Need Help Diagnosing MTH 20-2721-1 Santa Fe E-8 ABA w/PS2

Unlikely the class lights caused the blue wire to melt. That is a PCB ground (not chassis) ground. If the motors are not running. the slave board will need replacing. Look for a wire touching the motor case, or a wire touching the smoke unit casing,  There is no sound in the trailing A unit.

Chuck,

Thank you for that info. I'm aware the trailing unit doesn't have sound. The leading unit should have sound but doesn't. I should also mention that I hear the relay cycle in the leading unit when powered up. I'll continue to look for any shorted/bare wiring. Is it possible the slave board wiring back-fed the main PS2 board and fried that as well? If the aforementioned blue wire is the only burned wire, should I assume the issue is isolated to the trailing unit only? I haven't pulled the nylon wire ties off of the main harness yet but I think I'll have to dig a bit deeper. Thanks again!

Looking at your pictures, this might be a 5 volt board.  If it is, it may have failed completely and the short that melted the blue wire, likely, contributed to its demise.  Maybe one of the techs who repair these things will see this post and tells us for sure.

The 5 volt boards will have to be replaced and, I don’t believe they make slave boards anymore, so you will need two sets of boards.  MTH boards are scarce at the moment although one of the techs may have them.  If everything you have is Lionel, and you don’t have DCS, you should, probably, go with ERR boards.  The cost will be about the same and MTH items will soon become orphans, unless someone buy the company.

Good luck!

Danr,

I believe it's a 3V board based on the architecture. It has a factory BCR instead of a "9 volt" style battery. It also has the 2 pin charge port on the underside of the leading A unit. So, I have to check to see where the failure is and hope the 3V board is good and it's only a slave board issue. Thanks for the info.

I've replaced/upgraded my final MTH PS##  board. Danr hit the nail on the head... no certainty regarding future support. I bought MTH stuff, new and used.  I really like its products. But...

We my have our gripes with Lionel, I certainly have some, especially its marketing philosophy, but the point is that the brand has been around for 120 years! Post and prewar was stuff runs forever or repairable; and even Fundimentions stuff is repairable.

TMCC (and K-Line) also seems to be somewhat bulletproof and ERR is an easy fix. Legacy.... who knows?

All said, I will miss MTH, especially its support of our local train stores. However, going forward, MTH electronics will be replaced by ERR rather than MTH electronics.

John,

I agree. I have a lot of Lionel postwar loco's that run great. The obvious downside is the lack of command control. Obviously, I can retrofit all of them with ERR components but my goal is to keep them original. I've recently purged my collection of MPC era loco's and am now concentrating on TMCC & Legacy units. The only reason for letting the MPC era items go was due to lack of detail or they seemed to be cheaply manufactured using inferior materials. I've recently started grabbing MTH equipment that have issues. I've converted 2 PRR centipedes, C&O E-6,  Seaboard VO1000, UP H10-44, and SP AC-6 cab forward to TMCC. I like MTH's detail and construction but wanted to stay with one control system. I also have a few Lionchief pieces. Hopefully, someone will come along and carry on MTH's legacy. (No pun intended...) I have 2 MTH loco's that have remained original and I don't intend to convert them, for now anyway. They're equipped with PS1 so running them on the conventional track will suffice. As for this E-8 I'm working on, it's such a nice set and I'm having a hard time deciding if I should put forth the effort into repairing the board(s) or just gut them and install ERR equipment.

Hi Dan,

Also be aware that if the wires on the 10 pin male end connection of the B unit that hooks up to the slave A unit can be faulty.  I had to 2 brand new out of the box Premier E-8 B units cause the PS 2.0 3 volt slave A unit board to fry twice due to wires that were shorting behind the connection.  Luckily it was covered under warranty 2 times as the ABA and the extra B unit were purchased at the same time from the same MTH dealer.  My MTH tech went the extra distance and hot glued the wires behind the male connection in place to avoid any more shorts.  The have ran flawlessly ever since.

