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Smarty

On 2/14/2014 5:23 AM, wrote:
On Sunday, June 1, 1997 3:00:00 AM UTC-4, John Whitmore wrote:
I've recently acquired a Phase Linear 400. This was
an historically important audio amp, as it was the first of the
wave of high-powered amplifiers that came out of the 1970's.

This unit, though, has been through some tough times.
I've found lots of shorted and fried components, but the
main difficulty is in the output transistors.

There are four different types plugged in to the
sixteen TO-3 sockets. The outputs are four composite-Darlington
transistors, each having a single driver feeding three
paralleled output transistors. Someone in the past
replaced some of the paralleled outputs with various types.
So, I don't trust the types of transistors I see there.
Also, I don't know what the original drivers were.

Driver types: GE-37, DTS-701, RCA410
The first two are 700V, 1A; the third is 300V, 5A rated.

Output types: GE-37, PL-909
The first is clearly inappropriate in this application,
and the second is (apparently) a Fairchild special part
number for Phase Linear. I assume it's intended to be
a high current type, and possibly similar to 2N5264
(a Fairchild power transistor of the right era).

From the emitter degeneration resistance (0.22 ohms)
I suspect the output transistors should be roughly 5A rated.
Does anyone know? Should I just jam in MJ15003's?
Or maybe MJ410's (very similar to the RCA410)?

And as for the drivers; should they all be the same
type as the outputs? What were the original drivers?

Thanks for any info; this can't interest many folk,
so e-mail is preferred.

John Whitmore

If interested I have some XPL909 for sale

Service manuals for Phase Linear 400s, 700s, etc. with schematics, PCB
layouts, instructions, are available at numerous places for free. A
Google search turned this one up, among others:

http://www.vintageshifi.com/repertoi...ase-Linear.php