# A question about GP9 guts....



## dawinter (Jan 2, 2008)

Some of this story you've heard before...

I bought a GP9 that runs well.  I opened it up to install LEDs in the headlight ccts because both lamps were 'off' in both directions anyway.  When it was opened up I found that  (a) the number board lamps were only about 1/2 bright plus the class LEDs were just barely 'on' and the main board was more up to-date than my old 'plane-Jane' boards.  I also found both rectifiers attached to the same weight and getting quite warm....  

First I figured that headlamps might be shot.  Replaced them with LEDs as in my older GP9's but still nothing.  Paul in Ottawa told me he tests these smaller boards with a 6V batt.   I did.  They both work just fine.  Well, then I figure there was something wrong with the main board (Poorly attached rectifiers et all) and that the lamp boards were not getting a high enough voltage.  

So I order a new main board.  (That's a story in itself - there are THREE types of boards.  Who knew.)  Anyway, I installed the new board.  see below....










Nothing has changed.  Still no headlights.  Lamps or LEDs.  Still 1/2 bright number boards etc.  I pulled an old GP9 apart and found that the o/p to the lamp boards follows track power.  0V to 15V+ and everything works.  There is only 2 1/2 VDC at the pin outs of the newer board but a higher AC component.

Emailed USAT but no response as yet.

Any help here?  I really want to get this working and move on to something else.

Electronically challenged Dave.


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## Paul Norton (Jan 8, 2008)

The connectors and wires appear to be correct.
 








 








 
I really should update these fuzzy pictures and the MU plug article.
 
Did you wire the LED headlights in series or parallel?
 
What value of resistor was added to limit the current to the LEDs to 20 ma or less?


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## Curmudgeon (Jan 11, 2008)

I have yet to see a USA dismal where the control regulators were screwed to the same heat sink. 
They are opposite polarity. 
Remove both from the weights and try it.


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## dawinter (Jan 2, 2008)

Posted By Curmudgeon on 03/12/2008 8:56 PM
I have yet to see a USA dismal where the control regulators were screwed to the same heat sink. 
They are opposite polarity.


Exactly!

That's the main reason I pulled the original main board.  Figured the regulators were toasted and thus the bad o/p.  Sadly, that wasn't the case.  Now I'm out thirty bucks and I have two main boards that are probably ok.  /DesktopModules/NTForums/themes/mls/emoticons/whistling.gif

Paul.
 
I'm sure I did accurate drawings before I pulled it all apart.   I had to.  The schematics were completely different from my three much older units.  I also lifted the regulators off the weights to see if that would do anything.  Nothing.

I have GP9's with parallel LEDs and at least one with series LEDs.  Both work well.  There is a 560 ohm in there I think.  I'd have to pull it apart to see.  Never the less, that doesn't explain why the front and rear lamp boards don't work right even with NO headlights.  LEDs or otherwise.

Waiting for a response from USAT.  I may have to phone them.

Dave


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## Paul Norton (Jan 8, 2008)

Dave I checked the four lighting boards I removed from my GP-9s. Only one worked properly and the number board lights were dim at 6 volts (4 AA alkaline cells). A 75 percent failure rate seems to imply that all the light bulbs must be in good working order for the circuit to work properly.
 
Two of the boards, including the one that worked, had a 1/2 watt resistor (R1) banded orange, black and brown. The other two boards which did not work had a 1/4 watt resistor (R1) banded brown, black and black.


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## dawinter (Jan 2, 2008)

Posted By Paul Norton on 03/13/2008 3:33 PM
Dave I checked the four lighting boards I removed from my GP-9s. Only one worked properly and the number board lights were dim at 6 volts (4 AA alkaline cells). A 75 percent failure rate seems to imply that all the light bulbs must be in good working order for the circuit to work properly.
 
Two of the boards, including the one that worked, had a 1/2 watt resistor (R1) banded orange, black and brown. The other two boards which did not work had a 1/4 watt resistor (R1) banded brown, black and black.




Thanks Paul

That seems like a **** of a difference.  10 ohms vs 300 ohms.  Anyway, mine are all 300 ohms and the board lamps do come on but very dimly.  I'm sure the problem is still in the main board somewhere.  I've replaced both lamp boards already.

