Re: WORKING replacements for Zetex ZTX transistors in ZX Spectrum?

Linards Ticmanis <ticmanis@xxxxxx> wrote:
Hello,

I've just sort of given up on getting my hands on those hard-to-find ZTX
transistors over here in Germany.

Which other, available, types actually do work as a replacement?

As you will know the Spectrum has ZTX650 (or TIPP31), ZTX450, ZTX313,
ZTX213 and BC184 inside.

Here's what I came up with, but this is pure theory. What I'd need is a
confirmation which of these replacements actually do work in practice.
Also what works for the ZTX313 as the BSV26 I came up with seems just as
hard to get.

A transistor is a fairly simple device.
There're only a few variables that would affect its suitability as a
replacement... Those are...

Medium: Determines the voltage they saturate at, silicon is 0.7 volts,
germanium is 0.3, other substances have different characteristics.

Polarity: (pnp can only replace pnp/npn only replace npn)

Current load: This is a minimum of course, any transistor that matches or
exceeds the current load of the one you're replacing should do, as long as
it fulfills the other requirements...

Switching speed: Only really a concern if it's part of a digital circuit or
high quality audio amp or something. Most transistors have timing graphs in
their specs anyway. But, the faster the better, as long as it's as fast or
faster than the one you're replacing it'll work.

package size: well, the transistor's got to fit in the space the one it's
replacing vacates hasn't it?

So, as long as you find an adequately sized NPN (or PNP) transistor capable
of taking the current load of the original and capable of switching (if
required) fast enough, it'll work.

If it's just a power transistor that's part of the power supply you don't
need to worry about switching, only medium, polarity, size and current load
are important. Suppose there might also be a thermal range variable if
you're going to drive the thing very hot...

(NB: This is only for bipolar transistors... for FETs and MOSFETS, you've
got other concerns)
--
| |What to do if you find yourself stuck in a crack|
| spike1@xxxxxxxxxxxxx |in the ground beneath a giant boulder, which you|
| |can't move, with no hope of rescue. |
| Andrew Halliwell BSc |Consider how lucky you are that life has been |
| in |good to you so far... |
| Computer Science | -The BOOK, Hitch-hiker's guide to the galaxy.|
.

Relevant Pages

  • Re: DE switch matrix/transistor problem -- Fixed
    ... repair the mis-wired flipper (it was weak because it was ... I can't cause those switches to open/close at all. ... Tracked it down to a blown transistor on C8 in the matrix. ... Am I leaving myself wide open to keep replacing that ...
    (rec.games.pinball)
  • Re: Tech: Cyclone
    ... All the fuses were checked before the weekend, ...  I may have jumped the gun replacing it, ... transistor with a jumper wire since there's no large coil, ...
    (rec.games.pinball)
  • Star Wars relay problem
    ... Short circuit on my GI last night and the 4 yellow/white cables from ... GI relay doesn't work at all. ... Shorted the transistor + diode to ... replacing them with two new ones (tested OK before soldering them to ...
    (rec.games.pinball)
  • Tech: DE switch matrix/transistor problem
    ... Was having "Ball Missing" ... Tracked it down to a blown transistor on C8 in the matrix. ... replaced the chip. ... Am I leaving myself wide open to keep replacing that ...
    (rec.games.pinball)
  • Re: HELP! Tech question...
    ... While you may find that replacing the Cracked transistor fixes the ... The cause of the transistor going bad like that is often a bad protection ... diode 1N4004 on the associated coil is open or bad. ...
    (rec.games.pinball)
Loading