Allen Bong wrote:
> On Aug 20, 12:30 am, gearhead <nos...@billburg.com> wrote:
>
>>On Aug 18, 4:20 pm, Allen Bong <allenbsf6...@gmail.com> wrote:
>>
>>[snip]
>>
>>
>>
>>
>>> my friend showed me a circuit and wants me to duplicate
>>>it. The schematic
>>>is as follows:
>>
>>> Q1 10W
>>> 2N3055 0.1 ohm
>>> Vunreg (42V) ___ Vout (24V)
>>> o-----------------o---o----------- ------|___|----o---o------o
>>> | | \ ^ | |
>>> | | --- | .-.
>>> | | | +----+ | |
>>> | o------- --+ | | |2k2
>>> .-. | \ ^ mje3055t | '-'
>>> | | | --- Q2 .-. |
>>> 4k7 | | | | | | |
>>> '-' +--- --+ | | 1k |
>>> | \ ^ mje3055t '-' |
>>> | --- Q3 | |
>>> | | || | |
>>> +----------+--------o-----||--+ | |
>>> | \| || | .-. |
>>> | mje3055t |-------o------->| | |
>>> | Q4 <| | |1k | I=5mA
>>> | | '-' |
>>> |+ I=4.26mA | | |
>>> === o----------------------------+
>>> /-\ | |
>>> | | .-.
>>> | z | |
>>> | 1N5342B x 2 A | |1k5
>>> | 13.6V 5W | '-'
>>> | | I=10mA |
>>> | === |
>>> === GND ===
>>> GND GND
>>
>>>(created by AACircuit v1.28.6 beta 04/19/05www.tech-chat.de)
>>
>>[snip]
>>
>>Who designed that, the Geico caveman?
>>Probably not, 'cause he would have done a better job.
>>Check out the design in this next link
>>and consider how in its simplicity and rationality
>>it contrasts to your friend's circuit:
>>
>>http://www.rason.org/Projects/discreg/discreg.htm
>>
>>The following link explains some of the basics
>>about linear voltage regulating. You should read
>>a little bit before you jump into anything.
>>
>>http://www.national.com/appinfo/power/files/f4.pdf- Hide quoted text -
>>
>>- Show quoted text -
>
>
> Hi gearhead,
>
> I just found another design similar to my friend's. What do you think
> about it ? Is it more efficient? Is it ok to let the 7812 which is
> rated at 1A to work at 866mA?
>
> http://www.zen22142.zen.co.uk/Circuits/ ... 230psu.htm
>
> Allen
>

You can use the technique shown in that, but you really
need to scrap the schematic and start from scratch. The
one your link shows is totally inadequate for your 60A
requirement.

Start at the input. Your transformer will need to be
capable of providing over 100 amps at the secondary
if you want a 60 amp supply. Your rectifier will
need to be rated to handle that. That's two expensive
items. Your filter caps will also be expensive.
You do *not* want to use a 24 volt DC input to get
12 volts regulated out. At 60 amps, you'll be producing
720 watts of heat, meaning a huge area of heat sinking.
More expense.

If you *really* need 60 amps at 12 volts, using a 12 volt
deep cycle lead acid battery is likely to be cheaper and
easier for you.

In the meantime, you can experiment with much smaller
supplies - say 5 amps max - to learn, if learning
interests you. At lower currents, the learning experience
won't cost as much in blown up parts and burned fingers.

