Chaining power supplies together.


Torch
 

At the risk of being branded a philistine, not all Chinese power supplies are completely useless or disposable. I bought one of the early Korad KA3305P units and have been quite satisfied with it. Effectively 3 power supplies in 1, and the two variable 31V, 5.1A outlets can be chained in series or parallel with the push of a button. IE: it can deliver 62V @ 5.1A or 31V @10.2A.

I did a tear down at the time, which can be seen here: https://www.eevblog.com/forum/testgear/inside-the-new-korad-ka3305p-linear-psu/


Jim Ford
 

A technician at Lockheed back in 1993-1995 when I worked there told me that he'd seen lots of HP and other power supplies go out for repair but never in 30 years had he seen a Trygon need repair. I understand Trygon had something to do with Systron Donner. I have a Trygon triple supply and an HP 6111A thumbwheel PS, along with another no-name one that was given to me. Aside from some scratchy pots, all work just fine.

Also had a Lambda 5 V, 35 A boat anchor that I got for something like $5 at the TRW swap meet in the early 1990's. I put a power cable on it and installed some Pomona Electronics heavy-duty banana jacks/binding posts. But I never used it and sold it on eBay for around $50. Nice supply and built like a tank!

Jim Ford

------ Original Message ------
From: "-" <rrrr6789@gmail.com>
To: TekScopes@groups.io
Sent: 5/2/2021 7:53:51 AM
Subject: Re: [TekScopes] Chaining power supplies together.

Any of the TE grade ones built by HP. Even their economy class small
green plastic cased ones are better than the econo class Chinese meters.
Lambdas are also good but not as EASY to find service info on as just about
ANY of the HP PSs are.. Most of the other US built PSs built by any of the
major TE manufacturing companies are also good but none tops HP in terms of
reliability, durability, and the level of service information available. I
have at least one HP PS built in 1966 that is still running strong and has
never been recapped or had to be repaired. Needless to say that is a linear
supply and there's no digital electronics in it and it's HEAVY but as any
experienced machinist can tell you, HEAVY means that it's built to last.

True story, a few years ago a EE student at a nearby college rented a
room in a house next door to me and we became friends. He was an avid
electronic hobbyist with the arduinos but lacked any reaperience in
electronics in general and he was also poor as most students are. He needed
PSs, meters and other parts for his arduino projects but he couldn't afford
them. He'd never heard of a hamfest so I took him to several of them and he
was like a kid in a candy store! He had never imagined that TE and parts
could be bought so cheaply! I also took him to an electonics scrap yard
that is owned by a friend of mine. He walked out of there with THREE old
HP 54100 color scopes! My friend took pity on him and only charged him what
he thought that the scopes were worth in scrap value, $35. My neighbor
later told me that he got two of the three scopes completely working just
by disassembling and cleaning the tiny mechanical attenuator switchs in
them. But on the way out of the scrap yard, I looked over at one of the
scrap baskets and spotted an old Lambda power suply. I can't tell you what
model it was but it was a heavily built linear supply with dual analog
meters on the front and it had variable voltage and variable current
limiting and went to about 30 VDC. It had been sitting in the scrap yard
for MONTHs and was nasty looking but I pointed it out to him and said
"Here. This is what you need for your projects." He took one look at it and
thought that I was joking and that it would never work.I But I told him
that I was serious and that I would BET that it worked. He carried it home
and later that day he called me and in an amazed voice that "It works!".
He graduated several years ago and moved away but we still talk
occasinonally and just a few months ago he told me that he is STILL using
that PS and that it is still working fine. In my experience, I don't think
that I've ever found or seen a Lambda PS that didn't work!

On Sat, May 1, 2021 at 10:28 PM Harvey White <madyn@dragonworks.info> wrote:

What would you consider good power supplies given what you've said?

Harvey


On 5/1/2021 9:37 PM, - wrote:
> "Be worth obtaining an adjustable power supply if you plan on doing many
> board repairs. Why risk damaging boards?"
>
> Absolutely! And use a PS with an adjustable current limit and set the
> limit only slightly higher than the amount of current that you expect the
> item under test to draw. I used to keep notebooks full of notes about
> various repairs including how much power that model item actually drew
> under various operating conditions. I also STRONGLY suggest using a GOOD
> quality PS like those from HP, Lambda, etc and not one of cheap Chinese
> ones. Many of the cheap PSs contain large filter caps on their output in
> oder to reduce AC ripple but those large caps can provide enough power to
> fry your electronics before their *slow* current limiters can kick in.
> GOOD PSs are expensive when new but used ones are available just about
> anywhere (at least in the US and Canada) and are usually very cheap
(~$20)
>
> On Sat, May 1, 2021 at 8:45 PM Bill via groups.io <ko4nrbs=
> yahoo.com@groups.io> wrote:
>
>> Be worth obtaining an adjustable power supply if you plan on doing many
>> board repairs. Why risk damaging boards?
>>
>> Bill
>>
>>
>>
>>
>>
>>
>
>
>
>
>









