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I am in the process of upgrading a Weaver Milwaukee Road F6a 4-6-4 Baltic to PS-2. The Baltic has a Train America Studio smoke unit in it that has ("an auto shutoff circuit that prevents the element from burning up when out of fluid") The element is 10 ohms.

Since PS-2 smoke units have 2 16 ohm elements in parallel ( 8 ohms ) would it be save to wire the PS-2 board across the TAS element for smoke control from the PS-2 board or should I find an 8 ohm Element?

Another thought was to wire the TAS board to track power and wire the smoke motor to the PS-2 board for puffing smoke but would only do this as a last resort. I would much better prefer to have full control from PS-2 board. Thank you for your response.

Forest.

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Put 2 MTH resistors in the smoke unit, in parallel. You can solder them together under the PCB and stick 1 set of leads through the PCB to connect to the PS2 output. You don’t need the thermistor and you can cut the control circuit off. The circuit board just becomes a seal. Just drive it with the PS2 board.  I did this along time ago with an atlas loco that had a TAS unit in it.

Last edited by Boilermaker1

Put 2 MTH resistors in the smoke unit, in parallel. You can solder them together under the PCB and stick 1 set of leads through the PCB to connect to the PS2 output. You don’t need the thermistor and you can cut the control circuit off. The circuit board just becomes a seal. Just drive it with the PS2 board.  I did this along time ago with an atlas loco that had a TAS unit in it.

I think Forest wants to use the protection circuit?  I'm a big fan of these smoke units.  When working right, they prevent the wicking from burning up.  I pulled one apart in my Kline Berk installed 15 years ago and no charring what so ever.  Didn't even bother re-wicking.   You should be fine using the smoke unit as is,  connect the turbo smoke unit directly to the PS2 board to use the full protection.  remove the wires from the fan and wire fan to the PS2 board.  

Last edited by superwarp1

You will most certainly NOT be OK just connecting the TAS smoke unit directly to a PS/2 board!  You may get some smoke, but it might be the kind you don't want to see.

The PS/2 electronics is designed to feed a dual resistor array with two 16 ohm resistors totaling eight ohms.  Also, the variable smoke level feature will obviously never work with the TAS electronics in the mix.

I do not want to use the protection feature. I was looking at cutting the traces from the resistors back to the board and wire the smoke unit the same as any other PS-2 smoke unit. I stated about the protection circuit so as to verify what unit i was working with. Sorry for not being clear of my intent. My question is can I use the 10ohm resistor that is in the unit or should I get the value down to 8 as is used by MTH? Thank you.

Forest.

Wattage is important also, so I'd parallel the two 16 ohm resistors to mimic the MTH smoke unit.  The small smoke unit from MTH has one 8 ohm resistor, and it requires different firmware for PS/2 (or for PS/3 a different chain file).  That being the case, a single 8 ohm resistor will likely not give you the desired effect.

For best results here, mimic the PS/2 stock smoke unit.

I am considering going the route of two 16 ohm. Not being familiar with the TAS unit, one of the things I was concerned about with the 10 ohm element is not having enough smoke output. Boilermaker1 suggested soldering the two together. I'm not sure if the solder I have has a high enough heat rating to do that inside the chamber. It is Oatey 95/tin 5/antimony. I have been using it on the outside of smoke units with no reported problems. If anyone knows a brand solder that is better please let me know. I found it hard to find temperature ratings on solders that I looked into. Had the Oatey on hand and it seemed to work.

Maybe I can use a pin vise and put two new holes through the board for the second element. That would keep the soldering outside the chamber.

I am having a little trouble in the thinking of the watt rating. Discussed this with MTH today. Don first mentioned that the 10 ohm resistor would draw less current but then questioned the wattage rating of the ten ohm element. Being that the 10 ohm resister will pull fewer amps than the eight ohm, If your pulling fewer amps and the voltage stays the same shouldn't the element consume less wattage also.  I know just enough about Ohms Law to be dangerous.  Again thank you for your responses.

