Search found 22 matches
- Tue Oct 08, 2019 1:34 am
- Forum: Hardware
- Topic: Mystery 330 ohm resistor connected to X1
- Replies: 4
- Views: 3131
Re: Mystery 330 ohm resistor connected to X1
Both of them are issue 3 "ISS 3". Both have red solder mask on the underside, but one has a white top silkscreen and the other has a yellow silkscreen. The silkscreen is virtually identical except the yellow one has the number 8243 near the oscillator circuit. Yeah, I figured as much, suspecting it ...
- Mon Oct 07, 2019 2:54 am
- Forum: Hardware
- Topic: Mystery 330 ohm resistor connected to X1
- Replies: 4
- Views: 3131
Mystery 330 ohm resistor connected to X1
Just doing a bit of backward engineering and I discovered that two of my ZX81 boards have a 330 ohm resistor (orange-orange-brown; front and center in the photos below) that isn't on the schematics. This resistor is connected to the node where X1 and C6 are connected. The other terminal is to ground...
- Sat Dec 23, 2017 3:22 am
- Forum: Hardware
- Topic: Yet another ROM adapter
- Replies: 46
- Views: 20348
Re: Yet another ROM adapter
There ya go. ...looks great.
- Sat Dec 23, 2017 1:55 am
- Forum: Hardware
- Topic: Yet another ROM adapter
- Replies: 46
- Views: 20348
Re: Yet another ROM adapter
... Coming back to your adapter, could you use all components in SMD packages including both capacitors in next revision of the board? MLCC 4.7uF/10V is available in 805 size. In KiCAD you can also find components' footprint for hand soldering. Pads are longer and they are really handy. Yes, they r...
- Sat Dec 23, 2017 1:45 am
- Forum: Hardware
- Topic: Issue 3 16k internal RAM mod
- Replies: 23
- Views: 10055
Re: Issue 3 16k internal RAM mod
Kind of late to the party, but here's another completed mod (click on image for full size): https://s3-us-west-2.amazonaws.com/files.suncup.net/IMG_1395_sml.JPG https://s3-us-west-2.amazonaws.com/files.suncup.net/IMG_1396_sml.JPG No problem at all, here's the output of "PRINT PEEK 16388 + 256 * PEEK...
- Fri Dec 22, 2017 2:22 am
- Forum: Hardware
- Topic: Yet another ROM adapter
- Replies: 46
- Views: 20348
Re: Yet another ROM adapter
...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 solderi...
- Thu Dec 21, 2017 8:51 am
- Forum: Hardware
- Topic: TI99/4A KEYBOARD ADAPTATION
- Replies: 41
- Views: 21458
Re: TI99/4A KEYBOARD ADAPTATION
Nice now don't forget decals for logo! Mooredan>> Still needs to be cleaned up a bit and I plan to cut up a junk ZX81 keyboard and glued the them onto the key caps -- but it doesn't look like the functions will fit -- may have to either exclude them or shrink them. I cut up a laser print of keyboar...
- Thu Dec 21, 2017 8:47 am
- Forum: Hardware
- Topic: TI99/4A KEYBOARD ADAPTATION
- Replies: 41
- Views: 21458
Re: TI99/4A KEYBOARD ADAPTATION
That reminds me, I do plan on doing some debouncing mitigation on the keyboard. I seem to recall this sometimes showing its face. Here's a good reference: http://www.labbookpages.co.uk/electronics/debounce.html
- Thu Dec 21, 2017 8:40 am
- Forum: Hardware
- Topic: Yet another ROM adapter
- Replies: 46
- Views: 20348
Re: Yet another ROM adapter
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. Anyw...
- Thu Dec 21, 2017 5:38 am
- Forum: Hardware
- Topic: Yet another ROM adapter
- Replies: 46
- Views: 20348
Re: Yet another ROM adapter
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 jum...