2014 Lionel Vision Line Big Boy no Whistle, Chuff, or Tender Function

Well I know what I would do if I needed a 2014 Vision Line Big Boy version of a RCMC for a 4014.

Shows you how much I use the IR track read...

Hello All,   Dave....Thank you for your input specific to the 2014 Vision Line 4014 Big Boy (the Model I am having the issues with)...and Thanks to everyone who have taken the time to offer their insight into this issue. Last night I was ready to Order an SFC replacement Board from Lionel based on Gunrunner's logic and postings supporting his reasons for suspecting this Board.  Now, I have to say, after all the Postings today (Wednesday), I'm not sure if this Board is the issue..? Confused....You bet...Don't really want to pack up and ship this great Locomotive someplace halfway across the Country....I've had several "bad experiences" having expensive O Gauge Trains damaged in transit.... Because of it's size and weight, and the careless handling by most all of the Carriers, I fear "more damage" could occur in transit...Kinda leaves me with a $2700.00 Door stop at this point. Can I ask "all" who have been following, and contributing to this "Thread"...Is there "consensus" among most, if not all of you,  that "replacing" the SFC Board, based on the symptoms first described...(not starting up in command mode; instant "steam noise" when powered up with no way to "shut it off" using the Cab 2; No whistle or Blow-Off steam effect; stack Smoke works; No Tender Coupler response from the Cab 2; inability to switch the locomotive into reverse using the Cab 2; No Back up Light; but do have headlight and the Cab 2 will turn the lights "off" using AUX 2;  The Locomotive will run in "forward" only, with the Cab 2;  No Chuff at all in Command mode; the inability to blow the whistle in Command mode (whistle does "sound" using ZW whistle control button in "conventional mode", but no steam effect; Locomotive does reverse using ZW reverse button in conventional mode.....Well, that's the gist of it...I'm probably omitting something, but you get the idea......I want to add that I purchased this Locomotive in new/unused condition just shy of 3 months ago and while "all Legacy/TMCC functions did operate properly when purchased...It "Never" from "Day 1"  started up 100%  correctly in Legacy/TMCC mode...there was always a speaker "crackle", sometimes a little bit of steam hiss or some other minor sound bleed through when power was first applied to the Track...It would allow you to "address"  it's Cab No. and would then take Commands but the sound bleed thru when power was 1st applied bothered me.  I probably only have 2 hours (if that) of total run time on it...and it went from that start up, "static/hiss" sound bleed thru, to full blown steam roar  on start up and at that point no longer responding to the commands listed above...It would not respond to it's assigned Cab No. nor would it allow me to "reprogram" a different number...from that point on...it became unresponsive to most attempts to operate it using the Cab 2 Legacy Controller.  I might have omitted this from my original Post but when it first "crapped out" (for lack of a better way to describe it)... I did notice the "blinking Cab Light"...I didn't count the no. of blinks....and then the Cab light came on, as normal and worked as normal....but right in the beginning...."It Did Blink"...and I know that has something to do with diagnostics....So,,,In view of all this....Would you still agree that swapping out the SFC Board is "Where to Start"...??  Again, I want to "Thank All" for all your help...! One other thing....The Locomotive never "left the rails", or experienced and other type of "Short" when being operated...... PRREnola   

@zhubl posted:

One other thing on the parts front, John you might have a idea and I don't want to derail this thread so don't well on this but I've looked for parts for locomotive from 2020 and of course there's nothing listed so I call or email Lionel and on occasion they come up with a part and others they send me a list of dealers to call to see if they have a cosmetic part from a locomotive they haven't made a parts break down for. IF they don't have the part why on earth would any one of those service station randomly have whistle detail or sand dome cover for a GS-1

I can only imagine that the parts they're sending you out for were made for an earlier version.

@PRREnola posted:

Can I ask "all" who have been following, and contributing to this "Thread"...Is there "consensus" among most, if not all of you,  that "replacing" the SFC Board, based on the symptoms first described...(not starting up in command mode; instant "steam noise" when powered up with no way to "shut it off" using the Cab 2; No whistle or Blow-Off steam effect; stack Smoke works; No Tender Coupler response from the Cab 2; inability to switch the locomotive into reverse using the Cab 2; 

Well, most of the symptoms suggest the SFC for this engine, but I am bothered by one statement here.

inability to switch the locomotive into reverse using the Cab 2;

Explain that statement fully?  Are you saying the direction button on the remote won't reverse the direction of travel?  If the same remote works with other engines, that would point to the RCMC and not the SFC.

