Hi everyone,
I recently purchased a P1K GP15-1 and a MRC 1750 drop in sound decoder to go with it. It was working fine for several weeks, it sounded good and ran smoothly. I took my new layout to a local clubs open house yesterday and the loco ran back and fourth on the layout all day without a problem. I set up my layout back home this morning and the same loco is stalling/ the sound is cutting out every few seconds. At first I thought the layout wiring was damaged so I checked that with a meter and with other loco's, it's fine. Then I cleaned the track with a bright boy then rubbing alcohol. I also cleaned the loco wheels with rubbing alcohol, the same thing still happens. I then took the loco apart and tested the pickup wires with a meter, all 4 of them are fine. When the loco does stall it doesn't take much to get it going again, I just tap it and the sound restarts and it takes off. I'm thinking about adding a keep alive capacitor to the decoder and I'm trying to figure out where to begin. I've read this page http://www.members.optusnet.com.au/mainnorth/alive.htm and I'm trying to understand it. It seems to focus on soundtraxx decoders that are set up from the factory for a capacitor.
Here's what I want to do:
I want to add a capacitor that will keep the motor and sound system running for a short amount of time (1/2 second should be more than enough). This locomotive doesn't have a cab interior, so I can put the capacitor in the cab/ low hood area. I don't care it it's visible in the cab windows. I also don't care if the function outputs (lights) go out when the loco is running off the capacitor.
here' a picture of what I have to work with:
Any advice, ideas, or suggestions would be appreciated. I understand that keep alive technology is still somewhat experimental. Also if anyone has any ideas as to why this loco is suddenly having this problem it would be appreciated.
Thanks in advance,
Jamie
Cape Vincent Southern Railroad
HO scale Horseshoe Curve in 5’x10’
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If it worked fine before and now stutters and stalls, you have dirty wheels and/or pickups.
That out of the way, the four components to the right of where the two tabs are for the motor wires appear to be the main rectifier bridge as mentioned in Marcus's site. Exactly where to tap off for the capacitor you'll have to do some detective work for. The other side of the keepaliove, the plus side, is usually the blue wire fromt he decoder, or int his case one of the two center tabs at each end. If you trace the circuit board it would be the two that are connected together, if the instructiosn don;t label the connections.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
I cannot see the complete decoder but there is usually a main filter capacitor right next to the four diodes where the track power comes into the decoder. All I have seen have a brownish capacitor for the main filter cap. I don't see one though. There “might” be a C prefix for the component label number.
Look at the Marcus pictures. That “might” give you and idea.
Knowing how to read the capacitance of the component from the label might help also. A few times I did a search for the component number on the component and actually found the value at an electronics seller.
Once I traced the copper trail right to the main capacitor. A little detective work pays off.
Rich
If you ever fall over in public, pick yourself up and say “sorry it’s been a while since I inhabited a body.” And just walk away.
Just a WAG, the main cap "might" be on the bottom of the decoder.
The more I read your first post, the more I think you have a pickup issue somewhere or a defective decoder.
At one time, MRC decoders had a bad rap for similar reasons.
Take it back to the club and see how it runs. Sounds obvious to me.
Thanks for the help,
Tomorrow after work I'll disassemble the trucks and clean the pickups and see it that helps. I didn't think to check them because the loco is only about a month old. I just cleaned the wheels, so that's not the problem.
Randy: I'm going to re-read Marcus's site several more times until I understand it completely. The blue wire is the function common, which is usually the positive side of the light (function) circuit. This means the + tab in the photo (second from the bottom) should also the positive side of the capacitor if I add one.
Rich: I believe there are 4 capacitors already on the bottom of the decoder, the largest one is right under the 4 diodes in the photo. All of the capacitors on the bottom of the decoder are brown. I will take a photo tomorrow when I take the loco apart and clean the pickups. I'm not sure what these capacitors do. Do they provide some kind of keep alive capability already?
Also, taking the loco back to the club won't make a difference. I brought my layout to the club and ran the loco on it. It's the same layout that I tried to run it on today. I didn't run this loco on any other layout.
I'll start with the simple thing, checking the pickups. If that doesn't solve the problem I'll post more pictures of the decoder and see what we can come up with from there. If the decoder is defective the warranty is expired so i'll experiment until I can get it to work.
Thanks again for the help, I'll follow up tomorrow evening to let you know how it's going.