MTH RAIL KING CHALLENGER Smoke unit

Here's what the circuit looks like.  That may help your repair guy.

Stewart763 posted:

... I then put a 9vlt battery across the motor it ran very smooth so I put it back in the loco 

 

When you did this, was the motor still connected to the circuit board?  Or did you disconnect the 2-wire connector first?

As the schematic GRJ posted shows, the two contacts go directly to the AC track voltage.  You can see the white lettering where the 2 wires enter the board says "AC" and "ACG" (AC Ground).  Not sure what you mean by "negative" but because of the use of a bridge-rectifier in the circuit (the black component labeled DF04 near AC and ACG), nothing on the circuit board itself is at the same voltage as the loco chassis.  Practically speaking, if you are trying to measure voltages on the circuit board to troubleshoot with a meter, you can't use the loco chassis as the "negative" voltage.

 thank you  ref the little motor I was still connected to the board all I did was put the battery terminals on to the motor and it runs fine( ref negative ) you call it ground ( I think or is it the outer rail )  can we not just soldier wires to the copper pickups on the front of my loco and do away with the coils is there anything in the tender that has to do with the working of it via the  tether cable I know that the loco dose not move unless it's connected to the tender 

I would realy like a photo copy of the loco if you know what I mean.

I was sent a pic of the newer ones but there not the same

we just tried it again and it still will not work,

Bob has checked all the components with his meter and there fine 

this is a mystery to him 

would you have a picture of the the unit showing the wires

I'm wondering if I lost one when I took it to bits

thank you again 

Stewart 

Stewart763 posted:

 thank you  ref the little motor I was still connected to the board all I did was put the battery terminals on to the motor and it runs fine

If you the motor was still connected to the board when you applied 9V to the motor, this means you also applied that 9V to the IC chip "U1" on the circuit board.  This chip generates 5V DC which is the operating voltage of the motor.  I don't know if applying 9V to the 5V chip would do any harm but it also did not do any good!

( ref negative ) you call it ground ( I think or is it the outer rail )  can we not just soldier wires to the copper pickups on the front of my loco and do away with the coils is there anything in the tender that has to do with the working of it via the  tether cable I know that the loco dose not move unless it's connected to the tender 

The two input wires to your board are AC and ACG.  These come from the track voltage.  You should be able to see by inspection whether or not these two wires are connected to the roller/wheels within the loco itself.  I am not familiar with your specific engine, but most locos I've seen have connections to the center roller (AC) and wheels (ACG) such that the smoke unit will operate without the tender connected.

I would realy like a photo copy of the loco if you know what I mean.

I was sent a pic of the newer ones but there not the same

we just tried it again and it still will not work,

Bob has checked all the components with his meter and there fine 

this is a mystery to him 

What does that mean when you say Bob has checked all the components?  Checked them how?  I would use the schematic and follow the voltages thru the circuit.  In other words start at the AC and ACG.  Is the AC track voltage there?  If you are getting track voltage then don't need to directly solder wiring to eliminate the coil springs.  If are aren't getting AC track voltage it seems you should be able to find the disconnect by inspection.

Then is there DC voltage on the output of the bridge rectifier?  Does the smoke unit "warm up"?  Feel the metal smoke reservoir. 

Is there 5V DC at the 2-pin connector at the output of the IC chip "U1" which drives the fan?

would you have a picture of the the unit showing the wires

I'm wondering if I lost one when I took it to bits

thank you again 

Stewart 

 

yes we get 14V AC to the loco from my old power supply ( Transformer )  8B American flyer   that is or was made for the UK  7-15 v out controlled and  15 v uncontrolled 

Ref the 8B I had a 3 wire fitted to it for Earth we have 220V and use a 3 pin power plug

on every thing here in England unless it from Europe and they have 2 pin and no Earth

 as for the 2 pin connector it's about 2 V DC 

Bob thinks that is the problem not enough power to operate the small motor 

we get 14v at the nut where all the wires join and a good 14v on the two copper plates on the loco,

where the 2 coils come from under the main smoke unit board 

are those 2 coils very important or can we just soldier 2 thicker wires from there to the copper pickup plates  

yes the little plug was still in when I tested the impeller  

the bridge rectifier is working we also have the little light on 

My friend Bob is 68 years old and is a retired TV repair man he always has his tool box in the car,

he used a digital meter to check power etc

he also has lived your side of the pond so understands AC better than me

yes my middle track is powered 14V Ac 

So it may be that we need a new ic chip U1

( if it is that U1 can it be bought here in an English electrical shop) 

