For regular decoders

For regular decoders I always check the TCS website for installation hints.

http://www.tcsdcc.com/public_html/Customer_Content/Installation_Pictures/HO_Scale/HO_Search/search.html

Great site for decoder installations...

...but the Bachmann Spectrum GP30 isn't there...

Thanks, Peter, for the link! I'll keep it for future projects. Not directly relevant to my current project, but fun to look through to see how others have done decoder installs.

Ken Glover, Chief Engineer, Kansas Pacific Railway

Got any photos?

If we could see a photo or two, it might be easier to make suggestions.  Do you already have a decoder and/or speaker, or will you purchase to suit?

The SDH164D is the smallest sound decoder I have ever seen.  I have one, though I have not yet put it into a loco to see how it sounds.  That and a small speaker ought to fit somehow.  You might have to remove some portion of the weight, or use the cab area for an enclosure.  Do you have a preference how the speaker fires - up or down?

Sounds like fun project, and probably not all that difficult.

No Photos...

Ken,

I have not taken the loco apart yet. I have the exploded parts diagram from Bachmann and the  Wiring for DCC​ description. I had found a web site that had pictures someplace but didn't bookmark it and now I can't find it. No decoder purchased yet. I was thinking someone here would have some suggestions.

I do feel like the SDH164D with its speaker could fit. (I don't have one to play with). I am willing to do some work on the frame/weight to make room for the decoder. I was thinking the speaker could go in the cab, probably firing up. I'm not sure what the difference would be if it was firing down.

To add a little more background, I have a Digitrax Chief II DCC system (DCS 100) with a PS515 power supply and a  DT400 throttle. I am also using JMRI with a LocolBuffer-USB. My shelf layout is under construction (I have a blog here I need to update) and I am using the GP30 decoder install as a project for relief from track laying and turnout building. 

Thanks for your thoughts Ken!

Ken Glover, Chief Engineer, Kansas Pacific Railway

How much work are you willing to do?

I found a picture on line and the exploded diagram on B'mann's web site.  Does it look like this?

From that and another image on the same site I made this composite, to see how much room there might be internally:

Down to business.  If I were going to do this, and do it right, here's what I would do:

It appears that the truck bolsters have wings on either side which fit into slots in the frame.  I would assess whether it would be possible to screw these directly to the frame, using 2 screws per side per bolster.  If that is feasible, I would cut away the top of the frame, leaving it smooth along the entire length, instead of stepped as it is now.  It looks like the level of the steps is exactly the same as the bottom of the bolsters, which would make life easy.  Since that removes the center screw holding the frame together, I would make a splice plate out of .040" styrene, screwing it to the top of both frame halves.  The bolsters might do the job, but if not, it's easy to do.

With all that room opened up, I would replace the dynamic brake fan with an see-through design.  The radiator fans could be done at the same time, but they would be purely cosmetic (unless of course I put speakers there as well/instead).  I would then build an enclosure out of styrene which places the speaker (the largest that will fit - oval if possible) firing up and directly beneath the DB fan housing.  The enclosure would take up all of the available room, even the cab if that is acceptable.  I would mount the headlights on the ends of the enclosure, or even inside it if using LEDs.  There might be enough room for the decoder inside the nose.  If not, I would either put it inside the enclosure as well, or leave just enough room somewhere.  The ends look promising, with the decoder mounted vertically.  I would mount the enclosure using tape.  All that is needed is to keep it from rattling.

It sounds like major surgery, and it is, but the frame modification could be done with a hack saw and a file, since it's a simple straight cut.  One question would be whether there would be enough weight left for good traction, but there has to be a trade-off between weight and sound somewhere.  For optimum sound, I'd put a Tsunami in there - the better sound quality would probably make up for the slightly smaller enclosure.  I have heard a Digitrax sound decoder (on the Digitrax site, so take it for what it's worth) that sounded quite good, so I might be tempted to try the SDH164D and hope for the best.  It doesn't really look that difficult to me, although it sounds drastic.

Decoder install

First thing to check is the motor current at 12 vdc. No doubt both fame halves are connected to the motor brushes and have to be isolated.

