How much to replace modern conventional circuit board?

Modern conventional what?

It's easier to find parts if you enter the Product number into Lionel's parts search.

I searched Lionel 4115 and found this product number: 6-31945

And this description for a conventional Steam locomotive on their product site. http://www.lionel.com/products...kshrie-4115-6-31945/

Is this the one you have?

If so, below is a link to it's parts page.

https://www.lionelsupport.com/...2-8-4-Berkshrie-4115

The original board is no longer made, but this alternate E-Unit shows as available ($24 plus shipping):

https://www.lionelsupport.com/...C-MTR-ALT-6100107100

Thank you SteveH,

I had found the parts page and that the e-unit was unavailable, but didn’t catch the alternate part number listed. I am used to working out of the postwar manual, haven’t done anything with newer Lionel.

Appreciate the help as always.

Craig

The hot tip of the day is replace the TIP31 and TIP32 transistors on that board with the higher rated TIP41 and TIP42.

Again, here is what happens. User runs train for a while the factory TIP31 and 32s begin to heat up. The train slows down, so the user turns up the power. Eventually the transistors just go up in smoke. Replacing with a new board and not changing the situation results in the same failure.

A properly rebuilt upgraded E-unit is more likely to last than a brand new board using the same 30 series transistors.

Also, I buy in bulk the TIP41 and TIP42 from Amazon as well as the KSP13 or MPSA13 small TO92 transistors.

Replacing all 6 transistors is my typical repair/upgrade on one that has failed. 2 each 41s, 2 each 42s, 2 KSP13 transistors. If a brand new board or good working board before upgrade, then you can just replace the 41s and 42s.

Per your original board, you can see the numbers on them. They fail in pairs because that is how they were conducting and thus heating up during the failure (31 and 32 pair) and that may also burn out the small KSP13 or MPAS13 that drives the pair of larger transistors.

Again, factory, these boards come with the TIP31 and TIP32 which are rated for half the current the 40 series says.

@Vernon Barry  That all sounds like good advice.  Another thing to keep in mind (for others who may be unaware), is that the current ratings for TO220 output transistors assume adequate heat sinking.  Since the factory installations had none, adding something that will help dissipate the heat better from the output transistors will also improve their longevity.

If they will fit, something like these TO-220 Heat sinks would also be a good idea:

https://www.mouser.com/Product...BBvbrcRoCnw4QAvD_BwE

If you go that route, a good heat sink compound applied to the backs of the transistors is also recommended for better heat transfer to the sink.

I agree with Vernon Barry for instance on mth Slave boards the fet's short out from track derailments because the Fet's are under rated for the design, so I just put higher current fet's in the never seen a board fail again!

Alan

Agreed, but that is just it, most installs have zero clearance. Part 2 of that is, the physical spacing of the pairs is not enough and they must never short side by side. Last, it can never short to frame or shell and that's why you see the factory tape. Again, the pairs are connected back to back, however the side to side adjacent pairs must never touch.

Which is why I call it the repair and upgrade in one swoop. The 40 series has double the current rating of the 30 series  because it has less ON resistance so it generates less heat in the first place and then doesn't tend to go into thermal runaway. We are literally taking a 3Amp rated part and replacing it with a 6A rated part.

Again, completely understand your idea and if it can be made to fit for a given install, yes, that can help.

Example modular steam reverse board, Lionel did add aluminum heatsinks to the H-bidge pairs.

Key note is the arrangement is the same the 2 heatsinks cannot touch each other nor can they touch frame or shell.

Also keep in mind, the next weak link is the 1A rated rectifier diodes. As @SteveH rightly pointed out, thermal rating is a huge factor and can reduce or limit a current rating of a device. That's why the original transistors fail even though they are rated for 3A, that's with a heatsink and there is no heatsink in this application and yet the 1A diodes in the circuit do not fail. Moving up to the 40 series reduces the heating of the transistor keeping it in the sane temperature operating range.

I've been making these mods for a few years now, I have never seen a 40 series transistor board return failed. They will cook the motor before they cook the board.

I would say if you are not the soldering type, fine, then add  heatsinks to your factory TIP30 series transistor based reverse board if you can and make it fit. That's certainly better than factory.

However, if you already damaged your board, you are the soldering type, or you know someone, get the TIP40 series transistors (41 and 42) and repair your damaged board meanwhile upgrading it in the process. The transistors are cheap, maybe the same price or pennies higher than the 30 series. And, they are common and plentiful. Also replace the 2 small transistors that drive the larger pairs. Most likely they were KSP13 but might also be MPSA13 and either can be used.

Yes, your right but Lionell just wants to make there trains as cheap as possible so they can make the most profit and really don't care if their boards fail! so they do not use heat sinks or higher powerTIP31 and TIP32 transistors! 

Alan

@Alan Mancus posted:

Yes, your right but Lionell just wants to make there trains as cheap as possible so they can make the most profit and really don't care if their boards fail! so they do not use heat sinks or higher powerTIP31 and TIP32 transistors!

Quite truthfully, using any transistors for this task is less effective than using MOSFET's.  You can eliminate the need for heatsinks with the MOSFET as the voltage drop, and thus power dissipation, is very small across a FET.

One only has to look at the Lionel RCMC to see the difference.

Those four little D-PACK packages are the motor drivers that handle even the largest of Lionel's Legacy locomotives, no need for heatsinks.

John why don't Lionell use FET, s in their newer train designs!

Just curios of your opinion

What new designs are we talking about? Give me a current model.

In any case, I suspect they're saving ten cents by not bothering to redesign the reverse units to a modern version.  You'll notice any board that is of a newer design is using FET's, even the cheapest LionChief.

LionChief from 2016, no driver transistors or heatsinks in sight...

@Alan Mancus posted:

Yes, your right but Lionell just wants to make there trains as cheap as possible so they can make the most profit and really don't care if their boards fail! so they do not use heat sinks or higher powerTIP31 and TIP32 transistors!

Alan

Alan,

I hear ya, but with all due respect your analysis is fiction.  Isn't it also possible that the designer didn't anticipate that there was going to be a problem?  We have the benefit of hindsight here.  How much experience did he/she have when they designed it?

With your experience presently you almost certainly have much more than the original designer did.  You have a distinct advantage.

Why is every decision seen as a cost-driven "screw the customer" evaluation?  Can you see some management type ordering the designer not to put in TIP41/42s, in favor of TIP31/32s, just to save a few cents?  I can't.  Or eliminating a heat sink?  No.  The problem is that standard heatsinks didn't fit.

Except in high-volume production (50,000 units a year or more) designers aren't always forced to make trade-offs based on pennies.  Several dollars?  Yes.  But this doesn't involve dollars, and I doubt that these E-Units were made in high volume.

In the end the designer chose the components and configuration, crossed his/her fingers, rolled the dice, and lost.

This happens sometimes, just because it does, not necessarily because ridiculous cost constraints were applied.

Mike

Thanks to all the experts who have posted great information!

I have learned a lot, mostly that I should probably stick with my old trains that I can work on for now.

But I love learning new stuff and will probably have to have a whirl at working on some new stuff someday.

Thanks again to all,

Craig