Difference between revisions of "Buiding up and testing the ZX81+38 revision 1,9"

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All files you need are on my GitHub page here: https://github.com/mahjongg2/ZX81plus38
 
All files you need are on my GitHub page here: https://github.com/mahjongg2/ZX81plus38
  
 
+
== Start Building ==
 
Make sure you use the latest files for the PCB, BOM and component overview drawing, and schematic, at this moment these are revision 1.9.
 
Make sure you use the latest files for the PCB, BOM and component overview drawing, and schematic, at this moment these are revision 1.9.
  
Line 18: Line 18:
 
[[File:Low components first.jpg|1000px]]
 
[[File:Low components first.jpg|1000px]]
  
 
+
== Add the IC's ==
Then add the IC's be careful to place them in the right orientation, and the right spot referencing the component buildup drawing. Use the latest version of revision 1.9 of the component overview drawing, that is the drawing where the 15pF capacitors are BELOW the crystal.  
+
Then add the IC's be careful to place them in the right orientation, either up, or three to the left, and in the right spot, referencing the component buildup drawing. Use the latest version of revision 1.9 of the component overview drawing, that is the drawing where the 15pF capacitors are BELOW the crystal.  
  
 
[[File:ZX81+38 rev 1.9 component placement.png|1000px]]
 
[[File:ZX81+38 rev 1.9 component placement.png|1000px]]
  
Note that I'm not using sockets for the other IC's, but you can if you want, if to use dual wipe sockets, NOT round machined sockets, they are a disaster to put IC's into, and are not as reliable as they seem to be.  
+
Note that I'm not using sockets for the other IC's, but you can if you want, if you do use dual wipe sockets, NOT round machined sockets, they are a disaster to put IC's into, and are not as reliable as they seem to be.  
  
If you see a number like "08" in the middele of in IC in the drawing this means you need the HC version of the IC there so "08" means you need to place a 74HC08 there. A possible exception is the CD40007.  
+
If you see a number like "08" in the middele of in IC in the drawing this means you need the HC version of the IC there so "08" means you need to place a 74HC08 there. All logic IC's are HC type with A possible exception of the CD40007.  
  
 +
== place the Crystal ==
 
then place the 13MHz crystal
 
then place the 13MHz crystal
 
If you could not find an SMT type of this crystal, the one that comes with a plastic carrier and flat pins sticking out besides the metal can, then convert your pin though hole crystal to a SMT solderable one by sticking the pin wires through a piece of paper, fold the pins flat sideways, and cut the wires off just outside the paper isolation.then solder the pins to the solder pads beneath. If you are carefull not to cause a short between the pins and metal can you might leave out the paper isolation, see:
 
If you could not find an SMT type of this crystal, the one that comes with a plastic carrier and flat pins sticking out besides the metal can, then convert your pin though hole crystal to a SMT solderable one by sticking the pin wires through a piece of paper, fold the pins flat sideways, and cut the wires off just outside the paper isolation.then solder the pins to the solder pads beneath. If you are carefull not to cause a short between the pins and metal can you might leave out the paper isolation, see:
Line 32: Line 33:
 
[[File:Kristal legs bent.JPG|1000px]]
 
[[File:Kristal legs bent.JPG|1000px]]
  
 +
== next place the small ceramics ==
 
Now you can start with the small ceramic capacitors, use the component overview drawing and a highlighter marking which capacitor you have done. Start with all the special capacitors (all non 100nF decoupling caps) like the 15pF caps, and all the others, then add the 100nF decoupling caps. as in this picture:
 
Now you can start with the small ceramic capacitors, use the component overview drawing and a highlighter marking which capacitor you have done. Start with all the special capacitors (all non 100nF decoupling caps) like the 15pF caps, and all the others, then add the 100nF decoupling caps. as in this picture:
  
 
[[File:Then all ceramic caps.JPG|1000px]]
 
[[File:Then all ceramic caps.JPG|1000px]]
  
 +
== And the two electrolytic capacitors ==
 +
there are only two elco's in this design, a 100uF bulk capacitor, and a 1uF for reset.
 +
 +
= Add the connectors ==
 
After that you can start with the connectors, For the Cinch (RCA composite video out plug) I recommend the FC68391, do not use the reichelt CBP unless you have to, as its a very bad quality component. The fit is so tight that I had to wrangle the plug into it which promptly broke of the inner contact, I had to solder it back again. Not recommended, unfortunately Reichelt doesn't seem to sell any other suitable connector.  
 