I did a Walther's FM H12-44 and used a layer of Kapton tape between the motor halves and frame halves. In mine, each motor half is attached to each frame with nylon screws. Steel screws in the original install. I had to tap the holes since they were Metric. I had no Metric nylon screws. 

I had to chamfer the holes as the edges where slightly raised because of the tapping of the screw holes. That edge pushed through the Kapton tape.

I soldered a thin layer of 0.002 inch thick phosphor bronze to each motor brush and brought those out for connecting the decoder wires. Kapton tape between the PB strips and the frame.

I had to do a little routing with the Dremel for clearance of the two strips.

I think yours might have SAE threads and not Metric threads.

Rich

Some more info

The Bachmann GP35 seems to use a virtually identical frame design.  You might want to refer to the decoder install on the TCS site for some tips.  http://www.tcsdcc.com/public_html/Customer_Content/Installation_Pictures/HO_Scale/Bachmann/GP35/GP35.html

Looking at that model, it looks like it would be feasible to screw the truck bolsters in place.  It might also be possible to relocate the top frame screw if you wanted to, though I suspect you could get by without it quite easily.

Also, I don't like the idea of putting the speaker in the cab, because there is no place for the sound to go.  It needs open access, or it will be muffled.  You could grill openings in the frame and let the speaker fire down through the trucks, but it would have to bounce around in the trucks, gears, etc. and up off the layout, and it would probably be a lot more muffled and noisy.  Firing up through an open fan housing would make the most sense to me, and I'm pretty sure there are etched fan grilles which would make that job a snap.  You might get even better sound by using multiple speakers through multiple fans, if the decoder can handle it.

I feel that diesel sound is tricky.  Done well, it's great.  Done poorly, I'd rather do without.  Therefore, if I were going to tackle a diesel sound project, I would want to give it every chance of succeeding.

Speaker location

I used a 4 inch diameter bench mounted sander for grinding down the frame on my Walther's FM.

A belt sander would work also. I have done that before I got the 4 inch one off of ebay. $25.00 was quite reasonable but they are not available the last I knew.

Keep a bowl of water around if you do that. The frame will get quite hot. #80 grit paper on the sander does quite well.

Rich

Railmaster Hobbies has a small speaker w/ enclosure

that would mount directly below the fans in the back of the long hood pointing up.  The speaker is specifically designed to mount properly enclosed speakers in EMD models with scale width hoods.  He also sells both the full line of Tsunami and Loksound decoders, and will package whichever of his speakers you chose with them.

Smaller sound decoders are available

As a side note, the Digitrax SDH164D is not the the smallest sound decoder available, Digitrax also makes the SDN144PS which are quite small. They come with a half inch speaker which is not really adaquate for anything larger than N scale, but the speaker can be replaced with a larger one. I have installed several of these and they seem to work well.

Andrew

Wow! Thanks guys!

Lots of good ideas and suggestions. 

The frame for my GP30 is not the same as the GP35 exactly. Similar, but not identical. I am going to take some pictures tomorrow to show some of the differences and the exploded parts drawing. One thing that could be a major difference is the light board is attached to the top of the shell. Kind of makes putting the speaker below the exhaust fans difficult. Might consider doing something different with the lights so I could mount a speaker under the fans.

Thanks again Peter, Ken R.,Rich, Russ, and Andrew! I appreciate the comments and hope you will take a look at the pictures tomorrow and give me more thoughts.

Ken Glover, Chief Engineer, Kansas Pacific Railway

Pictures...

Well, here are some pictures of the GP30: 

First the light board in the top of the shell.

Just noticed there are resistors on the light board. Not sure what that means. It appears the lights are wired in parallel.

Next, the frame

I had a thought about determining the space available for a decoder/speaker. How about using modeling clay placed on top of the frame and replacing the shell? That should give you a good representation of the space available. Now all I need is some modeling clay.

I'm not really up for removing the entire top of the frame. I don't have the tools for that. 

Ken Glover, Chief Engineer, Kansas Pacific Railway

Single band marking

Those are diodes on the board not resistors. Directional lighting.

Ken, the locomotive will need to be completely disassembled.

