Re: HP-8753E Power Cycles at Start Up
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My mistake.The reset timer is a 555 and the EN (on my unit) is at 3v well above the 1.7v trip oint?(1/3 of 5v). Can anyone figure where the 3v comes from? R21 and R20 both connect to 5v. I guess the rectified overcurrent detection has?to be?doing that. The rectified voltage from the over current circuit drives it negative. The fault detection also connects to this pin and is the open collector of an LM339 comparator if my memory serves me correctly. I am just guessing that the circuit on the left is a delayed start from the?+10v Bias supply. The bottom circuit is confusing. The 10v Bias has to be higher than the?+5v? I need the fault to reappear while I have my 'scope connected.
On Mon, Aug 29, 2022 at 11:25 AM peter bunge via <bunge.pjp= [email protected]> wrote: The 5v supply MUST have a load on it or the other supplies will not be regulated?correctly (in the manual). I am running it connected to the 8753B and an easy test is to 'scope the trip EN to the reset timer and add more load until it trips. I can also jumper a resistor to force a trip as well. It is worth learning about anyway. Peter On Mon, Aug 29, 2022 at 10:59 AM Rich Miller via <av8torrich= [email protected]> wrote: Not to pile on - I have run the supply outside the case for over an hour. I see no ripple which would alarm me or make me suspect I have a bulk capacitance issue. I too am leaning towards overload trip point. I suppose I will have to figure out some way to load this supply down.?
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