16K/48K Lower RAM (4116) replacement.

protek

Zorn, does your module put less load on TR4/5? Could cheaper and more easily available substitutes to ZTX650/1 and ZTX213 then be considered?

Zorn

The module only uses the 5 V supply and so the voltage converter circuit will be more lightly loaded. The power it has to deliver even when 4116s are used is very small, though. Problems arise when it is overloaded, not during normal operation.

The ZTX653 and possibly other members of the ZTX65n line are still manufactured and fairly widely available from suppliers of electronic components and not especially expensive. Examples:

http://www.bowood-electronics.co.uk/index.php/semiconductors-transistors-c-24_100?page=6&sort=1a
http://cpc.farnell.com/diodes-inc/ztx653/si-n-120v-2a-1w/dp/SCZTX653

There aren't many physically small transistors that can handle the peak current a ZTX65n can, so I recommend sticking to this series.

TR5 is far less critical and many PNP transistors will work in this position. I often use a BC557.

stu232

Does anything like this exist for the ZX81?

1024MAK

stu232 wrote: »

Does anything like this exist for the ZX81?

What are you interested in?

A brand new modern RAM pack that plugs in to the expansion connector? Yes. You have a choice of just a RAM expansion, or the ZXpand, which offers a SD card reader as well. Go to www.SellMyRetro.com

Or an internal RAM upgrade? The internal RAM upgrade does require soldering. How much depends on what RAM chip(s) are fitted to your ZX81 and if so if a socket is fitted.

if you want more info, ask...

Mark

1024MAK

For ZX81 memory, see posters new thread... http://www.worldofspectrum.org/forums/forumdisplay.php?f=22

Mark