Here they are in action on my clubs layout and home layout.

Chas,

Those E-8’s are beautiful. As you mentioned, the B unit tether’s soldering job looks a bit sketchy. I tested all of the pins with an extra 10 pin socket and plug I had laying around. I didn’t experience a short anywhere in the wiring. I even articulated the couplers to see if they would move the wires to create a short. Good news is nothing shorted. The leading A unit’s socket looks good. I do have some good news though. On a whim, I cut back the trailing unit’s tether insulation about 1-1/2” where the slave board’s blue wire was good. I spliced in a new wire to replace the burnt section of wire and pinned back into the plug. When I was looking around and checking the basics, I checked the resistance between the rails and their respective screw terminals on the trucks. I must’ve briefly probed the wrong screw terminal and the thing took off in the forward direction. The board probably saw the necessary signal to switch into forward. I caught it and shut it down. I did it again but this time I was ready for it. I grabbed it and watched all 4 motors turn! The boards might still be good? During my initial test, I found high resistance between the negative screw terminal and outer rails. The wheels were caked with oil & grease. I cleaned them up and no more resistance. And that is why the blue wire fried in the trailing unit. The leading A unit was pulling the ground current through that tiny wire instead of its own trucks. I believe everything will work if I had an MTH transformer. My ZW and CW80 aren’t cycling the e-unit. Also, I believe the sound may be turned off. I checked the speaker, volume pot, etc. Everything checks out but still no sounds. Anyone have any ideas? Gunrunnerjohn ?

if the slave board has electronic issues they can usually be repaired ! did you try testing the FET's with the board disconnected and see if there shorted or open if you know how to test FET's ?

Alan

@Alan Mancus posted:

if the slave board has electronic issues they can usually be repaired ! did you try testing the FET's with the board disconnected and see if there shorted or open if you know how to test FET's ?

Alan

Alan,

I do know how to test them. I’ll take a look at them tonight. I believe there are only 2 on the backside of the slave board. As for the lack of sounds, the slave board won’t restore them. Maybe the chip is scrambled on the main 3V board if the sounds aren’t just turned off?Without an MTH controller, I can’t check for that. Thanks for the info.

Dan

Dave if it's a five volt board it will have a 8.4 volt battery, if it's a 3 volt board it will have a 2.4 vdc battery. so i guess you have a 5 volt board since you said is is a 9 volt battery. are u good at soldering real small ic's you could replace it I have THE 5 VOLT BOARD am1plifiers in stock!  p.s. track shorts cause the amp to blow in the ps 2 5 volt microprocessor board.5 volt amp part # TDA7056B ic

Alan

The 5V board amp is a thru-hole part, much easier to deal with than the very fine pitch SMT amplifier on the 3V board.

@Alan Mancus posted:

Dave if it's a five volt board it will have a 8.4 volt battery, if it's a 3 volt board it will have a 2.4 vdc battery. so i guess you have a 5 volt board since you said is is a 9 volt battery. are u good at soldering real small ic's you could replace it I have THE 5 VOLT BOARD am1plifiers in stock!  p.s. track shorts cause the amp to blow in the ps 2 5 volt microprocessor board.5 volt amp part # TDA7056B ic

Alan

Alan,

It’s definitely a 3V board. Previously, I mentioned it is has a factory BCR and NOT the 9 volt style battery. As of now, it sits in neutral without sounds. All of the lights and smoke units work. I got it to move twice while checking continuity/resistance between the truck screw terminals and the track. It took of at 16 volts! Lol. I didn’t have it in my test rollers. One issue I’m facing is I’m limited to either a Lionel ZW or CW80 transformers. I’m gonna go back to it in a little bit and continue checking it out.
Dan

@gunrunnerjohn posted:

The 5V board amp is a thru-hole part, much easier to deal with than the very fine pitch SMT amplifier on the 3V board.