The frame halves are wired to their respective rails through the wheels on the trucks.  Pretty much typical design used in N-scale locomotives.  You are going to need to take the frame halves apart (don't lose the insulators between the frame halves), and isolate the motor from the frame, and run new wires from the motor out from between the frame halves to a decoder. 

You will need to run wires from the frame halves to the decoder power connections.  You might as well remove and get rid of the lighting board all together.  I think the resistors in the lighting board are for directional lighting. 

I would measure the depth of the body less the lighting board, and also measure the distance from the flat part of the frame just above the fuel tank to the top of the frame.  The difference between those measurements will give you the space available between the top of the frame and the inside of the body to fit the decoder and speaker. 

Do the measurements before you take the frame apart, so if you need to remove material from the top of the frame, you can do it while the halves are split apart, and not get any shavings in the motor or gear boxes.

How do you plan to use this locomotive?  One problem with directional lighting is that switch engines used for local switching duties generally will have all of the lights turned on when switching.  The engineer does not turn on the forward light when forward and then turn it off and turn on the rear facing light when doing a reverse move.  On the other hand, when a locomotive is going to be used in a consist moving a train across country, the only light turned on will just be the headlights and ditch lights (where applicable) of the first unit in the consist.

There  may be a way to wire lighting so that one cv turns on the head lights and another cv turns on the rest of the light, but I don't know which ones would do that.  For that reason, I would suggest that you decide how you will use the locomotive most often and wire lighting with separate bulbs as needed.

Diodes...

That makes sense. It has been too long since I messed with any circuit level electronics.

Ken Glover, Chief Engineer, Kansas Pacific Railway

Lights...

Russ,

I knew I would have to disassemble the frame to isolate the motor. I don't want to do that until I am ready to do the install or mill the frame. Small parts, like the insulators, have a tendency to run off and hide when given too much free time! I will try your method of measuring the available space above the frame. (I still haven't found any modeling clay  

The more I look at it the more I think removing the light board is the best idea. It is really just in the way for a decoder/speaker install. It will also make it possible to fire a speaker up through the fans.

This loco will mostly be switching right now. Not much room for anything else on a 2 x 8 shelf.  At some point I would like to see it in service on a local turn. I think for me the best lighting scheme would be one that gave me independent control of each light. (all off, all on, short hood light on, long hood light on) Oh and add a rotary beacon on the cab! (I don't want much... lol)

Ken Glover, Chief Engineer, Kansas Pacific Railway

available space...

Under the dynamic brake blister there is an area about 1.5" long and 3/8" deep. Under the fans it is 1/4" deep. Actually more room than I expected.

Ken R., do you have actual measurements on the SDH164D and the speaker?

I would consider using multiple speakers under the fans and adding resistors to get back to the 32 ohm value the SDH164D needs.

Ken Glover, Chief Engineer, Kansas Pacific Railway

First of all, I'd strongly

First of all, I'd strongly suggest removing that light board.  For one thing, the decoder has all the circuits needed to control the lights already.  For another, it's in the shell, and you'll either have to wire it permanently to the frame and decoder, install a connector, or move it to the frame with everything else.  As I see it, you don't need it.

On modifying the frame.  I use a hardware store hack saw (nice and coarse - like 18 tpi) and a big mill file.  They're fast, and plenty accurate enough for most purposes.  For finer work or smaller areas, I use a straight 1/8" mill in a Dremmel tool.

It looks like you have a fair bit of room, and you might want to consider one of those pre-made speakers with the built in enclosures, such as Railmaster sells.

SDH164D dimensions... well, it seems that I have temporarily hidden it from myself.  Sigh.  This is why I don't buy stuff well in advance of using it.  Anyway, Digitrax says it is 1.273" x 0.67" x 0.25", with a 28mm speaker

http://www.digitrax.com/prd_mobdec_sdh164d.php

The light board is going...

I will replace the light board. Don't need it and it tales up space I want for the decoder and the a speaker. I figure I need to remove about 2.5 mm off the to of the frame to make room for a decent speaker and enclosure. The decoder will fit in the space in the dynamic brake blister and air filter. 

I have hack saw and file, so I'm good to go there.  

