Re: 7603 15+ rail dead. Options?


Dave Voorhis
 

Excellent; thanks!

I might even have suitable transistors already knocking around in my parts bins.

Without much thought, I’d assumed the use of a dual packaging meant there was some critical need to match temperature as closely as possible, but if it's non-critical enough to solve with discrete devices and heatsink compound, that’s good.

On 26 Feb 2018, at 15:31, Craig Sawyers <c.sawyers@tech-enterprise.com> wrote:

Here you go - PN2484, the plastic packaged version of the 2N2484. Mouser 42c each or $3.51 for 10. Buy
ten and find two with close hfe, shove them in.

A replacement Q931 (2N5189) is easily and cheaply found, but a new replacement for Q936 (2N2919)
costs about twice what I paid for the oscilloscope and Q926 doesn t appear to have a specified
substitute though I presume any small NPN transistor capable of handling 60 volts or so would be
fine.
On 26 Feb 2018, at 15:23, Craig Sawyers <c.sawyers@tech-enterprise.com> wrote:

The only reason that Tek used a dual is - well because they were more easily available back then. I
would just take two generic NPN TO92 parts with gains of about 100-200 (you could easily match from a
bunch of them to 10% or so) and a Vceo of 60V or so, stick them together with heatsink compound and
shove them in.

It is just a long tailed pair error amplifier after all.

The actual single device that is in the dual is a 2N2484 (according to the Tek parts catalogue), which
are easily available and cheap in a TO18 package. Buy a bunch and match 2 for hfe to 10% and strap
them together. Job done.

Mouser $2 each or $18.50 for ten. Possibly even cheaper if you shop around.

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