10EE 3C23 tube problems

Larrys Metal Fab · Oct 17, 2021

Well I'm slowly back at trying to figure out what's wrong with my lathe. I have pretty much figured it's the 3c23 tubes. I have ordered a number of them from eBay. When I installed them I get no blue light but I do get what appears to be moisture in the tube when the filaments have been on for a minute or so. Not being a tube guy I don't know what is going on other than the vacuum / argon has escaped over the years. I measured the filament voltage and I get 2.6 volts, so I know I'm getting the proper voltage but I have no idea what else is going on other than just bad tubes. If someone could give me a heads up on what's going on I would really appreciate it because this has been a very frustrating experience for me.

Thank you guys very much
Larry B.

rke[pler · Oct 17, 2021

Let the tubes warm a long time on the first usage if they've been changed, something on the order of 30 minutes would be about right. After that we can start looking at the inputs to the tube itself to make sure that the tubes are getting the right signals to generate the appropriate field. I don't have schematics available but seem to recall that the output of the EL1C is used by the 3C23s, do you have 120V output from there?

Larrys Metal Fab · Oct 18, 2021

waited about an hour and the c323 tubes were not glowing.

Thank you very much for your fast reply. This morning I went out, turned on the lathe and waited about an hour and the c323 tubes were not glowing. The el1c tube was glowing so I know it's working somewhat. I guess the question is that on the schematics there are no voltages shown or points to measure for the voltage. A little later today I will pull the tubes out and make sure they are seated correctly in the sockets and there are connections to the tubes. If you could tell me what that 120 volts is correct and how I could measure that voltage that would be fantastic. I also contacted the guy I bought the tubes from on eBay. This guy I think is a tube guru. He has given me all kinds of information so between the both of you hopefully I can figure this all out. Thank you very much again
Larry

Larrys Metal Fab · Oct 18, 2021

Afternoon [3C23 Update

This afternoon I did a little more trouble shooting and found that from what I can see all the connections are secure. The interesting part is that across one of the 2.5 MFD capacitors I get 18 volts DC and the other one I get 99. Both should be about 54 There is some kind of imbalance going on but I have no clue on what is causing it. In my experience with AC wiring it would either be a loose connection or an open neutral which there is no neutral in this machine. From what I can see all the connections and solder joints are good so there must be something else going on.

Thanks again
Larry

rke[pler · Oct 19, 2021

Between points 73 and A24 you should see 145VAC, same between 73 and A25. That'll check to see if you're getting the right voltage to the 3C23 plates.

If you're talking about the .25MFD caps you should see 54V DC and 39VAC, but that's assuming the right voltage on the supply and the proper grid voltage to the 3C23 plates.

Larrys Metal Fab · Oct 19, 2021

I will check into that

Okay, thank you I will check into that and let you know what I find.

Larrys Metal Fab · Oct 20, 2021

A little bit more checking
I did those measurements and I'm getting between across 73 and a24 and a25 158.5 volts. When I measured across the capacitors again on one capacitor I got 42.5 volts ac and the other one I only got 5.54 AC. I disconnected the capacitors to check them and they both were in range.
This lathe was originally set up for 460 volts 3 phase, being this is my home shop I have 240 volts single phase. I don't use the coolant pump, so I installed a single phase 460/ 230 volt transformer and hooked it up backwards. So at the disconnect I see a voltage of 478. This falls within the 10% voltage rule unless that was not the rule at the time.
I've had this lathe now for about 5 years and it has had its little problems and I was able to troubleshoot it and then fix it.
As I might have mentioned I do not have that much experience with tubes or DC motor control as a whole is knd of embarrassing for being electrician for 50 plus years but where I live there is basically no industry other than wine. Anyway, hopefully you can give me some more information. Thank you very much again. I really appreciate your help.
Larry

rke[pler · Oct 20, 2021

OK, swap the tubes and see if the low voltage follows the tube. If not then the problem is likely the .001MFD cap (working on the assumption that the .25MFD caps are OK and nothing has gone wonky with the wiring), if so then the tube on the low voltage side is likely bad.

None of this is industrial electrical, it's 50's electronics. I was raised at the tail end of the tube era and still forget lots of things. Lots.

The .001MFD caps are the ones on the back of the tube panel next to the tube sockets, below the red thyristors. There's a pic in this post: https://www.practicalmachinist.com/vb/monarch-lathes/10ee-motor-drive-timeline-309433/#post2625572 I recall that they're square mica caps.

Larrys Metal Fab · Oct 21, 2021

This morning I swapped the tubes and there was no difference. Attached is a picture of the tubes in place. You will notice the closest one appears what seems to be frost. I asked the tube guy I got these from and he said it was normal and it was the mercury vapor gas forming. Not sure what he meant but maybe that tube is bad. What do you think? I do have some of those small capacitors so when I get some time I will swap them out. It's just my big fat hands have a hard time manipulating small parts. Being 76 I'm not sure where I am with the tube era but I know it was in there somewhere. When I was a kid I used to love to play with Heath kits and other things like that but had no idea how it all worked. I just put it together and it worked. At least most of the time anyway let me know what you think about that tube. The only capacitors I haven't changed are these little ones and the ones on the armature circuit
Thanks again for all your help
Larry

rke[pler · Oct 22, 2021

Did you check to see if the voltage problem moved with the tube?

Also, is the tube warming up properly? You should be able to see the heaters glowing red/orange, if there's still mercury visible I'd think the tube was not getting warm.

