Balzers TPG251

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AngeloGomes
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Balzers TPG251

Post by AngeloGomes »

My vacuum gauge controller, a Balzers TPG251 just smoke.



It seems to be a voltage regulator the culprit.

Before changing the regulator, I need to know the value of the resistor R1 on the board.
It burnt but it is not open, I can measure 12-15 ohms, but I am not confident anymore to this value of resistance.

If someone has this device, can you open it and tell me the value of this R1 ?

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Richard Hull
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Re: Balzers TPG251

Post by Richard Hull »

Regulators almost never burn up! You have something like a capacitor shorted near the regulator. look for a domed top on any electrolytics. Remove the regulator and measure its output pad to ground it should be above 15 ohms but more like 100 ohms or more. The regulator does need to be replaced, of course. It burned up due to trying to feed a short!

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
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AngeloGomes
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Re: Balzers TPG251

Post by AngeloGomes »

Hi Richard.

Yes, the capacitors were at first when I saw the smoke. I already checked them for shorts to the ground but everything is Ok. In any case, I bought new ones to replace the, as well as the L7815 and L4960, the voltage regulators.

About the resistor, I was reading the L4960 datasheet and it seems to be related to it, I´ve found the test circuit on the datasheet that resembles what I see here.
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AngeloGomes
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Re: Balzers TPG251

Post by AngeloGomes »

Yes, the big cap C2 was in short

I've replaced all the electrolytic caps on the board. Now the problem is the value of the burnt resistor. Now it is 15 ohms, but I read that in this situation, the resistor decreases its value.

After a carefull check, it is connected to a capacitor at the input of a L7815 regulator, and then to the pin 1 of the L4960
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