Ed

On Aug 20, 1:08 pm, ehsjr <eh...@bellatlantic.net> wrote:
> Allen Bong wrote:
> > On Aug 20, 12:30 am, gearhead <nos...@billburg.com> wrote:
>
> >>On Aug 18, 4:20 pm, Allen Bong <allenbsf6...@gmail.com> wrote:
>
> >>[snip]
>
> >>> my friend showed me a circuit and wants me to duplicate
> >>>it. The schematic
> >>>is as follows:
>
> >>> Q1 10W
> >>> 2N3055 0.1 ohm
> >>> Vunreg (42V) ___ Vout (24V)
> >>> o-----------------o---o----------- ------|___|----o---o------o
> >>> | | \ ^ | |
> >>> | | --- | .-.
> >>> | | | +----+ | |
> >>> | o------- --+ | | |2k2
> >>> .-. | \ ^ mje3055t | '-'
> >>> | | | --- Q2 .-. |
> >>> 4k7 | | | | | | |
> >>> '-' +--- --+ | | 1k |
> >>> | \ ^ mje3055t '-' |
> >>> | --- Q3 | |
> >>> | | || | |
> >>> +----------+--------o-----||--+ | |
> >>> | \| || | .-. |
> >>> | mje3055t |-------o------->| | |
> >>> | Q4 <| | |1k | I=5mA
> >>> | | '-' |
> >>> |+ I=4.26mA | | |
> >>> === o----------------------------+
> >>> /-\ | |
> >>> | | .-.
> >>> | z | |
> >>> | 1N5342B x 2 A | |1k5
> >>> | 13.6V 5W | '-'
> >>> | | I=10mA |
> >>> | === |
> >>> === GND ===
> >>> GND GND
>
> >>>(created by AACircuit v1.28.6 beta 04/19/05www.tech-chat.de)
>
> >>[snip]
>
> >>Who designed that, the Geico caveman?
> >>Probably not, 'cause he would have done a better job.
> >>Check out the design in this next link
> >>and consider how in its simplicity and rationality
> >>it contrasts to your friend's circuit:
>
> >>http://www.rason.org/Projects/discreg/discreg.htm
>
> >>The following link explains some of the basics
> >>about linear voltage regulating. You should read
> >>a little bit before you jump into anything.
>
> >>http://www.national.com/appinfo/power/files/f4.pdf-Hide quoted text -
>
> >>- Show quoted text -
>
> > Hi gearhead,
>
> > I just found another design similar to my friend's. What do you think
> > about it ? Is it more efficient? Is it ok to let the 7812 which is
> > rated at 1A to work at 866mA?
>
> > http://www.zen22142.zen.co.uk/Circuits/ ... 230psu.htm
>
> > Allen
>
> You can use the technique shown in that, but you really
> need to scrap the schematic and start from scratch. The
> one your link shows is totally inadequate for your 60A
> requirement.
>
> Start at the input. Your transformer will need to be
> capable of providing over 100 amps at the secondary
> if you want a 60 amp supply. Your rectifier will
> need to be rated to handle that. That's two expensive
> items. Your filter caps will also be expensive.
> You do *not* want to use a 24 volt DC input to get
> 12 volts regulated out. At 60 amps, you'll be producing
> 720 watts of heat, meaning a huge area of heat sinking.
> More expense.
>
> If you *really* need 60 amps at 12 volts, using a 12 volt
> deep cycle lead acid battery is likely to be cheaper and
> easier for you.
>
> In the meantime, you can experiment with much smaller
> supplies - say 5 amps max - to learn, if learning
> interests you. At lower currents, the learning experience
> won't cost as much in blown up parts and burned fingers.
>
> Ed- Hide quoted text -
>
> - Show quoted text -

How can I tell if the transformer is having 100A capacity?
May be my friend bluff me saying that his PSU is giving 60A.

The dimension of the transformer core is as below:



6"
------------------------------------------------------
/ /
2.8" / /|
/ / |
/ / |
/-----------------------------------------------------/ |
| | |
| | |
| <-------------- 4" ------------------> | |
| +--------------------------------------+ | |
| | ^ | | | | |
| | | | | | | |
| | | | | | | |
| 1" | | | | | | |
|<---->| 3" | | | | |
5"| | | | | | | |
| | | | | | | |
| | | | | | | |
| | V | | | | |
| +--------------------------------------+ | |
| | /
| | /
| | /
-----------------------------------------------------|/
(created by AACircuit v1.28.6 beta 04/19/05 http://www.tech-chat.de)

To measure the second wire size, I'll need to cut open the insulator.
The filtering Caps are 6 pieces of 10,000uF 50V electrolytic.

