[Heath] The Heathkit IP-27

[MICHAEL TALLENT]

Guess I am going to clean off all the stuff on my IP-27 and start checking 
it out.  See more comments below.

Mike T  W6MXV

----- Original Message ----- 
From: "Kenneth G. Gordon" <kgordon2006 at frontier.com>
To: "Dave Edwards" <kd2e at comcast.net>; <heath at puck.nether.net>
Sent: Wednesday, June 06, 2012 8:58 PM
Subject: Re: [Heath] The Heathkit IP-27


> 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

The 2N2553 is a small transistor NOT a 2N301.
I have a lot of older transistors so I would probably start by trying a 
2N3645 or 2N(PN)2907A

>
> Q-4 and Q-5 are 2N2869.

The 2N2869 is the same as a 2N301, I have some and they are marked with both 
numbers, and are the large TO-3 case size.

>
> 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.

The 2N2869 is used for Q4,Q5 the TO-3 size series regulators and I would 
think that the TIP-34A would work here, the TIP-32A would work but is 
smaller in size to mount into a TO-3 socket.Also a 2N3791 or 2N3792.

>
> 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.

Hfe is the DC current gain and has nothing to do with "quickly".  Maybe you 
mean the Ft, but I don't think it matters in a DC power supply as you have 
all these big capicators so nothing is going to happen very 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.

The 2N3791 should also work here but you will probably need to change some 
resistor values in the current limiting circuit because of the higher Vbe 
voltage of the silicon.

>
> Anyway, that's where I am so far.
>
> vy 73,
>
> Ken W7EKB
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