Hi Gunrunner....The Cab 2 Remote works "Fine" with all my other Legacy and TMCC Locomotives...When the Big Boy is in Command mode....No, the Cab 2 Remote "direction control button" has absolutely "No Effect"....It will not change the direction of the Big Boy, nor does the Tender back up Light come on etc.  It will change direction in "conventional Mode" by  toggling the direction Button on the ZW....but no direction change with the Cab 2...nothing...

Hello again Gunrunner....I stand "corrected"....My Son, the originator of this "Thread" for me, informed me a short while ago that he,  in fact ",  was able to reverse direction of the Vision Line Big Boy with the Cab 2. When he tested everything "before" removing the Locomotive Shell (TMCC antenna wire still attached)...he did have the ability to reverse engine direction with the Cab 2.  It was afterwards, after Shell removal and of course unhooking the TMCC antenna Wire, that the locomotive would "not" reverse....That's probably attributed to poor reception of the TMCC Signal.  My Bad.... 

Hello All,  I just wanted to update everyone on the Lionel Vision Line Big Boy saga.......After working with fellow OGR Forum Member Dave Goodman I was able to confirm that the Big Boy "was" taking most commands and the primary (stack) smoke system was working which further confirmed Gunrunner Johns diagnosis that the "Main Board" was functioning and the issue was the SFC (SmokeFanControl) Board.  Careful disassembly of the Locomotive to remove the SFC Board "confirmed" the Board indeed was "bad".  The Large black Chip or whatever it's called, had a hole blown in the top (see the photo - it's the black component below the (4) white plug receptors ).  Definite bad Board. I ordered a "replacement Board from Lionel as Gunrunner had suggested and "thought" I was on my way to having the Big Boy back in service..."Wrong"...The Board came in today's Mail and my Son and I proceeded to carefully install it in the Big Boy tonight. Remember, prior to this we had carefully checked all wiring; checked for bad connections, made sure all plug in plugs were tightly plugged in etc. And, the Loco "did take most commands"; puffed smoke out of the main stack (with NO CHUFF SOUND);  had headlights; running lights; would reverse using the Legacy Hand Held etc. but had No Whistle sound or smoke; No blowdown smoke;, No Back-up (reverse) light on the Tender, and No Coupler control on the Tender...Steady Headlight Beam....OK, So, we placed the "new" SFC Board in the Locomotive and applied power. The Locomotive still was "not "quiet" upon powering up...still had a constant steam Hiss....My Son did notice the Fan on the whistle smoke Unit did "spin" when I would blow the whistle...."BUT NO WHISTLE SOUND"  and NO Chuff...and then....within about 30 seconds of powering up, while we were troubleshooting to try and figure out why it still was not working properly.....When.....POOF..!!!  The exact same Black Chip that had blown on the Original SFC  just "BLEW"  on the "New SFC"...!  Damm...What's going on here...??  The only thing learned was that it did not "blow" immediately upon powering up....like it would if there was a direct "short" someplace....No, this took about 30-40 seconds to "blow"....like excess voltage "built up" somehow and then trashed the Chip or whatever that Black rectangular component on the Board is...Blew out exactly like the original...??? So...This has to be telling us what or where to look for the "underlying cause" of the issue with this Vision Line Big Boy Locomotive....something that is causing the SFC to self destruct...Gunrunner...what do you think...At $68 after taxes and shipping I don't want to have to purchase too many more of these SFC Boards...In speaking with Dave tonight, he seemed to think it "might" be in the Light/Sound Board...or maybe a bad Thyristor in the whistle smoke or Blowdown smoke units leaking voltage into the SFC Board causing it to blow..?  To someone more familiar with the SFC Board....the part that has blown twice now....Is that a VR (Voltage Regulator) maybe....I need some more help. I am going to call Lionel in the morning and order another SFC as I obviously need "another one of those"....but what's trashing them..? I'm thing about ordering the Light/Sound Board but don't have anything to tell me that it could be this Board...?? Gunrunner....anybody have any thoughts...Major disappointment tonight gentlemen....when I saw the original SFC Board with the blown hole in the black component I figured a new Board and I'd be running the Big Boy but alas...It was not to be....Not yet.......Thanks all, for all your help......PRREnola     

Since that component is the microprocessor, I'd suspect something is connected to one of the connectors that directly goes to the chip.  Top suspect would be a grounded line as that's quite common.  Obviously, something external is amiss, I have two of these, and they don't eat that board.

One additional comment, this on posting style.

