Re: [ts-7000] SWITCHREG polarity and Debian version on 7800

[Jim George <>]

On Fri, Dec 25, 2009 at 8:13 PM, Steven Roberts <wordy%40microship.com> wrote:

> First, just to make a key piece of information Googlable and help
> others, the OP-SWITCHREG that we received is, incredibly, NOT labeled
> for polarity on the input connector. ÂIt is diode-protected from
> being hooked up backwards, but this is a one-shot protection method
> that destroys diodes, so it's good to get it right. ÂWe spent at
> least an hour examining the board, Googling, and sleuthing about...
> finally finding confirmation in an obscure forum post in which
> someone with the same problem guessed and got it wrong... making lots
> of smoke.

I had a similar problem with the 7260 - I had to look up the PCB
schematics to fins the polarity. In actual fact it is printed on the
PCB, but hidden under the connector itself; at least for the 7260.

You can use a multimeter with a diode test function to measure the voltage drop from the protection diode. One direction should give you either 0.6 or 0.2 volts (depending on whether it's a standard or schottky diode), the other direction should give you a variable voltage as the regulator input capacitor charges up during the test.

Another test would be to check for continuity between the terminals and a known ground point (output tantalum caps are marked with a positive stripe, the opposite end should be ground).

-Jim

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