yes the smoke box got warm when we switched the unit on from under the cab of my loco 

back to the smoke unit there was no way for me to hold the body on the chassis and check things if it's screwed to the inside of the body So I looked for the logical thing check the motor with a battery and after a drop of oil it ran smooth I also looked in side the chamber and checked the 2 heating coils there fine

  sorry to be a pain with my questions etc but your in a different Time zone to me

I think most of you are 5 hours behind me  

it's now 0815 Hrs England I hope that you all have a great Weekend 

Stewart

If the smoke chamber is warming up but the fan is not spinning, I'd say you need to change U1.  It is a 5V voltage regulator IC chip and you're getting only 2V.  You should be able to read the marking on it - 78L05A or something like that.  These are widely available here, in the UK, eBay, anywhere.  About 25 cents or so in the US...I guess these just got a bit more expensive in the UK with brexit (had to throw that in...).

Well, sure you could solder the wires to connect the board to the loco chassis but I don't see why you need to do this.

Stan2004 the 2 small coils were getting hot

and 1 broke one

�� so we removed both 

if you are aware of my loco you know that the unit goes into the top of the shell ☺it's easy to see what you are doing if it's secured to the 2 copper strips on the loco ��I'm sure that Bob will be able to find a chip like the one that is damaged ��

People think is a Proto one unit it's not 

I am in County Durham 

Could we have a phone call it would be easier to talk than text ��

Stewart 

Phone call to the UK?  Who pays for that!

I can Skype people for free of I will call the USA or any other place to get help ref my MTH Challenger 

my skype name is in my profile and so is my email I'm also on Facebook 

I must be mistaken I thought that I read that the part I need is here  I took that for England sorry 

who's Stan when it said these are widely available here I thought England   

Stewart

The 78L05A should be readily available, even in a 3rd world country like the UK.

Just kidding about the 3rd world, don't shoot me!  I can't imagine you would have any issue finding the 78L05A there.

it's 1500 Hrs in England now so  depending where you all are  I'm not going any where I'm still baffled why no one wants to send me a diagram of my loco not the electronic side but the wheels etc and what is all that stuff in the tender if it is an old loco then surly there's plans for it  some where 

thank you  for the advice I'm getting 

What makes you think any of us have such a diagram?

"all that stuff" in the tender is the reverse board and the whistle board.  That doesn't enter into the discussion of the smoke unit as it's powered from track power that's tapped from the locomotive pickups directly.

The four wires in the tether are center track, wheels, and two for the motor.

Will this one do?

Www.hobbytronics.co.uk/78l05-5v-voltage-regulator

Waiting now for the domino effect and the implosion of the EU

If you don't have diagrams how do experts fix things �� as for what is in the  tender I was asking incase something in amongst that lot was revalant�� I  noticed that there is a tiny Switch to stop the reverse working☺ so in my mind and not having a clue how it all works and there being a tether to the tender, there might have been something inside the old tender that had blown��now you have supplied the best reason why the little motor is not working ie I put my 9v battery to it to check it was working after I put a tiny bit of very thin oil on it ��then you could sayit's my own fault 

I'm sure Bob will be able to purchase the part needed and replace it 

Thank you again ��☺

I would never use a 9 volt battery for testing anything on a loco or any rolling stock.  Too much voltage.  It is also bad practice to ever apply power to a component while it is connected to a board that feeds it.

What's with all the � all over the post?

Truthfully, with most of this stuff, after you've seen it a dozen times or so, you pretty much know what goes where.  Some stuff has good documentation, other stuff has lousy to none, the nature of the beast.

As I stated, there is nothing in the tender that has anything to do with smoke on a standard PS/1 locomotive.

Thanks for that quick reply I am really grateful hopefully Bob will fix it 

GRJ, This is not a PS1 loco, but used a QSI DCRU.  Note the box shown above.  I have an RK-1107, which is the gray equivalent, and it just had whistle (until I converted it to PS2 some 12 years ago).  No battery.  But, as you pointed out, nothing in the tender has anything to do with the smoke. 

For what it's worth, the original smoke unit in mine failed under warranty, and the unit MTH used to replace it was slightly different.  So there could be differing smoke units out there.

It doesn't matter RJR, there's still nothing in the tender that will affect the smoke unit.  I think this one is out of warranty.

I wish I'd said that.

I do do think you are correct about the warranty.  I only mentioned it so readers would be aware that smoke units of that vintage would be aware they're are differences.