Sinclair ZX80 / ZX81 / Z88 Forums

sirmorris wrote: ↑Wed Dec 20, 2017 9:56 pm

rune wrote: ↑Wed Dec 20, 2017 7:37 pmPostage to UK is a very reasonable $2.33 - Probably as cheap or cheaper than buying a bulk lot and re posting within the UK.

Agreed.

Do you order one for me as well?

I'm having trouble .. there doesn't seem to be a way to select the item

Paul & Charlie

Sorry, I only ordered two as I hadn't heard from anyone and I wasn't sure if Id have time tomorrow.

Drop a line to Dan, he replies quickly and its an easy purchase.

Dave

Done. Nicely!

Leave one for me I have been sick and unable to order one... Got to get to bank blah blah blah

Please

gamma, send me your paypal email address and I respond with an invoice. It's the last one available.

Looks like there's enough interest to order another batch, ....but I'll wait for feedback for any potential design changes or improvements.

I'm on the verge of routing a wire from A13 over to the jumper to test addressing 16kB at a time, been busy writing some code to go in there.

Selecting 8kB banks at a time is working just fine.

I should have used a right angle style jumper for the A13 line. ...and probably used two resistors, instead of one, on the A13 tie up/down. What are we looking at, 10 uA max through a 1kohm = 10mV drop --- yeah probably OK, but not having the resistor in the path would just make me feel better.

Anyway, one solder job and we're in business. We now have the whole lower 16kB available to us.

The convenient spot to pick up A13 is right by the mounting hole:



...and here's with the jumper and ROM adapter in place:



OK, does it actually work:

Well, I'm working on this program:


Here's a small BASIC program to see what the first few bytes are in the "shadow" area:


...I'll let you do the decimal <--> hex conversion.

Very nice and useful adapter. It looks I'm late and no single board left One thing that I am not convinced with are surface mounted pin headers.

McKlaud and everybody,

I quoted you, "One thing that I am not convinced with are surface mounted pin headers."

I just received my order from Digi-key. I have a piece of a MPH100IMP40M-G-V-SM-ND in according to mooredan's own website. http://dlmeng.suncup.net/zx81-ts1000-rom-adapter-pcb/ I looked at the shape of male pin headers' contacts, they are round! Just use a precision machine tuned socket when you want to solder the headers onto the board.

Please mind the resistors' size, which is 2mm lengthwise x 1mm wide, when you are soldering them onto the board.

Cheers,
Dessony

...or just remove the ROM socket from the ZX81 board altogether and solder the adapter board directly in. If you can program an EPROM, there's really no need to ever have to remove the adapter -- that's what's the ZIF socket is for.

Yeah the 0805 resistors are about the limit for comfortably soldering by hand. I pre-fill the pads with a very small piece of solder that I cut off the spool with an X-acto knife. ...then use some tweezers to apply some downward pressure on the resistor while just touching the pad with the iron.