Alen

On Mon, 20 Aug 2007 11:04:31 +1000, "Phil Allison"
<philallison@tpg.com.au> wrote:

>"John Fields"
>" Phil Allison "
>>>
>>>>>
>>>>> ** Which is in no way similar.
>>>>>
>>>>> An active zener is a voltage clamp, unlike a series regulator.
>>>>
>>>> ---
>>>> The Zener keeps the base clamped to Vz and, since Vbe is a diode
>>>> drop, the voltage into the load will stay 'clamped' at Vz - Vbe if
>>>> either the load resistance or Vin change. Within limits, of course.
>>>
>>>
>>>** Which is in NO WAY similar to a ** voltage clamp ** !!
>>>
>>> An active zener IS a voltage clamp, unlike a series regulator.
>>>
>>> Are you ASLEEP !!!!!!!!
>>
>> ---
>> Clamp, schlamp. You know very well that we both know the difference
>> between a series and a shunt regulator and, regardless of all this
>> fol-de-rol, you should have noticed that I called his implementation
>> clumsy and offered him a better alternative with the series
>> regulator, which essentially gets rid of the constant dissipation in
>> the current-limiting resistor that the OP calls "Rload".
>
>
>** Read what the OP asked - you PITA fuckwit.
>
>" 2. Can I increase the wattage of a zener using a bipolar transistor
>arranged as below? "

---
Well, it seems the answer (a resounding "YES") should be obvious
even to the likes of

!!!!!***** SCHIZOID DINGO OFFAL*****!!!!!

like you.
---

> An active zener IS a voltage clamp, unlike a series regulator !!
>
> A 2 terminal device, not 3.

---
Ah, but that's not what the OP showed, which was basically:

+------------+
1| |3
VIN>------|--[Rs]--+---|--->VOUT
| | |
| [ZENER]|
| | |
+--------|---+
2|
GND>---------------+------->GND


Notice that I've changed the name of the resistor to Rs from Rl in
order to distingish it from the real load, which would be connected
from VOUT to GND.

Notice also that I have carefully labeled the terminals of the
regulator with numbers, clearly showing that it's a

!!!!! THREE TERMINAL DEVICE, YA BLITHERING DOOFUS !!!!!


Your two terminal device would look like this:

+--------+
1| |1
VIN>------|----+---|--->VOUT
| | |
| [ZENER]|
| | |
+----|---+
2|
GND>-----------+------->GND

and would depend on the impedance of whatever was suppling Vin to
provide the ballast necessary to keep from frying the Zener or the
load.
---

> There are not interchangeable and so one is NOT clumsy compared the other.

---
_They_ are not interchangeable. That's precisely right, but that's
not what makes the OP's implementation clumsy. What does is the
inefficiency of his scheme which has the series resistor dissipating
power

!*!*!* ALL THE TIME, OZWIPE *!*!*!

--
Cordially,

JF

On Aug 19, 3:32 pm, Allen Bong <allenbsf6...@gmail.com> wrote:
> On Aug 20, 12:30 am, gearhead <nos...@billburg.com> wrote:
>
>
>
>
>
> > On Aug 18, 4:20 pm, Allen Bong <allenbsf6...@gmail.com> wrote:
>
> > [snip]
>
> > > my friend showed me a circuit and wants me to duplicate
> > > it. The schematic
> > > is as follows:
>
> > > Q1 10W
> > > 2N3055 0.1 ohm
> > > Vunreg (42V) ___ Vout (24V)
> > > o-----------------o---o----------- ------|___|----o---o------o
> > > | | \ ^ | |
> > > | | --- | .-.
> > > | | | +----+ | |
> > > | o------- --+ | | |2k2
> > > .-. | \ ^ mje3055t | '-'
> > > | | | --- Q2 .-. |
> > > 4k7 | | | | | | |
> > > '-' +--- --+ | | 1k |
> > > | \ ^ mje3055t '-' |
> > > | --- Q3 | |
> > > | | || | |
> > > +----------+--------o-----||--+ | |
> > > | \| || | .-. |
> > > | mje3055t |-------o------->| | |
> > > | Q4 <| | |1k | I=5mA
> > > | | '-' |
> > > |+ I=4.26mA | | |
> > > === o----------------------------+
> > > /-\ | |
> > > | | .-.
> > > | z | |
> > > | 1N5342B x 2 A | |1k5
> > > | 13.6V 5W | '-'
> > > | | I=10mA |
> > > | === |
> > > === GND ===
> > > GND GND
>
> > > (created by AACircuit v1.28.6 beta 04/19/05www.tech-chat.de)
>
> > [snip]
>
> > Who designed that, the Geico caveman?
> > Probably not, 'cause he would have done a better job.
> > Check out the design in this next link
> > and consider how in its simplicity and rationality
> > it contrasts to your friend's circuit:
>
> >http://www.rason.org/Projects/discreg/discreg.htm
>
> > The following link explains some of the basics
> > about linear voltage regulating. You should read
> > a little bit before you jump into anything.
>
> >http://www.national.com/appinfo/power/files/f4.pdf-Hide quoted text -
>
> > - Show quoted text -
>
> Hi gearhead,
>
> I just found another design similar to my friend's. What do you think
> about it ? Is it more efficient? Is it ok to let the 7812 which is
> rated at 1A to work at 866mA?
>
> http://www.zen22142.zen.co.uk/Circuits/ ... 230psu.htm
>
> Allen- Hide quoted text -
>
> - Show quoted text -

