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All,

For those of you with K-Line experience, I need some tech advise w/ my K-Line K2439-0269 LIRR GP38-2 Diesel Loco. I picked it up online along with an Atlas RS-4/5. Both had running issues. The Atlas was a quick fix and that’s back up and running as it should. I’ll put that up for sale online soon. The K-Line GP38 is not so easy to diagnose. Let me start by mentioning this has K-line electronics, not Lionel or TMCC. I thought about retrofitting it w/ ERR parts but that’ll add $$$ to the repair.
When initially powered up, nothing would happen and the light on the transformer would flash indicating a short. I pulled it apart and noticed a bi-directional diode and capacitor across the + & - on the board which I believe the diode is faulty. On a hunch, I pulled them and retested. The loco now has sound and immediately runs in the forward direction when initially powered up. I believe it should start in neutral, no? If I press the direction button on the transformer, it’ll go into neutral and sound will continue to work. If pressed again (attempting to put it in reverse) the relays click on the driver board and the light flashes on the transformer indicating a short. My theory (without popping the relay covers off) is one of the contacts in the relay is welded closed. I’ve seen this with HVAC control modules before. Does anyone have any ideas or recommendations short of pulling all of the guts out and installing ERR or other? Any help will be greatly appreciated. 

Original Post

Well, after some more testing, I’ve come to the conclusion there must be something creating a voltage loss in the call-in signal/voltage to the relays after I press the direction button on the transformer to switch directions. When I used my multimeter to check continuity on the forward and reverse triacs, the meter closed the circuit and the loco ran forward and reverse with full sounds. I’m wondering if the transformer (CW-80) has anything to do with it? Low initial voltage somehow causing the e-unit to malfunction and relays to chatter? I dunno. I’ll have to look at it again tomorrow. 

Last edited by DanVW

Interesting. This has conventional K-Line electronics (sound board & separate reversing unit). It appears to have a small motor speed sensor board as well? I can now cycle through F-N-R-N but the motors twitch when it cycles to F or R and causes the transformer light to flash as a short. I had a similar issue w/ a TMCC DCDS board because the insulator pad wore away allowing the MOSFET transistor’s pad to ground out. I wonder; if they used the MOFSET to amplify the voltage to close the motor driver relays, that would explain why the relays are clicking. Not enough power to hold them closed? Maybe that’s no bueno? I’ll have to look. I’m without power right now. We just got smacked by those big storms.

GRJ,

The TMCC DCDR issue I was referring to was on a Lionel RS11 that I fixed previously. It had a similar issue when cycling between forward and reverse. The driver had a MOSFET grounding to the mount because the insulator pad had worn through.
The conventional K-Line board that I’m currently working on has 2 large relays at one end. They click when I attempt to cycle the e-unit to forward or reverse. They don’t act up when cycled to neutral. Here’s a pic of the electronic reversing unit I found online:

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Last edited by DanVW

GRJ,

If your interested to know, I found the issue. It looks like this loco took a pretty big voltage spike that fried the bidirectional diode on the power PCB and smoked the flip-flop semiconductor (IC) on the driver board. The semiconductor is supposed to oscillate between 2 different outputs when the direction button is pressed.  They independently power the call in circuits to the relays. However, it was sending voltage to both outputs simultaneously which caused the relays to click because they were back feeding voltage to each other. I picked up the parts at my local electronics store for about $5.00 and it runs good as new. One more loco repaired!

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