Regulated power supply help needed

[AB]

Good Day all,

I have been given a 100v variable and regulated power supply. It came
with a schematic and a partial parts layout, but I can't make out all
the component values although I can read the symbols just fine.

To make matters worse, the transformer core and one of the chips are
obsolete. It is also potted, so I can't look at the components to
determine their values.

It works great, although it's a black box at this point.

I've posted the schematic and some questions about it at:

http://www.uninets.net/~artky1k/100v.PDF

If anyone can give me some intelligent guesses regarding the circuit,
I'd sure like to hear from you.

Let me know if there are problems downloading it, I'll gladly email a
copy of the pdf, it's a small file.

Thanks to all for comments and suggestions.

AB

 

[mike]

Good Day all,

I have been given a 100v variable and regulated power supply. It came
with a schematic and a partial parts layout, but I can't make out all
the component values although I can read the symbols just fine.

To make matters worse, the transformer core and one of the chips are
obsolete. It is also potted, so I can't look at the components to
determine their values.

It works great, although it's a black box at this point.

I've posted the schematic and some questions about it at:

http://www.uninets.net/~artky1k/100v.PDF

If anyone can give me some intelligent guesses regarding the circuit,
I'd sure like to hear from you.

Let me know if there are problems downloading it, I'll gladly email a
copy of the pdf, it's a small file.

Thanks to all for comments and suggestions.

AB

It's not at all clear what help you need. If it works, don't fix it.

Looks like an open-loop switching supply that's inside the loop of
a linear regulator that sets it's input voltage.
Transformer turns ratio will be approximately the ratio of input
voltage to output voltage.
mike

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[fff3]

Regarding your questions:

Q1 looks like a series-pass regulator. A feedback signal applied to the base
controls the voltage passed to the emitter.

Perhaps U1 is an op-amp?

 

[AB]

Found some more information.

The 8212 chip is very obsolete, circa 1985. It is actually an ICL8212,
formerly made by National, Fairchild and Harris (Intersil). There is
no spec sheet available for it. I did find an ap note however. It has
a 1.15 volt reference, a comparator, a digital output that goes high
when the input exceeds the programmed voltage and programmable
hysterisis.

While the ICL8212 is not currently in production, the MAX2818 (Maxim)
is a modern low power replacement and is in production. Maxim claims
pin for pin equivalency, they even make it in an 8 pin dip. The Maxim
chip uses microamps instead of milliamps of supply current. Should be
able to use the Maxim spec sheet to get more information aboutt he
operation of the chip.

I also found one of the resistor values is 15 megohms, although I'm
not sure where it fits in the circuit. I can also gain access to the
leads on the voltage setting pot (don't ask). I'll measure it later
tonight.

I also might be able to probe the potted module. It is soft potting,
looks like black silicone RTV. I might try punching a sewing needle
through the potting material in selected places to try and take
resistance readings.

This little beast won't give up it's secrets easily.

Stay tuned and thanks for reading.

AB

 

[roma]

Good Day all,

I have been given a 100v variable and regulated power supply. It came
with a schematic and a partial parts layout, but I can't make out all
the component values although I can read the symbols just fine.

To make matters worse, the transformer core and one of the chips are
obsolete. It is also potted, so I can't look at the components to
determine their values.

It works great, although it's a black box at this point.

I've posted the schematic and some questions about it at:

http://www.uninets.net/~artky1k/100v.PDF

If anyone can give me some intelligent guesses regarding the circuit,
I'd sure like to hear from you.

Let me know if there are problems downloading it, I'll gladly email a
copy of the pdf, it's a small file.

Thanks to all for comments and suggestions.

AB

The 8211 is a programmable voltage reference "ICL 8212 " by Intersil
1981 catalog .
If you really need specific information data ( As the data covers ten
pages)send me an e-mail and I will forward copies .
Roma
[email protected]

 

[Mark Jones]

Found some more information.

The 8212 chip is very obsolete, circa 1985. It is actually an
ICL8212, formerly made by National, Fairchild and Harris
(Intersil). There is no spec sheet available for it. I did
find an ap note however. It has a 1.15 volt reference, a
comparator, a digital output that goes high when the input
exceeds the programmed voltage and programmable hysterisis.

While the ICL8212 is not currently in production, the MAX2818
(Maxim) is a modern low power replacement and is in
production. Maxim claims pin for pin equivalency, they even
make it in an 8 pin dip. The Maxim chip uses microamps instead
of milliamps of supply current. Should be able to use the
Maxim spec sheet to get more information aboutt he operation
of the chip.

I also found one of the resistor values is 15 megohms,
although I'm not sure where it fits in the circuit. I can also
gain access to the leads on the voltage setting pot (don't
ask). I'll measure it later tonight.

I also might be able to probe the potted module. It is soft
potting, looks like black silicone RTV. I might try punching a
sewing needle through the potting material in selected places
to try and take resistance readings.

This little beast won't give up it's secrets easily.

Stay tuned and thanks for reading.

AB

Anyone know of a way to remove the potting material, without damaging the
components? A release agent, perhaps?

 

[Frithiof Andreas Jensen]

This little beast won't give up it's secrets easily.

If you already have the schematics - and it looks OK to me except some
missing RC net on the 4000 CMOS for the 10kHz - it will be far easier to
re-engineer the circuit with current components than trying to identify the
components in the original circuit.

You may even improve it to better fit your application:

What you have is a linear regulator followed by a step-up inverter. The
output voltage is regulated by controlling the input voltage to the
converter using an internal reference in the 8214 chip. The circuit is
fine - or not - depending on what you want the circuit to; there are many
ways to skin that particular cat!

 

[rstlne]

Anyone know of a way to remove the potting material, without damaging the
components? A release agent, perhaps?

No real easy way to get it off, we used to use it at work for a few reaons
so other companys couldnt "easily" look at it or mod it
and then ingress protection, We also used it in our EXd type equipment, and
you can buy the potting material, I have cut some of it off before and was
able to look at what I needed to, but you can forget trying to get it down
to a clean board (especially if they used the hard non transparent stuff)

 

[Winfield Hill]

AB wrote...

Found some more information.

The 8212 chip is very obsolete, circa 1985. It is actually an ICL8212,
formerly made by National, Fairchild and Harris (Intersil). There is
no spec sheet available for it. I did find an ap note however. It has
a 1.15 volt reference, a comparator, a digital output that goes high
when the input exceeds the programmed voltage and programmable
hysterisis.

While the ICL8212 is not currently in production, the MAX2818 (Maxim)
is a modern low power replacement and is in production. Maxim claims
pin for pin equivalency, they even make it in an 8 pin dip. The Maxim
chip uses microamps instead of milliamps of supply current. Should be
able to use the Maxim spec sheet to get more information aboutt he
operation of the chip.

The correct maxim replacement parts are the MAX8211 and MAX8212.

BTW, I can send anyone who's like a copy of the ICL8212 datasheet.
That was a useful part for me in my serious micropower design days.

Thanks,
- Win

 

[AB]

Good day all,

I've found spec sheets, determined the pin outs and corected the
component values. I found 2 wiring errors in the original schematic as
well.

I've posted a revised schematic at:

http://www.uninets.net/~artky1k/version2_100v.PDF

I could really use some suggestions regarding which pot core to use
and the primary inductance needed.

The load will be a cockcroft-walton multiplier, I can send a schematic
of the load if needed.

Thanks again to all who made suggestions!

AB