GML Enterprises

[peteski]

Does your multimeter have automatic or manual range selection?  The voltages you seeing on the meter make no sense.
I would think that you should not see any voltage (AC or DC) of more than 25 Volts.

What multimeter do you own?  Brand, model?  Maybe post a photo of it?
Test your multimeter using a 1.5V and 9V batteries if you have them handy.  Use the DC voltage range. If the multimeter has manual range selection, dial up 20V.  You should see voltage readings close to the battery's rated voltage.

[nkalanaga]

If you're getting 182 volts AC, on a device powered from 110-120 volts, it has a REAL problem.  Even 82 volts DC sounds way too high.

[mmagliaro]

I like Peteski's plan... first measure a AA or a 9v battery with that meter to make sure the meter is working and you are using it correctly.  Those readings are crazy.  And yes, the model number and brand of the meter would help.
I would expect something between 16 and 24 volts, DC, across those rectifier + and -.

You can also set the meter on volts AC and measure across the two INNER legs of the bridge rectifier.  That should give us
the AC output from the transformer.

[Peavine]

Ok. Lets prove my ignorance with this stuff...

first, a brand new “D” battery. 2.1 vdc. I Moved the lead on the multimeter to the battery position.

Next, I measured the AC input from the transformer that I’m using to test this to the unit.20.4 vac

Then I measured across the inner two pins, and the result was 23.6 vac. The green lead is connected to the other inner pin. This was a PITA doing it one-handed and taking pictures with the other!

Next I measured across the outer two pins, the result was 58.5 vdc.

Does this make any sense to you guys?

I’ve gone back and measured this a couple of times since I took the pictures, and I’m getting a consistent 24 V AC in from the transformer even though the photo only shows 20.4

[Peavine]

Here’s a cleearer picture of the front of the meter

[Peavine]

Here is what the front of the unit looks like. I took these measurements with the pulse off

[mmagliaro]

What this tells me is that the DC ranges on that meter are whacked.
Try reading the voltage of a D battery on the DC VOLTAGE ranges, NOT on those "battery" ranges you used.
But no way should it be reading 2.1v for a D battery.  If it's a brand new battery, it should read 1.55v, and a digital
meter should easily be accurate enough to show this, even a cheap one.  2.1 is way wrong.

The 23.6v AC you are getting from your power pack and on the inner terminals of the rectifier make sense.
The 58.5v DC is crazy.  And it DOES look like you had the meter on a DC range to measure that. 

 In fact, it's impossible. If 23.6v AC is going in to the rectifier, you should expect, even no-load with capacitors across it, you might get about 33 volts DC.

So... retest the D battery on your DC voltage meter setting (not "battery") and see what you get.  But I think that meter is
hosed.

As an aside, did the instructions for the GML say it was okay to feed it 23.6 volts AC as its power source?  That seems much higher than necessary.  About 16-18 would make more sense.

[Peavine]

Ok, I checked the battery again, and got another new one. This time I got 1.66 vdc on both.

My conclusion here is that I have a shopportunity.

I’ll go get a new meter this afternoon and check this stuff again

As for the transformer voltages, the transformers i bought from GML provide 23.6 vac.

[mmagliaro]

Ok, I checked the battery again, and got another new one. This time I got 1.66 vdc on both.

My conclusion here is that I have a shopportunity.

I’ll go get a new meter this afternoon and check this stuff again

As for the transformer voltages, the transformers i bought from GML provide 23.6 vac.

So, did you get 1.66 using one of the DC ranges instead of the "battery" range?  That's better, but still pretty bad.
Yes, time to get another meter.
It doesn't have to be expensive.  A $25 meter will be plenty accurate and have all the ranges you need.
Something like the Tenma 52AC3273 is one example.

[Peavine]

Ok, facepalm time.

It turns out that the little battery icon on the meter display actually means something.

With a new battery in the meter, The D cell batteries showed 1.515 V, and 1.532 V. The AC power coming from the transformer shows 17.8 V AC, and the two inner pins show 17.8 V AC. Unfortunately, I am still showing 47 Vdc across the pins in the plus and minus holes.

[mmagliaro]

Ok, facepalm time.

It turns out that the little battery icon on the meter display actually means something.

With a new battery in the meter, The D cell batteries showed 1.515 V, and 1.532 V. The AC power coming from the transformer shows 17.8 V AC, and the two inner pins show 17.8 V AC. Unfortunately, I am still showing 47 Vdc across the pins in the plus and minus holes.

Okay, that is at least believable.  The battery voltages are right, and 47 is within the realm of possibility because he
could have the two capacitors wired across it to form a voltage doubler circuit.
17.8 x 1.414, nominally gets you a peak of about 24.9, but a doubler configuration would get you around 48-49 volts.
That's pretty unusual however,  to need 48v for anything in a throttle.  So let's find out.

First, here's what a voltage doubler would look like (I swiped this off the internet and relabled it):


Put one meter probe on a convenient ground (I'll take a guess here and hope the metal case of that thing is grounded).
Put the other on the "+" from the rectifier, and see if you get around +24 volts.
Then touch ground and the "-" with the probes and see if you get -24 v.
(the digital meter should show a "+" or "-" sign for the voltage polarity).

If you do, then that's probably how it's wired, and odd or not, the rectifier and caps are probably okay.

Let's try for some more clues now.

You are powering this thing from the AC terminals of your other power pack?   Are you able to follow the connections from where that comes into the case, and see if both leads go straight to the inner legs of that bridge rectifier?

That 5- terminal thing (the one I circled and said it had bad solder joints on it...
Can you read any numbers or markings on it?

[peteski]

While totally off-topic, what is the surface on which you are working on while taking measurements?  Looks like aluminum panels and bunch of screws.  Is it some sort of a fuselage? 

If it is a metal surface, it might not be good idea to work on exposed electrical electronic circuitry there.

And as others said, don't use the 1.5V/9V/Battery range. Only use the DC and AC ranges.

[Peavine]

Sorry it’s been a few days. Had to run down to El Salvador for a last minute work assignment. The front bezel of this thing is plastic, so not a ground. instead, I touched one probe to the aluminum strip along the bottom. The + side gives me 47 volts, the - side gives zero, so not sure that’s helpful to you.

I am powering it from the AC terminals of a power pack, but when it’s installed it is powered by an AC transformer provided by GML. I checked and yes I can find a direct line from each of the ACs into the bridge rectifier inner legs.


In terms of the doodad with the Janky looking Solder, I looked for numbers on it. It appears that were at one time, I’m not sure if they just faded or were removed. I found that if I shined a light at an angle I could get the best look at what the numbers might’ve been. I pulled two other units that I have and did the same thing with the same result. Here are the pictures. Not sure if the numbers are more legible to you or make any sense.

[peteski]

Well, the guy who built those throttles ground off the part numbers.  You can clearly see the depressions in the black epoxy case.  The partial numbers he didn't bother to remove are just part of the date code (useless).

That is an unusual component (that is probably the reason he made it hard to cross reference).  It looks to be a standard TO-220 case size, but with 5 leads instead of the typical 3.  It is likely some sort of power amplifier.

Seems like he wanted to make sure that nobody but himself was able to service these throttles, or copy the design. Protecting his intellectual property I guess.  If he was still alive, I doubt he would have shared any details of the design (like a schematic diagram).

[Peavine]

Yeah, that wasn’t the only components I saw in there with the part numbers Dremeled off. Luckily for me the ones I bought off eBay came today, so tonight I’m going to install that unit and run some trains. Or just grab another Manhattan and finish this nice cigar in the backyard...