Calculate the heat dissipated in the 7812. Following the voltage
drops conveniently labeled in the diagram, you have input to the 7812
of 24-4=20 volts. Output is 12, so you have 8 volts across the chip
and .866 A, for about 7 watts. That's a lot of heat, and you would
need a very good heatsink. Here's a link that shows a way to reduce
the current through the chip:
http://www.rason.org/Projects/vreg/vreg.htm
Now, I tried that circuit and it doesn't give tight regulation. If
you want a good tight output voltage you should stick with npn pass
transistors and a voltage divider on the output feeding back to some
kind of voltage regulator chip, in which case you'd stay with the
bacic topology you started with and get it working right. John
Popelish has given you some good advice.

On Mon, 20 Aug 2007 05:08:44 GMT, ehsjr <ehsjr@bellatlantic.net>
wrote:

>You can use the technique shown in that, but you really
>need to scrap the schematic and start from scratch. The
>one your link shows is totally inadequate for your 60A
>requirement.
>
>Start at the input. Your transformer will need to be
>capable of providing over 100 amps at the secondary
>if you want a 60 amp supply. Your rectifier will
>need to be rated to handle that. That's two expensive
>items. Your filter caps will also be expensive.
>You do *not* want to use a 24 volt DC input to get
>12 volts regulated out. At 60 amps, you'll be producing
>720 watts of heat, meaning a huge area of heat sinking.
>More expense.

Yes. I had forgotten that the OP eventually wrote, "The output was
supposed to give 60A of regulated 24V supply." Sheesh!!

This alone should indicate, if linear approach is used, that a custom
transformer is in order or else finding the right match. And that is
going to take some very close examinations of the details to get done
well. The transformer output should be closely crafted for the
desired supply, at this level of current.

Average current is only one part of the consideration. And the OP
writes, "The filtering Caps are 6 pieces of 10,000uF 50V
electrolytic," almost as though one can just throw caps down without
doing some thoughtful design. How much of the AC cycle will the caps
be supplying current to the rest of the power supply? How long will
the transformer have, then, to supply the necessary Coulombs to
recharge them? What will that peak current look like and what
implications are there for the transformer? How much ripple will get
through the later supply and what is acceptable? What value of
capacitor is then appropriate as a balance between all these things?

And so on.

Jon

On Aug 19, 2:32 pm, Allen Bong <allenbsf6...@gmail.com> wrote:
> The output was supposed to give 60A of regulated 24V
> supply.
Allen what purpose does this 1440 watt regulated power supply serve?
Welding?
If you need that kind of power and you try to do it with a linear
regulator
instead of getting practical about it and just putting a couple of car
batteries
together or using welding equipement, you may have headaches.
Anyway, that transformer you put up the diagram of doesn't look to me
like a
piece of equipment in the 2 KiloVA category.
If you really want to build a linear regulator, which I applaud and
encourage
you to do so, you should probably aim a little lower.
20 amps? At 24 volts, that's a nice chunk of change --
and still a lot for a linear regulator.
By the way, a simple trick nobody mentioned for when you have too big
of a voltage drop
across a linear regulator is simply to put a power resistor between
the filter cap
bank and the regulator. Chose the power resistor value so that at max
intended current
it drops x amount of voltage, enough to get the voltage across the
regulator low but not so
low that it drops out of regulation. Then most of your heat
dissipation occurs in the
power resistor instead of the semiconductors.

On Mon, 20 Aug 2007 15:38:05 -0700, gearhead <nospam@billburg.com>
wrote:


>By the way, a simple trick nobody mentioned for when you have too big
>of a voltage drop
>across a linear regulator is simply to put a power resistor between
>the filter cap
>bank and the regulator. Chose the power resistor value so that at max
>intended current
>it drops x amount of voltage, enough to get the voltage across the
>regulator low but not so
>low that it drops out of regulation. Then most of your heat
>dissipation occurs in the
>power resistor instead of the semiconductors.

