Lionel Mohawk L-2A 6-38053 Wireless Tether Issue

If you place the tender alone on the tracks and do not get sounds when you apply power to the tracks the problem is in the tender.
If thats the case forget the engine and if you can replace each board in the tender one by one to try and find the bad board.
Edit. Reading your description further, the chips in your RS board have a problem. If cleaning the pins does not help you may have to replace your audio boards.
Lionel no longer supports this engine so if you can’t finds another steam Railsounds board you may have to go with ERR Railsounds.

A tender alone on the tracks reacts the same as it would in conventional. No serial data required to make sounds so no engine needed.

Pete

Let’s start off easy, trying to understand all the back & forth you did is kinda confusing,……

1. When the tender is back together as it should be 100% stock, you had no sounds under command?……what happens when you place just the tender on the track and power up?…..it SHOULD wake up in conventional, and have the start up sounds.

2. a diesel RS board isn’t going to react correctly ( sounds sequence ) in a steam engine. The radio board needs to be programmed for a diesel. ……so whatever the diesel RS board does sequence wise, isn’t any kind of a test.

3. Most common problem I’ve seen on this particular Mohawk is chaffed IR wires on the locomotive side. Look carefully,

you kinda jumped all around, so it’s a little hard to figure out exactly what’s going on….so just keep it simple, …..

Pat

I would recommend trying to keep those sounds as they very nice and will never be replicated. Moving the two chips from one audio board to another would be my last resort after checking everything else.

When testing the IR tether in command mode, the easiest thing to check to see if it’s working is to pop the coupler or change direction and look at the backup light. If that works, then you can move onto troubleshooting the sounds or lack thereof. The two common failure modes for the tether are ‘misaligned’ and ‘not there’. Misaligned will give you the rapid clicking sounds until alignment is restored, no IR at all should bring the sounds up in conventional mode.

@Norton posted:

If you place the tender alone on the tracks and do not get sounds when you apply power to the tracks the problem is in the tender.
If thats the case forget the engine and if you can replace each board in the tender one by one to try and find the bad board.
Edit. Reading your description further, the chips in your RS board have a problem. If cleaning the pins does not help you may have to replace your audio boards.
Lionel no longer supports this engine so if you can’t finds another steam Railsounds board you may have to go with ERR Railsounds.

A tender alone on the tracks reacts the same as it would in conventional. No serial data required to make sounds so no engine needed.

Pete

Pete,

You are correct sir! Well, partially. After giving your response some thought, I figured that might be the case for the lack of sounds in the tender so I tried a few things. I wired up a spare diesel board with a speaker and the Mohawk audio chipset doesn’t work in multiple RS boards that I tried. So, it’s pretty safe to say that chipset is bad. I have another generic large steam RS4 board laying around which works fine in the Mohawk tender so that’ll have to do for now.

But I still have a problem with the tender not responding to remote commands while the drawbar is lined up. Previously, when I tried the diesel RS board in the tender, I should’ve gotten some sort of response when I pressed the horn, bell, and rear coupler buttons regardless of which RS board was in the tender, correct? As stated in my first post, I went through the drawbar wiring and all looks good. I think I’m going to throw a new drawbar at it and go from there unless you have any better ideas?

Thanks again!

Dan V

@Norm Charbonneau posted:

I would recommend trying to keep those sounds as they very nice and will never be replicated. Moving the two chips from one audio board to another would be my last resort after checking everything else.

When testing the IR tether in command mode, the easiest thing to check to see if it’s working is to pop the coupler or change direction and look at the backup light. If that works, then you can move onto troubleshooting the sounds or lack thereof. The two common failure modes for the tether are ‘misaligned’ and ‘not there’. Misaligned will give you the rapid clicking sounds until alignment is restored, no IR at all should bring the sounds up in conventional mode.

Norm,

Thanks for your insight. I wish I could retain the factory Mohawk’s RS chipset but it looks like they’re bad. I already tried the things you suggested without success. I’m not getting any response from the tender while the drawbars are connected. With the known working RS board installed, the sounds come on with or without the transmitter and receiver aligned. And, the fact that I can’t see the IR light through my phone’s camera leads me to believe the drawbar’s transmitter is bad. So, for now, I think it’s going to get a new drawbar and then I’ll go from there unless someone out there has a better idea?

Thank you!

Dan V

If you're swapping boards, the first board to check if serial data isn't coming over the IR link is the AD-20A.

However, I'd find someone with a similar TMCC rig and see if you can for sure isolate which end is the problem.  My experience with the camera detecting the IR drawbar signal from the locomotive is it's usually fairly noticeable.  If it's very dim, it could be an issue with the locomotive and not the tender.

Dan, I have a complete Motherboard and 2 draw bars from a Mohawk L-3 I converted into a CSS Aux Tender. It has the board that GRJ mentioned above. It also has the power supply and RS3 Mohawk sound card. Send me an email if your interested. I dont know the status of these boards, but I can tell you they made some noise when I put power to them before I gutted the tender. I also have the metal speaker cover. If you need the speaker...I still have that in the tender, but I can remove it since its not needed.

