SW 1500

Welcome to the club!  I need one for the same reason.  I'm using an 8 ohm one since I had one the right size.

Why didn't I think of that?  8-ohm vice 4-ohm would not be an overload.  Is there still adequate volume?

It's not as good, but sufficient for a little switcher.   The original wasn't all that loud either.

Uh oh!  Just checked the original, and it's 16-ohm, not 8.  A "Unison" U4516BC1, 0.7 watt.

Thank you VERY  much GGG.  I'll check the space tomorrow.

The MTH part # is BF-0000013 for the 3 volt system. I have one in stock or MTH shows them available.

The existing speaker is about 9.5mm thick, and 45mm diameter, so I don't think any mentioned by GGG would do the job.  Chuck, what's the depth of the BF-0000013?

I wish MTH would put its master parts list on line.  Seems they don't even put individual lists on line any more.

This is not a speaker for 3V system.  This is an 8 ohm speaker used on PS-1.  Volume will be subdued. 

Robert, do you more clearance than 9.5mm.  Won't the BF-48 or 50 clear?  Is there a hole in the chassis for the 17mm to clear? 

I try to keep all the 4 ohms in stock.  G 

The taller speakers don't fit GGG, I have the same locomotive and had the same issue.  No room for any larger speaker.

My 8 ohm one is slightly smaller in diameter, I dropped if farther into the "hole" and put a baffle behind it to enhance the sound. 

Interesting, well I would hope the 11mm would fit, though it is in an oval plastic enclosure.  These are the speakers used in the climax as an example.

Just checked and MTH has this model in PS-2 3V and now P-3, so I would ask midge what part number is in that model and see what she says.  They may not have it, but they should be able to get it. Unless they modified the fuel tank.

Looking at the diagram for 5V it does how a hole in the chassis.  I have had to grind them open before to allow for speaker magnet room, than use a diesel hardware kit to provide clearance to mount the board over the speaker.  Just need to ensure there is height room in the shell.  I would think you could afford 2 to 9mm of clearance depending on what speaker you choose.    G

OK, let me back up for a moment. You had a 5 volt system in the SW-1500. It went bad and was replaced with a 3 volt system. So the fuel tank is the original one that had the 5 volt speaker? The fuel tanks changed when the run for the 3 volt system started, so the speaker mounting changed. 

I guessed the fuel tank probably changed as there wasn't an appropriate 4 ohm replacement listed.

Well I need to correct myself again. The 3 volt SW uses BF-0000041. It is a 4 ohm, 3 watt.

At 17mm, there's no hope of that fitting in the older SW-1500

Ya,

 you are probably right. The only 'easy' solution is to order a replacement fuel tank.

As I recall, the issue was there was no room above the fuel tank.  Does the speaker fit lower in the new tank?

Yes, there isn't the 'shelf' that the speaker sits on, it sits lower.

Why MTH lists a upgrade file for this engine is beyond me, since the appropriate speaker is not available.

Because when the 5 volt board goes, something has to be done.

Iam going totry to install a Dayton Audio speaker, but the magnet sits hard against the plastic holder for the 3 volt board.  I wonder if the magnetic field so close will have an effect?

I upgraded one years ago and I do think I used a pancake 8 ohm, or you use the original 16 ohm and live with the reduced sounds.

I still think a BF-48 or 50 could be made to work.  How tall is the shell compartment at the board location?  G

I doubt the magnetic field will have any effect.

The reason for the shelf is to provide clearance for the trucks.  If it weren't there, and tank front & back went straight down, the trucks couldn't turn.  I was thinking I had some space above the loco frame, but just realized that's only because I still haven't fastened the board down. 

I can put a 1-1/4" Dayton audio speaker in facing upwards and almost touching the PS2 board.  Don't know how much sound would get out.  I my toolbox, I also came across a pair of 3/4" x 1/2" 8-ohm speakers, that could both fit side-by-side, and wired in parallel, would give 4 ohms.  (out-of-phase?).

I note a suggestion above to use the original 16-ohm speaker.  I wonder how much sound would come out with a 4 ohm amplifier output????  If the 5-volt boards used 8-ohm speakers, it's interesting that MTH used a 16-ohm speaker; maybe that's all they could get that fit.

