Help needed!

@Buco posted:

... got some TVS's that I was assured would be right for my application.

... part number for the TVS's I purchased is:  SA24A+ TVS DIODE, 500W, 24V, UNIDIR, DO-204AC

Where did you get the advice on component selection?

1) You need a bi-directional (not UNIDIR) TVS.  Unidirectional is generally for DC operation.

2) 24V is too low of a clamping voltage for a RS1 18.5V AC output.  The peak voltage of an 18.5V AC output is over 25V.  So a 24V TVS would be engaged on each AC line cycle in "normal" operation.

See this OGR post for some suitable bi-directional TVS parts.

I'm surprised you didn't see the dreaded magic smoke wafting from the TVS. 

Stan has the answer, just follow the posted link. Actually 33 and 36 v TVS's are recommended. Even though Lionel wants you to run their trains at 18 volts, many transformers can put out much more. Z4000s put out 22v+, and some others can output 24v. Multiply those numbers by 1.4 to get the minimum voltage rating of the bipolar TVS needed.

Pete

Hi here is the correct tvs diodes 33 n 36 volt 1.5KE33A and 1.5KE36A ARE THE 2 DIODES used! digikey.com

Alan

@Buco posted:

... Peter in sunny Queensland, Australia

Shipping charges from DigiKey in the US might be a factor.  If you bought these at a local store that carries a limited selection of TVS diodes, find the clerk that assured you the SA24A+ would work and swap them for the SA33CA+ .   That's what "assured" means to me!

The markings on bidirectional parts should contain the letters "CA" (not just "A") and there should NOT be a silver band on one end. 

Out of curiosity, did said individual tell you which way to install the banded TVS - whether the banded side goes to center or outer-rail wire nut?  You can install the bidirectional TVS either way.

@stan2004 posted:

Out of curiosity, did said individual tell you which way to install the banded TVS - whether the banded side goes to center or outer-rail wire nut?  You can install the bidirectional TVS either way.

The end result would have been exactly the same with that TVS regardless of which way the band was.

If by end result you mean abject failure.

Actually, if installed the other way, I'd think the Bell might have turned on (rather than the Horn).  That is, a Uni-directional TVS will clamp at 1-diode drop or, say, 1 Volt on each half-cycle.  I believe this is what created the DC offset as seen by the engine - thereby triggering the Horn.  Of course, this would generate massive current, heat, and rapid component failure. 

So, yes, same end result but I was curious about the intermediate result.

I figure that the TVS would smoke fairly soon.  Actually, I'm a little surprised that it didn't blow, I've never tested one of these to destruction, but slamming it with 10A AC should kill it.

Thank you one and all for your replies and assistance!!!

Stan2004:  I didn't see any "magic smoke" coming from the TVS when I tried it a couple of times on the track, before I gave up and finally removed it from the wire nuts. When I did this, everything went back to normal.

And yes, the sales assistant at the electronic store did say that the "banded" end must be fitted to the centre rail hot wire, that's why the TVS's were sold in strips with red tape and white tape at each end. The red tape indicates this is the end to go onto the + (hot) wire, and the white tape end goes to the - (ground) wire.

Guess where I am off to this morning (Monday down-under here) with a strip of TVS's in my hand!!

Just a final comment......Stan2004 and Gunrunner John's comments made me smile (laugh out loud actually), and added a bit of levity to something that absolutely frightens me to death - modern electronics. Thank you both!!!

Peter (Buco Australia)

Buco, I hope that you are able to get your hands on the TVS diodes that are recommended.  They are a bit of insurance that will pay for themselves.  It's nice that folks Down Under still have electronics stores they can walk into and pick up supplies.  I'd  like to know where there's one in the Chicago, Illinois area.  Really doubt there is one.

Phil

Just an update on the TVS saga.

Well I went back to the electronic's store (Jaycar) with the errant TVS'S, and was promptly told they did not have the Bi SA33CA+ in stock. Told them what had happened when I installed the SA24A+ TVS and they didn't seem to understand what I was going on about.

