Is this a burnt vacuum tube? Bridgeport Servo ecf series 3109

[AdamPrince2]

I have a table servo for a bridgeport knee mill. I plugged it in and the forward and reverse lever with the rheostat did not work. However, upon pressing the rapid transverse button it did move. Then some white smoke came out so I stopped. Does the vacuum tube look burnt out?

 

[Rollerman]

View attachment 385107
I have a table servo for a bridgeport knee mill. I plugged it in and the forward and reverse lever with the rheostat did not work. However, upon pressing the rapid transverse button it did move. Then some white smoke came out so I stopped. Does the vacuum tube look burnt out?

There is no vacuum tube in the servo control.

 

[Milland]

There is no vacuum tube in the servo control.

There does seem to be a glass tube just above the resistor at the bottom left. But it's not a "traditional" vacuum tube, perhaps it's a relay/switch of some form?

 

[technocrat]

There does seem to be a glass tube just above the resistor at the bottom left. But it's not a "traditional" vacuum tube, perhaps it's a relay/switch of some form?

could well be a neon light, that was my guess but the picture is not good enough to tell. It's unlikely to be a mercury switch unless the unit tilts somehow and it is using microswitches as the switch technology. It looks like the wiring smoked, probably a short to ground.

 

[technocrat]

could well be a neon light, that was my guess but the picture is not good enough to tell. It's unlikely to be a mercury switch unless the unit tilts somehow and it is using microswitches as the switch technology. It looks like the wiring smoked, probably a short to ground. It is a fairly basic scr/triac speed control, it should not be hard for an electronics person to fault find, but parts may be difficult to get.

 

[EmGo]

It's unlikely to be a mercury switch unless the unit tilts somehow

2012 OSHA requirement, safety shutoff in case of 2.5 richter earthquake or larger

 

[EPAIII]

I have seen a lot of old electronics, but it is really hard to tell what that is from the photo, which is not very sharp. There were some tubes that had wire leads instead of a socket mount and it could be one of them. A big clue would be the number of wires going into that glass envelope. If it is just two, then it is certainly not a tube. Three wires would be a bare minimum for that. But if it has 3, 4, 5, or more wires, then it probably is a tube.

Also can you see anything inside the glass? Relays have contacts that move. And a coil to move them. Tubes usually have a central heater element, possibly a cathode that surrounds that heater, and at least a plate that surrounds everything else. The plate is usually shaped like a tube that's around 3/4s of the tube's diameter and about 3/4s of the inside length.

From the looks of that thing, I would chuck it in the trash before it burns my shop down and build a new control from scratch. If it just controls table movement, it can't be very hard to duplicate.

 

[jim rozen]

Glass doesn't burn. If that was a tube, and if something smoked, it wasn't the tube. Try cleaning all the spooge off the board and photograph again.

 

[Joe Gwinn]

I very much doubt that there is a vacuum tube in there, and as others have said, it would not emit smoke if it burnt out. But the photo is pretty much useless. A new photo of the cleaned unit taken with two lights flanking the camera, so one can see deep into the corners without shadows, would help. Also, the more light, the better photos the phone or camera will take.

For the record, I've had good experiences with Servo's low-cost (~ $400) replacement for the traditional Servo unit that is probably what's on that Bridgeport.

 

[Larry Dickman]

Could be the trenule pipe. Check your differential girdle springs.

 

[AdamPrince2]

It just has two wires. Looks like cutting oil entered it. I will clean the board and desolder the light and check for continuity.

I have seen a lot of old electronics, but it is really hard to tell what that is from the photo, which is not very sharp. There were some tubes that had wire leads instead of a socket mount and it could be one of them. A big clue would be the number of wires going into that glass envelope. If it is just two, then it is certainly not a tube. Three wires would be a bare minimum for that. But if it has 3, 4, 5, or more wires, then it probably is a tube.

Also can you see anything inside the glass? Relays have contacts that move. And a coil to move them. Tubes usually have a central heater element, possibly a cathode that surrounds that heater, and at least a plate that surrounds everything else. The plate is usually shaped like a tube that's around 3/4s of the tube's diameter and about 3/4s of the inside length.

From the looks of that thing, I would chuck it in the trash before it burns my shop down and build a new control from scratch. If it just controls table movement, it can't be very hard to duplicate.

 

[EPAIII]

No, glass does not burn. What does happen with electronic elements in a vacuum, inside a glass envelope is the metal can be driven off the surface of one or more of those elements and then deposit itself on the inside of the glass. So the glass can become opaque.

Glass doesn't burn. If that was a tube, and if something smoked, it wasn't the tube. Try cleaning all the spooge off the board and photograph again.

 

[EPAIII]

Just two wires means it is not a tube. Possibly a neon lamp. And the most likely purpose for such a lamp would be just a Power On indicator. Can it be seen from the outside when the covers are in place? That would make it almost certainly a Power On light.

If it is a Power On indicator, it has nothing to do with the operation of the circuit and can be ignored. Your trouble will be elsewhere. You could start with capacitors: they are a frequent offender. In something that old I would replace ALL of them just on general principles. That one technique has repaired many old electric and electronic items and saved a lot of time with actual troubleshooting.

Do you have or can you get a schematic diagram? That would be a big help if replacing the capacitors does not help.

It just has two wires. Looks like cutting oil entered it. I will clean the board and desolder the light and check for continuity.

 

[Lewie]

It sure is interesting to see the electronic answers by machinists. :-)
lewie (retired electronics engineer) :-)

 

[Bill D]

Could be an overload. Similar to a fuse but it resets automatically. Maybe a diode?
Bill D

 

[jim rozen]

"What does happen with electronic elements in a vacuum, inside a glass envelope is the metal can be driven off the surface of one or more of those elements and then deposit itself on the inside of the glass. So the glass can become opaque."

Sub-miniature tubes like that are always opaque (silvered) as they have a full getter across the entire envelope.

 

[DDoug]

It sure is interesting to see the electronic answers by machinists. :-)
lewie (retired electronics engineer) :-)

..and your helpful post is where ?

 

[rons]

Lift up the wires on the right side of the bulb and take a picture.

 

[JST]

Since there is a nice looking device that is in the upper right, which appears to be a triac or SCR, there will almost certainly be no tubes anywhere in that.

The nasty-looking item at bottom left is almost certainly a neon bulb. They were sometimes used in place of a "diac" in fairly old-school drives.

The diac (or the bulb) does not conduct until a certain voltage is across it. That is used with other components to set the firing point for the SCR.

I have no idea what is wrong with the drive, but the neon tube is a possible culprit. It looks as if it had too much current through it, or it is just old, since the electrode metal appears to have been evaporated and deposited on the inside of the glass.

There are very few components in that, and none of them other than the bulb are obviously showing any issues. The control potentiometer should be looked at, since it is also in the circuit with the neon bulb and the resistor and capacitor at the bottom.

Used in that way, the neon bulb is actually worked fairly hard. To trigger the SCR takes a pulse of reasonably high current, considerably more than a neon bulb normally would be carrying. That could account for the appearance.

 

[jim rozen]

Good call on the NE2 - was unaware they sub'd for diacs. Still does not explain the white smoke though. Any other components under the board?