Other alternatives include making a fuel tank with sides only, or doing some minor cutting out of the current tank.  And aren't impedance matching transformers available?

I do appreciate all the ideas y'all are posting.  They are all thought provoking.

PS-2 5V did not use 8 ohms, they used 16 ohms, but MTH made plenty of pancake 8 ohm speakers for PS-1.  G

Finished the conversion tonight, except I'm waiting for the Varta batteries to come in.  This is the last time I order from that source in Asia.  Ran loco w/o the shell so it could hold a regular battery and it's fine. 

For what it's worth, the installed sound file is for a B&M GP-7.  The horn is much better than the SW1500 files, and I expect the EMD engines sound the same.

I used the original 16-ohm speaker, and the sound volume is more than adequate.  That is a pleasant surprise.

I had to turn the heat sink 90 degrees, so that the tab is in front of rather than alongside the board.  Unfortunately, MTH does not position the screw holes to easily permit this. 

There is a diesel heatsink with the hole out the end, but I can't seem to find a part number to order them.  I'd like to have that as an option as well.

I can't get the screw in, but it seems to me that sink is tight enough for good heat transfer

You can't get the screw that squeezes it on the rectifier in?  That's the most critical heat transfer point, that needs to be tight.  You should also use thermal compound there.

When heat sink is off the front, the holes may or may not line up.  Best I could get is 1/2 hole diameter off, and some were worse.  Because it's so close, I don't see drilling and tapping another hole in the sink.  I do use compound.

I recall a recent post that someone has made heat sinks that only contact one side of the rectifier, and I would guess that removes less heat than omitting the screw?????

I wonder how much heat the rectifier generates?  Radio Shack similar rectifiers of higher ampacity don't mention need for a heat sink.

As an aside, I decided to replace the single rollers with doubles and find the latest have what appears to be a black nylon insert at each edge, as well as being lesser diameter.  I wonder what is the purpose???

The rectifier is the critical path as the diode drop internally is .7 volts.  If you're drawing three-four amps, that adds up.  The FET driver doesn't dissipate nearly as much power.  That's why on both the 5V and 3V boards the heatsink attaches to the bridge.  The 5V has small heatsinks on the FET's, but not like the rectifier.

Then prudence would direct that I remove the heat sink from the completed loco, drill another hole through it, offset so as not to break into the exiting hole, and use a 4-40 or smaller machine screw and nut or tap it to clamp the heat sink firmly.

Sounds like a decent plan.

Some times that screw goes in at an angle, but normally it will grip and close up the sink.  The rectifier at that point doesn't have any critical material.  But if for some reason the hole is really off, you can break off the bottom and than use it as a nut.  Just make sure you trim it so it can't touch the legs of the rectifier.  G

That raises the question as to whether which is better at removing heat from the rectifier:  (1) A bracket that it tight on both side, with heat sink compound, but not screwed or (2) a bracket screwed tight, but on one side of the rectifier only?

I express no opinions, and since my game plan is to apply the fix I mentioned above, I am not soliciting any.

If any MTH R&Ders are reading, I suggest the screw hole in the heat sink bracket be relocated slightly to permit mounting bracket from front or side.

Like I said, there is a bracket that has the hold-down screw in-line with the board, not out to the side.  I just don't know the part number of it to order them.

It would save MTH money, by not having to carry 2 styles in inventory, to just move the hole very slightly.

The other comes in the Diesel hardware kit.

As far as heat removal, MTH uses a one sided sink with a screw to attach the rectifier, so I think it is ample removal.

Again, I am pretty sure you can screw it in.  G

Where do they use a one-sided HS with a screw?  Are you talking about 5V boards?

I know the other HS comes with the diesel kit, but you can order the side mount one alone, I'd like to be able to order the diesel style HS alone.

I'm curious.  Has anyone ever felt the bottom of the loco, where the heat sink attaches, to see if it's warm?

You need to run it with a load of cars for some time to warm things up.  Just the engine running around would probably work with no heatsink.  I can run them on the bench rollers with no heatsink and the bridge doesn't feel much warmer than room temperature.