[/url]IMGP9325 by Joe DuBois, on Flickr[/img]

Hope this works.   Joe

All I saw the info for Photo Bucket. I have Flickr. Can't figure it out.   Joe

 I did one I have. I tried to post a photo but no luck. I can send you an e mail telling you how I did it.And a photo. Let me know.   Joe

It's cheaper to buy the sound boards from Bachmann. :https://estore.bachmanntrains.com/index.php?main_page=product_info&cPath=68_573&products_id=10483&zenid=764an321egse8grdbkg9jpjeg7

And speaker:https://estore.bachmanntrains.com/index.php?main_page=product_info&cPath=68_573&products_id=7121&zenid=764an321egse8grdbkg9jpjeg7
I did one I have. I tried to post a photo but no luck. I can send you an e mail telling you how I did it.And a photo. Let me know.   Joe

There is a tab in each corner plus one on each side of the cab. It looks like the side of the cab towards the bottom needs to be spread out a bit to get it off.      Joe

 I have one and no problems like yours. Do a decoder re-set. I think it's  a value of 8 in CV8. Turn off power to track or lift loco off track. Waite 20 or so seconds and put power back on or lococ on track. Headlights will flash showing the re-sat took. Address will be 3.   Joe

Remover the 2 screws holding the couplers on. Remove the screw holding the fuel tank cover on. Remover 2 screws that hold body to frame.   Joe

 What decoder brand? Same one in each? Sounds like 1 might be running on 28 speed steps the other on 128. Look in the front of your system manual for decoder status. Not all decoders support 128 speed steps.       Joe

Will this work? Similar ones for the F7A/B, GE 70 Tonner.   Joe

http://estore.bachmanntrains.com/index.php?main_page=product_info&cPath=66_68_189&products_id=1344

http://estore.bachmanntrains.com/index.php?main_page=product_info&cPath=66_698&products_id=10496

Sound value decoder. Compare the old DD40 board to the newer sound board. If the mount the same the above decoder will work. You will need speakers also.   Joe

What DCC system are you using? Try a re-set. Program CV8 with a value of 8. Turn the power off to the track or remove loco for 10 seconds or so. This will reset the address to 3. If you want to replace the decoder, try a Tsunam Econami. The board should fit fine. This does not come with a keep alive capacitor though. Soundtraxx sells the harness to add a keep alive cap to this board. Part number 810158.I don't think their current keeper will fit.    Joe

Did you change any CVs? A reset might do the trick.   Joe

 From Soundtraxx web site: Fault Light
When the decoder encounters a fault, the red fault light and all installed lighting will flash an
allotted number of times to report an error code. The number of times the light flashes
corresponds to a specific error. Error 10: Over-Voltage Fault
Voltage is monitored during normal operation to automatically deactivate sound and motor
processes when voltage exceeds the decoder's voltage limit. Settings resume when the voltage
is reduced to within limits and will vary between decoder models.  You may have a voltage problem some how. What system are you using?   Joe

I turn the volume on my decoders to about half to 2/3. The enclosure is  available with out speaker as well so you could use a better speaker. A sugar cube speaker might work in it's place. Soundtraxx has 2:  810154 and 810155. I may try one of these instead of the
Bachmann enclosure.    Joe

 Bachmann sells their sound  value decoders.   
http://estore.bachmanntrains.com/index.php?main_page=product_info&cPath=66_698&products_id=10482
also speaker enclosure
http://estore.bachmanntrains.com/index.php?main_page=product_info&cPath=66_68_602&products_id=7121
   I installed a Tsunami and the baffle listed but had to modify the enclosure.     Joe