-
 

I had to go look at the model numbers but I have an HP 6111A and a HP
6114A Precision Power Supply siting on my workbench right now. Both date to
about 1972 IIRC but I recently checked them against my HP 3456A meter and
both are still *well* within 0.02% accuracy. I don't use these for
powering circuits in general but I do use them when I need a Precision
supply for simulating reference voltages in TE.

A freind of mine owns a much newer HP (agilent?) HP 66312A Power Source
that I've repaired for him and that I've used briefly and boy is that one
sweet! it's really a power supply but they called it a Power Source
because besides being able provide power, it can also *absorb* power! it's
intended to simulate a rechargeable battery in a circuit so it has to be
able to both source, and sink power, without damage. It's also extremely
accurate in both modes of operation. My friend works in designing and
testing Laser Diode LASERs so he needs that kind of regulation and
precision to drive the diodes as hard as possible without damaging them.

On Sun, May 2, 2021 at 10:55 AM - via groups.io <rrrr6789=
gmail.com@groups.io> wrote:

Any of the TE grade ones built by HP. Even their economy class small
green plastic cased ones are better than the econo class Chinese meters.
Lambdas are also good but not as EASY to find service info on as just about
ANY of the HP PSs are.. Most of the other US built PSs built by any of the
major TE manufacturing companies are also good but none tops HP in terms of
reliability, durability, and the level of service information available. I
have at least one HP PS built in 1966 that is still running strong and has
never been recapped or had to be repaired. Needless to say that is a linear
supply and there's no digital electronics in it and it's HEAVY but as any
experienced machinist can tell you, HEAVY means that it's built to last.

True story, a few years ago a EE student at a nearby college rented a
room in a house next door to me and we became friends. He was an avid
electronic hobbyist with the arduinos but lacked any reaperience in
electronics in general and he was also poor as most students are. He needed
PSs, meters and other parts for his arduino projects but he couldn't afford
them. He'd never heard of a hamfest so I took him to several of them and he
was like a kid in a candy store! He had never imagined that TE and parts
could be bought so cheaply! I also took him to an electonics scrap yard
that is owned by a friend of mine. He walked out of there with THREE old
HP 54100 color scopes! My friend took pity on him and only charged him what
he thought that the scopes were worth in scrap value, $35. My neighbor
later told me that he got two of the three scopes completely working just
by disassembling and cleaning the tiny mechanical attenuator switchs in
them. But on the way out of the scrap yard, I looked over at one of the
scrap baskets and spotted an old Lambda power suply. I can't tell you what
model it was but it was a heavily built linear supply with dual analog
meters on the front and it had variable voltage and variable current
limiting and went to about 30 VDC. It had been sitting in the scrap yard
for MONTHs and was nasty looking but I pointed it out to him and said
"Here. This is what you need for your projects." He took one look at it and
thought that I was joking and that it would never work.I But I told him
that I was serious and that I would BET that it worked. He carried it home
and later that day he called me and in an amazed voice that "It works!".
He graduated several years ago and moved away but we still talk
occasinonally and just a few months ago he told me that he is STILL using
that PS and that it is still working fine. In my experience, I don't think
that I've ever found or seen a Lambda PS that didn't work!

On Sat, May 1, 2021 at 10:28 PM Harvey White <madyn@dragonworks.info>
wrote:

What would you consider good power supplies given what you've said?

Harvey


On 5/1/2021 9:37 PM, - wrote:
"Be worth obtaining an adjustable power supply if you plan on doing
many
board repairs. Why risk damaging boards?"

