RE: Some G08 FAQ updates . . .

    Actually, because a bipolar transistor is a somewhat symmetrical device,
all bipolar transistors can be reversed (i.e. emitter and collector can be
reversed) to some extent.
 
    I carefully used the words "somewhat symmetrical" because even though
the emitter and collector are both P-type material (in a PNP transistor like
the MPS-U60) they are doped differently, resulting in a "reverse beta" which
is different (lower) than the normal "forward beta."
 
    If the reverse beta is high enough, the circuit may still work properly
with the emitter and collector of a bipolar transistor reversed. Therefore,
if the confusion about what terminal was connected to the case of the
transistor resulted from hooking it up with the case connected where the
emitter should be connected, it is very possible that things actually worked
fine.
 
    However, other than being academically interesting, I can't really think
of too many useful reasons to hook up a BJT backwards.
 
    Also, any MOS device is perfectly symmetrical, and the source and drain
can always be reversed. Just be careful that the bulk (substrate) remains
connected to the source if that is the way it was originally configured (and
there is a separate connection for the bulk.)
 
l8r,
 
Joe
 
     

  _____

From: owner-vectorlist@vectorlist.org
[mailto:owner-vectorlist@vectorlist.org] On Behalf Of Rodger Boots
Sent: Sunday, February 22, 2004 12:44 AM
To: vectorlist@vectorlist.org
Subject: Re: VECTOR: Some G08 FAQ updates . . .

Christopher X. Candreva wrote:

I've sent Mark Jenison some updates for the G08 FAQ. I've documented all the

parts that are on the solder-side of the HV board, and suggest adding a

reminder that the input protection board doesn't have part IDs screened on

it.

I also discovered that, should you break the emitter pin off one of the

MPSU60's -- that would be the pin with the red wire soldered directly to it

-- the metal case tab is the emitter, and you can solder the red wire

directly there just fine.

Sorry, the tab is the COLLECTOR (almost always is) and I can prove it!
Datasheet here <http://www1.cedar-rapids.net/00000028/ihs/mpsu60.pdf> .
It's an odd transistor, we're so used to having the collector lead as the
center leg these days.

For power transistors, my G08 has two 2N6259's and two MJ15022's . The FAQ

doesn't mention MJ15022s, and the list archives have 2 mentions of them (and

the MJ15024, an even heavier duty version). Both are basically questions
from

people who tried them and they seemed to work. I guess I would be number

three. Specs on the MJ look as good or better than the 6259, but perhaps we

could get a "final ruling" (Rodger ?:-) on the MJ15022/4 being a suitable

replacement for the discontinued 6259.

Datasheets for the 2N6259
<http://www1.cedar-rapids.net/00000028/ihs/2n6259.pdf> , MJ15022
<http://www1.cedar-rapids.net/00000028/ihs/MJ15022.pdf> /4
<http://www1.cedar-rapids.net/00000028/ihs/MJ15022.pdf> , and (oh why not?)
the NTE388 <http://www1.cedar-rapids.net/00000028/ihs/nte388.pdf> .

All have the voltage, current, and power handling capabilities if on a big
enough heatsink. The killer is secondary breakdown. The NTE388 doesn't
spec that, the 2N6259 is still the best, but the MJ15022 is close enough to
be used. Seems there was another version of the G08 that used the MJ15022
and it's PNP equivalent in a complimentary/symmetry output stage insead of
the all-NPN 2N6259.

The whole key to not blowing the transistors is to keep them out of the
secondary breakdown area. To do that you need the following:

    1) Don't hold the red reset button in for any length of time
    2) Grounds and +5 power to the boards have to be perfect, John has told
of ways to improve those connections
    3) Keep the monitor power supply voltage where it should be. Line
voltage these days is too high and the power transformer doesn't have a tap
for it. 125 volts going into a 110 or 115 tap makes for too much voltage to
the monitor which makes it run way too hot.
    4) Make sure the fan works and consider mounting another one at the top
of the case blowing OUT of the game cabinet.

Having the boards tell the monitor to deflect off the screen and stay there
will blow the transistors.

Mouser, incidently, doesn't carry the MJ and recommends the NTE388 at $7.50

each. DigiKey carries the 15022 and 15024 at $3.75 each.

http://www.vectorlist.org/Vectorlist/2002/10/0143.html

http://www.vectorlist.org/Vectorlist/2002/07/0231.html

http://www.ampslab.com/PDF/mj15024.pdf

==========================================================

Chris Candreva -- chris@westnet.com -- (914) 967-7816

WestNet Internet Services of Westchester

http://www.westnet.com/

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Received on Tue Feb 24 00:46:16 2004