Please break up the posts into manageable paragraphs, usually no more than five or six lines long.  Reading an amorphous block of text like that is a lot harder than when it's broken up into bite-sized chunks.

John, do you think a bad thermistor in either the whistle steam or blow-down smoke units could have caused this?

Not sure if the thermistors used are NTC type or not.  These will increase in resistance as they are heated.  A possible failure mode would be an open (no resistance) circuit and the smoke unit would pour power to the heating element.  Just a thought.  I am not sure what the failure mode would be if either side of the thermistor went to ground.

I think it would have to be a larger issue than a bad thermistor!  According to Jon Z. the thermistor is only used as a limiter during startup when they boost the power to the smoke unit momentarily, during normal running it's not a factor.  The thermistor connects to the 5V side of the smoke motor and the thermistor input.  The thermistor input is an A/D channel that should be happy with any value of resistance.

I'm thinking more along the lines of something shorted to frame ground, that will really cook things!

I would agree.  I suggested testing all leads to and from the board for possible short.  Even the testing of the switches that control the smoke units.

Well, the switches that control all the stuff go directly to the RCMC, so any shorts there would cause the RCMC distress, not the SFC board.

I agree "something" appears to be shorted or otherwise malfunctioning....What I don't understand is why this would just suddenly occur in a Locomotive that had been operating with all systems performing normally, and was still in "as delivered" condition, having never been opened up...would suddenly "develop" a "short" of this type..? Nothing inside the Locomotive was disturbed to cause such an event. A component going bad, I can understand, but to just develop a short circuit, to me anyway, doesn't seem likely. What would cause it..?

@PRREnola....

You'd be surprised! I bought a brand new engine (albeit it is a MTH FP45) that ran great for quite a while; then started acting up. Luckily I pulled the shell off of the frame and sure enough; a wire was pinched between the shell and the edge of the frame.

Luckily the wire's insulation was not cut all the way through. But over time it started sporadically shorting out to the frame. I ended up cutting the wire, slipping on some heat shrink tubing, soldering the wire back together and pushed the heat shrink tubing over the solder connection.

I then carefully pushed all the wire's back under the shell and tripled checked the seam between the shell edge and frame edge to make sure nothing else was pinched.

The engine's been running great ever since.

Yep, I've opened a ton of locomotives of all styles over the years, and I've seen many pinched wires from the factory.  I've also seen internal wires stretched around smoke units or motor edges rub right through the insulation and kill things.

@PRREnola posted:

I agree "something" appears to be shorted or otherwise malfunctioning....What I don't understand is why this would just suddenly occur in a Locomotive that had been operating with all systems performing normally, and was still in "as delivered" condition, having never been opened up...would suddenly "develop" a "short" of this type..? Nothing inside the Locomotive was disturbed to cause such an event. A component going bad, I can understand, but to just develop a short circuit, to me anyway, doesn't seem likely. What would cause it..?

What would cause it..?

vibrations, all the spinny thingies inside, heat, ….you name it,…a short is always looking for a place to happen,…..😉

Pat

So we did a bit more testing this week. The 2 smoke units seemed to check out ok...no wires were shorted to ground on either.  However...I noticed that I get continuity on both the black and gray wires that are in the 2 pin plugs that go on the smoke unit board and rs lite board?  See attached pics.  These appear to be marked 3rd and ret on the boards...but it seems odd that both wires would be connected to each other as well as the chassis?  Does anyone know if this is expected?  And if not..where to start hunting for the short circuit?

Thanks, Lee

Anybody know if those wires should all have continuity?

Looks like incoming power plug. A quick check with a pin out and looks correct. You definitely shouldn’t have continuity from the center rail to the outer rail that’d be a direct short somewhere. Of course the chassis is grounded with the outside rail. Witch is different than DC ground on any one of the boards in the locomotive.

Yep it's the power plug..the one marked 3rd and ret.  I have continuity between those 2 wires and from each wire to chassis.  I would think that's a direct short also but wouldn't that be popping the transformer breaker?  It doesn't act like a direct short between the center rail and outer rails.

@PRREnola posted:

Yep it's the power plug..the one marked 3rd and ret.  I have continuity between those 2 wires and from each wire to chassis.  I would think that's a direct short also but wouldn't that be popping the transformer breaker?  It doesn't act like a direct short between the center rail and outer rails.

Yes, they would have "continuity" when read by a meter with no context or understanding. That's a huge piece of this- being able to use a meter and understand what it's telling you in the context of what you are measuring.

