The HP 8600A Problem has Returned

[Chris K]

That’s what I figured. So would compensating for a fault by installing a more robust regulator cause harm? I suppose it depends on what’s causing the issue.

[Kevin Kuehn]

My concern would be how HP has the current limiting set, vs how a stock 7800 series regulator will provide whatever max current it can. If there's something down stream loading the power supply, you don't really want to provide unlimited current...

On the regulator circuit board that toasty looking .56 ohm resistor is the current sense resistor(in series with the output voltage). The 723 monitors voltage drop across that resistor through pin 1(current sense), which in turn limits current to some set value. Off hand I don't know how to calculate the current limit. The pass transistor for that 5 volt supply is supposedly mounted on a heat sink attached to the chassis. The two transistors on the circuit board are for the + - 15 volt supplies. How big physically is that series pass transistor?