Forest

Put 2 MTH resistors in the smoke unit, in parallel. You can solder them together under the PCB and stick 1 set of leads through the PCB to connect to the PS2 output. You don’t need the thermistor and you can cut the control circuit off. The circuit board just becomes a seal. Just drive it with the PS2 board.  I did this along time ago with an atlas loco that had a TAS unit in it.

Do you recall what solder you used to solder them together. Is that unit still working today. Thank you,

Forest

Well, I went the route of using two MTH elements. Drilled two new holes for second element using #60 drill bit. Fed the first element into the existing holes and soldered it in. Then fed the second element into the new holes. Wrapped the leads around the first element leads and soldered them. Fitted new smoke batting and installed into housing. First time installed one of the elements was touching the case causing an short. Took it back apart, readjusted and reinstalled. Second time turned out well.

I mounted the PS-2 board. I then fitted the charging port into the switch bracket. The tender had a bracket for the Volume control, Run/Program switch, Signal Sounds switch, and a cruise switch. I am using the cruise switch for smoke unit switch since it is labeled on/off. Keeping the volume pot. I removed the other two switches and filed the one hole out to fit the charging jack. All the easy stuff is finished.

Next comes the rebuilding of the tender harness. I have to rebuild the tender harness to eliminate the 90* male plug. Had to mount the 10 pin engine harness in upside down after a lot of grinding of the brass housing to make it fit and not short out. The 90* plug would be turned down instead of up so I have to make a new 10 pin male harness using a straight plug. I will be ringing each wire and then solder the leads from the original harness to the appropriate leads on the new one. It is just a matter of taking the time to be sure everything is wired correctly. If I ever do another like this I will definitely have to charge more than I quoted for this job.

I appreciate all of your thoughts on the smoke unit. I also cut the circuit board clean off the unit so as to eliminate any chance of back feed onto the elements. I took some pictures and will try to post them latter on. I have to be on the road next two days so it will be sometime after that. Again thank you everybody.

Forest.

95/tin 5/antimony has a much higher melting point (464°F) than 63/37 tin/lead (361°F), so I can't imagine it won't do the job.  If it's getting that hot, you have a problem anyway.  I have soldered countless smoke resistors into MTH and Lionel stuff with 63/37 solder, never had a problem.

Thank you John. My concern about the solder came from one of the service classes down at MTH. We were shown a smoke unit board that supposedly had too low of a temp solder used which melted into the board destroying it. The lesson was to use high temp solder on the smoke unit to avoid destroying it. I asked what solder they used but never got a direct answer. I know the stuff I am using takes a lot more heat to melt then the solder I use for wiring. I turn the soldering unit up to 775* or above to get good flow without taking too long. I solder wiring using a little over 650*. I like to have enough heat to get on and off as quick as possible.

Well, high melting point solder is a double-edged sword when you are doing PCB work.  Higher temperatures will quickly lift the traces off your PCB, something to keep in mind.

FWIW, I've soldered a ton of resistors into MTH smoke units with my standard 63/37 tin/lead solder, and I've never had one melt down.  There are really low temperature solder types that melt at less than 300°F, those might actually be problematic.

Well, high melting point solder is a double-edged sword when you are doing PCB work.  Higher temperatures will quickly lift the traces off your PCB, something to keep in mind.

FWIW, I've soldered a ton of resistors into MTH smoke units with my standard 63/37 tin/lead solder, and I've never had one melt down.  There are really low temperature solder types that melt at less than 300°F, those might actually be problematic.

I will take note of what you are saying and thank you for your input on the matter.

Forest.

I will be the contrarian here.  I have left the original TAS units alone that have 10 ohm resistors.  They seem to be high watts, and size of the smoke chamber matters.  The smaller MTH smoke has two issue. Small element with lower watt rating, and a small chamber which increase effect of heat.

TAS is a large smoke chamber with larger element.  Now if you love heavy smoke, then going to the 2 elements to drop effective resistance to 8 ohms, is the way to go.  G

@GGG posted:

I will be the contrarian here.  I have left the original TAS units alone that have 10 ohm resistors.  They seem to be high watts, and size of the smoke chamber matters.  The smaller MTH smoke has two issue. Small element with lower watt rating, and a small chamber which increase effect of heat.

