Monarch 10EE Speed control problem HELP!!!!

I'm new to this forum and would appreciate any assistance with a speed problem on a 10EE. This machine was produced 8/61 and has the three tube thyratron DC drive setup. The machine runs fine in back gear up to 1000rpm.
In Open belt setting, it will only run as low as 1600 rpm and runs up to 4400 rpm using a digital tach. It won't run 1000-1600
rpm range for reasons unknown. The first C16J
tube intermittently energizes when the speed control is reduced to minimum in open belt.
There is also a knocking sound at about 1600-1800 rpm and this goes away as rpms are inceased. The first C16j tube energizes steadily until 2000 prm when the second tube comes in and energizes fine.
To complicate matters, the machine was sabotaged at its former location by a laid off employee prior to his departure. Most of the damage seems to be corrected now.
I'd deeply appreciate any advice you all can give me to "rectify" this problem.
Thanks!!!!!

That's a goodie.......no telling what got done to it.

But, when it won't run slow, it sounds like a field problem, unless the speed control flat won't work.

The knocking sound is likely the banging of gears etc as the torque varies when the tube intermittently energizes.

I have nada for schematics on a three-tube machine, but the intermittent tube operation sounds way wrong. Something is not correct, likely a connection, possibly parts.

Anything from bad connections, busted wire that the guy didn't quite get cut at first or bad control pot on up could cause it.

You need a schematic, and then need to go through and check things to see if they match. Problem could be due to original damage, or possibly to wrong repairs, especially if a bunch of wires were cut, etc.

I've got a copy of the schematic for the 3 tube 10EE lathe posted on the following web site:
Members.aol.com:/bodgit2/myhomepage/10ee1 and
" " " /10ee2.
These two pages can open with adobe Acrobat only and are .pdf files so the detail is excellent .
Print them and paste them together for the complete schematic.
I'd appreciate any helpful advice. The machine is partially dismantled at present. I haven't had an opportunity to do any more work on it yet.

I can't get there from here....sure the URL is OK?

This schematic will load immediately if you have abobe acrobat. Please email me if anyone wants a copy sent by email. [email protected]

Better url: http://members.aol.com:/bodgit2/myhomepage - that'll get you to the base directory from which you can load the pdfs.

Does anyone know of a good way to test the C16J thyratron tubes? It seems like a real problem and an expensive one to sort out. It seems like many others have this issue.
Steve

Most tubes test best in-circuit by their operation (or failure to operate).

In the case of that bad tube that was stuck on in the other post, if he had given voltage readings as a couple folks suggested, the problem would have been immediately clearer.

In your case, the sabotage is a better starting point than a guess at a possible tube failure.

Again, voltage readings are the item needed. NOBODY can be sure of suggesting the right solution without diagnostic tests.
Naturally, the symptom you mentioned DOES sound similar, and it could be the same or similar problem, or not.

Your schematic is very clear (and the circuit is a LOT simpler than the all-tube version). There is very good voltage data available at top left.
My suggestion would be to go through the measurements indicated and post the results.

If I were on the spot, that's the first thing I would do (after a general look-over), since you can't see electrons flowing without a meter.

There appears to be light at the end of the tunnel!!!! After following up all of the helpful suggestions by the generous members of the 10EE bulletin board, it appears the problem is the 5 hp dc motor. We substituted another old 10ee motor from a friend's machine and it worked perfect. The motor's at a good local motor shop now for analysis and repair. We think it's a bad armature. I'll post the final results of this job soon so that maybe it'll be useful for someone else.
Thanks to you all for your advice and help!!!

Here's the rundown from the motor shop. Bad bearings, very dirty motor and irregular comutator that caused the brushes to bounce at the lower speeds resulting in the C16j tube intermittently energizing at lower rpm's. They will clean the motor, turn the comutator down, replace bearings and brushes. They fortunately don't have to rewind it. The work should be done in a few days and then it wil be reinstalled. Hopefully that will be the end of this saga for a while!

How much did it cost to do that job on your motor? and Who did it?
Thanks.