 84 and removed 41s and it smokes. I hate to ask this but what is the B+ line?
RE: New and already smoking(literally) - Mondial - 02-05-2014
If the 84 has a short, most likely it will cause the resistor to smoke almost immediately, while if it takes 20 seconds or so then it indicates that the short is external to the tube.
Even there is a dead short across the B+ line, there would be no current through the resistor until the 84 warms up. Since Fibber mentioned that it only took 5 seconds for the resistor to get hot my guess is that the 84 is bad. He also mentioned that he put an ohmmeter from B+ to ground and found no short ( across filter cap 58 ).
The B+ line is the output of the rectifier and filter which supplies operating voltage to the plates and screen grids of the tubes.
Try another 84 tube and see if it cures the problem.
There is a guy on ebay selling new military surplus 84's. I would trust these more than buying a used tube.
http://www.ebay.com/itm/SYLVANIA-JAN-6Z4-84-TUBES-/400597564193?pt=US_Radio_Comm_Tubes&hash=item5d4579bb21#shpCntId
RE: New and already smoking(literally) - Fibber Mcgee - 02-05-2014
I will order one but is there a way to test the one I have with a multimeter? Also,does this help my chances of not needing a transformer?
RE: New and already smoking(literally) - skyscraper - 02-05-2014
Using the pinout here: http://www.radiomuseum.org/tubes/tube_84.html you can test for a heater cathode short by measuring resistance from pins 1 or 5 to 4.
When the 84 is pulled and radio is unplugged, check the resistance between 2 and 3 of its socket. It should be about 350 ohms. If all the other tubes are heating and the transformer isn't getting overly hot, it is probably good. There are only two windings.
RE: New and already smoking(literally) - morzh - 02-05-2014
Jerry
if the rectifier is shorted from A to K, it does not need to heat up and due to the AC going right through and shorting via the first electrolytic AND the second electrolytic which will act even not quite like a cap due to the voltage being AC it might deliver a large current via the 60 and 59 resistors, with most power disspated across 60.
This is why we are asking, if the smoking occures almost immediately or the rectifier has to warm up first.
RE: New and already smoking(literally) - morzh - 02-05-2014
Fibber
Please answer the questiron about the timing of the smoking AND for the lack of a better way, could you simply take a meter and buzz A to K in the 84 rectifier?
RE: New and already smoking(literally) - TV MAN - 02-05-2014
Few more thoughts... Fibber says it takes 5-10 seconds for the resistor to start to smoke. Looks like an indirect heater tube, so it shouldnt start to conduct until about the 15-20 second mark, so I'd say it is immediate. Like Mike says, if this thing is passing a/c, those filter caps will act like a piece of wire. If one of those caps failed originally, it could have cooked the tube to the point it shorted. A h-k short would have to return via that resistor. Could have even melted down the tube to the point of a p-k short. Also, I havent heard mention of checking the 15ohm resistor "59". Is it open, or overheating also? Fibber, the B+ we talk about is your main power coming off your power supply to the rest of the set, (usually after the final filter cap) looks like 185v in this set.
Have you checked your speaker field coil (the coil on the back of the speaker - looks like it has one from the diagram)? If the new 84 doesnt help things, then looks like you are going to have to measure some voltages, maybe disconnect some wires (one at a time and with notes/drawings). I am quite curious what the voltages are doing in this set. This - after you have replaced the 84. Watch that new tube very carefully when you power up the radio. The only part that should "light up" is the heater/cathode, in the very center of the tube. If the outside (plates) start to glow red hot, cut the power immediatly and check for shorts, etc. Ok, my 2 cents...