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Old 20th March 2017, 05:40 PM   #1
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Default Bio-Rad 500/200

Good afternoon everyone,
Does anyone have any experience using the Bio-Rad 500/200 in their experiments?

Thanks
Ray
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Old 20th March 2017, 10:24 PM   #2
Matt BH is offline Matt BH  United Kingdom
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I'm guessing your talking about an electrophoresis supply?

Not sure about the particular one you are asking about but some them throw the toys out if you connect the negative terminal to ground.

There is a thread on here about an older type one that has been successfully modified by several people. I don't have a link but believe it was the Isco 494.

Cheers
Matt

Last edited by Matt BH; 20th March 2017 at 10:30 PM. Reason: Spelling, doh
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Old 21st March 2017, 12:43 AM   #3
kevinkr is offline kevinkr  United States
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I had an ISCO 494, by now many samples probably need new capacitors, but it was capable for relatively high voltages. I used it solely for tube testing and got rid of it years ago.
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Old 13th April 2017, 05:10 PM   #4
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I found a listing for this Bio-Rad 500/200 that shows the insides.

Being rated at 500V 0.2A, I guess the xfmr is about the right size for a linear regulated power supply. Odd place for the fan though, unless there are air passage holes under the heatsink.

Did anyone try this for a power supply? A lot cheaper and more capable than the usual Heathkit power supply.
Attached Images
File Type: jpg Bio-Rad 500_200_1.jpg (273.3 KB, 111 views)
File Type: jpg Bio-Rad 500_200_2.jpg (280.2 KB, 111 views)
File Type: jpg Bio-Rad 500_200_3.jpg (207.8 KB, 106 views)

Last edited by smoking-amp; 13th April 2017 at 05:31 PM.
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Old 13th April 2017, 05:47 PM   #5
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One of my colleagues at work used to be with Bio-Rad, and he says that almost all electrophoresis supplies have circuitry that disables the output unless a load is present. I suppose this was to help prevent lighting up hapless bio-tech types. Anyway, a supply that appears dead might just be looking for a load. 5-10k might be the ticket.

I have one of the Bio-Rad supplies in question in my basement. I've never found a schematic, but it does use an unobtainium Motorola linear IC. If I have time, I might try slinging the lid back on the thing to see if a resistive load will make it perk up. The next step would be to figure out that output disable circuit and disable it.
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Old 13th April 2017, 07:11 PM   #6
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Hmm, If you can read the number on that IC, the IC datasheet might give some clue to how the disable circuit works. If the IC is unobtanium, then not so attractive for a bench supply. I got an International Power 250V fixed supply for cheap that was missing the IC, but it was just an LM723.
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Old 13th April 2017, 07:45 PM   #7
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I'm not sure the IC has anything to do with the disable, just noted in passing that it's in the design and no longer available. The IC had original markings, and I was able to look it up.
I was thinking at one time of stripping out the innards and replacing them with a linear regulator of my own design using either MOSFETs or IGBTs as pass elements. If I can get the supply to basically function, I'll forgo that, as I have better uses for my time. If I remember correctly, the supply functioned on the bench at work when I received it, but not when i got it home. Maybe it was just a question of load...
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Old 13th April 2017, 08:07 PM   #8
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Quote:
I've never found a schematic, but it does use an unobtainium Motorola linear IC.
The unobtainable Motorola chip is the MC1466 / MC1566. It is a unique floating regulator chip that runs on an separate floating power supply allowing the chip to be used in high voltage / high current power supplies. It was a unique design in the 70's but never became an industry standard part like the 723 regulator. I had several of the chips, but tossed all of that stuff a few years ago when it became obvious that I was going to move.

Motorola made (or had made by a contractor) a line of bench power supplies sold through their repair division, intended for use in a Motorola shop for repairing portable two way radio equipment. These power supplies appeared on the market while I worked in the calibration lab at Motorola (1974 - 1984). We bought a bunch of the "small ones" and modified them by removing the analog voltmeter and adding a digital panel meter. I performed that surgery on several dozen units. The power supplies were quite reliable (unlike some Mot branded test equipment) and rarely blew up despite my abuse. There was a bigger bench supply, but we did not use them in the plant, so I don't know if it has the same chip.

As of about 5 years ago the replacement chips were still available through Mot's National Parts Depot, but you would need the in house part number. Anyone that I know that would be able to help with some info was laid off long before I was, so that's a dead end. All of the old production line test equipment was scrapped years ago when US production ceased. They can still be found at hamfests and sometimes on Ebay.

I tried searching the web to find some leads, like the model number of said power supply without much luck. A manual would have the part number, which will start with 51, but you can't find a manual without the model number.

I did find one of the power supplies still in modified condition for sale on Ebay. It was obviously used inside a Motorola plant. The test equipment control number tag is still present telling me that this particular power supply was used in Plantation Florida, where I worked. Who knows maybe it is one that I modified. Unfortunately the model number is not visible in any of the photos.

Motorola DC Power Supply 20 Volts 10 Amps | eBay
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Old 13th April 2017, 08:34 PM   #9
Matt BH is offline Matt BH  United Kingdom
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Wow! George that is cool. How come you guys back then chose to use a digital meter for current? I would chose an analogue one to be able to see quickly any change.

I have been gathering parts and building piece's of the mother of all bench supplies for valves/tubes. I decided that I wanted digital meters but also needed the immediately recognisable deflection of an analogue meter. I have built a pair of nixie meters with IN13 bargraph under them to see that S#&* it's going wrong moment.

Cheers
Matt
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Old 13th April 2017, 09:58 PM   #10
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I would have replaced the 1466 circuit with a regulator that floats around the output voltage. This makes voltage and current sensing really easy as long as you can generate a supply for the control circuit referenced to the output voltage. Standard filament transformers are generally specified at 1500V secondary isolation, so they are good candidates for the floating supply. Many years back I threw together a linear bench supply supply like this using a bog-standard 1458 IC for the brains, and it was rock solid. It got replaced with Topward bench supplies that had more output capability.
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