Williams problem--help!!

[sulafool]

OK heres a good one for you smart people:

I have a twin motored Williams PA, 2 cans, no sound or horn. The original reversing card got toasted somehow (Would not reverse) so I replaced it with a QSI DCRU. When switching into reverse it will run a couple seconds then pop the breaker of my RW transformer. Forward runs OK, but still seems to load the xformer more than it should, judging by the hum of the transformer vs its idle state. If I go with more power (KW) it will run both directions but gets the pickup rollers REAL hot--also the frame as it is the heatsink for the DCRU. Only takes a few seconds to be too hot to touch.

1) the DCRU us hooked up correctly

2) if I disconnect one motor (either one) it still happens 

3) if I isolate the motors and apply true DC to them they run fine in either direction, each mtr drawing less than 1/2 amp which is what I'd expect, I think

4) can't blame the RW, it has been overhauled and should easily handle 2 can motors 

5) no shorts to be found, pickups and wiring are fine, all insulators in place

6) no binding from the trucks/axles 

7) I suspect whatever is wrong is what did in the original board (got so hot 2 of the  power transistors de-soldered themselves!) Don't want to cook this one...

This just seems too simple to be so hard; what should I try next?

 thanks, 

[lionelsoni]

Make sure there is no direct electrical connection between the motor wiring and the locomotive frame.  You say that the frame is the heatsink for the "DCRU".  Make sure there is no electrical connection between the parts of the DCRU and the frame.

[otftch]

I'd leave the DCRU hooked up and remove the motor and disconnect the wires from one truck and try it.Disconnect the wires and tape them temporarily. Then try it with the other truck.This should eliminate them.You seem to have access to a DC transformer.Why not hook the engine up as DC and try to run it.This should eliminate evrything but the DCRU.
                                                                                            Ed

[phillyreading]

Here is what I did with a Williams that I wanted to control the direction of, I put an 8 amp bridge rectifier in and deleted the wires to the circuit board, only draw back is that now I have forward only.   Connected the incoming hot wire to one terminal of the bridge rectifier and the ground to the opposite terminal and connected the motor wires to the other two terminal.

Hot to upper left terminal, ground to lower right terminal, motor wires to remaining terminals.

H .  . m

m.  .G

Lee F.

[sulafool]

Thanks for all the suggestions!

Bob, there are no components or wires touching the frame, except for the rectifier (which is supposed to as it needs the heat dissipation).

Ed, I forgot to mention I had already tried disconnecting the pickups (no success). I did just bypass the DCRU and ran it on the track with DC. Worked fine, which then leads one to believe the DCRU is to blame--but what would make it act the same with the original, factory board? Could 2 boards of different design have the same problem and if so what the devil would it be?

Lee, if it were mine I'd do it your way but this unit belongs to a customer and I'm sure he wants the thing to run as originally intended.

BTW, near as I can tell, the unit draws less than 1 amp total when running under DC on the bench. How can the DCRU cause such a huge current draw? (Can't measure it with my puny meter) and why more so in the reverse direction? Also, this is the DCRU-WD made specifically for Williams twin can motors.

AAAARRRRGGHHHHH!! 

[sulafool]

Was able to borrow a decent ammeter. In neutral, the engine draws 7.7 amps! Forward is 8.5, and Reverse is 10.6. I guess that explains why my poor RW can't hack it. Is this normal?

It seems very excessive to me; why does that stupid card draw so much? 

[ChiefEagles]

See if someone here has a Williams "card" they have left from a conversion.   I might have some Lionel ones.

[dwiemer]

That does seem excessive.  With the new meter, what is the draw on each motor?  I would start with a regular overhaul of the engine, clean and lube and it will give you a chance to check all internals.  Since it fryed the original reversing board, I suspect a problem there.  Look for any signs of an open armature, or field coil.  Please post your findings.  I have not worked on the Williams, just trying to apply other experience.

Dennis

[daan]

Was able to borrow a decent ammeter. In neutral, the engine draws 7.7 amps! Forward is 8.5, and Reverse is 10.6. I guess that explains why my poor RW can't hack it. Is this normal?

It seems very excessive to me; why does that stupid card draw so much? 

That's too much. Even 2 amps would be huge for those can motors. I would try to measure the amps of each motor. I think the motors are bad. When a can motor has been overpowered it still runs, but uses a huge amount of power. I had that with a RC car. In that case the motor had a short somewhere in the windings, still would go, but used a huge amount of power.

Since the other direction unit also burnt itself into pieces, I guess the problem is not in the board, but in the motors..