A circuit board plugged in has capacitors to charge, regulators, and other load- so yes, just blindly measuring a bus circuit like 3rd rail and ground power in a multi-board system with multiple boards plugged in- yep- absolutely might be enough load that the meter registers a low enough impedance to trigger "continuity" on your meter.

That's where you step up your game, you change the setting on the meter to pure resistance, and make a note of that reading. If it's not extremely low-1-2 Ohms or less, it's not a "short".

Just to recap this and to attempt to provide some guidance and experience. I had a problem on a Visionline challenger where the dynamo smoke unit metal smoke funnel/duct would short to the solder points of the smoke unit board when flexed or under pressure as installed in the engine with the metal boiler shell,  This causes a short of the resistor or thermistor- and results in blowing the smoke unit control board.

Problem is- open with the shell removed- you might not see this short. That's because without the shell in contact with the metal duct- and even then that is somewhat hit or miss, the short only happens in situ.

Again, the bad here is- OK, you blew up the board. You replaced the board- and blew up the board again.

You then went down this rabbit hole of trying to pin out and check for shorts- with limited context and experience of what you are trying to measure- let alone find a true real short and the cause of the issue.

Again, in my case, this metal funnel/duct, is supposed to have cutouts so it cannot touch the metal solder joints of the smoke unit resistor and thermistor- however, combination of errors and solder joint height led to a short. I ended up using a Dremel tool to reduce the height of the solder joints and a piece of plastic as an insulator for the metal smoke funnel to the PCB interface.

So based on your bigboy parts diagrams and support page

https://www.lionelsupport.com/...boywiringdiagram.pdf

My #1 top suspect would be the whistle smoke unit, but also could be the blowdown unit given they might be subject to the similar smoke duct being very close to contacts on the small smoke unit PCBs.

Also looking at the parts diagram for the bigboy, I can see what definitely appears to be similar metal smoke ducts for the small smoke units.

Parts number 45 and 46 in this diagram https://www.lionelsupport.com/...LOCO-ONLY-6101437001

Again, those funnels or ducts screw to the top of the small smoke units, but the solder joints of the resistor and thermistor also poke up and depending on nothing more than air clearance gap. Then if that same metal smoke duct shorts to boiler shell when assembled- poof goes the smoke control board.

Hello, 

I get a reading of 3 Ohms and about 5.6 Ohms between the 3rd rail and return wires. However I'm pretty sure I did disconnect that circuit from all the boards.  I will have to double check though.  Yes I understand if there are other components in circuit that you can and will get a "reading" between them. Which is why I tested with all the plugs out. However I did not undo the splices where that harness is spliced in...so there could be something still in circuit.  Would that also give me a reading to chassis ground?  I guess it could if the return wire is to chassis ground.

@gunrunnerjohn just noticed you are from Hennings...thats in Lansdale correct?  We're not that awful far from there.  Would you be willing to take a look at it if we were to take a drive down?

As for checking those funnels...would I have continuity from the funnel to ground if one is shorting?  We blew the 2nd board with the shell off..so nothing should have been pressing on them. 

Would it be safe you think to try powering up with the 2 smoke units disconnected and the new sfc board in to see if the sound immediately comes on?  And if so cutting power immedialty?

Sad to say that depending on what is eating the SFC board, just powering up could immediately smoke it.  The way I approach these things is to verify ALL the inputs and make sure nothing is present that should kill the board, then I install it and cross my fingers.  Usually it works, but not always.

I'm less than 15 minutes from Henning's shop.  I do repairs and upgrades for them, and I also sell my product line through their store.

Hello Gunrunner,  I'm not too far from you....maybe 90 min up the Pa Turnpike  a couple exits before Steamtown in Scranton....Would you be interested in my driving down with the Locomotive and having you give it a once over "in person"..?  You could give me a heads up on what you charge...I could bring the (2) new Boards I purchased from Lionel and the Big Boy Loco (minus shell) and have you "take a look"...?  Are you far from the Turnpike..? Let me know....Thank you.... PRREnola

@Alex M hello...not sure if you've seen this thread yet but would you have any suggestions on anything else to check? Or would you be able to look at it if gunrunner does not? 

P.s.  I checked for shorts from the funnels tonight and there are none. The funnels on this engine are plastic.   I also ohmed out the thermistors which both read ~56 ohms across and open to ground.  The elements read 8 Ohms. 

Lastly I double checked the power plug wires again to chassis...on the black wire I get 0.2 ohm which I'd expect...on the Grey I get 3.8 Ohms. Not sure if that is normal or not without a reference.  Across the plug I also get 3.8 Ohms.

