IP-27 Transistors

[Ken Simpson, W8EK]

We used a lot of Heath IP-27s at the college I taught at before I
retired.  It has been a few years, but I am fairly sure my memory is
correct on various points.

1)  The 2N301 is a critical component.  Using another manufacturer
resulted in problems.
2)  Most of the problems were caused by either high leakage currents,
or a shorted 2N301.
3)  The 2N301 would often short (C to E) if one turned the voltage
selector switch too fast.  We assumed that this was caused by spikes
exceeding the CE voltage rating of the 2N301.  We added a 56 V zener
across the C to E junction, and that problem went away.
4)  The DTG 600 transistor was even more critical than the 2N301.
5)  Gain did not seem to be a problem in any of the cases, but leakage
was.

To put it another way, do not expect the circuit to work if you
substitute for the 2N301.

73,

Ken, W8EK



----- Original Message -----
From: "Mark Graalman WB8JKR" <wb8jkr at JUNO.COM>
To: <HEATH at LISTSERV.TEMPE.GOV>
Sent: Wednesday, October 02, 2002 11:06 AM
Subject: Re: IP-27 Transistors


>   Greg,
>
>  Sorry, allow me to correct myself. I didn't realize the
> 2N301 was a PNP device so the 2N3055 wouldn't work
> without design changes in the supply, but any like rated PNP
> silicon device in a TO-3 case should.
>
> 73,  Mark  WB8JKR
>
> On Tue, 1 Oct 2002 22:20:43 -0400 WB8JKR at juno.com writes:
> >  Hi Greg,
> >
> >  Those are germainium but I see no reason why silicon
> > units wouldn't work. Any silicon with TO-3 case,
> > col E rating of about 70 v and 5 to 10 amps with a Hfe
> > of at least 80 should work fine. Actually, a 2N3055
> > would probably work.
> >
> > BTW, the 2N301 crosses to a ECG 121
> >
> > Mark  WB8JKR
> >
> >
> > On Tue, 1 Oct 2002 17:49:50 -0700 Greg WB8NGA <greg at BOWSER.COM>
> > writes:
> > > Just wondering if someone knows of a good replacement
> > > for the two series pass transistors for the IP-27 power
> > > supply?  Mine are 2N301's but they aren't being made
> > > anymore.
> > >
> > > Thanks in advance,
> > > Greg
> > >

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