Author Topic: Solartron 7075 Power Supply Schematic  (Read 957 times)

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Offline cbutleraTopic starter

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Solartron 7075 Power Supply Schematic
« on: August 25, 2019, 06:16:58 pm »
I got fed up with not having a schematic for the power supply PCB of my 7075, so I reverse engineered it.  The power supply schematic in the 7075 PDF, available on various websites, bears only a superficial resemblance to my unit.  I have attached the schematic below, as it may be of help to other 7075 owners with the same power supply.  No guarantees, there may be the odd mistake, but I think that it is pretty close.

It also gave me the chance to play around a little with KiCad, which I hadn't used before.  I didn't use the current version, just V4.0.5 from the Debian Stretch distribution, so I expect I have missed out on a lot of functionality.
 
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Online tggzzz

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Re: Solartron 7075 Power Supply Schematic
« Reply #1 on: August 25, 2019, 07:25:56 pm »
Thanks. I wish I had had this when looking at my three 7075!

Luckily the PSU wasn't a problem, and I now have two functional 7075s :)
There are lies, damned lies, statistics - and ADC/DAC specs.
Glider pilot's aphorism: "there is no substitute for span". Retort: "There is a substitute: skill+imagination. But you can buy span".
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Offline cbutleraTopic starter

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Re: Solartron 7075 Power Supply Schematic
« Reply #2 on: August 25, 2019, 08:09:31 pm »
Thanks. I wish I had had this when looking at my three 7075!

You're welcome.  Three!  I only have the one, so I am trying to look after it well.  I spent some time setting it up with full remote control and logging, so I would be very sad if it suffers a terminal failure.

Studying the power supply was part of my unending quest to improve its performance.  I am a bit of a low-rent, part-time volt-nut.

One thing that I noticed while I was studying the PCB, was that the mounting tab for TR12 (one of the TIP54 drivers for the main transformer) was dangerously close to the pads of C10.  I couldn't slip a sheet of paper into the gap.  TR13 had a mica insulator, but not TR12.  So I added a mica insulator.  I don't know if this was just careless assembly of my unit, or perhaps someone got in there, but it is something worth checking.
 

Online tggzzz

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Re: Solartron 7075 Power Supply Schematic
« Reply #3 on: August 25, 2019, 09:26:42 pm »
Two plus bits, and I shotgun replaced the PSU electrolytics, and inserts a diode so the front panel TTL wasn't operating at 5.3V

The metal bits are being incorporated in (non electronic) projects. I'm wondering what to do with the working display panel.

As for voltnuttery, your next steps are to get a stable low noise voltage source (which you will canibrate) and a seven decade KVD to allow you to calibrate other ranges and do linearity tests  >:D Thereafter you can get serious !

Don't forget to head over to the TEA thread :)
« Last Edit: August 25, 2019, 09:29:35 pm by tggzzz »
There are lies, damned lies, statistics - and ADC/DAC specs.
Glider pilot's aphorism: "there is no substitute for span". Retort: "There is a substitute: skill+imagination. But you can buy span".
Having fun doing more, with less
 


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