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DC to DC converter pinout

My brother brought me a device known as a Tech-2 scanner, which is used by GM dealers to troubleshoot and diagnose problems with GM cars (my brother is the shop manager). He said the tech that was using the scanner heard a POP, and then the device went dead. To get it repaired via normal channels would cost over $800, so he wanted me to take a shot at it first. I took it apart and the trouble appears to be in a DC to DC converter that is mounted on the main circuit board. It is made by BTCPower, and the part number is 4BE-01T-02. The IN voltage is 7-18vdc, and the out is 5vdc at 2000ma. I went to the BTCPower website and found the specs on the device, but apparently these things can sometimes be manufactured custom. In the case of THIS converter, the IN consists of THREE pins, a +, - and one labled "R". The PDF on the web site does not have this extra "R" pin, so I'm assuming it's a CUSTOM version the 4BE-01T device referenced on their web site, specifically designed for use in the Tech-2.

I found and ordered a replacement from JAMECO electronics (#216961), but it, like most other replacements I looked at, does not have this "R" pin. I applied power (exactly 12v) to the old converter and measured the voltage between ground and pin "R", and I read 4.77v. If I raise the input voltage, the voltage across ground and "R" goes up a little. If I lower the voltage the voltage across ground and "R" goes down a little. So I'm thinking it some sort of "reference" voltage used by the scanner for some reason.

Unfortunately when I examined the circuit board the "R" pin *is* connected, to a small resistor. So it does SOMETHING, I can't just leave it unconnected. That means I need to figure out what the "R" pin is on the old converter, or the new one I install probably won't work right.

By the way, forget about tracing the "R" circuit. The Tech-2's main circuit board is jammed with high density, probably proprietary, ICs on BOTH sides of the board, not to mention it's a high quality, multilayer circuit board. I can diagnose the bad converter, test some surface mounted devices such as diodes and capacitors, but that's about it.

Any suggestions?

Thanks,

Bill

Reply to
bill
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Put a scope on it and power it up. With processors it is common enough for the power supply to tell the processor that the voltage is good - R may be a reset line that is held high when power is within acceptable limits.

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Reply to
default

R may be a voltmeter for the test unit..

Reply to
Michael Kennedy

It may also be an input to trim the output voltage. Vicor used this method on a lot of their power supplies.

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Reply to
Michael A. Terrell

On Sat, 15 Jul 2006 22:50:05 -0700, bill put finger to keyboard and composed:

Pullup resistor for Remote on/off?

See

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Reply to
Franc Zabkar

Shoot, I didn't think of that at all! In my testing I did ground the "R" pin, since the ground pin was right next to it. Doing that made no difference, there was still no 5vdc output. I neglected to put a positive voltage on it. The Tech-2 DOES have a front panel on/off switch (momentary). Now you've got me thinking the converter is NOT at fault, it just needs voltage on the "R" pin to enable it. If that is the case, I just spent 40 bucks at Jameco for a replacement I won't need.

When I get back to the office tomorrow I will test pin "R" with a simulated "pullup" voltage to see if that makes any difference with the output of the converter. If the converter still tests dead and the function of "R" is, indeed, an "on/off" switch, then I can live with that. All we will loose is the ability to power down the device when it is connected to power.

Thanks,

-Bill

Reply to
bill

I didn't see your pdf reference until after I sent you my original reply. According the spec sheet, if the remote pin is >5.5vdc OR AN OPEN CIRCUIT, the circuit should be ON. That is how I have been testing the converter, with nothing connected to pin "R", yet I have no 5vdc output. That makes me feel better, although I will confirm tomorrow when I get back to the office where I can test it.

If the converter proves to be defective, and the function of the "R" pin if for remote on/off, I'm fairly certain the Jameco replacement will work, aside from not having the ability to turn the device on/off from the front panel. That is no big deal, since the Tech-2 is a hand held device that is normally plugged into the vehicles 12vdc power system when it is in use.

-Bill

Reply to
bill

I was finally able to locate a suitable replacement converter from Digikey. The "R" pin is, indeed, a remote on/off. Digikey had a 15W V-Infinity converter that is the same size as a 10W unit, same pinout, etc, AND has the remote on/off pin. As a side benefit the output current is rated at 5VDC @ 3000ma, while the original is rated at

2000ma. I installed it today and it works like a champ!

-Bill

Reply to
bill

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