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

Ed

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

Ed

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

Ed

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@...> 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

"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=
[email protected]> wrote:

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

Bill

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=
[email protected]> 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@...> 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=
> [email protected]> wrote:
>
>> Be worth obtaining an adjustable power supply if you plan on doing many
>> board repairs. Why risk damaging boards?
>>
>> Bill
>>
>>
>>
>>
>>
>>
>
>
>
>
>