10EE Round Dial - fwd/rev S-D contactor

[Skywalker]

I’ve finally gotten the 10EE powered up and spinning via VFD. Everything works great except the forward rotation. Reverse works perfectly. I inspected the drum switch, cleaned it, and tried switching terminals. Switch checks out. Following the schematics on my machine it lead me to the Struthers-Dunn RPXA595A contactors for forward and reverse. One contact point looks pretty cooked. It seems replacements don’t exist anymore. I wouldn’t mind switching these to gain forward and lose reverse, until a solution could be made. Is there an easy way to address this before I pull everything out of the box??
Any advice would be appreciated.

 

[Skywalker]

Update: I was correct in the fact that only one set of contactors was working. But now, I have no DC power at all. Reverse the switch, and contactors pull in, but no rotation .Forward nothing at all.

 

[rakort]

Well if the one contactor pulls in it means you have exciter voltage which is good.

You can reverse a DC motor by flipping the F1 and F2 wires at which point the reverse contactor will make you motor run forward.

The forward contactor is always way more beat up than the reverse contactor.

Someone may have a spare control panel from a drive conversion you can use for parts.

Sounds like the FWD contactor coil is burnt out. You can check the resistance of the coil and see if it is open (burnt out).

Now as to why it won't run in reverse now? I'm not sure but probably a bad / dirty contactor contact, stuck brush, stuck relay, burnt out resistor....hard saying after these things have been sitting.

Somewhere around here I thought Cal had made a troubleshooting guide for the MG setup, but I can't find it now.

Don't be poking around in the panel with the MG running. The DC voltages are deadly. Only make meter connections when the MG is off.

 

[Skywalker]

Well if the one contactor pulls in it means you have exciter voltage which is good.

You can reverse a DC motor by flipping the F1 and F2 wires at which point the reverse contactor will make you motor run forward.

The forward contactor is always way more beat up than the reverse contactor.

Someone may have a spare control panel from a drive conversion you can use for parts.

Sounds like the FWD contactor coil is burnt out. You can check the resistance of the coil and see if it is open (burnt out).

Now as to why it won't run in reverse now? I'm not sure but probably a bad / dirty contactor contact, stuck brush, stuck relay, burnt out resistor....hard saying after these things have been sitting.


Somewhere around here I thought Cal had made a troubleshooting guide for the MG setup, but I can't find it now.

Don't be poking around in the panel with the MG running. The DC voltages are deadly. Only make meter connections when the MG is off.

THANK YOU!!!
I thought there was a way to swap the DC direction...easy enough.
YES, its strange, it was up and running for several nights of testing,
as I was going thru the steps tracking down the forward issue.
Now, I have nothing. As I mentioned above...contactor pulls in for reverse. Im sure they get way less use than forward. The machine set for decades, so i expect some problems.
A troubleshooting guide would be excellent.
THANKS for the warning with the DC voltage. Im a mechanic by trade,and know enough about electric to respect it and fear it. LOL
-Luke

 

[Skywalker]

I just put a meter on all of the contractor coils. I don’t show any open circuits from a bad coil.
Not what I expected.
Luke

 

[Skywalker]

I found an issue. It looks like a brush hung up, sucked into the spring clip and frayed the lead, which arced out.
see the damage on the wire too behind the brush holder. Not Good.
Luke

 

[rakort]

Well the coils should be ok then as along as the F/R switch was in the off position such that you didn't pickup resistance through the rest of the circuitry. This then suggests there may be a bad wire or such. The next thing I would check is if the coil in question is being presented DC voltage when the F/R switch is in the respective position. There could also be other things going on like the mechanical interlock that prevents both contactors from pulling in at the same time. It is a lever on a pivot between the two contactors. Maybe that is hanging up preventing the fwd contactor from pulling in?