Absolutely! And use a PS with an adjustable current limit and set
the
limit only slightly higher than the amount of current that you expect
the
item under test to draw. I used to keep notebooks full of notes about
various repairs including how much power that model item actually drew
under various operating conditions. I also STRONGLY suggest using a
GOOD
quality PS like those from HP, Lambda, etc and not one of cheap Chinese
ones. Many of the cheap PSs contain large filter caps on their output
in
oder to reduce AC ripple but those large caps can provide enough power
to
fry your electronics before their *slow* current limiters can kick in.
GOOD PSs are expensive when new but used ones are available just about
anywhere (at least in the US and Canada) and are usually very cheap
(~$20)

On Sat, May 1, 2021 at 8:45 PM Bill via groups.io <ko4nrbs=
yahoo.com@groups.io> wrote:

Be worth obtaining an adjustable power supply if you plan on doing
many
board repairs. Why risk damaging boards?

Bill

















-
 

Any of the TE grade ones built by HP. Even their economy class small
green plastic cased ones are better than the econo class Chinese meters.
Lambdas are also good but not as EASY to find service info on as just about
ANY of the HP PSs are.. Most of the other US built PSs built by any of the
major TE manufacturing companies are also good but none tops HP in terms of
reliability, durability, and the level of service information available. I
have at least one HP PS built in 1966 that is still running strong and has
never been recapped or had to be repaired. Needless to say that is a linear
supply and there's no digital electronics in it and it's HEAVY but as any
experienced machinist can tell you, HEAVY means that it's built to last.

True story, a few years ago a EE student at a nearby college rented a
room in a house next door to me and we became friends. He was an avid
electronic hobbyist with the arduinos but lacked any reaperience in
electronics in general and he was also poor as most students are. He needed
PSs, meters and other parts for his arduino projects but he couldn't afford
them. He'd never heard of a hamfest so I took him to several of them and he
was like a kid in a candy store! He had never imagined that TE and parts
could be bought so cheaply! I also took him to an electonics scrap yard
that is owned by a friend of mine. He walked out of there with THREE old
HP 54100 color scopes! My friend took pity on him and only charged him what
he thought that the scopes were worth in scrap value, $35. My neighbor
later told me that he got two of the three scopes completely working just
by disassembling and cleaning the tiny mechanical attenuator switchs in
them. But on the way out of the scrap yard, I looked over at one of the
scrap baskets and spotted an old Lambda power suply. I can't tell you what
model it was but it was a heavily built linear supply with dual analog
meters on the front and it had variable voltage and variable current
limiting and went to about 30 VDC. It had been sitting in the scrap yard
for MONTHs and was nasty looking but I pointed it out to him and said
"Here. This is what you need for your projects." He took one look at it and
thought that I was joking and that it would never work.I But I told him
that I was serious and that I would BET that it worked. He carried it home
and later that day he called me and in an amazed voice that "It works!".
He graduated several years ago and moved away but we still talk
occasinonally and just a few months ago he told me that he is STILL using
that PS and that it is still working fine. In my experience, I don't think
that I've ever found or seen a Lambda PS that didn't work!

On Sat, May 1, 2021 at 10:28 PM Harvey White <madyn@dragonworks.info> wrote:

What would you consider good power supplies given what you've said?

Harvey


On 5/1/2021 9:37 PM, - wrote:
"Be worth obtaining an adjustable power supply if you plan on doing many
board repairs. Why risk damaging boards?"

Absolutely! And use a PS with an adjustable current limit and set the
limit only slightly higher than the amount of current that you expect the
item under test to draw. I used to keep notebooks full of notes about
various repairs including how much power that model item actually drew
under various operating conditions. I also STRONGLY suggest using a GOOD
quality PS like those from HP, Lambda, etc and not one of cheap Chinese
ones. Many of the cheap PSs contain large filter caps on their output in
oder to reduce AC ripple but those large caps can provide enough power to
fry your electronics before their *slow* current limiters can kick in.
GOOD PSs are expensive when new but used ones are available just about
anywhere (at least in the US and Canada) and are usually very cheap
(~$20)

On Sat, May 1, 2021 at 8:45 PM Bill via groups.io <ko4nrbs=
yahoo.com@groups.io> wrote:

Be worth obtaining an adjustable power supply if you plan on doing many
board repairs. Why risk damaging boards?

Bill













toby@...
 

On 2021-05-01 10:28 p.m., Harvey White wrote:
What would you consider good power supplies given what you've said?
Walter has a bunch for sale:
https://www.sphere.bc.ca/test/stuffday.html#power
(not affiliated, just very happy customer)

Personally I use an HP E3631A and I love it.

--Toby

Harvey


On 5/1/2021 9:37 PM, - wrote:
"Be worth obtaining an adjustable power supply if you plan on doing many
board repairs.  Why risk damaging boards?"

