[Heath] The Heathkit IP-27

[Kenneth G. Gordon]

On 6 Jun 2012 at 8:00, Dave Edwards wrote:

> Post the transistor number....There are a lot of junk boxes on the list!!
> 
> ....Dave

Oh. OK, Dave. Good idea.

Q-1 is really weird: it is a DTG-600.

Q-2, and Q-3 are either 2N2553 or 2N301

Q-4 and Q-5 are 2N2869.

I ***think*** I may have found Si equivalents for all:

For the 2N2553 or 2N301, the TIP-32AG looks very good.

For the 2N2869, the Fairchild FJAF4210-OTU is almost identical other than being Si.

For the DTG-600, there are two possibilities: 1) the SDSG-200 or 2) the TIP-36CG

I suspect that the reason the DTG-600 was chosen for that particular circuit (current limiter) 
was that for the time it had a fairly high hFE: min was 65 and max was 300, and therefore 
would react quickly.

The SDSG-200 (which is a Darlington pair) has an hFE that can be MUCH too high: like 15K

The TIP-36CG has a typical hFE of 45, but max is about 600.

Anyway, that's where I am so far.

vy 73,

Ken W7EKB