Voltage converter in Timex FDD 3

3 messages · 2004-10-26 → 2004-10-29 · Yahoo Group era · View archive on archive.org

Participants: Jarek Adamski, Jeff Burrell

Preserved from the Timex/Sinclair 2068 Yahoo Group (2001–2019), which is no longer online. Text reproduced from the archive.org archive; email addresses masked.

Messages

1. Voltage converter in Timex FDD 3

Jarek Adamski · Tue, 26 Oct 2004 22:23

Hello,

Could someone meassure the negative voltage produced
by converter on top board of Timex FDD 3?

My produces -18V and the transistor is very hot.

I forgot to check how it works on the original board,
before I mounted YABUS.TF3 board. Now it is too late
to resolder the elements back...

The YABUS.TF3 schematics in YTF3008s.png file on:
 http://8bit.yarek.pl/upgrade/yabus.tf3/
and the converter is bottom left corner. Could someone
tell me is the -18V normal, or how can I decrease the
voltage to -12V and limit power on MPS6727 transistor?
Will 100uF capacitor in place of 22uF help?

Jarek Adamski

2. Re: [ts2068] Voltage converter in Timex FDD 3

Jeff Burrell · Thu, 28 Oct 2004 19:07

Jarek

  Increasing the value of the capacitor probably won't help with the transistor power dissapation.  It will decrease the ripple voltage, though.


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3. Re: [ts2068] Voltage converter in Timex FDD 3

Jarek Adamski · Fri, 29 Oct 2004 11:13

Cytowanie Jeff Burrell <[email]>:

> Increasing the value of the capacitor probably won't help
> with the transistor power dissapation.  It will decrease the
> ripple voltage, though.
Thanks. I've solved this replacing 2k2 base resistor with
3k3 one. Got -15V (finally on MC1488 pin 1) and the
transistor has normal temperature. But I didn't try to
load RS232 outputs and still don't know how hot is in
original circuit.

Jarek Adamski

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