Transformer issues on S gauge layout... help!

Simple answer- you are talking about failures in modern electronic transformers. They use transistors (TRIACs or FETS) to control the variable output from a fixed voltage core transformer.

So- you seem to be generating voltage spikes from inductive loads that open circuit frequently.

So put a TVS on the output of the transformer to block inductive spikes in voltage coming back and killing the internal devices inside the transformer.

Yes, if your layout is that bad and abusive, the TVS diodes may fail and fail shorted, so when you see them short- just replace them.

Otherwise, use an older conventional transformer without electronics that varies the voltage.

https://ogrforum.com/...vs-diode-suppressors

https://ogrforum.com/...postwar-transformers

https://ogrforum.com/...80#72805549112847180

Image by @CAPPilot in the above topic

https://ogrforum.com/topic/which-tvs?page=1

Again, also betting those damaged transformers can be repaired. I know the K-line most likely is a TRIAC, where the Zcontroller has a few variations on the control circuit board and could be a TRIAC or FETs and also recent ones have an internal TVS that can fail shorted.

https://ogrforum.com/...ontroller-repairable

https://ogrforum.com/...99#74918006353997999

All reasons why putting an external TVS can hopefully prevent these internal components from being killed by a spike.

I haven't experience with TVS units, but would, as was suggested already, recommend moving to a postwar AF 30B transformer.  It lacks the electronics and is rated at 300W as compared to the 100W of the units that you've fried so far.  You may need to service the 30B to put it in fine tune again, but once there it's terrific for running S gauge trains of any era (my fave).   Also, if your layout is that "spikey" I suggest you protect the electronics inside your modern engines with a DCC Specialties PSX-AC on every loop.  They are, in my opinion, the best spike and short circuit protection device on the market and I have years of experience with them at home and on our club layout .  They make several models.  Get the one for use with AC, but their units for DCC are fantastic as well.  I use them too.  

@Sgaugian posted:

I haven't experience with TVS units, but would, as was suggested already, recommend moving to a postwar AF 30B transformer.  It lacks the electronics and is rated at 300W as compared to the 100W of the units that you've fried so far.  You may need to service the 30B to put it in fine tune again, but once there it's terrific for running S gauge trains of any era (my fave).   Also, if your layout is that "spikey" I suggest you protect the electronics inside your modern engines with a DCC Specialties PSX-AC on every loop.  They are, in my opinion, the best spike and short circuit protection device on the market and I have years of experience with them at home and on our club layout .  They make several models.  Get the one for use with AC, but their units for DCC are fantastic as well.  I use them too.  

Granted, I like PSX-ACs too, but they have their own issues.

#1 The problem with a PSX-AC when used in a conventional control (varying voltage) layout is that there is a minimum voltage before they turn on, as well as a delay. They are "electronic" breakers and so the electronics are powered by the incoming power, and since it's a microcontroller that turns on the transistor- power is not instantaneous passthrough- in fact below 8V may not even turn on. Again the problem on a conventional control layout, as you raise the source transformer voltage, below a threshold voltage, the PSX-AC will not turn on, and then there is also a slight delay. The end result is a jerky start with a minimum speed based on the threshold starting and holding voltage of the PSX-AC. https://ogrforum.com/...6#153603996675657866

I even went as far as going the steps other suggested in that above link to separately provide logic power to the PSX-AC and found I still had trouble with the low slow rise of voltage turn on point. The PSX-AC would show fault when just the logic was powered with 5V and no AC or DC input, and then once it rose above a certain level, it then would kick in, no longer show a fault and turn on the MOSFETs. Point being, my attempt to work around this problem for conventional failed miserably.

#2 Right in the manual- they describe the TVS diode (transorb) built into the INPUT side of the PSX-AC. So you do have experience with a TVS, you just completely missed that. That is why it can protect (within a limit) a peak voltage spike. That said, it's not exactly easy to replace and if it fails it shorts the input making it look like your PSX failed with an internal short. Point being, you are better to add external and easy to remove and replace TVS (not to mention beefier ratings).

