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Heidenhain Positip 850 Help Required

adrian

Cast Iron
Joined
Jan 11, 2005
Location
Kent, UK
I managed to find a small ATX power supply some time ago and it works fine.
Just a little metal work was required to fit, but very pleased.
Hopefully some more years of life left in the old display.

Ciao Adrian.
 

DeadMahoDude

Aluminum
Joined
Oct 30, 2016
Fitting went rather easy for me, piece of plywood as backing plate for isolation and 4x2holes for a couple of zip ties. :D
 

adrian

Cast Iron
Joined
Jan 11, 2005
Location
Kent, UK
Assuming it's the switch mode supply that you need, an open frame power supply will do the job.
The difficulty is finding a small enough unit to fit inside the Heidenhain case.

It needs +5V -5V +12V and -12V supplies at relatively low current, probably a couple of amps per voltage.

These units are still made by specialized companies for use in third party equipment but will be expensive.
Best have a trawl through eBay for a new old stock item. I found one in Germany but that was some years ago.


Heidenhain psu.jpg
 

Flyinfinn

Plastic
Joined
Apr 21, 2022
Thank you Adrian. I looked for those voltages, I assume in ac, but don't get any of them on the wires on the board on the right. Does that mean it's that board that's bad or the one on the left? I get no voltages on the connector that's at the top on the board on the left.
 

adrian

Cast Iron
Joined
Jan 11, 2005
Location
Kent, UK
The voltages quoted above are DC.

Enclosed is a photo of the original Heidenhain power supply. The two wires outlined in red are the 240/110V AC input and those outlined in blue are DC outputs.

With no outputs the first thing I would check is the fuse adjacent to the AC input.
When these power supplies fail they generally loose one voltage rail not all.
 

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Flyinfinn

Plastic
Joined
Apr 21, 2022
The fuse tests good and I get 120v at the ac input. I noticed that R12 and R15 have been removed, is that normal? On the output what colors get what voltage?
 

adrian

Cast Iron
Joined
Jan 11, 2005
Location
Kent, UK
I wouldn't worry too much about missing components, pcb's often have option parts not required, more important to look for any burnt out damaged components.

The voltage colours are shown in the attached photo in my reply on the 22th April on the left hand side.
It shows the small linear power supply voltages and switched mode unit which is 0V black, +12V brown, +5V red and -12V yellow.

The drawing on the right was the pin out of the replacement supply I fitted and not of much use to you.

Working a a switch mode power supply is not for the faint hearted and to be honest unless you have the technical skill and test equipment required it's best to find a replacement.
 

ballen

Titanium
Joined
Sep 25, 2011
Location
Garbsen, Germany
Now that you have checked the fuse and confirmed input voltage, the next thing is to check that you have about 170 VDC on the large capacitor in the middle (the black one that says 400V 100uF on top). But be careful, that voltage can easily kill you!
 

adrian

Cast Iron
Joined
Jan 11, 2005
Location
Kent, UK
The Heidenhain 850 does not need a -5V supply.

However if you get a AT or ATX type replacement power supply which are designed for P.C's they come with a -5V along with the actual voltages you do need.
 

Flyinfinn

Plastic
Joined
Apr 21, 2022
Ballen, I get no DC voltage there but 60v ac when I measure between either of the input pins and either of the capacitor pins
 

ballen

Titanium
Joined
Sep 25, 2011
Location
Garbsen, Germany
The diode bridge is the small black item with four pins. It should have 120ac across the two pins with wavy lines, and 170DC across the +- pins. Does it?


Sent from my iPhone using Tapatalk
 

ballen

Titanium
Joined
Sep 25, 2011
Location
Garbsen, Germany
The 170 dc should connect directly to the 400v 100uF capacitor. Why do you not see the same voltage there?


Sent from my iPhone using Tapatalk
 

Flyinfinn

Plastic
Joined
Apr 21, 2022
Sorry my mistake, I must not have had the meter set right. Yes I get 170dc across the cap, I also get 170 on some of the pins of the transformer that those traces go to.
 

Flyinfinn

Plastic
Joined
Apr 21, 2022
BTW thank you so much for helping me with this. On the other side of the transformer (towards the top of the board) between pin 1 and 2 I get 4vdc, from pin 2 to 3 I get -3vdc, from pin 1 to 6 I get 4vdc
 

ballen

Titanium
Joined
Sep 25, 2011
Location
Garbsen, Germany
You're welcome. For the next step you need an oscilliscope.

At the bottom of the middle compartment is a little coil sitting on a green pad. That's the high-frequency transformer,
which is converting a chopped version of the 170 VDC into a lower voltage higher current signal. You want to first
connect a scope across the fine red wires, which are the high-voltage input (primary). You should see a roughly sinusoidal waveform at something between 50kHz and a few MHz. (Any online users know what frequency this runs at?) Then you should check the low voltage side, which is the thicker wires, where there may be several pairs. There you should see a sinusoid at the same frequency, but lower voltage.
 








 
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