At this point I just gave-up (they are definitely not model train people) and asked them to refund me the original purchase (minus one TVS), and to order me the correct ones. They said they will have to place an order with Elemant14, their supplier in Sydney (1,000km away, and it may take a week or two to get them up here.

Good news, the correct TVS's have arrived, and I have fitted them to four of my MTH RailKing diesel loco's, with perfect results!!!!  Everything works on each loco, just as it should.

Thank you guys for all of your help. I have another four MTH loco's to go, and the full fleet will now be protected.

Just a quick aside:

How will I know if the TVS has done its job and protected the circuit board?

After a "spike" will the TVS be rendered useless, and in need of replacing?

How will I know if the TVS needs to be replaced.....does it get that "burnt component" appearance?

Peter......in sunny (well its finally raining!!!) Queensland, Australia

@Buco posted:

How will I know if the TVS has done its job and protected the circuit board?

The engines keep running.

After a "spike" will the TVS be rendered useless, and in need of replacing?

No, the TVS diode is good for pretty much infinite spike suppression as long as it's overall ratings aren't exceeded.

How will I know if the TVS needs to be replaced.....does it get that "burnt component" appearance?

You won't know if they fail open.  However, the most common failure mode is shorted, that you will notice!

In a long thread about TVS, I posted a simple cheap circuit that can shed some insight if a TVS has failed open or shorted.  It does require a DC voltmeter.  It's a you-get-what-you-pay-for... no refunds!

In order to test a TVS for an open, it really needs to be removed from the circuit, in that case for a 50 cent part, I'd just put a new one in.

Thank you GRJ.......that is exactly the information I was after.😁

Everyone can rest easy tonight!!!!

Peter on an overcast Gold Coast in Queensland, Australia.

Having a problem with WiFi.   Everything works fine with the DCS remote.   I am UNABLE to connect with WiFi and run trains with my iPad.    The WiFi comes on when I power up and I am able to read and connect my iPad to the MTH_dcs_wi-fi setting.   The blue Wi-Fi light is on, the Power light is on and the Purple light is on indicating it is connected to the TIU.   The message I get on my iPad when I try to run trains:  No WIU/TIUs Found, Make sure your IOS device is connected to the same network your WIU is on.    It has worked in the past.  

I did have a short that caused me to have the TIU serviced, it is working fine today.   Ever since the repair, I am unable to use the run-my-trains app because no WIU/TIU found.   Help!

Any suggestions?

Dave

NOTE:  Wi-Fi setting!

Note all the appropriate lights indicate connection:  

BUT!

HELP!

Is it configured correctly? Has it been updated?

Are you using your home router to connect? Is it dropping the MTH DCS WIFI?

Have you tried another device to control the WIFI?

@darlander

My spare WIU did this same thing to me the other day. I tried it with multiple TIU's, Changed between MTH & HOME modes, and used different serial cables. I finally reloaded the 6.1 Firmware and made sure to not check mark the "Keep Settings" option.

This may or may not solve your problem but it is worth a try.

EDIT & UPDATE: As Engineer-Joe points out below, I meant to say I reloaded the WIU Firmware version 1.1 (not 6.1 which relates to the TIU). I did not have to make any changes or firmware updates to the TIU.

Joe, based on his screenshot he is using it in MTH mode.

Dave, go into the app and select MORE, at the bottom right. Go to app settings and make sure that DCS WIU is selected.  Back out of that and go to ADVANCED FEATURES, select SYSTEM SETTINGS then TIU SETTINGS and see if it is showing your TIU and make sure it is selected.

Thanks everyone for the suggestions.   My TIU is running 6.1 and I am using my home router, but I switch the settings on my iPad to the MTH system.  I will try again tomorrow, and will follow your suggestions.   Thanks again for your response.

Cheers, Dave

@H1000 posted:

@darlander

My spare WIU did this same thing to me the other day. I tried it with multiple TIU's, Changed between MTH & HOME modes, and used different serial cables. I finally reloaded the 6.1 Firmware and made sure to not check mark the "Keep Settings" option.

