If the tender has a speaker hole, SoundTraxx has recommendations for decoder and speaker at their site. Just remove any capacitors from the PC board. The two Inductors that look like resistors are not an issue. I have done a few other Bachmann steamers a few years ago.

Just remember. When you pull a shell on a DCC loco you should have some DCC knowledge.

Rich

Amazon seems to have the complete set for sale. I did some searching. It comes with the 2-8-0 which might be capable of being converted to DCC and sound if you have the abilities. No mention of DCC ready so do not assume. I could not tell if wires ran between the loco and tender. You could ask a question if you know how to use Amazon. I buy a lot through Amazon. Free shipping if you have Prime.

Good luck.

Rich

Kits are sold now. Do a search.

Rich

Right now it sounds like a voltage issue.  Track wiring might not be correct. Connections between sections of track. The power pack is sending voltage not amps. The loco draws the amps it needs. For HO, usually less than an amp.

If an engine cannot make it around correctly, you have wiring, track connection issues.
I have seen a Bachmann power pack running a loco at a train show for quite a while with no issues.

Rich

Today with SMT components, you can make a small light flasher quite easily. Many circuits on the Internet.
Back in the 80's I made a few with the LM555.

Rich

Some have bought HO ones from Shapeways and seem to like them from a little I heard and the axles for older Bachmann locos. Maybe they have to be run in. No idea.But a lot has to be learned about 3d printing. A new technology. I have not seen any discussions yet.
Not sure they sell N scale gears.

Rich

That is all part of Model Railroading. You have to make it work.
Today gears are mass produced in plastic molding machines from what I understand and quality can be fluctuating.
I use to have a friend that worked at a facility that ran molding machines and I saw thew rejects.

Rich

Cannot help with wiring but you need a photo hosting site to upload photos to forums. Search for free photo hosting sites for 2021. You will easily find them.

Rich

Check Walther's. They sell a N scale coupler gauge. I think Amazon sells it also.]

Rich

The "Snap" is a surprise. Is it a SoundTraxx decoder? I only have one Bachmann HO loco with the onboard SoundTraxx decoder.

Rich

If the loco did not run on address 3 it could be the decoder or motor. Most probably decoder.  maybe a wire. No idea if you are into troubleshooting DCC locos with a multimeter.

I have the Power Cab and it is reliable.
I would contact the Service department next.

Rich

Oops. Wrong scale. My bad.

Rich

You can buy the Kadee #205 coupler height gauge and the trip pin pliers or switch to Kadee couplers.
The Kadee page shows many different types of couplers. The standard was the #5 for many years.
Good track work is important also.

Rich

You might call the Bachmann repaid service tomorrow.
Below is a link I found.

https://www.emgs.org/wp-content/uploads/MANUAL_2_5_3_1_pages_all.pdf

There are more if you search for quartering model train locomotives.
I did it years ago bot with different HO trains with the quarterer that fit.
Shapeways.com makes axles for older 4-8-4 Bachmann that have plastic axles that can break.

Good luck

Rich

I( have been using LaBelle oil and grease for years. On Amazon. Grease with PTFE is very good for gears.
I know Bachmann sells their own versions.

Rich