---
The caveat there is that with no, or low current into the load the
voltage dropped across the series resistor won't be enough to keep
from exceeding the regulator's absolute maximum input voltage spec.


--
JF

On Aug 20, 6:41 am, John Popelish <jpopel...@rica.net> wrote:
> Allen Bong wrote:
> > On Aug 19, 8:11 am, John Popelish <jpopel...@rica.net> wrote:
> >> Allen Bong wrote:
> (snip)
> >>> As for Q #2, my friend showed me a circuit and wants me to duplicate
> >>> it. The schematic
> >>> is as follows:
> >>> Q1 10W
> >>> 2N3055 0.1 ohm
> >>> Vunreg (42V) ___ Vout (24V)
> >>> o-----------------o---o----------- ------|___|----o---o------o
> >>> | | \ ^ | |
> >>> | | --- | .-.
> >>> | | | +----+ | |
> >>> | o------- --+ | | |2k2
> >>> .-. | \ ^ mje3055t | '-'
> >>> | | | --- Q2 .-. |
> >>> 4k7 | | | | | | |
> >>> '-' +--- --+ | | 1k |
> >>> | \ ^ mje3055t '-' |
> >>> | --- Q3 | |
> >>> | | || | |
> >>> +----------+--------o-----||--+ | |
> >>> | \| || | .-. |
> >>> | mje3055t |-------o------->| | |
> >>> | Q4 <| | |1k | I=5mA
> >>> | | '-' |
> >>> |+ I=4.26mA | | |
> >>> === o----------------------------+
> >>> /-\ | |
> >>> | | .-.
> >>> | z | |
> >>> | 1N5342B x 2 A | |1k5
> >>> | 13.6V 5W | '-'
> >>> | | I=10mA |
> >>> | === |
> >>> === GND ===
> >>> GND GND
> >>> (created by AACircuit v1.28.6 beta 04/19/05www.tech-chat.de)
> (snip)
> > Hi John,
>
> > You're quite right about something I didnt mention in the circuit. Q1
> > is actually 6 x 2N3055 in parallel mounted on 2 pieces of heatsink
> > measuring 12" x 4" each. The heatsinks were cooled by 2 mini fans on
> > each end. And I also know that using MJE3055Ts as drivers were
> > overkill. Maybe the original designer had too many 3055 in hand or
> > got them in bulk. Can you help me with what transistors are adequate
> > for Q2-Q4 ? The output was supposed to give 60A of regulated 24V
> > supply.
>
> Well, that explains what the .1 ohm resistor is there for
> (to help balance the current division between multiple
> transistors), but it still means that the wasted power is
> pretty scary at 170 watts per transistor.
>
> > What is the best way to reduce the amount of heat wasted on Q1 ?
> > Reduce the Vin to say 32V ?
>
> Or lower. You want the input voltage as low as you can get
> it while still leaving a few volts to drop across the pass
> transistors at the bottom of the ripple voltage at low line.
> Any more than that is just room heater.
>
> Do you really need 60 amps continuous capability?
>
> > Change 2n3055 to something better? What
> > about 2N3772 or 2N3773?
>
> I hate to use a pass transistor above the current where its
> gain falls to less than half the peak value.
> For a hot 2N3055:http://www.onsemi.com/pub/Collateral/2N3055-D.PDF
> that is about 2 or 3 amperes.
> The 2N3055 is really not much of a 15 amp transistor.
>
> Keep in mind that whatever you use for the pass transistors,
> they have to stay well below the safe operating area curve
> for DC. This transistor is red lined at about 10 volts drop
> at 10 amperes. The 17 volt drop in the design is outside
> this safe area, though the DC input may sag enough to just
> get in inside. Too close for me unless the input voltage is
> lowered. And if the output is ever shorted all bets are
> off, even if you add short current limit to the design,
> because there will be 24 volts extra dropped under that
> condition. It takes a moment for a fuse to blow, and in
> that moment, you could fry a half dozen transistors.
>
> >http://www.onsemi.com/pub/Collateral/2N3771-D.PDF
>
> Much more capable as a 10 amp pass transistor. It has good
> gain out to 10 amps and a 15 volt 10 amp DC safe operating
> area. Pretty safe with a 5 to 10 volt drop at 10 amps.
>
> >http://www.onsemi.com/pub/Collateral/2N3773-D.PDF
>
> I wouldn't use this as a linear pass transistor above 5 amps.
>
> A cheap transistor that is good for linear operation out to
> about 7 amps is the TIP35. I would use about 8 of them in
> parallel for 60 amps.http://www.ortodoxism.ro/datasheets/Pow ... Xqwzus.pdf
>
> One of any of these would work for Q2, the next driver down
> the chain, but there should be a low value resistor from its
> emitter to the output, to speed up the response of those
> output transistors. Something like 2.7 ohms 2 watts.
>
> A much smaller transistor could drive that. Perhaps Q3
> could be a TIP31:http://rocky.digikey.com/WebLib/On-Semi/Web%20Data/TIP31_A_B_C,%20TIP...
> It should also have a load resistor from its emitter to the
> output, to speed the response of Q2. Something like 100
> ohms 1/4 watt.
>
> This chain could be used as the pass device for an LM723
> based design, also, except that you would be able to add
> current limit and current limit foldback on short circuit
> functions.
>
> TIP31 could also be used for Q4.
>
>
>
> > I have no intention to change the design to a SMPS but just to improve
> > it. Any other suggestions are welcome.
>
> > I totlly agree with you and I'll study the A.N. of LM723 as suggested.
>
> > Allen- Hide quoted text -
>
> - Show quoted text -- Hide quoted text -
>
> - Show quoted text -