@gunrunnerjohn posted:

If you're swapping boards, the first board to check if serial data isn't coming over the IR link is the AD-20A.

However, I'd find someone with a similar TMCC rig and see if you can for sure isolate which end is the problem.  My experience with the camera detecting the IR drawbar signal from the locomotive is it's usually fairly noticeable.  If it's very dim, it could be an issue with the locomotive and not the tender.

GRJ,

I started troubleshooting and working my from the loco side components and wiring because that’s where the serial is generated. I got to the drawbar and haven’t gone any further yet. I’m not seeing the violet glow like your picture shows. I pressed various commands on the Legacy remote and measured a small 300mv-ish change at the serial wire but definitely no glow in the camera display. I unsoldered the IR LED from the tiny PCB and applied 1.5VDC and still no glow. This leads me to believe the IR diode is bad or one of the tiny SMD drawbar components is bad. Lionel has a replacement in stock so I’m going to order it along with a few other things I need. So for $20, I’ll throw a new drawbar on it and recheck the IR LED’s performance. By chance, do you know what the voltage across the IR LED should be? Or, what the voltages should be at the end of the 3 tether wires? Obviously one is ground. One should be +5VDC ? And the serial?

Thank you!

Dan V

@Jayhawk500 posted:

Dan, I have a complete Motherboard and 2 draw bars from a Mohawk L-3 I converted into a CSS Aux Tender. It has the board that GRJ mentioned above. It also has the power supply and RS3 Mohawk sound card. Send me an email if your interested. I dont know the status of these boards, but I can tell you they made some noise when I put power to them before I gutted the tender. I also have the metal speaker cover. If you need the speaker...I still have that in the tender, but I can remove it since its not needed.

Absolutely, thanks! It won’t hurt to have an extra AD20A for troubleshooting and the proper sounds will be nice to retain. I’ve sent you an email.

Dan V.

Dan, the shortcut is to use another TMCC engine with a wireless drawbar. Exchange tenders and see whats not working. The engine or the tender. Then go from there.

Pete

@Norton posted:

Dan, the shortcut is to use another TMCC engine with a wireless drawbar. Exchange tenders and see whats not working. The engine or the tender. Then go from there.

This is the time honored way to narrow it down quickly.  However note that I got a surprise with one Lionel model, the 6-28704 PRR Atlantic E6, the serial data is inverted from my other TMCC models with a wireless drawbar.  That was a bit of a surprise.  I'm sure that's not the only one, but it's the one I tripped over here.

@DanVW posted:

I started troubleshooting and working my from the loco side components and wiring because that’s where the serial is generated. I got to the drawbar and haven’t gone any further yet. I’m not seeing the violet glow like your picture shows.

Before you give up on diagnosing the locomotive, try a different camera. It's been pointed out to me that some newer phone cameras are not seeing the IR like they used to, especially new iPhones.

@DanVW posted:

Absolutely, thanks! It won’t hurt to have an extra AD20A for troubleshooting and the proper sounds will be nice to retain. I’ve sent you an email.

Dan V.

Be sure your model has the separate AD20 and a separate audio ( power board ) Lionel chunked a curve ball at us  around this time frame, there’s a combination audio power & IR interpreter board on some models…….you can use the AD20 if your set up has 3 modular boards……2 boards means the audio power board and the IR board are one in the same……

Pat

@Norton posted:

Dan, the shortcut is to use another TMCC engine with a wireless drawbar. Exchange tenders and see whats not working. The engine or the tender. Then go from there.

Pete

Pete, that would’ve been my first action. But, as I noted in my original post, I don’t have another wireless loco in my roster. I just realized that while working on this one. Crazy, huh. Everything I have has a wired tether.

Dan V

@gunrunnerjohn posted:

This is the time honored way to narrow it down quickly.  However note that I got a surprise with one Lionel model, the 6-28704 PRR Atlantic E6, the serial data is inverted from my other TMCC models with a wireless drawbar.  That was a bit of a surprise.  I'm sure that's not the only one, but it's the one I tripped over here.

Before you give up on diagnosing the locomotive, try a different camera. It's been pointed out to me that some newer phone cameras are not seeing the IR like they used to, especially new iPhones.

John, that’s very true and that’s why I mentioned the R2LC’s code 74 in my original post indicating the serial is not inverted. Reset code 740 would be inverted serial, correct? Also, the loco side drawbar has 3 wires indicating it’s the transmitter side. The tender has 2 wires indicating it’s the receiver side. Lionel produced some models where the drawbar has only 2 wires on the loco side. Unfortunately, I don’t have another loco with the wireless drawbar (side note: my E6 is tethered). Lame, I know. 😉 I need to get with the times.
As far as my camera goes, I’m using my iPhone 8+ which I’ve always used to view IR LED’s without issue. There are typically 2 different UV wavelengths used, 850nm and 940nm. I haven’t had any issues viewing either of them in the past so I should be good.

Thank you!

