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Replacing a 8590 HP SMPS by another with the same dimensions

Question asked by sturm.hanskarl on Jun 16, 2017
Latest reply on Jul 20, 2017 by sturm.hanskarl

Replacing the SMPS of an 8590 HP-Spec by another SMPS with the same dimensions


Hello friends,

I had heavy problems with the power supply of an elder HP 8590 Spek, version up to 1,8 GHz. I lokalized the optocouplers as to bring over no signals, i drawed out the additional print with the switchmode ic, I understood the additional second protecting line with a shoot down thyristor by overvoltage, I noticed the supplyvoltage for this steering print by an addional

coil on the main transformer with rectifier and condenser, I drawed out the section of generating the variable duty cycle for

the SK 538, the delon doupler in the ac section was analysed, but nothing was able to bring up the smps to run.

So I made up my mind to buy a fitting switchmode powersupply here in switzerland by distrelec suisse and I was successful. You have to provide a stablisized +5 volt up to max 5,3 volt, 2 voltages + 15 and -15 volt and +12 volt for the

fan and others with max 1 amp.

This smps is in store, 5 volt 4 amp is adjustble, +15 and -15 volt are present, but the fourth voltage of 12 volt is missing.

But by opening this smps i noticed a fourth line and the place for an L7812 was provided, but you have to change the connections between in, ground earth and dc +12 volt out. You have to make a bridge to +15 volt, you have to solder an

additional elyt with abt 470 uf 16 volt, the soldering holes are already present, and the additional 12 volt output is ready at the "nc" srew. Now you are interested, what to do with the connector. You have to solder it out from the 8590's smps, make a little print and have care with the running currents. You copy the distance of the soldering holes and you make a new print

with sufficient copper lanes, more is always better. This print you fix with two rectangular angles and 4 x 3mm srews.

Have care to combine the right wires to the Mean-Well, a shoot down is the death o the hp....

The original smps had additional stabilisation-ics for +15 und -15 volt, 12 volt was erected by +5 volt plus an additional coil

on the main transformer and rectifiing a tension of + 7 volts, very expensive and hardly to understand why they did so...

Now take care what to do with the overvoltage protection at the POR connector, but it is simple to understand. The TL7705ACP is an overvoltage protector with an internal timer and a laser adjusted comparator switching on the output

at 4,55 volt, but it is better to study the datasheet by downloading this sheet. You have to solder out 2 condensors with

0,1 and 10 uf, the reset output is connected to +5 volt over an 1 kohm resistor 1/4 watt metalfilm or so.. and you have

all the missing connections for the "new" power supply. The stabililisation factor of the korean Mean-Well smps ist rather

good, by going up to 5,3 volt in the main line you have + 16 volt and you have to decide to stabililize 16 volt to 15 volt with a

low drop down, but with 5 to 5,1 volt it seems not to be necessary..An internal switch allows the smps to change to 110 volt by using the SIEMENS technology with delon doubler and 2 lowvoltage elyts with additional thumb to one of the ac recifiers connectors, in german we say " Mittelpunktschaltung ", you can change to 220 volt by going around the delon doubler.

I was astonished, the dimensions of the Mean-Well smps are really the same like the old hp smps, but you have to copy the new holes and a little mechanical talent is advantageous, but it is to be mastered.


The order number of the Mean-Well smps at distrelec nänikon near zurich is 169-05-930, +5,+15 and -15 volt are available and the missing +12 volt is provided at the "nc" srew, so don't hesitate to order this smps, the costs are low at about sFr 40.- plus a little us-tax. Distrelec is to be found by Google, but you can give in the ordering number and you are successful.


Greetings to all and good success 


73 de HB9CSU Charly..


Addtioal hints, because the Mean-Well smps has a very disturbing switching frequency of 63 kHz, which will produce mixing

products with the displayed input-frequency of the HP spec 8590


The original 8590 smps has very efficient filters in the main line to suppress radiations into the input of the spec. Replacing the broken hp-smps by a store-available Mean-Well smps you get unbearable deformations of the displayed spektrum and

the effekt of producing intermodulation between the smps' switching frequency and the input frequency ist going up to the analyser's boundary frequency of 1,8 GHz. The reason is found in the analysers input mixerdiodes, which make no difference between the incoming oscillations, and therefore the arising crossmodulations you can't bring out.

But the solution is simple. You order an additional mains-fiilter i.e " Schaffner FN2090-1-06 " which has an attenuation factor

of -50 db @ 60 kHz and is giong up to nearly -90 db@ 150 kHz and more. The filter has 2 Pi-filter symmetrical in series and

is fully metal encapsulated. Additionally the filter has deviation condensers to ground, this makes the excellent data of the filter believable.The connection from the filters output to the mains connector of the Mean-Well should be as short as

possible and the wires should be shielded and grounded on both ends, The Mean-Well itself ist shielded too and the main-wires shield are linked togehter without interruption, like a good coaxial cable....


This is the only way to keep the switching frequency out from the analysers input and is the king's way....


73 de HB9CSU Charly