hello the group

I am looking for the service manual for the power supply of the hp 8593e because I have no more voltage -15volts and I can not find anything other than the diagram gives on KO4BB and I cannot find the denomination of the pins of the DB37 connector of this diet.

can someone help me in this search.

thank you all

JOEL ON4LJ

Hi Joel

There are no complete schematics available for the 8593e power supply. Have you lost all power supplies or just the -15VDC?. There are a number of LED voltage indicators on the power supply, are they all illuminated?

73 George G6HIG Dover UK

Hi Joel

I have circuit diagram for the secondary DC voltage board, will send it later today.

This power supply consists of three PCB's in a U formation, one is the High Voltage input board (lethal voltages present), the second is the low voltage DC output board (your fault will be on this board or you may have an external overload), the third is a surface mount component control board for which no schematic has yet been found.

73 George G6HIG Dover UK

JOHN,

sorry but I can not find the db37 connector it is well at ko4bb that you put it or elsewhere?

thank you

JOEL

Hi Joel

Although the attached circuit diagram is for a different SA PSU you should be able to use it for yours. The 37pin D connector pins are on the right of the first drawing.

If you have any problems I do have a 8593 PSU that I can check for you.

Yell if you have problems.

George G6HIG Dover UK

Hi Joel

Sorry you misunderstood what I was saying, I don;t have a spare supply for sale. What I meant was I have one that I can give you information from.

Good luck with the repair, it should be a simple one, the problem comes with the smaller SMD control board, but this looks like it is working OK. Standard fault with these supplies is that they will not turn on at all.

George G6HIG Dover UK

Hi

I must start with a word of warning, the 08563-60064 board carries out two distinct functions. If you look at it with the transformer T301 uppermost and looking at the component side, to the right hand side of the transformer T301 is the low voltage regulator feedback side which is coupled back to the left hand switching controller side via the U308 optical coupler. All of the left hand side is at high voltage with lethal currents available DO NOT USE ANY GROUNDED TEST EQUIPMENT TO LOOK AT THE LEFT HAND SIDE when the PSU is connected to the mains supply as the PSU high voltage side is permanently energised, if you do so there are considerable health risks to you and you WILL destroy the power supply.

I would recommend that the 08563-60064 board is removed and independently powered by a 12 to 15VDC current limited power supply, set for a low current limit, to test and repair it. If you do it this way accidental probe slippages will not destroy the 08563-60064 board.

The main switch mode power supply is turned on/off by using the remote control pin 10 of the NE5560D switch mode controller U309. The front panel on/off switch does no more than shorting out a winding on T301, pins 1 and 4, via a 10R resistor, this provides an voltage isolation barrier for the power supply. T301 forms part of an oscillator using pins 5 through 8 and part of U303 and surrounding components which is prevented from oscillating by shorting out pins 1 and 4 of T301, with the 08563-60064 board externally powered you can just hear the oscillator running.

I have never drawn the schematic for the 08563-60064 board myself so you will have to trace the control signal from the T301 oscillator to the control pin 10 of U309 yourself. Pay particular attention to the diodes around U303, CR301, CR302 and CR306, sometimes these are the cause of the power supply not switching on by going leaky. In the past a number of individuals claim to have reverse engineered the 08563-60064 board, but as far as I know the resulting schematic’s have never been made available.

There are a number of power supply protection circuits implemented using U302, U304, U306, U307 and possibly using U301 as a reference voltage for them, but these should not prevent at least an initial turn on of the supply. Bizarrely one of the protection circuits appears to turn the switching stage, and as a result the SA, on when the incoming mains voltage exceeds a set level, I presume this is done to protect the main bulk storage electrolytic capacitors from being subjected to over voltage by applying a load to them.

In the past I have made a number of notes regarding the 08563-60064 board, in time I may be able to help you further from them. This switch mode power supply will not operate without a minimum load on the +5VDC supply. I say again, this power supply is fully energised on the incoming AC/DC side whenever it is connected to the mains, be very careful.

Hope that this helps you.

73 George G6HIG Dover UK