Thanks very much John, I have studied all your suggestions very
carefully and I will use it as a guide to improve the power supply
unit.

But one thing I dont understand, which part of the datasheet of 2N3773
makes it a poor choice for my application? It seems to me it is
better than 2N3772.

Allen

"John Fields"


>> An active zener IS a voltage clamp, unlike a series regulator !!
>>
>> A 2 terminal device, not 3.
>
> ---
> Ah, but that's not what the OP showed,


** You totally misinterpreted what he showed.

A zener voltage clamp must have some impedance in series to allow it to
work.

R load is just that.


** They are not interchangeable and so one is NOT clumsy compared the
other.


> _They_ are not interchangeable. That's precisely right, but that's
> not what makes the OP's implementation clumsy. What does is the
> inefficiency of his scheme which has the series resistor dissipating
> power


** You are WRONG again.

The OP did not mention or ask for a voltage regulator.

His schem was for an active ( ie high powered) zener.


You are ONE FUCKING IGNORANT ASSHOLE - Fields.

DROP FUCKING DEAD.




......... Phil

Allen Bong wrote:
(snip)
> But one thing I dont understand, which part of the datasheet of 2N3773
> makes it a poor choice for my application? It seems to me it is
> better than 2N3772.

I reviewed the 2N3771 and 2N3773.

The 2N3772 is similar to the 2N3771 (both rated 20 amps and
good for 10 amps), except that the 2N3772 has a higher
voltage rating.

The 2N3773 is a 16 amp rated transistor that is good for
about 5 to 7 amps.

"John Popelish"
> Allen Bong wrote:
> (snip)
>> But one thing I dont understand, which part of the datasheet of 2N3773
>> makes it a poor choice for my application? It seems to me it is
>> better than 2N3772.
>
> I reviewed the 2N3771 and 2N3773.
>
> The 2N3772 is similar to the 2N3771 (both rated 20 amps and good for 10
> amps), except that the 2N3772 has a higher voltage rating.
>
> The 2N3773 is a 16 amp rated transistor that is good for about 5 to 7
> amps.


** The last 2N3771 ( branded as RCA ) I bought prove to be a fake - it
proved on test to be a low current, high voltage switching type that had
been fraudulently relabelled.

If you buy a Motorola (or ON semi) 2N3773 - it will not be - it will be
an MJ15003.

They have been selling their MJ15003 as one for 20 years by relabelling it
as various other numbers, like MJ802.

Same goes for a great many "vintage" power transistors in TO3 pack.





........ Phil

Phil Allison wrote:

> ** The last 2N3771 ( branded as RCA ) I bought prove to be a fake - it
> proved on test to be a low current, high voltage switching type that had
> been fraudulently relabelled.
>
> If you buy a Motorola (or ON semi) 2N3773 - it will not be - it will be
> an MJ15003.
>
> They have been selling their MJ15003 as one for 20 years by relabelling it
> as various other numbers, like MJ802.
>
> Same goes for a great many "vintage" power transistors in TO3 pack.