No answer I guess.  Perhaps I'll send it off for repair by someone who has more than 35 years in electronics. /DesktopModules/NTForums/themes/mls/emoticons/blush.gif

JeeZ

Dave


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## dawinter (Jan 2, 2008)

*"BUMP"

*Just in case there's someone with the answer who missed the original post.

On the other hand, has anyone been able to get trouble shooting information and answers from speaking to USAT people on the phone?  This looks as if it's the only answer right now as everything is new and all my connections seem to be correct.  Although I did make a mistake once before. /DesktopModules/NTForums/themes/mls/emoticons/blush.gif

Dave


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## Greg Elmassian (Jan 3, 2008)

Dave, I have company this weekend. If you make no headway, I'll try to pull one of mine apart next weekend and figure out the power to all the lighting circuits. 

One item of caution: reading the resistance on a COLD incandescent bulb will NOT give your a correct reading. All incandescent bulbs change their resistance RADICALLY between COLD and operating. (That's also the reason light bulbs burn out mostly when first switched on). 

You need to calculate resistance based on voltage drop WHEN OPERATING. 

My two GPs are very new, but the one that is "open" has a QSI board in it, so can't use that to measure. 

Regards, Greg


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## dawinter (Jan 2, 2008)

Thanks Greg.

I'd appreciate any help I can get on this.  If your using the same main board the o/p voltages would sure be a place to start.  At least I'd know which direction to go from there.

Dave


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## big Jerr (May 7, 2008)

what was the verdict on this ? I have one im putting a sound unit in and the lights are half as bright in reverse as foward @ same voltage cant figire thias out ?


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## dawinter (Jan 2, 2008)

Well, here's the thing. I never did get it right. 

But 205 is running with the rest of them..... 










I pulled the paired LEDs (headlights) out of my cct along with the 560 ohm resister that I used in the older models and soldered paired LEDs (with no I limiting resister) straight across the track power input at the 'other side' of the lights ON/OFF switch. They now come on full bright just like the older GP9's and I let the device do it's own polarity check. I never run over 10 volt track power anyway. Looks good and has been working steady for three weeks. 

Now why didn't I have any intensity on the classification lights? I played around with the 300 ohm resister on the light boards. Buy soldering a 100 ohm resister across it I effectively wound up with a 200 ohm cct and it worked well. That's the way it is now and they are as bright as they are in older units. 

Number boards? Still very dim. Of course they would be. They're 12V lamps in a 3 volt cct. I can't find a 3 volt lamp that fits the screw in socket. LEDs can be soldered in but are very bright for that application. The local electronics store said there are defused LEDs that might work but I'm playing with opaque paint right now. We'll see how that works over time. 

Everything I did is/was wrong so no need to point that out. I just don't understand the basic question so I have no idea about the answer. Why do I even have to do this at all??? 

Dave


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## Skip (Jan 2, 2008)

FWIW, I bought two of Art Knapp's TH&B variants that came in last fall, and on a 24v track power set-up run under a TE in direct mode they light up just fine. Haven't had the covers off to see what's in there yet. Under PWC control, not so good. The controler has to be at about 3/4 power before the lights come on, and then they sort of jump on quickly. Motors behave ok either way (very smooth running locos). In direct mode the class lights work and polarity sense fine, but power does have to be about 35-40% before they come on (loco will move way before the lights come on). 

In contrast, the pair of Alco S4s that I have are a delight, especially on PWC. The lights and smoke spool right up to full brightness while the loco quietly sits there, a little more throttle and they just glide out. THAT'S the light/power circuit USA should use in their locos...!


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## dawinter (Jan 2, 2008)

Posted By Skip on 05/07/2008 7:02 PM
FWIW, I bought two of Art Knapp's TH&B variants that came in last fall, and on a 24v track power set-up run under a TE in direct mode they light up just fine. Haven't had the covers off to see what's in there yet. Under PWC control, not so good. The controler has to be at about 3/4 power before the lights come on, and then they sort of jump on quickly. Motors behave ok either way (very smooth running locos). In direct mode the class lights work and polarity sense fine, but power does have to be about 35-40% before they come on (loco will move way before the lights come on). 