Thanks!

@PRREnola posted:

P.s.  I checked for shorts from the funnels tonight and there are none. The funnels on this engine are plastic.   I also ohmed out the thermistors which both read ~56 ohms across and open to ground.  The elements read 8 Ohms.

The thermistors on the smoke unit should ring out to a whole lot more than 56 ohms, more like 56K ohms!

@PRREnola posted:

Lastly I double checked the power plug wires again to chassis...on the black wire I get 0.2 ohm which I'd expect...on the Grey I get 3.8 Ohms. Not sure if that is normal or not without a reference.  Across the plug I also get 3.8 Ohms.

You have to disconnect things to get a meaningful reading.  I can't figure out what you're measuring here.

It had to be 56k ohms...I hate the **** auto range function on this meter because I always forget to notice if theres a little K or M next to the number.  I doubt both of them  would be bad...and they both were reading the same.

Are you able to look at it for us if we brought it to Hennings? 

@PRREnola posted:

Are you able to look at it for us if we brought it to Hennings?

Yep, but I obviously can't give you any estimate without seeing it.  The fact that you have gone through two boards suggests something more is amiss.

Would you be able to diagnose/possibly repair it this Saturday the 22nd?  Or a Saturday or Sunday if this weekend doesn't work?

@PRREnola posted:

Would you be able to diagnose/possibly repair it this Saturday the 22nd?  Or a Saturday or Sunday if this weekend doesn't work?

Any update that you can share?  I'd be interested in what was found to be the issue that caused the SFC boards to fail.

Thanks.

Hello Dave,  My Son and I packed up the Lionel Big Boy and took the sick Locomotive to "Dr" Gunrunner John 's "Repair Facility"  in Lansdale, it will be 2 weeks ago tomorrow. Gunrunner graciously welcomed us into his Home Repair Facility and spent close to (3) hrs troubleshooting; testing; and analyzing the Big Boy.  John did find a bad component (and replaced that component) on the "Railsounds/Lite Board (cs-691RSL3038-p). We felt pretty confident he had found the issue, and after several other tests (using some of John's self designed and built electronics Board Test Rigs), began a final series of tests to prove we had found the problem. John placed the new Lionel Smoke/Fan/Control Board (cs-691SFC3101-p) in the chassis and began to very slowly introduce power to the Loco on the test track....and once again, the component that had "failed" on the original SFC Board began seeing much more amperage than it should at that point in the start-up sequence. He immediately cut power before that component on the Board "blew".  Not knowing for 100% certain if the "replacement Board could have been faulty or it was a repetition of the original problem,  we halted testing at that point as John felt there must be a problem (or short) deeper into the wiring harness which would require complete disassembly of the chassis to find and John did not have any more time to continue with the diagnosis. He suggested sending the Loco to Alex for further analysis.  However, my Son, being a Computer /IT engineer decided he would "take th locomotive down to the Frame and inspect every inch of wiring for a short/bad solder connection etc.  He did do just that (see photo)  and "all" wiring; solder connections checked out 100%. I just purchased (and received another 691SFC Board), and my Son's thought is to completely remove both smoke Units and whatever else is controlled by that Board and if the Board remains viable, begin adding components one at a time while  carefully the power draw of the SFC Board. Any thoughts.. 

I omitted the word "Monitoring" in my previous Post in the last sentence, right after the word carefully....Sorry...My bad

Thanks for the update.

Wow. This is a persistent problem that does not want to be found!

I attached the wiring diagram for this engine (John posted this same diagram) earlier. When looking at the connections to the SFC3 control board I was trying to figure out what could cause the board to pull amps.  Here are my thoughts.

• Power is supplied to the board with direct track voltage.  This will provide the potential energy to kill the board.
• I would guess both the Aux Smoke unit (blow-down) and Whistle Smoke unit have been looked at several times and checked for shorts.  As you suggested, having your son test the SFC3 board with both of these disconnected is what I would do.  I would also re-check these smoke units.  I have had issues with the Aux smoke unit on my big boy.
• I would take a real close look at the switches.  See the note on the diagram that the commons cannot be tied to the RCMC switch commons.  I would also disconnect this wiring to the switches during your testing.
• Look for shorts,not only in the engine chassis, but the wiring in the engine shell.  Take a real close look at the wiring around the switches.
• When looking for shorts, take a close look at the connectors themselves.  Make sure the wires are cleanly connected to the pin connectors, etc.

Hope this helps.

