Atlas O GP35 with EOB for parts needs to have a good mother board

If it's the standard EOB board, I believe I have one of the motherboards in my parts box.  If you're interested, I'll dig it out and test it to make sure it's 100% functional.  A picture of the one you have would be useful.

OK John, I'll get one but its gonna take me about a week. Its the one with the daughter ot component boards mounted parallel to the motherboard

I snapped a picture of the one I have.

It looks like John has you covered but I have a few of them also. If the problem is lack of motion you can replace the triacs and their drivers but its a PITA to do. These things were not made for easy servicing.

Pete

I've replaced the drivers on a couple of them, and you're right, a major PITA!   They way they secured them to the heatsink requires you to remove all the drivers and replace them as a set.

The only thing that works is the front coupler and it gets fuzz on the speaker and some of the lights come on, tested all the daughter cards and they all work just fine. Found one of the chips in the middle of the board has a burn hole in it. That one looks like exactly what i need but ill double check when i get in front of the loco. Im out of town at the moment

A burn hole is not good.

No its not, my thought was component replacement then I figured if I could even get a part number since its got a burn hole the part number is burnt off so not a chance and plus even if I did finde the right part there maybe more unknown issues so im just gonna replace the board. How much do you need to get for yours? Once I verify it is the proper part of course

If you're feeling adventurous, the part is the TLC548ID, an 8-bit A/D converter.  Shoot me an email and we'll make a deal for my board.  Maybe I'll take that on in trade and take a shot at repairing it.  I suspect something caused that chip to go, so maybe it's an exercise in futility, but it's hard to say.

It was Elliots track voltage being at 21

YIKES!  That's too high for TMCC/Legacy.

The A/D is only used in conventional cruise mode, so you don't have to replace it if you run in command mode.  But I suspect something else more serious caused it to blow.  Sounds like gunrunnerjohn has you covered, but if you need more help, email me.

That might help explain why I'm having so much trouble.

However, in my defense, I thought I was running at 18.9V by using three 6.3V transformers ganged together in series. I only recently got a digital meter, and that's when Matt actually measured it.

It will be easy enough to lower it. All I have to do is move one wire on each of the 6 supplies, over a terminal or two (lots of intermediate taps). 

How low is too low? 15V?

I like to run in the 17-18 volt range.  My reason being that some electrocouplers don't fire below about 16 volts, and also if you have a minor voltage drop somewhere it doesn't really cause any issues.  Many TMCC and Legacy manuals specify 19 volts as the maximum, so 21 is pushing it pretty hard.

You can run on 14-15 volts, but when I get that low I notice that the speed control with a large consist has problems with any grades or successive curves.

Thanks John. I haven't read a manual in years. I'm not even sure where mine are, but I never throw anything away, so they're here somewhere.

Voltage drop shouldn't be a problem, even though some of the runs are over 50'. I use 12 gauge for my bus wires with drops every 3' section of Gargraves. Overkill for most people, but I already own the stuff to do it.

It will probably be down one notch to get into that range. I need the electro couplers and the ability to get trains up the helix, even though I don't run anything of great length. It's all single unit, dual can, with a 15 car max and modern trucks.

I'd shoot for 18 volts, with your wiring that should yield good results and not put the TMCC stuff at risk.

I'll move that project to the top of the list. Half hour or so should do the job to fix all six.

  Your locomotives will thank you, and so will your wallet!

True, but we wouldn't want Matt to starve to death.  I'm sure I'll find other things for him to do.