New and already smoking(literally) - Printable Version
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RE: New and already smoking(literally) - TA Forbes - 02-05-2014
I'm betting that it's the transformer. Of the two issues, either an H to K short in the 84 tube, or a bad power xfrm, the tube problem is not as common. However, IF the 84 does have an H to K short, I still bet the transformer caused it or went along for the ride.
Having worked on several Zs that employed the venerable 6X5 tube/tubes, that is usually the damage incurred.
Power transformers are NOT had to find for this set, be it an original OR an aftermarket replacement.
With respect to the B+ issue being caused by the 41 tube circuity, that is a logical place to check, but I would have checked the power transformer/rectifier/filter circuitry first, as that is where most B+ issues originate from..
RE: New and already smoking(literally) - Mondial - 02-05-2014
Well Tom, I'm going to bet the transformer is still ok.
When he removed the 84 and powered it up, no smoke and the other tubes filaments lit up. I guess he can check the secondary AC voltage and leave it on without the 84 to see if the transformer gets hot.
RE: New and already smoking(literally) - TA Forbes - 02-05-2014
Yes, you are right. If the transformer stays cool it is usually, well, mostly NOT the xfrmr. After going back and reading the account(s) of what he has done thus far, agree that it is a positive sign that no smoke was encountered when he pulled the tube. AND you are correct about the other tube fils, since the 84 is a 6V rectifier.
The scenario I was thinking of would involve a separate rectifier filament winding in the xfmr.
BUT if the HV winding is bad, then what I stated can still be true. Resistor 60 goes to CT of the HV winding.
Proof will be pulling the 84 and allowing the set to stay on for a few mins to see if the xfrmr gets hot. OR measuring ohms between the two plate pins of the 84 socket.
RE: New and already smoking(literally) - Fibber Mcgee - 02-05-2014
I am going to go post by post above and try the suggestions tonight ( no work). I was told these transformers ARE hard to get but you guys would know more than the guy who said they were hard to get. How much are the transformers for these sets? I'm in this now and WILL get it fixed , with your help. Thanks everyone. Now I have a Glenn Miller Orchestra concert to go to at 7:30 so I will post on here tonight what I find out when I get home.
RE: New and already smoking(literally) - TA Forbes - 02-05-2014
No, a suitable replacement would not be hard to find.
A difficult transformer to find would be like one for a Crosley 146, which has a 2.5V rectifier winding, two 2.5V filament windings, a 6.3V filament winding, and a HV winding.
Finding a Philco replacement might be a little tough, but not impossible.
Keep us posted. Between Mike, Mondial, and the other real techs and also hackers like me you will get it good to go.
RE: New and already smoking(literally) - Fibber Mcgee - 02-06-2014
I did some checking and this is where I'm at . First I pulled 84 and left set on for 3 minutes and all tubes lit up and there was no smoke and the transformer was cool to the touch. Second I checked number 84 socket between 2 and 3 and had 270 ohms. I also checked resistors 59 and had 16.2 and 60 had 150. Third I checked 84 tube pins and had 1.5 ohms between pin 1 and 4 and 1.9 between 1 and 5 pins. I'm still going to look for bad wires just to be safe. So what's this look like. I'm thinking the transformer is okay but I don't know what the 84 tubes resistance should be.
RE: New and already smoking(literally) - Mondial - 02-06-2014
The 84 tube definitely is bad. So far the transformer and resistors look ok
If you read anything but infinite resistance between pin 1 and 4 then there is a heater to cathode short. Pins 1 and 5 are the filament and you should read a low resistance between them.
[Image: http://www.bunkerofdoom.com/tubes/syl43/DATA/1943/P208.GIF]
RE: New and already smoking(literally) - TA Forbes - 02-06-2014
+1
RE: New and already smoking(literally) - morzh - 02-06-2014
1 and 4 should not conduct - the filament is isolated from cathode. Not sure if it is the reason but this ain't right.
RE: New and already smoking(literally) - TA Forbes - 02-06-2014
That's what he is saying, that ANYTHING less than an open means that there is leakage between the heater and the cathode.
Hickok testers usually allow for > 200K ohms leakage between tube elements, but in the case of H to K leakage my personal opinion is that any leakage can be problematic.
RE: New and already smoking(literally) - morzh - 02-06-2014
OK, looked at the sch - it IS the problem as the filament of 84 will connect to other filaments and those are grounded, and the 84 filament shorted to cathode is thus connected to B+, so what we have is creating a short between the GND and B+, hence the smoke.
84 is bad. Replace it.
RE: New and already smoking(literally) - Fibber Mcgee - 02-06-2014
I already ordered two 84s just in case. Hopefully they will be hear I'm a few days and I will try again. Anything I should watch for when I plug the new one in? I really appreciate all this help not only are we getting this fixed but I'm learning a lot.
RE: New and already smoking(literally) - morzh - 02-06-2014
Next time check all your tubes.
As a matter of fact when you plug it in....still check all your tubes.
BEFORE TURNING A DEVICE ON EVERY POTENTIALLY DESTRUCTIVE FAILURE-INDUCING COMPONENT SHOULD BE CHECKED.
This includes tubes, capacitors, transformer, and some resistors.
RF Coils are not that important, though checking continuity beforehand will save you from troubleshooting aftewards.
RE: New and already smoking(literally) - Fibber Mcgee - 02-06-2014
I knew not to turn it on before checking capacitors but not tubes. Like I said I'm learning, now I'm going to learn how to check tubes.
RE: New and already smoking(literally) - morzh - 02-06-2014
Well.....if you are serious about getting into this hobby you will need a tube tester. A tube tester should be such that tests for shorts among the other things.
People here will gladly share their experience about various brands and models.