Lionel 32930 Modern ZW not working on right handle, track 1, AU

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've only seen one used for lights though if I recall correctly there is a reset procedure. Hopefully that will help. I'm sure others here have more experience with these.

Yes, this unit does not come with a command/conventional switch. And even though full power is on it will not operate an engine in TMCC/command mode.

JPThut

@Vernon Barry posted:

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.

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.

FWIW, they also did steer you in the correct direction https://www.digikey.com/htmlda...2oQzVoIaAtI6EALw_wcB

that is even better specs than the IRF540NPBF.

Again here is that part over at Mouser https://www.mouser.com/Product...G3Opsb41Ano6vg%3D%3D

When you remove the FET's for replacement, Check the board for shorts and opens.

@gftiv posted:

When you remove the FET's for replacement, Check the board for shorts and opens.

Yes.  It would be nice to know what caused the FETs to fail in the 1st place.

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?

You need to clean the circuit board and parts to see which is bad.

DP is Diode pair?

Thanks.  I cleaned the board with some Isopropyl alcohol.

The device in the DP12 position does have a defect in the top of it.  Thanks for the reference to diode pair.

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.