In contrast, the pair of Alco S4s that I have are a delight, especially on PWC. The lights and smoke spool right up to full brightness while the loco quietly sits there, a little more throttle and they just glide out. THAT'S the light/power circuit USA should use in their locos...!




That sounds like the same issue I have. As I said, I never run up over 10 volts using 'DC' (I'm indoors with 15 cars, at most, behind two engines) so nothing really works well on the light boards. This is what I call a second generation main board. At the same time, my four very early GP9's run early and bright at anything over 5 volts track power. They use very simple 1st gen main boards. No components except the four switches. 

Perhaps I'm asking it to do something that was never intended. 

Dave


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## big Jerr (May 7, 2008)

I messed with it to long, my guess is the regulators @ the wieghts mine has two diff brands but both are mk 317 but diff makers and the werd thing is no voltages are the same any where thought about changing the regs but two much work and it could be in the board itself . so I just pulled the light bulbs out an stuck a led souderd to the soket no resister since it still dont come on till trains movin,led head lights driven by the sierra . if I had the patience Id just rip the boads out altogether and start from scratch . very unsaticfied with this unit , like it was built with leftovers (The electronics )


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## Paul Norton (Jan 8, 2008)

Big Jerr, our club members usually gut a locomotive before converting it to self-contained, battery power and radio control. I currently use Aristo-Craft’s 75 MHz receivers which control both the motors and lights, so the factory, power distribution circuit board(s) and switches are redundant. Removing the factory installed electronics leaves more room for battery packs and the receiver. 



















Wiring a locomotive yourself usually simplifies the wiring and allows you to better understand how things work. I build my own Super Sockets for the receiver which have: 
-	Screw terminals for easier wiring. 
-	Radio noise suppression components (4 large chokes) for improved radio range. 
-	Board mounted resistors for LED lighting. 










Although I run battery power, the Super Socket can also be used for track power by hooking up the track power wires instead of the battery leads. 

I also build my own LED lighting circuits as they are: 
- Easier to understand (LEDs in series with one or two resistors). 
- Constant and brighter directional lighting than bulbs. 
- More power efficient which extends battery pack, run times. 

As an example my GP-9 lighting boards draw less than 20 milliamps, compared to the 1/2 amp that the factory boards draw. They also light brightly before the locomotive starts to move.


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## dawinter (Jan 2, 2008)

That's a nice little gismo you've built there. 










Perhaps that is the final answer. 

But it begs the question: Why do we have to do that? 

Cheers


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## Skip (Jan 2, 2008)

Speculating here, but I wonder if USA has now rated them for an anticipated higher track voltage? With Bridgewerks putting out as much as 30v, maybe they were burning out too many having them light up at lower voltages, then cooking them when the power gets turned up(?) Whats the track voltage on DCC in LS (since I don't run it, I have no idea).


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## dawinter (Jan 2, 2008)

Posted By Skip on 05/08/2008 7:29 PM
Whats the track voltage on DCC in LS (since I don't run it, I have no idea).




I'm not a DDC user but the fundamentals are such that 'full track power is applied to the rails at all times' thus full bright lights all the time etc. The decoder in each engine receives a unique signal from the throttle that will turn functions on/off (lights) when required by the operator. Motors for example are selected to use varying amounts, and polarity, of that full track power to control speed and direction. 

Bad description I know but.... 

I thought full track power in large scale uses was 24 volts. 

Dave


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## SteveC (Jan 2, 2008)

Paul

If I'm not mistaken the max voltage spec. on the rails, for DCC in Large Scale is 22 volts.


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## dawinter (Jan 2, 2008)

Posted By SteveC on 05/10/2008 1:20 AM
Paul

If I'm not mistaken the max voltage spec. on the rails, for DCC in Large Scale is 22 volts.




Your probably right. A DCC guy would know for sure.


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## big Jerr (May 7, 2008)

very nice work Paul; I wish I had the elec. talents . some day Im going to do it over . thanks for the info J.W.


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## Greg Elmassian (Jan 3, 2008)

22 volts is supposedly max, but I read somewhere 24v... I have 23 to the rails, I had my NCE systems tweaked (by them) to allow up to 24 volts. The normal max voltage did not give me a high enough top speed on a certain passenger train. 

Regards, Greg


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