Re: G08 transistors

There is nothing wrong with the 2N6259 and you are going to be
hard pressed to find a better part. Just because the NTE388 LOOKS to be a
better part doesn't tell the whole story. There is not much out there that
has better secondary breakdown characteristics than a 2N6259, but you'll
never tell that by looking at just numbers, you need to see a breakdown
chart. This will show you where secondary breakdown is.

For example, looking at the 2N3716 data sheet at
http://www.mot-sps.com/books/dl111/pdf/2n3715rev7.pdf you will see on page 5
that at full voltage (80 volts) the part will withstand .2 amps. That's
only 16 watts allowed for what's supposed to be a 150 watt part! Compare
that with a 2N6259 that can take 200 watts of dissipation with 90 volts
across the part!

What kills the 2N6259 is over voltage, plain and simple. The part is rated
for (I think) 125 volts, maybe as high as 150. But the G08 uses + and - 63
volts, IDEALLY. So when the amplifier swings to the rail during a fast
vector draw you have close to 125 volts.

Remember I said IDEALLY? That's with the game plugged in to a 110 volt
line, since that's what the Gremlin/Sega power transformer was designed
for. Is there any of you with only 110 volts coming out of the wall? More
like 120 to 130, isn't it? THAT'S why I keep saying the game needs to be
restrapped to match the powerline. Either buck out the extra voltage with
some filament transformers or whatever, but DO reduce the voltage. And what
happens when the occasional power line spike comes along? The monitor blows
up, that's what.

In my Showbiz Pizza days we used to use NTE388's in an Eliminator at about
$10 per part. They still blew up until one of the techs (not me) ran the
power into the 110 and 240 taps of the game power transformer. The result
was a 130 volt winding. The transistors quit blowing. It was just that
simple.

Mark E Davidson wrote:

> Ok, Last week I said that my G08 puffed. It seems that the two
> transistors supplied in the Zanen cap kit (2n3716) shorted,
> smoking at least 3 resistors in the 100 to 180 ohm range on the
> deflection board and some of the add on boards. There may be more damage
> but that's a different issue. Could this line be fused to prevent new
> damage? ( just a thought I had)
> It has long been said that the original 2N6259 transistor is no
> longer available. This is untrue! I ordered and (received) 20 this
> weekend from my local supply house, But again that is not were Im going
> here. In looking for a cross reference, I found NTE388 to have higher
> specifications then the 2N6259. I put a table together comparing the two
> at http://www.basementarcade.com/arcade/library/vlist/ntevs2n6259.html
> Is it possible that a better part does exists in today's world? Would
> the NTE388 also be a better replacement for the 2n3716 in a WG6100?
>
> -=Mark=-
Received on Tue Nov 2 02:29:19 1999