[lionelsoni]

You say, "there are no components or wires touching the frame, except for the rectifier (which is supposed to as it needs the heat dissipation)."  But is there any electrical connection?  Do you read infinite resistance between motor leads and frame with the motors disconnected?  And are you sure that the metal part of the rectifier is intended to have an electrical connection to the frame?  It is possible and not unusual to have a thermal connection without an electrical connection, using for example a mica washer.

I don't know what's in the "DCRU"; but there's probably a bridge rectifier in there somewhere.  When the one side of the input to a bridge rectifier is the frame of the locomotive, the output had better not also be grounded to the frame.

[sulafool]

Thanks Chief!

Dennis, these are DC can motors

Daan, the motors run fine independently or together if DC is applied directly to the brush terminals. Each is < 1/2 amp

Bob, the rectifier is a bridge rectifier, mounted on the bottom of the board as is the original Williams version. The "can" of the rectifier is electrically isolated from its terminals, so there is no grounding due to that touching the frame. It appears to be the same rectifier Williams used, both having a hole thru the center and used to mount the board to the frame. QSI does not mention a mica washer or any other insulation between the bridge and the frame. The card gets its ground via a separate wire connected to the motor cans. If by "motor leads" you mean just the terminals on the motors themselves, then yes resistance is infinite. If you mean the unconnected leads from the card, one is grounded and the other is about 1.5 ohms.

I guess I could try QSI, but it looks like they farmed out their old product support. I'm also thinking of just putting in a good old fashioned mechanical e unit? 

 

 

 

[ADCX Rob]

Is this the DCRU you are using?

I don't see a bridge rectifier for mounting on the board - the DCRU 104/WD.  Is it hidden from view in the above pic?

Rob 

[sulafool]

Rob,

That looks like it...you're right you can't see it in that pic. It's underneath the board, on the right end as the picture is oriented.

[lionelsoni]

It seems like the trouble isn't external to the reversing unit.  But I wonder why you read no resistance between one side of the output to the motors and "ground".  By "ground" do you mean the locomotive frame, connected to the outside rails and, apparently, to the motor cases?  If so, that doesn't seem right at all.

I would have put in an e-unit myself.

[daan]

Is this the DCRU you are using?

I don't see a bridge rectifier for mounting on the board - the DCRU 104/WD.  Is it hidden from view in the above pic?

Rob 

The bridge rectifier is not on this board as one unit, the 4 barrels with the silver line in front of the print are together forming the bridge rectifier.

But, as Lionelsony already did mention, if one or both of the motors connect to ground on any place directly from the power inlets, you will have a hard shortcut between AC (which is on the ground part) and DC, making shortage half of the time. If that is the case, the connection between the ground and the powerlugs on the motor needs to be removed somehow.

A bridge rectifier makes DC out of AC, If the motors have a direct link to ground from one of the sides where DC is added, the continuous + will short with the - part of the sinewave of AC and vice versa. You don't run motors only in that case, but also heat up your entire layout, since it will act as a giant resistor.

[ADCX Rob]

Is this the DCRU you are using?

I don't see a bridge rectifier for mounting on the board - the DCRU 104/WD.  Is it hidden from view in the above pic?

Rob 

The bridge rectifier is not on this board as one unit, the 4 barrels with the silver line in front of the print are together forming the bridge rectifier...

Which is exactly what I saw, and I am wondering if he's trying to run the DCRU on DC from some other bridge rectifier mounted to the floor of the loco instead of track AC.  This couldn't be the case, could it?

Rob

[Anonymous]

Is this the DCRU you are using?

I don't see a bridge rectifier for mounting on the board - the DCRU 104/WD.  Is it hidden from view in the above pic?

Rob 

The bridge rectifier is not on this board as one unit, the 4 barrels with the silver line in front of the print are together forming the bridge rectifier...

Which is exactly what I saw, and I am wondering if he's trying to run the DCRU on DC from some other bridge rectifier mounted to the floor of the loco instead of track AC.  This couldn't be the case, could it?

Rob

I'm wondering if some pictures aren't in order by now... pic of the open engine and the DCRU?

[sulafool]

Let's see if I can post a couple pics:

Here is the installation: 

 

Here is the rectifier; I don't know what the diode farm on top of the board is, but the rectifier on the bottom looks like the original Williams one in picture #3:

 

Williams original, removed from board:

 

here's the other side of it, as you can see it is potted and complete unto itself; I see no reason to believe the QSI one is any different (the discreet diodes on top notwithstanding)

I have tested the Williams rectifier as a standalone component and it seems to work fine. Therefore I believe I will use it in conjuction with a Lionel mech. e-unit and be done with it.

Phooey on all this newfangled electronic junk!