Ken, I understand about hiding things from yourself. I have a lot of model RR "stuff" and tools packed away for 10 years. I either go " I know it's in here someplace..." and/or "Rats! why didn't I find that before I bought another...". The SDH164D should fit the space with no problem.

The journey continues..............

Ken Glover, Chief Engineer, Kansas Pacific Railway

SDH164D PROBLEMS

Ken-

Before you go ahead and decide to use the SDH 164, have a look at the Digitrax Yahoo group concerning these decoders. They use an odd 32 ohm speaker (very large 28 MM) that is next to impossible to find a smaller 32 ohm replacement for. There are also other complaints with these decoders.

The SDN 144 PS mentioned in an earlier post is a smaller decoder (physically) that uses an 8 ohm speaker that would be much easier to find a replacement for. The Railmaster speakers are excellent, as are the Soundtraxx ovals.

The SDN decoder might fit without hacking the weight if you remove the light board and replace the lights with LEDs. If you could live with the 1/2 inch speaker that comes with it and replaced the rearmost fan with an open design, you could install the speaker facing up and fit a small enclosure below it. You might be able to do this without cutting up the weight as well, or cutting less than needed for an oval speaker.

The SDN will handle 1 amp, your Bachmann should draw much less.

Russ has the best idea, use a Tsunami. Yankee Dabbler has the best prices and will have anything you need in stock.

Another picture...

A photo of the disassembled loco.

Jeff: The SDH164D will fit without any frame modification based on Digitrax's dimensions. It is the speaker that will require modifying the frame. I would like to use an oval speaker that will fit in the long hood. I just don't have the depth for a a speaker and enclosure. I hesitate to use the SDN decoder when I have space for the higher amp one. I like to be sure I have spare capacity just in case I need it. I would like to consider the Soundtraxx Tsunami but I haven't found any dimensions so I don't have a feel for the fit. (I didn't find dimensions on the Soundtraxx web site). They have the right sound for the GP30 (567D Turbo) so it would be better to have. I will check out the Digitrax Yahoo group on the SDH164D. I don't see adding 24 ohms to the speaker circuit as a big deal to not over drive an 8 ohm speaker with the SDH164D.

Ken Glover, Chief Engineer, Kansas Pacific Railway

Tsunami size

From the SoundTraxx site:

• TSU-750 - 1" x 1/2" x 0.22"
• TSU-1000 - 1.68” x 0.68” x 0.25”

The 750 is the micro-Trunami, and has a .75A rating.  The 1000 has a 1A rating.

Tsunami Micro 750

Be aware that the 750 is sensitive to heat buildup. Been discussed on the Yahoo Soundtraxx Group. Some attach a metal plate to the bottom of the decoder.

Rich

Speaker

Ken-

The 164 needs a 32 ohm speaker. Sound quality suffers badly when an 8 ohm speaker is substituted, according to the Yahoo group postings. The substitution also affects the running quality of the driven loco, especially when the horn or bell are activated. 

I've used the SDN in a Bachmann B23 (my first trial sound project) and had no problems. The sound was ok but tinny. A larger speaker with the SDN may be better sounding, I don't know. The next project was a Tsunami TSU 1000 and oval speaker in a Stewart VO 1000. The sound qualities of the Tsunami are excellent, a world above the SDN. Since then all my sound installs have been Tsunami, in a Stewart AS16, Stewart F7 ABA, and three Atlas / Kato RS3s.

True, the SDN is rated at 1 amp, but with a 2 amp peak. There is no way your geep will draw over 1 amp. Any loco should be tested for amp draw before deciding on a decoder anyway, so when you check yours you'll find the SDN will be more than sufficient. The 8 ohm speaker requirement of the SDN makes speaker substitution easy. 

I'm not knocking the SDH164. I have two of them waiting to be installed in an old Athearn BB PA / PB pair I have from my first foray into this hobby when I was much younger (and the reason I'm back in today). But these will be able to fit the large 28 mm speakers, and the proper sounds can be installed in the Digitraxx decoders

I just wouldn't want to see you go through all the trouble of doing the 164 install and subbing a non-32 ohm speaker and being disappointed with the finished project. Using the SDN and a higher quality oval 8 ohm speaker might make you happy with the result. 

Jeff