TAS is a large smoke chamber with larger element.  Now if you love heavy smoke, then going to the 2 elements to drop effective resistance to 8 ohms, is the way to go.  G

Guess we're possibly gonna have lot of smoke. Board has been set up with two MTH 16.8 ohm elements. Could you possibly explain if I am figuring the wattage wrong. As I understand it the MTH smoke circuit puts out a pulsed power to the smoke elements. But just saying that it put out 6v constant. I = E/R at 10 ohms a 6 volt suppy would draw .6 amp, and if  W=IxE it would be 3.6 watt. If that is correct then I=E/R at 8 ohms would be .75 amps or 4.5 Watts. With that I agree that the two MTH elements will get hotter. (more watts). Twice now I have been told or thought I was being told the TAS 10 ohm resistor might be too high a wattage. It doesn't seem to be that way.

If the two MTH resistors put out too much smoke I can always put the 10 ohm back in. Either that or figure out how to install a smoke pot for manual control. One of the schematics should show that. I am a MTH tech but don't get a lot of MTH work up here in central PA. All my upgrades until now have been MTH Proto1 to Proto2 upgrades so I never had to consider the amp and watt ratings from a different smoke unit.

Next I have to either find a way to mount the ten pin engine harness upside right or I have to build a custom tender harness. I was going to get some shims to mount it while down at MTH today but didn't think it through in the right way and was thinking they wouldn't work. Now that I am back home I have to rethink this as they very well may. I will try to post some photos and video once it is finished. Have been on the road last two days so haven't had any progress during so.

Thanks, Forest.

Going to a MTH set up will work, so does the TAS.  I just finished a diesel and it smoke quite well on single element.

Building custom harness for brass is a given many times.  So is having to  file open the shell some times.   A lot of extra work.  If insufficient room for diodes, remove them and then put them off the motor leads inside engine.  Another have to do a lot thing with brass.   G

I have to move the diodes on at least half the upgrades I do, it's part of the process many times.

@Forest posted:

If the two MTH resistors put out too much smoke I can always put the 10 ohm back in. Either that or figure out how to install a smoke pot for manual control. One of the schematics should show that. I am a MTH tech but don't get a lot of MTH work up here in central PA. All my upgrades until now have been MTH Proto1 to Proto2 upgrades so I never had to consider the amp and watt ratings from a different smoke unit.

Since the PS/2 board allows smoke volume control, if you get too much smoke, turn it down in the configuration.

I abandoned the smoke pot. Took another look at the engine plug and managed to mount it in the right position. Still have to trim the length of the tender harness wires and figure out how I am going to secure the tender harness in the tender.  I thought I had some small metal butterfly style straps but haven't been able to locate them. The opening in the front of the tender is to large to use a simple tie wrap around the harness to keep it from pulling out. Tomorrow is another day.

Forest.

I was finally able to download photos from my I phone. Some kind of compression software that they are using on the new phone was making it almost impossible to download from the phone to my computer. Here are the photos of the rebuilt smoke unit. You can see the two new holes and how I tied the new element into the other..  Works like a charm. High smoke level will fill the room in short order. Medium output works perfect in my opinion.

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Here is the first test run. Speed is off by quite a bit. I had to set chuff rate to 9 to get close to 4 chuffs per revolution. It will run much slower. I ran it with a PS-3 steamer and 10 mph on the rebuild equaled about 22 mph on the PS-3 engine. The original MTH tach stripe had 48 stripes. 24 black 24 white. I took 48 and divided by 22 then multiplied by 10 and cam up with 22 stripes. Made a custom tape but it did not seem to make any difference on speed. At 2 mph it is running about 5 and still had to leave chuff rate at 9. Don't know why the speed didn't change with 26 fewer stripes. Maybe someone can chime in here.

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Here it is running at a nice speed were you can have a better look at it. Really really close to 4 chuffs per rev. Still set at 9. I made a remark about the end of the stripe being folded over in the video. It made last white stripe double wide. I glued the loose tab of the tach stripe back in place but it made no effect on final speed output. I sent a video to my customer and he was quite happy with it.

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