GRJ,

It’s definitely a 3V board. I don’t know if the amp chip is cooked yet. The sounds might simply be turned off. Is there a way to initiate the sounds using a Lionel transformer? Or what equipment will I need to reset the loco? Currently, it’s sits on the track in neutral and doesn’t move when the direction button is pressed on either transformer. When powered up, the main 3V board’s relay cycles, but not the slave board’s relay. The tether connections check out fine and don’t have an open wire or resistance. Also, nothing is/was obviously burnt other than 3” of the slave board’s tether wire which I replaced and re-pinned. I deduced the wire failed due to the high amperage draw because the leading unit’s wheels were caked with dirt and oil. I’m guessing the leading unit was trying to draw it’s ground voltage through that thin blue wire. Does that sound plausible? Any thoughts?
Thank you,

Dan

Lose the slave and get the main board running first.

Does the trailing A unit run by itself when not tethered to the leading A? Use the ZW, not the CW.

Chuck, that's a set with a slave board, so it won't run without the lead A.

Yes John, but a bad slave board the trailing A will run forward only without the lead A.

Correct Chuck, hence my previous recommendation, divide and conquer!  No sense in trying to take a big bite when you can work with small bites.

@gunrunnerjohn posted:

Lose the slave and get the main board running first.

Okay, then I wonder if the lead A runs ok without the trailing A connected.

That was my question Chuck.  When I get one of these in, my first step is to get the powered unit running by itself, then I move on to the other pieces.

@gunrunnerjohn posted:

That was my question Chuck.  When I get one of these in, my first step is to get the powered unit running by itself, then I move on to the other pieces.

GRJ & Chuck,

The trailing unit does not move while separated from the leading A unit. So after digging deeper into it, if found a few things. I had previously mentioned that I was able to get both A units to move while testing for high amperage draw/continuity between the truck screw terminals and rails while they where tethered together. That got me thinking. What if it’s a battery or charging circuit issue? As GRJ suggested, divide and conquer. I checked the battery voltage and charging circuit while the track was powered to 12VAC. My meter was only reading .8VDC on the charging circuit but 2.0VDC at the battery. I pulled the 2.4V NiCd battery out and found the red wire had broken and the solder joint on the plug but the heat shrink was hiding it. I fixed that and retested. Charging voltage is now 2.1VDC which seems low but still .1VDC higher than the battery itself. My guess is either the battery is old and won’t take a full charge or the charging system has a fault in it. Charging circuit should be around 2.4-2.9VDC. At 2.0VDC, the battery is pretty much dead. After track-charging the battery for an hour at 12VAC track voltage, the charging circuit never metered above 2.1VDC or battery above 2.0VDC. I ordered a replacement battery and I’ll see if this fixes it. If not, I’ll move on knowing the battery is fresh and rule it out as a contributing factor. Is there a known process to check the charging voltage without the battery connected? Thanks again guys!

Dan

The charging circuit should have around 4V or more if you put a 1K resistor across the battery connection.  If it's hanging around 2V, it sounds like there's a charging circuit issue.

@gunrunnerjohn posted:

The charging circuit should have around 4V or more if you put a 1K resistor across the battery connection.  If it's hanging around 2V, it sounds like there's a charging circuit issue.

Thanks for the info GRJ. I’ll check it tonight and see what it meters.

Thank you,

Dan

Hey GRJ,

Would you happen to know the resistive value of R36 on the upper 3V main board? I can’t clearly see the markings but it’s either an R030 (.03 ohm) or R330 (.33 ohm) sensing resister. I read another post where GGG commented that it’s a .3 ohm resistor. Is that correct? It’s definitely toast though. It’s metering out at 7.7 ohms. Everything else looks unaffected. I cleaned up the board after removing it and the traces are still good. I’ll replace it as soon as I determine the correct value and test it again. Or, is it not repairable or may have cooked something else?

Thanks,

Dan

@gunrunnerjohn posted:

Lose the slave and get the main board running first.

R36 is a zero ohm resistor, aka a fuse.  I believe it's purpose is to blow before the PCB traces.