    Absolutely! And use a PS with an adjustable current limit and set the
limit only slightly higher than the amount of current that you expect the
item under test to draw.  I used to keep notebooks full of notes about
various repairs including how much power that model item actually drew
under various operating conditions.  I also STRONGLY suggest using a GOOD
quality PS like those from HP, Lambda, etc and not one of cheap Chinese
ones. Many of the cheap PSs contain large filter caps on their output in
oder to reduce AC ripple but those large caps can provide enough power to
fry your electronics before their *slow* current limiters can kick in.
GOOD PSs are expensive when new but used ones are available just about
anywhere (at least in the US and Canada) and are usually very cheap
(~$20)

On Sat, May 1, 2021 at 8:45 PM Bill via groups.io <ko4nrbs=
yahoo.com@groups.io> wrote:

Be worth obtaining an adjustable power supply if you plan on doing many
board repairs.  Why risk damaging boards?

Bill












Harvey White
 

What would you consider good power supplies given what you've said?

Harvey

On 5/1/2021 9:37 PM, - wrote:
"Be worth obtaining an adjustable power supply if you plan on doing many
board repairs. Why risk damaging boards?"

Absolutely! And use a PS with an adjustable current limit and set the
limit only slightly higher than the amount of current that you expect the
item under test to draw. I used to keep notebooks full of notes about
various repairs including how much power that model item actually drew
under various operating conditions. I also STRONGLY suggest using a GOOD
quality PS like those from HP, Lambda, etc and not one of cheap Chinese
ones. Many of the cheap PSs contain large filter caps on their output in
oder to reduce AC ripple but those large caps can provide enough power to
fry your electronics before their *slow* current limiters can kick in.
GOOD PSs are expensive when new but used ones are available just about
anywhere (at least in the US and Canada) and are usually very cheap (~$20)

On Sat, May 1, 2021 at 8:45 PM Bill via groups.io <ko4nrbs=
yahoo.com@groups.io> wrote:

Be worth obtaining an adjustable power supply if you plan on doing many
board repairs. Why risk damaging boards?

Bill








-
 

"Be worth obtaining an adjustable power supply if you plan on doing many
board repairs. Why risk damaging boards?"

Absolutely! And use a PS with an adjustable current limit and set the
limit only slightly higher than the amount of current that you expect the
item under test to draw. I used to keep notebooks full of notes about
various repairs including how much power that model item actually drew
under various operating conditions. I also STRONGLY suggest using a GOOD
quality PS like those from HP, Lambda, etc and not one of cheap Chinese
ones. Many of the cheap PSs contain large filter caps on their output in
oder to reduce AC ripple but those large caps can provide enough power to
fry your electronics before their *slow* current limiters can kick in.
GOOD PSs are expensive when new but used ones are available just about
anywhere (at least in the US and Canada) and are usually very cheap (~$20)

On Sat, May 1, 2021 at 8:45 PM Bill via groups.io <ko4nrbs=
yahoo.com@groups.io> wrote:

Be worth obtaining an adjustable power supply if you plan on doing many
board repairs. Why risk damaging boards?

Bill






Harvey White
 

Overvoltage would take a zener, or an SCR/zener trigger (IMHO).

A straight back biased diode (say 3 amps at 100 volts or so) should take care of back biasing the power supply.   (reverse polarity here).  It does not protect against positive current being driven into the supply's outputs.

The problem with charging a battery is that the output is lower than the battery voltage, so current flows the wrong way.  PUtting a series diode between the supply and battery (say 50 to 100 PIV) and rated for more than the PS current, would protect the supply You'd have to figure in that your output voltage is 1 diode drop lower than the supply voltage, except that for batter charging, you *may* be more concerned with the current, not the voltage.

While you may be able to play games with the sense inputs, I have no idea of the internal wiring, and don't know (based on no schematic how the circuit might behave).

This is for trying to constant current charge a battery, though.

Harvey

On 5/1/2021 6:10 PM, Dave Peterson via groups.io wrote:
So by protection diode, you're not talking about over-voltage, you're talking about accidentally driving another source. So a forward biased diode that would prevent current into the power supply.

That much I got. No, don't drive into the PS, either setup in parallel, or attempting to drive some other source. Yeah, I wouldn't do that. (On purpose).

Dave


On Saturday, May 1, 2021, 02:52:35 PM PDT, Harvey White <madyn@dragonworks.info> wrote:
Definitely.  Most power supplies take a very dim (as in permanently off)
view of reverse voltage applied to their terminals.  Most also don't
like to be tied to another power supply in parallel unless designed for it.