A Transorb (namebrand) is a TVS (Transient Voltage Suppressor).

PSX-AC manual- edit- link added https://www.dccconcepts.com/ma...cc-specialities-psx/

Thanks for the additional info.  Myself and about 30 others have used them (PSX-AC) on our modular S-gauge club layout for over 5 years with nary a complaint or observation to my knowledge of slow or jerky starts with postwar or modern (electronic conventional, TMCC or Legacy, etc.) equipment.  But they've saved the day many times by shutting power off during derailments, and the like.  Wouldn't run without them.  

Your external TVS's might also be a great idea and/or addition.  What manufacturer, specs, and source to buy them from do you recommend?  Thanks.

At home PSX-1 (DCC) units sometimes cut out and then restore power in a couple of seconds when power is first applied with a toggle switch.  They sense load on the tracks and since DCC is a fixed level of power the spike protector can throw itself down depending on the current drawn by the engine(s) sitting on the rails at the time until it senses the coast is clear.  You can adjust that sensitivity.  We also run banks of their DCC units on the permanent HO DCC club layout I run on as well.  They work terrific there too.  

We've also not blown a PSX (DCC or AC) at home or on either club layout, so far.  They can be set to manual or automatic reset.  We prefer automatic, but tried manual.

I don't work for them or have any commercial interest in the company.  I've just had great results with their PSX and RRAmpmeter products for years with AC, DC, and DCC model trains.

PS To be more explicit, I haven't experience with externally installed TVS units.

@Sgaugian posted:

Your external TVS's might also be a great idea and/or addition.  What manufacturer, specs, and source to buy them from do you recommend?

I typically use Digikey as my supplier but there are lots of places and these are fairly common now (Mouser, Newark, A*****,*bay)

For O scale, we typically recommend https://www.digikey.com/en/pro.../TP1.5KE36CA/6174234

@Vernon Barry posted:

https://ogrforum.com/...vs-diode-suppressors

https://ogrforum.com/...postwar-transformers

https://ogrforum.com/...80#72805549112847180

Image by @CAPPilot in the above topic

https://ogrforum.com/topic/which-tvs?page=1

Again, please do not take my message as saying anything bad about DCC Specialties PSX-AC. I think they are great and the HO team at the club obviously uses the other family of PSX products.

It's just specifically a limitation of the design and limitation when used in certain conventional (varying AC track voltage) operating ranges. In O scale, we have some items that are really moving at 8-9V AC RMS and running quite fast at 10-11V.

Also to be fair, I personally own some original American Flyer S gauge, and we have one loop at the local club for testing and running - and we considered putting in PSX-ACs, however bench testing prior to implementation, we just have too many folks who run conventional and felt the turn on delay would confuse and anger members (we use Z4000 transformers and starting voltage is roughly 5V).

I realize that American Flyer S scale items do react differently and have slightly different starting and running ranges and this may or may not be a perceived problem on your layout, with your trains and typical speeds.

I'm just trying to cover broad spectrum.

Thanks for the tip, specs, and link.

All of the responses appreciated!   I discovered that the problem (this time) was not using an old AC motor loco, but was running a modern Lionel legacy AF Diesel.

I'm trying to narrow down what could be wrong, but so far the layout's 2 simple loops have fried 3 different Kline Powermax transformers that otherwise worked fine.

@eddiem posted:

All of the responses appreciated!   I discovered that the problem (this time) was not using an old AC motor loco, but was running a modern Lionel legacy AF Diesel.

I'm trying to narrow down what could be wrong, but so far the layout's 2 simple loops have fried 3 different Kline Powermax transformers that otherwise worked fine.

Again, 2 things:

#1 a TVS simply across the transformer output could hopefully prevent another electronic based modern transformer from damage. Also helps protect modern engines.

#2 Those K-line transformers likely could be repaired. Now cost, who is going to do it, labor, shipping, all VS another working transformer come into play, but strictly speaking, the failure of them is likely a "repairable" electronic component. If I remember correctly, I think the K-line transformers many were riveted housings- causing most folks to not repair them.