@gunrunnerjohn posted:

R36 is a zero ohm resistor, aka a fuse.  I believe it's purpose is to blow before the PCB traces.

GRJ,

Do you happen to know what the screen printed number is on the resistor or possible DigiKey part #? I’ll have to order a replacement and I want to make sure I have the right specs. Much appreciated!
Thanks again for your help.

Dan

Dale CRCW06030000Z0EAC RES 0 OHM JUMPER 1/10W 0603

Digikey appears to have about one million in stock.  There are a ton of other choices as well.

@gunrunnerjohn posted:

Dale CRCW06030000Z0EAC RES 0 OHM JUMPER 1/10W 0603

Digikey appears to have about one million in stock.  There are a ton of other choices as well.

Thank you!

Dan

@gunrunnerjohn posted:

Dale CRCW06030000Z0EAC RES 0 OHM JUMPER 1/10W 0603

Digikey appears to have about one million in stock.  There are a ton of other choices as well.

GRJ,

Not to question your expertise, but I was able to pull up a picture of the PS2 3V board from MTH's website and the R36 resistor is marked "R030" indicating it's a .03 ohm 1 watt current sensing resistor. Do you think you it'll make a difference? As you stated previously, it's basically a fusible link to prevent damaging other components. Furthermore, was there a change in design where MTH altered the spec's on this particular resistor? I'm assuming your tech info is more current than a pic I pulled from the internet with an unknown date of manufacture. Thoughts?

Well, we can certainly entertain changing it to one of those, it may well make a difference.  I measured zero ohms, and the board I looked at didn't have any nomenclature on the resistor.

Current sensing actually makes more sense.

0603 .033 ohm resistor.

I'm embarrassed to say, I checked the ASC manual and they even mention the resistor and it's value.

@gunrunnerjohn posted:

Well, we can certainly entertain changing it to one of those, it may well make a difference.  I measured zero ohms, and the board I looked at didn't have any nomenclature on the resistor.

Current sensing actually makes more sense.

0603 .033 ohm resistor.

I'm embarrassed to say, I checked the ASC manual and they even mention the resistor and it's value.

Well there ya go. I think we have our answer. I'll place the order now. Thank you for looking into this.

Dan

@Alan Mancus posted:

Dave if it's a five volt board it will have a 8.4 volt battery, if it's a 3 volt board it will have a 2.4 vdc battery. so i guess you have a 5 volt board since you said is is a 9 volt battery. are u good at soldering real small ic's you could replace it I have THE 5 VOLT BOARD am1plifiers in stock!  p.s. track shorts cause the amp to blow in the ps 2 5 volt microprocessor board.5 volt amp part # TDA7056B ic

Alan

GRJ & Alan,

Here’s where I’m at; I replaced the R36 .03 ohm resistor and retested. Still nothing. My guess is the IC chip @ Q8 is cooked. I’m still only getting 2.1 or 2.5 VDC battery voltage at the 2 pin battery socket J9. With the battery unplugged, I metered 4.8VDC. I tested with 2 different batteries. 1 of the 2 is brand new and meters 2.5VDC. The Q8 chip traces back to the - side of the plug. Since R36 fried, I’m assuming it took out IC chip @ Q8 too. Any thoughts? I can’t find the chip anywhere on the internet. Chip is marked F D512-4420A. Any help will be greatly appreciated.

Thank you,

Dan

Doubtful.  Turn board over and look at U-10 and Q-23.  G

@GGG posted:

Doubtful.  Turn board over and look at U-10 and Q-23.  G

Thanks again GGG for the quick diagnosis and replacement board. It's back up and running as designed. I reused the original heatsink and mounting bracket. No issues to report as the installation of the new PS3/2 board was pretty straight forward. Do you want the factory PS2 3V board for parts?

-Dan-

No, you keep it.  If you ever need to ship just a 3V Power Supply use that to ship it.  Protects the fragile pins from breaking off in shipping.  G