If you're going to charge a battery with a Chinese (or many other types)
power supply, put a series diode in so that the supply can't be fed by
the battery.

Harvey


On 5/1/2021 5:38 PM, Ed Breya via groups.io wrote:
Be sure to add an external reverse protection diode across each output, in case there isn't one built in.

Ed













Bill
 

Be worth obtaining an adjustable power supply if you plan on doing many board repairs. Why risk damaging boards?

Bill


Ed Breya
 

Say you have two or more supplies stacked to get the sum of output voltages. Fine and good. Now short the total output and think about what will happen if you have no reverse clamp protection on the individual outputs.

Ed


Dave Peterson
 

So by protection diode, you're not talking about over-voltage, you're talking about accidentally driving another source. So a forward biased diode that would prevent current into the power supply.

That much I got. No, don't drive into the PS, either setup in parallel, or attempting to drive some other source. Yeah, I wouldn't do that. (On purpose).

Dave

On Saturday, May 1, 2021, 02:52:35 PM PDT, Harvey White <madyn@dragonworks.info> wrote:

Definitely.  Most power supplies take a very dim (as in permanently off)
view of reverse voltage applied to their terminals.  Most also don't
like to be tied to another power supply in parallel unless designed for it.

If you're going to charge a battery with a Chinese (or many other types)
power supply, put a series diode in so that the supply can't be fed by
the battery.

Harvey


On 5/1/2021 5:38 PM, Ed Breya via groups.io wrote:
Be sure to add an external reverse protection diode across each output, in case there isn't one built in.

Ed






Dave Peterson
 

Here's a specific example of what I'm thinking of doing with such a scenario:

I'd like to be able to run 465 boards on the bench to test them before reassembling on the chassis. I have a variety of power supplies available to me: TM503 with a PS503A (+/- 20v), a Systron-Donner TL8-3 bench supply that can drive 32v, and more.

Can I chain these together to make, for example, +55v without doing harm?

Dave

On Saturday, May 1, 2021, 02:52:35 PM PDT, Harvey White <madyn@dragonworks.info> wrote:

Definitely.  Most power supplies take a very dim (as in permanently off)
view of reverse voltage applied to their terminals.  Most also don't
like to be tied to another power supply in parallel unless designed for it.

If you're going to charge a battery with a Chinese (or many other types)
power supply, put a series diode in so that the supply can't be fed by
the battery.

Harvey


On 5/1/2021 5:38 PM, Ed Breya via groups.io wrote:
Be sure to add an external reverse protection diode across each output, in case there isn't one built in.

Ed






Harvey White
 

Definitely.  Most power supplies take a very dim (as in permanently off) view of reverse voltage applied to their terminals.  Most also don't like to be tied to another power supply in parallel unless designed for it.

If you're going to charge a battery with a Chinese (or many other types) power supply, put a series diode in so that the supply can't be fed by the battery.

Harvey

On 5/1/2021 5:38 PM, Ed Breya via groups.io wrote:
Be sure to add an external reverse protection diode across each output, in case there isn't one built in.

Ed





Dave Peterson
 

Could you elaborate Ed? Seems such diodes might need to be robust. Any particular type that's appropriate? I take it these need to have a reverse breakdown voltage above the supply? But are there particular ones for these voltage levels? Would this be at each supply - from out to common of each?

Seems one thing to understand a reverse diode as protection in theory, another in practice.

Thanks for the input.
Dave

On Saturday, May 1, 2021, 02:38:59 PM PDT, Ed Breya via groups.io <edbreya=yahoo.com@groups.io> wrote:

Be sure to add an external reverse protection diode across each output, in case there isn't one built in.

Ed


Ed Breya
 

Be sure to add an external reverse protection diode across each output, in case there isn't one built in.

Ed


Dave Peterson
 

I just want to check myself. I don't want to overlook something and break my toys:

Is it safe, and a typical thing to do, to daisy chain power supplies to get a higher voltage than any one supply can provide?

I'm talking about TM500/5000 plug-in power supplies with one or two outputs with an ungrounded common. Say I have two 20v supplies: can I tie the common of the 2nd to the output of the 1st and get 40v between the common of the 1st and the output of the 2nd? Safely?

Seems appropriate, but haven't seen it done or talked about before. I don't want to blow anything up if I'm forgetting something fundamental here.

Thanks,
Dave