Dan V

@harmonyards posted:

Be sure your model has the separate AD20 and a separate audio ( power board ) Lionel chunked a curve ball at us  around this time frame, there’s a combination audio power & IR interpreter board on some models…….you can use the AD20 if your set up has 3 modular boards……2 boards means the audio power board and the IR board are one in the same……

Pat

Thanks Pat! It does have 3 separate boards. I’m pretty well versed in the variations of the AD20 boards also 👍🏻 But at this time, I’m going to focus on replacing the drawbar IR LED.

Dan V

@DanVW posted:

John, that’s very true and that’s why I mentioned the R2LC’s code 74 in my original post indicating the serial is not inverted. Reset code 740 would be inverted serial, correct?

That's what is supposed to happen, but neither of my test locomotives respond to that.   I have the previously mentioned Atlantic and the Virginian Allegheny, and they're incompatible.  Programming the Atlantic for 4, 74, or 740 didn't change anything.

@gunrunnerjohn posted:

That's what is supposed to happen, but neither of my test locomotives respond to that.   I have the previously mentioned Atlantic and the Virginian Allegheny, and they're incompatible.  Programming the Atlantic for 4, 74, or 740 didn't change anything.

John, I’m curious to know what the wiring configuration is on the 2 loco drawbars? That might be the difference.

Dan V

The Atlantic is a 3-wire, the Allegheny is a 2-wire.  I never suspected there would be a difference in the serial data, but maybe...

Serial data is the same from two wire or three wire loco side LEDs. The difference is three wire have a transistor on the LED board to buffer serial data. Its what I replace two wire transmitters with when a Cruise M sucks down the serial data signal. The third wire in a three wire LED board goes to +5v.

Pete

@Norton posted:

Serial data is the same from two wire or three wire loco side LEDs.

Yep, this is the first time I've run across a locomotive with the inverted serial data.  I know it's inverted as I can fire up the tender on my test board, and when I flip the switch to invert the serial data, all is well, and the tender responds.

Strange stuff...

FWIW, Legacy IR data is inverted when compared to the "standard" TMCC data.

Maybe I should rephrase it. You can interchange two and three wire tether LEDs on a particular engine. I suspect any inversion is done before sending the signal to the tether.

Also late TMCC and I think all Legacy have the serial buffer on the Mother board and use two wire LEDs.

Pete

I haven't seen a serial buffer on the Legacy motherboards, I have a number of them in my parts drawers.  I don't say none have it, but certainly not all of them have any active components on the motherboard.

Not surprising as the transistor is the size of pin head.

Pete

@Norton posted:

Maybe I should rephrase it. You can interchange two and three wire tether LEDs on a particular engine. I suspect any inversion is done before sending the signal to the tether.

Also late TMCC and I think all Legacy have the serial buffer on the Mother board and use two wire LEDs.

Pete

Thanks for the clarification and information. Good stuff right here! 👍🏻

Dan V

@Norton posted:

Not surprising as the transistor is the size of pin head.

Pete

The transistor on the drawbar’s PCB is definitely tiny. It appears to have a 0402 capacitor (1mm X .5mm) as well. It’s hard to see any traces on the board with the naked eye.

Dan V

I'll have your parts in the mail today and shoot you a tracking number via email.

@Jayhawk500 posted:

Dan, I have a complete Motherboard and 2 draw bars from a Mohawk L-3 I converted into a CSS Aux Tender. It has the board that GRJ mentioned above. It also has the power supply and RS3 Mohawk sound card. Send me an email if you’re interested. I dont know the status of these boards, but I can tell you they made some noise when I put power to them before I gutted the tender. I also have the metal speaker cover. If you need the speaker...I still have that in the tender, but I can remove it since it’s not needed.

Thanks to all of you who chimed in during the diagnosis and repair of my wireless tether on my Mohawk L2a. It’s finally completed! And a special thanks to Chris for the Mohawk RailSounds boards and drawbars. This project started out as a complete retro fit into a K-Line Mohawk chassis along with GRJ’s Chuff Generator and Super Chuffer. I have to say, this thing is badass.
Without another wireless tender, I had to throw parts at it ($20 loco side drawbar from Lionel) to try to rule that out and see what else it could be. Well, it turned out to have a faulty drawbar receiver on the tender side. In addition to that, gunrunnerjohn took my Super Chuffer back to repair it and help me trouble shoot a couple things. And he didn’t even charge me for the repair! Such a gentleman. I can now button it up and run it.

I do have a couple other questions to throw out there; This loco has a +6vdc regulator board. The +6vdv output is connected to the DCDRS board at the #3 PWM pin. The loco’s wireless tether +5vdc is connected to the #3 pin on the PWM connection on the motherboard. So, the +5vdc going to the tether is coming from the motherboard. What’s the purpose of the +6vdc regulator connected to the DCDRS? The DCDRS has FM3 code on it. I know when an ERR Cruise M is used, the +6vdc regulator is omitted because the Cruise M has its own +5vdc. What does the regulator power on the factory DCDRS?

Also, this loco has a semi-smart smoke unit (8ohm) with external regulator. I was thinking of removing the reg., replacing the smoke unit’s element with a 20ohm resistor, and powering from the motherboard’s smoke output. Since the fan is powered by the Super Chuffer, will this work without issue? I’m trying to get more smoke volume at idle or low speed.

Thanks again!

Dan