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Hello,

My modern ZW, part 32930, has quit working correctly on the right side handle (AU) which is programmed as Track 1. If operating with a Cab 1, a slight turn of the big red knob causes it to come on at full power. I first discovered the problem while attempting to run Postwar trains which I like to do in December. If I start with the handle in the off position - same thing. A slight start of moving the handle and it's full power. Any suggestions would be appreciated.

Thanks,

JPThut

Last edited by JPThut
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This sounds like one or more of the FETS failed and when they fail, they fail shorted. That's the how and why you would get 0 to full power from either handle or CAB1. Unlike the powermaster, there is not a command VS conventional switch right?

Again, 1 of 2 things is happening. Either it thinks it's in command mode so only full on or off state, or one of the output devices failed, and so it's conducting power instead of being triggered.

Product support page

https://www.lionelsupport.com/...r-Supply-Set-6-32930

Again, the clue is this part

Again, the tendency is MOSFETs often fail shorted. Since this is trying to manipulate AC, likely there are at least 2 MOSFETS per channel- maybe more. So one is working, the other is stuck on= the symptom of off or full power, but no variable.

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Images (1)
  • mceclip0

This sounds like one or more of the FETS failed and when they fail, they fail shorted. That's the how and why you would get 0 to full power from either handle or CAB1. Unlike the powermaster, there is not a command VS conventional switch right?

Again, 1 of 2 things is happening. Either it thinks it's in command mode so only full on or off state, or one of the output devices failed, and so it's conducting power instead of being triggered.

Product support page

https://www.lionelsupport.com/...r-Supply-Set-6-32930

Again, the clue is this part

Again, the tendency is MOSFETs often fail shorted. Since this is trying to manipulate AC, likely there are at least 2 MOSFETS per channel- maybe more. So one is working, the other is stuck on= the symptom of off or full power, but no variable.

I verified that one (or more) MOS-FETs are blown on my ZW-C. Two (A&B) out of the four channels now operate.  Do you have a suggestion as to an equivalent that would work as well or better?

When I looked at the original MOS-FETs their number is MTP33N10E.  These are also obsolete from Mouser, but I think some are available on the Bay.  An equivalent I was given was:  P/N:  SUP70090EGE3 or NTE2396.  Not sure which one of these is better (or worse).

I also did a cross reference of the Lionel referenced part IRF131ONPBF.  These again have slightly different specs than the what was original (MTP33N10E) MOS-FET in the transformer.  Maybe the replacements are better??

I'm not an electronics wiz, so I do not know which is better or if there are others that would work better.

Any suggestions from other members would be greatly appreciated.

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Images (2)
  • 20230130_124756: Failed MOS-FET on Lionel ZW-C
  • 20230130_125551: Up-close of MOS-FET (number) on Lionel ZW-C

Dave,

Saw your email but wanted to answer here in public. Sadly, while I know about these and somewhat how to repair this specific model, this is one of those devices I just have not yet had hands on repair experience.

The data sheet tells us what we need to know for equivalent. Typical N channel MOSFET, 100V rating, 33A.

This has better specifications (not surprising, the key feature is lower ON resistance (RDS ON)

IRF540NPBF



Also I would replace all 4 devices given the errors and state of things.

Quick update -

I ordered the new MOSFETs.  They should arrive next week.

I removed both MOSFETs from each channel (C&D) for a total of four from the main control board.  One MOSFET on each channel was bad (the lower position). I ran my multi-meter on the empty pads/spots where they were mounted.  All typical response except on the lower MOSFET position (Q11) on channel D.  I get 300 ohms across the gate (top tab position of the MOSFET) and source (bottom tab position of the MOSFET).  The center tab position (drain) was open and appears normal when compared to other readings.  When I attempted to follow the traces from the Q11 position, I think there is a surface mounted chip that is damaged in the DP12 position shown on the attached photo. No idea what it is. My guess is that this will render channel D non-usable.

Maybe I will look for a spare "bad" board (Lionel P/N 691ZWPC100) that I can salvage parts (chips) from.

Any thoughts?

Attachments

Images (2)
  • 20230201_143809: ZW-C main board "front" side
  • 20230201_150911: ZW-C main board "back" side
Last edited by DaveGG

The diode pair chip that is damaged looks to be the same as one on Channel A in the DP16 position.  On the top of the DP chip is "Y 5 2".  On the one one that is damaged, only the 2 is visible.  The remainder of the top of the chip is damaged.  I did a search on this and came back empty handed.  Any help would be appreciated.

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