Larrys Metal Fab · Oct 22, 2021

I did switch the tubes and there wasn't any difference. The tubes get hot almost too hot to handle so I know the filaments are getting voltage.
Today I decided to change all the capacitors, but I'm having a problem. The problem is I don't know what kind of wire they used, but the solder does not wet in very well. Do you know if they put some kind of coating on The wire? Am I supposed to strip the wire then dip the end in acid? I don't think I've ever had this problem before but I'm not having much fun with it. I think I might just replace some of the wire with copper wire either 16 or 18 gauge. I have no problem with new copper wire or old if it's just cleaned up a little.
After I finally get the capacitors in, I'll test it again, but it might not be until Sunday before I get to it.
I thought the tube had moisture in it but now from what you said it's Mercury. I can't remember checking the tubes when they were exchanged in different sockets to see if the Mercury was present in same tube socket

Thank you again
Larry

rke[pler · Oct 23, 2021

Are you sure you're not mistaking getter for mercury? Here are mine, undisturbed for a few years.

On seeing them glow - they won't until the start button is pressed and the field failure relay latches. The voltage measurements likely depend on that as well. The glow won't be as pronounced if the speed is maximum, you want the speed control in the lower half for any of the field checks.

doug8cat · Oct 23, 2021

I think I have a handle on tube problem, My other question is regrauding the capacitors. Old caps become leaky over time especially, waxies and old or por-quality caps. They begin to leaky, not electrolyte (is possible). They become electrically leaky and thus become resistors. So take a look at what you have and if they have ever been changed. I you find wax or lod style caps, chances are you should just re-cap the entire thing.

Larrys Metal Fab · Oct 23, 2021

The field failure relay does not latch. That is the main problem I am having. I have read through the troubleshooting part of the manual a number of times, and tested the tubes other than the 3c23. Monarch makes a machine but in this case their documentation stinks.
When I press the start button the contactor closes but immediately opens when I release it. Checking out your tube picture I see the darkness on the top. From what I understand the getter is put there to make sure all the vacuum is sucked out of the tube. If you check out my picture you see that what I call moisture is on the bottom part.
As far as the capacitors are concerned I am in the process of changing every one of them. Like I stated in my last message I'm having a hard time soldering those new capacitors to the old wiring. There must be some kind of coding or something on that wire that is not allowing the solder to flow in correctly. I might try separating the strands, dipping them in something like acid that will remove whatever on them and then try soldering again.

Briney Eye · Oct 23, 2021

Mercury thyratrons are not vacuum tubes. The ionized mercury in the tube enables them to conduct more current than a vacuum tube. Some plating on the inside of the glass is normal when they're heating up and vaporizing the mercury. They will tend to clear up as they heat and after power is applied. They must have a minute or more of preheat to vaporize the mercury before applying power.

doug8cat · Oct 24, 2021

wire, oxidation and Gremlins

As this post progreses I hear more things that suggest to me that your looking at restoration here. You mention that soldering is not going well, this would isuggest to me that the green death or oxidation has moved up the wire and is now under the insulation. I am glad to hear you are re-capping, bear in mind that even non elctrolylitic capacitors have a foil side, although in this application I am not sure it matters. After all it not a radio transmitter or audio amplifier. Due you have a vacuume tube tester? I was able to get one when they were basically giving them away in the mid 80s (along with a lot other folks.).

doug8cat · Oct 24, 2021

I looked up the data shhet for the 3c23 tube, just cause.
You are probably already aware that the grid voltage (First # "3" in this case is your grid voltage AC or DC.).
Data sheet indicates 2.5 +/- 0.125 volts
Also indicates the following:
Avoid cold starts, the heat shielded oxide coated filament should be energized before the anode voltage is applied..
Hope some of this helps you out.

rke[pler · Oct 24, 2021

doug8cat said:
I looked up the data shhet for the 3c23 tube, just cause.
You are probably already aware that the grid voltage (First # "3" in this case is your grid voltage AC or DC.).
Data sheet indicates 2.5 +/- 0.125 volts
Also indicates the following:
Avoid cold starts, the heat shielded oxide coated filament should be energized before the anode voltage is applied..
Hope some of this helps you out.

I think you're confusing grid with filament. Grid voltage should be more like 20-30V (can be 500), filament is 2.5V.

As for cold starts, the drive has a built-in 60 second timer before you can try and activate the field current supplied by the 3C23s.

rke[pler · Oct 24, 2021

Larrys Metal Fab said:
The field failure relay does not latch. That is the main problem I am having. I have read through the troubleshooting part of the manual a number of times, and tested the tubes other than the 3c23. Monarch makes a machine but in this case their documentation stinks.
When I press the start button the contactor closes but immediately opens when I release it.

This is after waiting for the warm up, right? Have you looked at the top of the tubes when you have the start button pressed in?

Larrys Metal Fab · Oct 27, 2021

Update
Well the rain has ceased here a little in Northern California so I had a chance to go out and do a little more work on the 10EE. Since my last post I changed all the capacitors. Today I did some fooling around and found that the start button would not hold in the contactor. But I did find out that if I shorted across the field failure relay I would get one of the 3c23 tubes to glow blue but the other one didn't. The one that did work if you were looking at the tombstone it would be the one on the right. I wanted to see if the relay coil was any good so I checked across it and got a little over 8 ohms. I did check with a voltmeter to see if there was any voltage to ground on either one of those terminals, and I did but I forgot what it it was and I forgot what terminal it was, so I know I got at least half of the circuit working but the other side is what I'm going to find out. Well I guess that's the update for today. I totally appreciate everybody putting in their suggestions.

Thank you
Larry

PS I would love to rewire this machine but I have so much work for it that is going to be a while. While this one's down I'm using an 11 inch Sheldon lathe, but that's kind of like comparing a Volkswagen to a Duesenberg

10EE 3C23 tube problems

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