ZX81 denigrated! (was Re: Approaches to projects)

From: Tony Duell <ard_at_p850ug1.demon.co.uk>
Date: Tue Nov 30 18:56:09 2004

> I've got a Stella "Stellaphone ST454" four-track reel-to-reel (electron tube
> based.. warms the room in winter :) here - the connector I've got for the
> inputs looks like this:
> O | O

That was a farily standard connector on Philips tape recorders. The
middle pin is a locator only -- the real reason for it was to stop the
plug going into European mains scoksts (!). One of the outside pins
should be martked with an earth symbol, the other is (of course) the
signal pin. The original plug was unpolarised, but carried a red dot to
indictate the signal pin.

> .. as in, two round pins, with a vertical pin in the middle. It's labelled
> "R" on the connector panel ("Record Player or Radio Input"). There are also
> two connectors that consist of three round pins - two large ones on the
> outside, and a small one in the middle. They appear to be used for the

That was the convention. A flat locator on inputs, a round one on

My Philips (I forget the model number, I can look it up) uses those for
the speaker outputs. The inputs, line-level output (on the same connector
as the radio 'diode' input) are DIN sockets.

Said machine is Stereo, 4 speed (including 15/16 ips [1]), can copy one
mono track to the other while mixing in the microphone input, and so on.
The speakers are somewhat Heath-Robinson. There's one in the case, used
for mono playback and the left stereo channel. And another in the lid.
For Stereo playback you uncoil a lead from a slot inside the lid and plug
it into the RH extension speaker socket. Then put the lid on the right
side of the machine, about 2m away. Of course you can also connect up a
pair of speakers or a stereo amplifer/speaker system...

[1] Yes, the quality is lousy. It's useful in the same way that the
HP82161 [2] is useful. In case some swine gives me a tape recorded at
that speed.

[2[] On-topic at last. The 82161 is an HPIL mini-cassette drive used with
the hP41, HP71, etc. It works, but it's fairly slow, and the tapes are
essentially unobtaium (and they are not the same as any normal audio tape
cassette). I use a 9114 disk drive with my HP calculators, that uses 3.5"
DD disks whioch are much easier to obtain, faster, and store about 5
times as much. But I keep the 82161 going because I sometimes have to
copy tapes for other HPCC members, etc.

> speaker and headphone outputs. The microphone input is a 3-pin DIN.
> The ST454 needs some restoration - there's a brown stain in the inside of the
> top plastic (polystyrene, according to the destructions) cover (from the
> tape?) and the cabinet covering is peeling away. It is, however, fully
> functional (electronically speaking). Valve complement is - EF86, ECC83,
> ECL82, EM84, EZ80.
> If anyone's got a set of schematics for the ST454 (or knows which Philips

It's not in Poole and Molloy, at least on that I can find. Can you give
me more description, so I can see if I can identify the Philips equivalent.

In particular :

It's 4 track, does it have a Stereo socket [3]?

What's the cabinet made of (most were rexine-covered plywood, a few later
ones were plastic)

How many speeds, what are they

What controls and connectors do you have?

[3] Another odd idea of Philips. On some later 4 track machines there was
a 3 pin DIN socket, the connections being the lower (track 3) head
winding, ground, and +16V (normally obtained by potting down the HT+
line). You could connect a special Philips pre-amplifier there and :

a) play back steereo tapes (LH channel throug hte machine, RH channel
through the pre-amplidier and the pickup input of your radio set!)

b) Monitor track 3 on headphones (the pre-amp could drive the Philips
headphones) while recording on track 1

c) Copy track 3 to track 1 (link output of the pre-amp to the input of
the recorder) while mixing in another signal (these models had separate
recordign level controls for the microphoen and radio/pickup input, thus
giving a simple mixer).

> recorder it's equivalent to), please let me know!

I will see what I can do....

Received on Tue Nov 30 2004 - 18:56:09 GMT

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