A Question About Lionel Smoke Regulators

Leave as is, the compound won't help any with the rubber insulator.

I believe that is a thermal pad, not a rubber insulator.  I suspect it is a product by a company called Bergquist.  

Lou N

 Chuck and Lou....Thank You for your replies.  I was not aware Lou of the use of pads and their relationship to the paste.  Interesting.

Did some research and it seems that the pads are okay but not as good as paste.  Some also claim the pads need frequent replacement.  I suppose that would depend on actual use in terms of heat.

I suspect this was a cheaper and cleaner way for Lionel to manage this issue.

It would seem that the pad is okay but if one choose to remove and replace with the paste,  it  might be something to think about while the hood was off. ??

I replaced the resistor from 6 OHM to 8 OHM as recommended. 

Just looking to take as much stress off the Regulator as possible......to prevent it's demise from overheating.

I've replaced them and they are are a pain.

Dave

Be aware that the silicone pad also usually acts as an electrical insulator to isolate the tab of a heat generating device from ground, yet provide good heat transfer. If  electrical insulation was not needed, they would have bolted it straight to the frame, perhaps using paste. So I would not change it unless you are sure it is not also an insulator. My info shows that paste results in a thermal resistance of about 0.8 degree C/watt whereas a dry silicon pad is rated at 1.5. Lower values are better in this instance. The numbers mean that for every watt of heat transferred there will be 0.8 and 1.5 degee C of temp difference respectively.

Rod

Silly question... If the metal Phillips head screw in the picture is in contact with the regulator and screwed INTO the metal frame; have we not in essence connected a portion of the regulator TO the frame?  Or am I missing something here?

Thanks Rod and Dave for your replies.

Any other Regulators I have replaced were directly to frame with paste.  This is the first I've seen with the pad.  From the pics you can see that the screw does bolt the Regulator to frame.  I don't think it requires isolation....unless Lionel changed something.....?   The metal part on the bottom of the heat zinc would contact the frame if paste were used.

There is a lot of heat generated to this Regulator.  Lionel used a 6 OHM resistor only to find out it was too much for the Regulator and consequently was prematurely taking them out.  They recommended that owners change the resistor to 8 OHM to lighten the load on the Regulator.

So I guess we are back at the beginning.....would the introduction of paste while I have it apart be a better choice or does it matter?

Thank You

Dave Garman posted:

Silly question... If the metal Phillips head screw in the picture is in contact with the regulator and screwed INTO the metal frame; have we not in essence connected a portion of the regulator TO the frame?  Or am I missing something here?

The fact that it screws directly into metal in this case certainly means it is not electrically insulated. Which begs the question, why didn't Lionel just use paste? I would say you could improve heat transfer by switching to paste, just to be safe. A lot has to do with the mass of metal which the heat is being transferred to, which looks to be substantial in this case. But let's hear what others have to say on the subject! 

Rod

The regulator is insulated from the frame. The screw is going through the plastic part of the case, and the metal side is insulated by the pad. Don't remove and use grease.

Stop the presses! Is that black surface on the top side of the reg just under the screw head, is that a plastic material? If so, that's your insulation and it carries thru the screw hole as I see it. This would mean that the silicone pad is definitely needed for electrical insulation. Am I seeing this correctly?

Rod

Okay Guys......pics to follow.

The Regulators I have seen to date are all fastened to the frame with a screw and paste.

As mentioned, this is the first I have seen with the pad.  I really can't tell if the heat zinc is isolated or not or should be.  It seems that the screw may be surrounded by plastic.

You will see in the pics....a new Regulator from Lionel.....break open the shrink wrap.....raise the heat zinc and fasten it to the frame.  No screw or pad included.

Chuck....have you seen the Regulator attached both ways?  Is it possible that it was never suppose to be attached directly to frame and this may have been the issue all along with their premature demise?

Thank You

How much of a load it runs determines if it is heat sinked to the frame or kept in heat shrink wrapping. The regulators that are bolted to the frame directly are all in-cased in plastic, or whatever that material is. They have no metal back, and can only carry a minimal load. If you are adventurous enough, you can remove the regulator and mount to the frame with a insulator piece for better heat dissipation. Heat sink grease is usually used with Mica insulators.

Thanks Chuck

So to recap so I fully understand. 

In the pic of the new Regulator I opened.....since it has a metal back.  I could mount it to the frame but use a PAD...not Paste?  Because is was to be insulated from the frame.

This would be a better option for heat distribution than leaving it wrapped up in shrink wrap?

If I encounter a heat zinc that appears to be all plastic with no apparent metal back.....paste can be used to fasten to the frame?

Would this be a better choice on this one as opposed to leaving it in the shrink wrap?

Appreciate all the help Gentlemen.

Dave

The center pin (main terminal) of that triac is connected to the metallic heatsink surface on the case.  You most CERTAINLY have to insulate that from the frame or it will most certainly release the magic smoke!  I can't imagine you've ever seen one of these bolted directly to the locomotive frame that was still working.

Yes, that is correct Dave. When Lionel first released their scale NKP 2-8-4 around 2000-2002 They had a problem with the smoke units shutting down after a couple of minutes. They sent a memo back then to service stations to remove the shrink wrapping and mount and insulate the power regulator to the loco frame. This took care of the thermal shutdown.The smoke units worked fine after that.

Chuck Sartor posted:

Yes, that is correct Dave. When Lionel first released their scale NKP 2-8-4 around 2000-2002 They had a problem with the smoke units shutting down after a couple of minutes. They sent a memo back then to service stations to remove the shrink wrapping and mount and insulate the power regulator to the loco frame. This took care of the thermal shutdown.The smoke units worked fine after that.

And then they went right back to not heat-sinking the triac and the regulators fail regularly!  You have to wonder what they were thinking!  Feeding track power into that little triac and then feeding an 8 ohm resistor just begs for excessive heat! 

Also remember that these types of device can come in various forms.  Some are full metal tab, some are partial plastic coated, and others are fully coated depending on application.  So as Chuck and John have said you must use the insulator pad.  Look at your typical MTH PS-1 setup.  They chose full metal tab devices, but have a nylon insert for screw insulation and use paste and mica for tab insulation.  Many way to skin cat, but most of these devices need an insulator.  G

Chuck, John and GGG.....Thank you for your replies and help with this issue.

Leaves me to wonder.....

How long would it take to cook the Regulator if it was mounted without insulation.  Is it a quick or slow process?

Dave

Soo Line posted:

Leaves me to wonder.....

How long would it take to cook the Regulator if it was mounted without insulation.  Is it a quick or slow process?

If it actually is making contact with the frame, it will be instant.  However, I've seen parts mounted without the proper insulation and just the thermal compound insulated them, but that could fail at any time.

Quickly, cause that is shorting out the regulator.