After some additional thought.  here are some other things to check and/or consider.

• Could the leads to/from the RCMC to the SFC be "back feeding" and causing an issue?  Check each of the four wires for short to each other or to ground.  Zachariah posted the pin-out of the SFC board earlier in this thread.  That may help in determining what each wires function is, etc.
  If any of these wires are shorted across each other or to ground, I would again pause and ask for help.
• The other connector that we have here, is the 2 wire connection to the railsound-lite board. You stated John had to fix a component on that board.  I would disconnect the RS board just in case, both to protect the RS board and eliminate it from the cause of the SFC board failure during your check-out.
• My reasoning, which may be flawed here, is you stated early on on that the RCMC board is a bit flaky during start-up.  Maybe the issue is indeed, the RCMC board.  While its main function works (controls the motor and main smoke unit), could it be causing the other boards to fail? Maybe others could comment on this??  I'll edit out any of my non-sense given any responses.

Who cares about the writer strike. If we can get this to go on till next fall, we’re all for some great entertainment.

I too wonder if it's the rcmc sending voltage down the wrong path... since I don't know what each pin should see I have no reference. 

We put a new rslite board in actually as well since the original one after the rectifier was replaced still wasn't quite right. It was quiet on John's test rig...and the whistle did not blow.  The new one was much louder and whistle works.

I am going to start with just the power to the new sfc board....when we did that the microcontroller chip that wants to blow would begin to heat up.  With only the power connected.  But...we did not try that before connecting other components initially so that's why we couldn't rule out a bad board from Lionel. 

There were no shorts to common or chassis on any of the smoke unit wired or switch wires.  Checked that multiple times.  Unless there's a factory wiring error which if there was I wouldn't have thought it would have worked at all...but when we 1st got the Loco it did work for at least a few laps around the track.

Finally got back to working on the locomotive this evening...and have some news. 

We got what is now sfc board number 4 (Lionel replaced board 3 at no charge due to possible defect).  I proceeded with the plan described above...one connection at a time and test starting with only the power.  And everything was fine...the cpu on the sfc did not heat and after I had connected the power, serial, and rcmc the engine worked perfectly just sans whistle or blow down smoke.  But most importantly the tender functions once again worked (coupler and backup light) and after being powered up for several minutes the cpu on the sfc remained cool as a cucumber.

So...that left only the 2 smoke units remaining to be connected.  I first connected the blow down smoke unit, applied power (keeping my finger on the cpu to monitor it) and within seconds it began to heat up rapidly.  Immediately cut power, disconnected the smoke unit and tested again.  All previous functionality still worked and the cpu remained cool.  Thought great, we've found the culprit....it must be the blow down smoke unit right?  So leaving that one diaconencted I went ahead and connected the whistle smoke unit.  Got the same behavior...Cpu on the sfc got really hot in a flash.  I again immediately cut power and disconnected that smoke unit.  Retested and board still seems ok.  With neither smoke unit connected the sfc seems happy and everything else works.  But the second either auxiliary smoke unit is connected to the sfc the problems begin. 

I did one final test with the switches disconnected and one smoke unit connected just to try to rule out the switches or their wiring...but had the same behavior...cpu on the sfc board heats up rapidly.

I am really at a loss....how could not one, but both smoke units be causing this when neither appears to have any faults?  No leads were shorted to chassis ground and no leads are shorted with adjacent leads.  I get ohm readings between some of them but that I would expect.  And both of them provide similar readings.

Plus I disassembled both smoke units earlier on and found nothing amiss. The elements and thermistors appeared to test good with appropriate resistance readings on the meter.

What the heck is going on with this thing?  What sort of fault would be causing not one but both smoke units to want to fry that microprocessor on the sfc boards?

Again...with the smoke units disconnected everything else functions correctly...serial communication is present and reaches the tender properly, and the sfc board microprocessor remains cool even after power has been applied for several minutes.  But the instant either one of the 2 smoke units is connected...the chip instantly heats up and wants to blow again.

Thanks,

Jeff

This engine was not cheap to begin with.  Why don’t you bite the bullet and send it out to a qualified Lionel technician to have it properly diagnosed and fixed.  Your time is expensive and this is would allow you to move on to other things.  Time is the currency of the 21st century.  Be done with it and move on.  I don’t know how old you are, but if the tank is down to 1/3rd of a tank or less, best to use what you have left on other things that give you less frustration.  I am assuming this project is not enjoyable, or maybe you are enjoying this mystery.  You are the only one that can answer that question.  Good luck in what ever you do.