Good info. I would have to have a very good reason to make
anything with TO-3 transistors, when the TO-218 are easier
to mount with fewer holes. That is why I added TIP35 to the
choices. Have you seen substitutions for these?

"John Popelish"
> Phil Allison wrote:
>
>> ** The last 2N3771 ( branded as RCA ) I bought proved to be a fake - it
>> proved on test to be a low current, high voltage switching type that had
>> been fraudulently relabelled.
>>
>> If you buy a Motorola (or ON semi) 2N3773 - it will not be - it will
>> be an MJ15003.
>>
>> They have been selling their MJ15003 as one for 20 years by relabelling
>> it as various other numbers, like MJ802.
>>
>> Same goes for a great many "vintage" power transistors in TO3 pack.
>
> Good info. I would have to have a very good reason to make anything with
> TO-3 transistors, when the TO-218 are easier to mount with fewer holes.


** Shame how they cannot dissipate the same power as a TO3 pack.

Shame how single bolt mounting barely works.


> That is why I added TIP35 to the choices. Have you seen substitutions for
> these?


** What I have or have not personally seen in the way of fakes is utterly
irrelevant - since I do my level best to avoid buying any.

Stick with the authorised agents and major parts suppliers and your chances
of getting a fake device is absolutely minimal.

Buy from a anonymous, bargain priced, on-line " parts launderer" and you get
a lucky dip.




........ Phil

On Aug 20, 6:53 pm, "Phil Allison" <philalli...@tpg.com.au> wrote:
> "John Popelish"
>
> > Allen Bong wrote:
> > (snip)
> >> But one thing I dont understand, which part of the datasheet of 2N3773
> >> makes it a poor choice for my application? It seems to me it is
> >> better than 2N3772.
>
> > I reviewed the 2N3771 and 2N3773.
>
> > The 2N3772 is similar to the 2N3771 (both rated 20 amps and good for 10
> > amps), except that the 2N3772 has a higher voltage rating.
>
> > The 2N3773 is a 16 amp rated transistor that is good for about 5 to 7
> > amps.
>
> ** The last 2N3771 ( branded as RCA ) I bought prove to be a fake - it
> proved on test to be a low current, high voltage switching type that had
> been fraudulently relabelled.
>
> If you buy a Motorola (or ON semi) 2N3773 - it will not be - it will be
> an MJ15003.
>
> They have been selling their MJ15003 as one for 20 years by relabelling it
> as various other numbers, like MJ802.
>
> Same goes for a great many "vintage" power transistors in TO3 pack.
>
> ....... Phil

Check out the sci.electronic.components thread "Counterfeit parts
alert on Ebay"

"gearhead"

>
> Check out the sci.electronic.components thread "Counterfeit parts
> alert on Ebay"