I just put a meter on all of the contractor coils. I don’t show any open circuits from a bad coil.
Not what I expected.
Luke

 

[rakort]

View attachment 337468
I found an issue. It looks like a brush hung up, sucked into the spring clip and frayed the lead, which arced out.
see the damage on the wire too behind the brush holder. Not Good.
Luke

I see the damage. Not sure what to think about that. Trying to make sense of your assessment. Is the braided lead that connects to the brush now disconnected from the brush?

 

[Skywalker]

Partially disconnected. It was barely attached.
I’ve removed it now, and checking with Monarch for replacements.

 

[rakort]

I studied the picture some more and I thought the brush wire looked disconnected, but you are saying no. That doesn't explain the arching on the wires for the stator coils.

I'd definitely look at replacing the brushes and also taking some resistance readings on the DC motor to verify something isn't shorted.

 

[Skywalker]

OK,
The mystery deepens...
See attached picture. I am clearly missing an element in the control box.
When I got a work light and started disassembling everything, I noticed 4 brass nuts
in the bottom of the box. This is when I noticed an empty space and four shiny threads sticking out.
(Far upper right of the panel)
ANY ideas??

 

[Skywalker]

I pulled the entire DC motor out, so I could better inspect it,
and make needed repairs.
Here is the 4 wire connection, labeled F1 F2 A1 A2
assuming field and armature respectively.
To correctly check resistance across these, what is the proper procedure?
-Luke

 

[Skywalker]

Missing resistors!!!!
Found a picture and some info. That explains a bit.
-Luke

 

[rakort]

OK,
The mystery deepens...
See attached picture. I am clearly missing an element in the control box.
When I got a work light and started disassembling everything, I noticed 4 brass nuts
in the bottom of the box. This is when I noticed an empty space and four shiny threads sticking out.
(Far upper right of the panel)
ANY ideas??
View attachment 337543

Yes I have an idea. The Dynamic Braking Relay has been removed and is missing. I'd have to research the wiring diagram and try to "clue" together why you had it running in reverse and not forward (for likely other reasons) for a short period of time.

 

[rakort]

I pulled the entire DC motor out, so I could better inspect it,
and make needed repairs.
Here is the 4 wire connection, labeled F1 F2 A1 A2
assuming field and armature respectively.
To correctly check resistance across these, what is the proper procedure?
-Luke
View attachment 337544

All the info is here.....someplace, unfortunately I have a hard time retrieving it.

 

[rakort]

Missing resistors!!!!
Found a picture and some info. That explains a bit.
-Luke

No Luke, you are not missing the resistors. You are missing the entire relay known as the dynamic braking (DB) relay. That relay mounts on top of those 4 studs. Cal has a better name for it, IIRC, based on what it actually does. I think you were looking at a picture of a different iteration of the control panel which has several ceramic wound resistors located in that corner of the control panel.

There are several iterations of this panel.

Here is a picture of a panel that came out of my 1940's ish piggy back MG setup. I circled your missing relay and a difference regarding what appears to be a capacitor that your panel has and mine doesn't




Your missing relay is available "ish" in surplus (ebay radwell, etc), but will require some research and reverse engineering to determine the appropriate coil voltage.

Here are examples of available surplus or used relays that fit the bill (if the coil voltage is right or appropriate compensating resistors).

 

[rakort]

Let me correct myself. I believe the relays I shared/proposed are not the correct style for your panel, but regardless it still appears you are missing a relay up there yonder in that corner of the control panel.

 

[Skywalker]

I thought perhaps the missing components could have something to do with dynamic braking. Could this be the scenario——
Without the braking relay, switching back and forth from forward to reverse could be dangerous to other components?? That’s why it originally worked in reverse, then completely failed after secondary damage?
It still doesn’t explain the original issue.
I’m trying to soak up knowledge here, but there is so much to sift thru.
I do appreciate the help.

 

[Skywalker]

I have my factory wiring schematic. Let me see if it calls out for a specific brake relay.

 

[Skywalker]

Now questioning the AP relay as well.
The more I learn, the less I know. Lol.
I did find a spec on the DB relay.
Now to check availability.