This may or may not solve your problem but it is worth a try.

so we're clear here, you mean you re-loaded the 1.1 software into the WIFI. Not 6.1 into the TIU.

@Engineer-Joe

Yes Joe, You are correct!!!  I reloaded the 1.1 Firmware into the WIU. I didn't have to do anything with the firmware on the TIU.

Check the usb cord / jacks from the WIU to TIU. I had a problems with the contacts getting bent inside the TIU's USB jack.  Got it working again, but it really needs a new jack soldered in.

The WIU USB power connection is VERY FRAGILE!  It was not soldered correctly when these were built, so far I've repaired about half a dozen of these with the same issue, the connector on the PCB has broken loose and is flopping around inside the case.  Don't put ANY strain on that connector if it's still working!

@gunrunnerjohn posted:

The WIU USB power connection is VERY FRAGILE!  It was not soldered correctly when these were built, so far I've repaired about half a dozen of these with the same issue, the connector on the PCB has broken loose and is flopping around inside the case.  Don't put ANY strain on that connector if it's still working!

What about the solder connection on the TIU 9 pin port.   Could this be a problem source?   However, the WIU purple light is on showing connection with the TIU.   Wouldn't this be blinking if it could not connect to the TIU because of a bad contact?

Dave

@Engineer-Joe posted:

so we're clear here, you mean you re-loaded the 1.1 software into the WIFI. Not 6.1 into the TIU.

I am unable to re-load any software, I live in the Mac world.   I had my TIU upgraded to 6.1 when I added the WiFi system.   I had it done by my MTH service Tech.   Would you suggest having the WIU re-loaded?  

Thanks, Dave

Dave, the WIU interface is web based. As long as your mac has a web browser and the WIU is on the same wireless or wired network, you can reload the firmware on the WIU. The TIU is another story that requires a PC or virtual PC for sure.

Yes I mistyped earlier, I'd try reloading the firmware on the WIU with version 1.1 from the MTH website found here.

I don't think you power connections to the WIU or data connection from your USB-to-Serial adapter nor the db9 port on your TIU are an issue. The WIU appears to have steady power, and the TIU light is solid purple light indicating it has found the TIU.

@Danr posted:

Joe, based on his screenshot he is using it in MTH mode.

Dave, go into the app and select MORE, at the bottom right. Go to app settings and make sure that DCS WIU is selected.  Back out of that and go to ADVANCED FEATURES, select SYSTEM SETTINGS then TIU SETTINGS and see if it is showing your TIU and make sure it is selected.

Dan, when I got to the TIU settings:  No Active TIU Found was the reply!   Both items are working but not communicating.   Must be a cable issue.  Any thoughts?

Dave

@H1000 posted:

Dave, the WIU interface is web based. As long as your mac has a web browser and the WIU is on the same wireless or wired network, you can reload the firmware on the WIU. The TIU is another story that requires a PC or virtual PC for sure.

Yes I mistyped earlier, I'd try reloading the firmware on the WIU with version 1.1 from the MTH website found here.

I don't think you power connections to the WIU or data connection from your USB-to-Serial adapter nor the db9 port on your TIU are an issue. The WIU appears to have steady power, and the TIU light is solid purple light indicating it has found the TIU.

What are the steps to reloading the firmware from my iPad?    I down loaded it on my iPad but how do I find it and how do I get it to the WIU?    You are stretching my understanding and technical skills a little beyond my current knowledge and ability.   But thanks for you help.    

Dave  

PS:  I found it on my iPad but what do I do next?  

Dave, since the TIU is working with your remote, we can assume that problem is the Wi-Fi.  Either, or maybe both, H1000 or GRJ might be right.  Since you live in a Mac world, can you download a Windows emulator?  That would allow you to communicate with the Wi-Fi and update the firmware.  Alternatively, take it back to your MTH tech, tell him the problem, and have him check the firmware and USB port.