** See ABSE for my pics ( Double Headed Fake) of an even more blatant
example of a counterfeit Motorola TO3 part.




........ Phil

Allen Bong wrote:
> On Aug 20, 1:08 pm, ehsjr <eh...@bellatlantic.net> wrote:
>
>>Allen Bong wrote:
>>
>>>On Aug 20, 12:30 am, gearhead <nos...@billburg.com> wrote:
>>
>>>>On Aug 18, 4:20 pm, Allen Bong <allenbsf6...@gmail.com> wrote:
>>
>>>>[snip]
>>
>>>>>my friend showed me a circuit and wants me to duplicate
>>>>>it. The schematic
>>>>>is as follows:
>>
>>>>> Q1 10W
>>>>> 2N3055 0.1 ohm
>>>>> Vunreg (42V) ___ Vout (24V)
>>>>> o-----------------o---o----------- ------|___|----o---o------o
>>>>> | | \ ^ | |
>>>>> | | --- | .-.
>>>>> | | | +----+ | |
>>>>> | o------- --+ | | |2k2
>>>>> .-. | \ ^ mje3055t | '-'
>>>>> | | | --- Q2 .-. |
>>>>> 4k7 | | | | | | |
>>>>> '-' +--- --+ | | 1k |
>>>>> | \ ^ mje3055t '-' |
>>>>> | --- Q3 | |
>>>>> | | || | |
>>>>> +----------+--------o-----||--+ | |
>>>>> | \| || | .-. |
>>>>> | mje3055t |-------o------->| | |
>>>>> | Q4 <| | |1k | I=5mA
>>>>> | | '-' |
>>>>> |+ I=4.26mA | | |
>>>>> === o----------------------------+
>>>>> /-\ | |
>>>>> | | .-.
>>>>> | z | |
>>>>> | 1N5342B x 2 A | |1k5
>>>>> | 13.6V 5W | '-'
>>>>> | | I=10mA |
>>>>> | === |
>>>>> === GND ===
>>>>> GND GND
>>
>>>>>(created by AACircuit v1.28.6 beta 04/19/05www.tech-chat.de)
>>
>>>>[snip]
>>
>>>>Who designed that, the Geico caveman?
>>>>Probably not, 'cause he would have done a better job.
>>>>Check out the design in this next link
>>>>and consider how in its simplicity and rationality
>>>>it contrasts to your friend's circuit:
>>
>>>>http://www.rason.org/Projects/discreg/discreg.htm
>>
>>>>The following link explains some of the basics
>>>>about linear voltage regulating. You should read
>>>>a little bit before you jump into anything.
>>
>>>>http://www.national.com/appinfo/power/files/f4.pdf-Hide quoted text -
>>
>>>>- Show quoted text -
>>
>>>Hi gearhead,
>>
>>>I just found another design similar to my friend's. What do you think
>>>about it ? Is it more efficient? Is it ok to let the 7812 which is
>>>rated at 1A to work at 866mA?
>>
>>> http://www.zen22142.zen.co.uk/Circuits/ ... 230psu.htm
>>
>>>Allen
>>
>>You can use the technique shown in that, but you really
>>need to scrap the schematic and start from scratch. The
>>one your link shows is totally inadequate for your 60A
>>requirement.
>>
>>Start at the input. Your transformer will need to be
>>capable of providing over 100 amps at the secondary
>>if you want a 60 amp supply. Your rectifier will
>>need to be rated to handle that. That's two expensive
>>items. Your filter caps will also be expensive.
>>You do *not* want to use a 24 volt DC input to get
>>12 volts regulated out. At 60 amps, you'll be producing
>>720 watts of heat, meaning a huge area of heat sinking.
>>More expense.
>>
>>If you *really* need 60 amps at 12 volts, using a 12 volt
>>deep cycle lead acid battery is likely to be cheaper and
>>easier for you.
>>
>>In the meantime, you can experiment with much smaller
>>supplies - say 5 amps max - to learn, if learning
>>interests you. At lower currents, the learning experience
>>won't cost as much in blown up parts and burned fingers.
>>
>>Ed- Hide quoted text -
>>
>>- Show quoted text -
>
>
> How can I tell if the transformer is having 100A capacity?
> May be my friend bluff me saying that his PSU is giving 60A.
>
> The dimension of the transformer core is as below:
>
>
>
> 6"
> ------------------------------------------------------
> / /
> 2.8" / /|
> / / |
> / / |
> /-----------------------------------------------------/ |
> | | |
> | | |
> | <-------------- 4" ------------------> | |
> | +--------------------------------------+ | |
> | | ^ | | | | |
> | | | | | | | |
> | | | | | | | |
> | 1" | | | | | | |
> |<---->| 3" | | | | |
> 5"| | | | | | | |
> | | | | | | | |
> | | | | | | | |
> | | V | | | | |
> | +--------------------------------------+ | |
> | | /
> | | /
> | | /
> -----------------------------------------------------|/
> (created by AACircuit v1.28.6 beta 04/19/05 http://www.tech-chat.de)
>
> To measure the second wire size, I'll need to cut open the insulator.
> The filtering Caps are 6 pieces of 10,000uF 50V electrolytic.
>
> Alen
>

Nice diagram. That is not a 100+ amp at 30V (secondary)
transformer - too small. Why 30 volt? Because the rectified
and filtered DC output from a transformer providing 30 volts
AC would be about 42 volts, so I'm guessing the transform
provides 30 v AC.

You *really* need to forget about building a supply that
provides 60 amps output. It is a dangerous and expensive
project, and you need to *know* what you are doing if
you build one. It is *not* the kind of project where you
can get a schematic from the internet and a bunch of
cheap parts, connect them up and have a good result.

Ed