Williams SD-45 reverse board hot?

I am not a fan of the boards with the transistors for motor current switching in large, heavy locomotives. I prefer the boards with the relays. Far less heat. I haven't seen boards with heatsinks on the power transistors. Mine are just grouped together with the mount tabs unattached to anything. Did you check the motors for binding? I would test them outside of the chassis to see how they run without any load and listen for a noisy one and look to see if one is running slow. That could cause excessive current draw across the output transistors and cause heat issues. 130 degrees is warm, but not crazy for a transistor under that kind of load. They can get way hotter and will usually be heatsinked in those applications. I would try to reposition the board to get more clearance between the board and the shell. If the shell isn't discolored or damaged due to heat, I wouldn't think it is an issue. Especially if it is obviously used. Chances are if is used then it has been running fine just as it is. If it is bothering you, I recommend replacing it with the board with relays.

Thanks! It doesn’t show any signs of heat damage on the shell, but it didn’t have signs of heavy use either. I’m assuming it was run before, someone cared enough about how it looked to add frosted “glass” to the cab windows.

There’s definitely no binding in the trucks. I cleaned and lubed all the gears shortly after it was delivered (of course I gave it a quick run straight out of the box just to make sure it wasn’t DOA). It seems to run just fine!

Here’s a shot of the board... looks like a couple relays to me... there’s a transistor on the bottom of the heat sink in the middle, and that’s what’s getting “hot”. A bit longer running showed 140*F on the heat sink. No sign of heat damage on the inside of the shell, or any components on the board. Maybe it’s fine and I’m just being paranoid...

Okay. I see what you have now. None of my Williams locos have that board or those weights. I am not familiar with that board, so I really can't tell you if you have a problem for certain. I can say that the heatsink is going to get quite warm under normal usage. In my opinion, it is probably nothing to be concerned about. It seems to me if there were an issue, then there would be some heat damage of some sort.

After further examination, I see there are wires in direct contact with the heatsink. If there were excessive heat coming from the heatsink you would see discoloration or perhaps some melting of the insulation on those wires. These are not high grade wires and that insulation is not rated like commercial or mil-spec wiring and would be more susceptible to heat damage. I would reposition that harness to get it off of the heatsink, regardless of heat generated by the heatsink because wires chafing on the heatsink could cause problems later.

I’ll definitely clean up the wire routing, a short would definitely make things unhappy...

I think I’m gonna run it, and just keep an eye on things for a while...

Thank you very much for your input!

I think I inadvertently fixed the heat issue! I re-configured the headlights and removed the cab light.

I’m pretty sure the cab light was not original (different color wires, not attached to the board the way the other wires were, different style bulb, held to the roof with electrical tape...) and I think it was somehow overloading the transistor. I’ve been running the “long” train for a while now and the roof is only slightly warm to the touch over the reverse board... Yay!

I have repaired a lot of Williams engines (some SD-45) for the San Diego 3-Railers and I have never seen that reverse board configuration, or the round weights.  I wonder if that is a custom board.

The board definitely says “Williams” on it. I did read somewhere that the earlier SD-45’s didn’t have traction tires, and had the weights. Apparently when they started using traction tires they no longer had the weights. 

It's just older Williams, One of my Williams F7's has the weights in the powered unit and the older reverse board.

Jeff

These are the Williams E-units that I see the most.  They have the white plastic JST connectors.  I have seen some older E-units that have wires soldered directly to the PC board.  But still never like the picture you posted.  Yours must be an earlier version.  Probably made after the Civil War but before World War I.  (Ha, ha. Just kidding!)

Anyway, these E-units mainly operate with big rectifiers and relays.  And I found that with heavy pulling action, these rectifiers do start "going bad".  And by "going bad" I mean they just get slow.  On a good E-unit, if I put 12v AC on the input, I would get 11.5v DC on both the forward and reverse rectifiers.  But if an engine has been pulling heavy loads (long trains and track cleaning cars at out club), for the same 12v AC input I would get only 9v DC on the forward rectifier, and maybe 11v on the reverse rectifier (because nobody likes to run in reverse).

My solution to this is to replace the rectifier.  I have a supply of these rectifiers that I bought at Allied Electronics (I think) and I just un-solder the forward rectifier and replace it.

He has a very old Williams board, small wonder it might be getting warm.  I don't know that the newer ones run hot at all.

I have seen some heat discoloring around the leads of the rectifiers, but that's about it.

@gunrunnerjohn posted:

He has a very old Williams board, small wonder it might be getting warm.  I don't know that the newer ones run hot at all.

Just curious, how old is “very old”?

It’s running much cooler since I removed the cab light that a previous owner installed. Not sure what they tied it into but the board apparently wasn’t happy with it...

I don't know the exact age, but that's one of the really old ones before they made more professional looking boards.