I have a Power/Mate BPA-10E with issues. It is adjustable from
~2.5VDC to ~13VDC (The panel meter is 0-10VDC, so I assume that that's
what it should be adjustable throughout). I'm checking the output
with a calibrated Fluke 87, so it's not just that the meter needle is
offset or something of that nature. I'm trying to figure out what's
going on in the unit. Does anyone happen to have any schematic or
service manual for this unit? The unit regulates properly on both
current limiting and voltage regulation, but it seems to be offset by
~2.5V. It's possible someone modded the supply to run at 12 or 13V so
they could run car equipment or something like that, I don't know the
history of the supply, I just don't want to be using it if something's
wrong. I suspect that a voltage reference in the regulator circuit
has gone high, all I've found are three zeners, two 13V's and one
6.3V, I haven't gotten them off the board to test them yet, and I'm no
good at reverse engineering from board to schematic and these zeners
might not even be the original parts. Any thoughts on this subject.

(note, how do the "pros" test zeners? I want to see if I test them
the same as you guys)

Same song, second verse. This unit has five output transistors (one
drive and four outputs, from what I can tell). Their labelling is

QP0010
274
date code

Any idea what these original transistors are? Via diode test they are
NPN devices. This supply is 10V 10A, linear, so assuming they
dissipate maximum voltage of 10V, maximum current of 2.5A each, they
are 25W or so (I know, very brutal calculations, please don't tear me
apart for it). Should common new transistors such as 2n3055's or
something along that line work? Any idea what the originals are, what
their ratings are?

I know the info is vague, but any help is appreciated.

Thanks,
Steve

In article , sck0006 wrote:

I have a Power/Mate BPA-10E with issues. It is adjustable from
~2.5VDC to ~13VDC (The panel meter is 0-10VDC, so I assume that that's
what it should be adjustable throughout). I'm checking the output
with a calibrated Fluke 87, so it's not just that the meter needle is
offset or something of that nature.
..
..
Any idea what these original transistors are? Via diode test they are
NPN devices. This supply is 10V 10A, linear, so assuming they
dissipate maximum voltage of 10V, maximum current of 2.5A each, they
are 25W or so (I know, very brutal calculations, please don't tear me
apart for it). Should common new transistors such as 2n3055's or
something along that line work? Any idea what the originals are, what
their ratings are?

Steve-

Not being familiar with that power supply, it isn't clear what your
problem is. Exactly what is it that is "offset by ~2.5V"? Does the
built-in meter read something different from your Fluke? If the panel
meter agrees with your Fluke, then it would appear to be working properly.

Power dissipated by the transistors is computed by voltage DROP, not
output voltage. Measure the voltage between collector and emitter while
the supply is delivering rated current, multiply by rated current and
divide by the number of transistors.

It is possible that the maximum current rating only applies at maximum
output voltage. I assume you have checked the manufacturer's web site for
data.

Without a cross reference to the Power/Mate proprietary part numbers, the
best you can do is guess. The 2N3055 is as good a guess as any.

Fred

On Thu, 02 Mar 2006 13:35:48 -0500, (Fred McKenzie)
wrote:

snip

Not being familiar with that power supply, it isn't clear what your
problem is. Exactly what is it that is "offset by ~2.5V"? Does the
built-in meter read something different from your Fluke? If the panel
meter agrees with your Fluke, then it would appear to be working properly.

Power dissipated by the transistors is computed by voltage DROP, not
output voltage. Measure the voltage between collector and emitter while
the supply is delivering rated current, multiply by rated current and
divide by the number of transistors.

It is possible that the maximum current rating only applies at maximum
output voltage. I assume you have checked the manufacturer's web site for
data.

Without a cross reference to the Power/Mate proprietary part numbers, the
best you can do is guess. The 2N3055 is as good a guess as any.

Fred

Sorry, didn't mean to be unclear. The panel meter (analog meter) is
correct, agrees w/ the fluke. THe voltage at a minimum is about 2.5v,
and max is around 12.5V. That's what I meant by the offset, the
supply I believe should be adjustable from 0 to 10, not 2.5 to 12.5
(the panel meter is 1-10V). I was trying to be clear that the meter
was not the problem, and ended up being more confusing than anything.

Yes, I now realize my errors in the calculation. Funny, that's why I
wrote that note about the calculations being brutal, because I knew I
was doing something wrong but was too tired to figure it out.

I wasn't able to find specs on the supply anywhere. The only
Power/Mate website I could find is www.pduke.com, which doesn't seem
to be the right company, or they switched.

Anyway, thanks for the reply, hope I cleared things up.

I guess I just need to start checking parts on the board, there really
aren't that many, and I can just check them all (really efficient...).
Should solve the problem.
I hope
Steve

In article , sck0006 wrote:

Sorry, didn't mean to be unclear. The panel meter (analog meter) is
correct, agrees w/ the fluke. THe voltage at a minimum is about 2.5v,
and max is around 12.5V. That's what I meant by the offset, the
supply I believe should be adjustable from 0 to 10, not 2.5 to 12.5
(the panel meter is 1-10V). I was trying to be clear that the meter
was not the problem, and ended up being more confusing than anything.

Yes, I now realize my errors in the calculation. Funny, that's why I
wrote that note about the calculations being brutal, because I knew I
was doing something wrong but was too tired to figure it out.

I wasn't able to find specs on the supply anywhere. The only
Power/Mate website I could find is www.pduke.com, which doesn't seem
to be the right company, or they switched.

Steve-

As far as I can tell, Power Mate Corporation may have been absorbed by
another company. They don't seem to be doing business under that name any
more. (If you had a 20-year-old Allied catalog, it might have more data.)

I found several of their power supplies for sale at various surplus
outlets as well as on eBay.

One BPA-10C was listed on eBay as being 0 - 10 Volts at two amps. With
your four output transistors, ten amps might be possible at the higher
voltage if the power transformer and rectifiers can handle it. Otherwise,
four might be necessary to deliver two amps at minimum voltage since
voltage-drop is greater.

Typical power supplies of this class used a uA723 voltage regulator IC to
drive the transistors. If yours has an IC, even if it has a proprietary
part number, look for typical circuits on a 723 data sheet and see if
anything looks familiar.

It is possible that yours is working perfectly, and that your assumption
it can be adjusted all the way to zero is incorrect. Being able to adjust
it above 10 volts is misleading, since it may not be able to maintain the
higher voltage under full load.

Fred