# MTH PS2 Smoke & Sound issues



## sporadic (Nov 27, 2012)

I picked up a MTH Bantam S2 6-8-6 Turbine (5V PS2) off fleaBay and she just arrived yesterday. This engine, which was listed as in "excellent condition" and "runs very well", didn't take into consideration a toasted speaker and faulted smoke system... Needless to say I was a little upset last night when I put my new toy on the tracks. Here's the listing: http://www.ebay.com/itm/370966169360?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649. I'll be contacting the seller on this too.

First, the sound issue. Very low, near inaudible volume and distorted. Some googling led me to articles about failing speaker with flaking chrome. Sure enough, mine was showing some pretty heavy flaking but still measured out at 16 ohm. Pulled the speaker anyways and separated the magnet from the cone and oh my goodness what a mess.. Pretty sure that problem is identified. Hopefully the amp section of the PS2 board is still ok.


MTH Speaker by smerrick, on Flickr

Now to the smoke issue. The motor spins up fine, the elements show around 8 ohms resistance, but the elements themselves are only getting around .5-1V when the smoke system is turned on. I don't have any DCS gear and have only been able to do the 1-whistle / 5-bell reset. From what I've read, the elements are supposed to receive pulsed DC voltage? Sounds like there's a failed transistor somewhere. Are there any schematics of the PS2 boards available and what are the functions of the two boards? I'm assuming one for control and one for power? Anyone know where the drivers for the heating element are before I pull the board and start tracing everything?

thanks for the help!
-shelby


----------



## gunrunnerjohn (Nov 10, 2010)

The speaker issue is a widely known problem with the 5V PS/2 models, I keep speakers in stock for that reason.  If you didn't lose the sounds totally, you are probably fine with the board, lucky you got it when you did.

Before you start tracing stuff, get it to a location with the full DCS and do a factory reset on it. There are no schematics for the boards available, even for MTH technicians. It sounds like the smoke is in the low smoke setting.

If you want to send me the board set, I can run it on my test stand and see if there's an issue with the smoke outputs. If you want to take the shotgun approach, you can try replacing the following component. However, without a reset, you may just be risking damage to a working board.

No Smoke Heat: Replace Q311 (IRLL2705)


----------



## sporadic (Nov 27, 2012)

Even better John, thanks!! I just checked the FET and there's no drive at the gate when the smoke system is enabled. From the other symptoms I'm seeing, it sounds like a proper DCS reset and flash of the engine would greatly help. Unfortunately, we don't really have any local shops (a dismal hobbytown) and I don't know anyone down here with a DCS setup. I posted about this here as well. Here's the latest to bring this thread up to speed. Thanks much for your help John!!

EDIT: Just to double check, the FET is supposed to be switching the full DC potential (22VDC in my case)? I'm assuming the micro is just using PWM to drive the elements for various output levels?



> Yeah, I'd really like to hang on to this provided I can get her properly functioning. The price seemed right so I'm not screaming too much yet. I cleaned all the chrome powder that had flaked up out of the voice coil and magnet. Using some strong hard drive magnets really helped to pull the metallic dust off the driver magnet. Much louder and clearer than before, but definitely could use a speaker upgrade. However, I have another sound related issue now... Whistle and Bell work fine, but there's no engine or yard sounds. The speaker was in such bad shape before I couldn't tell if there were engine sounds or not. Could barely hear the whistle until I cleaned it up. I'll put it into neutral and passenger/yard mode and she sits silent. In this mode, the whistle won't work either which tells me its actually in the yard mode according to what I've read. I've done multiple 1-whistle 5-bell resets with the 2 blast confirmations and still no love. Another oddity I've noticed is that the volume changes significantly between resets. One reset, the whistle will be very quite, next one will have it much louder. Seems to alternate each reset. Basically, the only sounds I'm getting are whistle and bell with sporadic volume changes between resets. Really wishing I had a DCS setup so I could flash the engine!
> 
> Haven't started tracing the smoke element driver circuit yet. When enabled, the fan pulses with the would-be chugs so at least that works. Even though it's a turbine and should sound / steam like one, but I'm aware it's a pitfall of the Bantam version.
> 
> ...


----------



## sporadic (Nov 27, 2012)

Ordered two different 16 ohm 2" speakers to try out and compare. I have high hopes for the first one. The 2nd was only $.85. Since I was already paying shipping figured I'd see how it performs.
http://www.parts-express.com/visaton-k50wp-16-2-full-range-water-resistant-speaker-16-ohm--292-540
http://www.parts-express.com/2-round-frame-mini-speaker-16-ohm--289-131


----------



## gunrunnerjohn (Nov 10, 2010)

Either of those are probably better than the stock speaker. The major issue is the space for the speaker, if they fit, you're good to go.


----------