After that you can start with the connectors, For the Cinch (RCA composite video out plug) I recommend the FC68391, do not use the reichelt CBP unless you have to, as its a very bad quality component. The fit is so tight that I had to wrangle the plug into it which promptly broke of the inner contact, I had to solder it back again. Not recommended, unfortunately Reichelt doesn't seem to sell any other suitable connector.  
 
Then solder the two 3.5mm audio jacks, tree models without in-built switches, make sure to buy the correct types with just three pins, there are other with  completely different pinout, so be careful what you buy.
 
Then solder the two 3.5mm audio jacks, tree models without in-built switches, make sure to buy the correct types with just three pins, there are other with  completely different pinout, so be careful what you buy.
 
lastly solder in the USB type-B (square) socket, I know its old and ugly, but it is the only suitable (USB) socket that is pin through hole.
 
lastly solder in the USB type-B (square) socket, I know its old and ugly, but it is the only suitable (USB) socket that is pin through hole.
  
 +
= And the transistors ==
 
then you can add the level 2N3904 transistors, if you bought the versions that have all three pins in a single line you might want to prepare the transistors, as otherwise it almost impossible to enter then in the PCB, so bent the middle pin towards the rounded part of the plastic, and then bent the wire up again a few mm (1/10 of an inch) so the pins are now in a triangle. The middle pin is now a few mm shorter than the other two, this helps inserting the pins, but it will be even easier when you also cut a few mm of rom one of the other two pins, ao all pins have different lengths, like this:
 
then you can add the level 2N3904 transistors, if you bought the versions that have all three pins in a single line you might want to prepare the transistors, as otherwise it almost impossible to enter then in the PCB, so bent the middle pin towards the rounded part of the plastic, and then bent the wire up again a few mm (1/10 of an inch) so the pins are now in a triangle. The middle pin is now a few mm shorter than the other two, this helps inserting the pins, but it will be even easier when you also cut a few mm of rom one of the other two pins, ao all pins have different lengths, like this:
  
 
[[File:2N3904 bent and cut for easy insertion.jpeg|1000px]]
 
[[File:2N3904 bent and cut for easy insertion.jpeg|1000px]]
  
 +
 +
== Optionally add the joystick connector ==
 
If you want to add the joystick port you can add the male DE09 connector (often erroneously called a DB9 connector). But you may wait if you plan to use the original ZX81 enclosure, as you have to hack an opening in the case and you might not want to do this.
 
If you want to add the joystick port you can add the male DE09 connector (often erroneously called a DB9 connector). But you may wait if you plan to use the original ZX81 enclosure, as you have to hack an opening in the case and you might not want to do this.
  
Line 56: Line 65:
 
[[File:Opgebouwd maar niet werkend.JPG|1000px]]
 
[[File:Opgebouwd maar niet werkend.JPG|1000px]]
  
 +
== test it! ==
 
If all is well and you have chosen composite video (or AV) in on your monitor, if you power the board on, the power led should light up immediately, and the screen will turn white, and after a a second or so the inverse K prompt will appear.
 
If all is well and you have chosen composite video (or AV) in on your monitor, if you power the board on, the power led should light up immediately, and the screen will turn white, and after a a second or so the inverse K prompt will appear.

Revision as of 18:07, 7 May 2023

Project Building up the ZX81+38
Diodes op zx81+38.JPG
A manual on how to build the ZX81+38
Status Initializing
Contact mahjongg
Last Update 2023-05-07

For those planning to build the ZX81+38, note this kit is NOT suitable for people who are not proficient in soldering. The ZX81+38 is not easy to solder, the design is dense and the solder pads are smaller than in most other designs. Also you will need to have the right tools, and probably a loupe or soldering microscope. You also need to own an EPROM programmer. I suggest using the minipro TL866CS to program a 27C256 with four copies of the ZX81.ROM file.

All files you need are on my GitHub page here: https://github.com/mahjongg2/ZX81plus38

Start Building

Make sure you use the latest files for the PCB, BOM and component overview drawing, and schematic, at this moment these are revision 1.9.

Start by soldering the lowest parts, that is , te flat lying resistors, and the resistor packs, and the diodes (the nine 1N4148 and the single BAT46 shottky diode), note their orientation! Also now place the three main sockets. see this picture:

Low components first.jpg

Add the IC's

Then add the IC's be careful to place them in the right orientation, either up, or three to the left, and in the right spot, referencing the component buildup drawing. Use the latest version of revision 1.9 of the component overview drawing, that is the drawing where the 15pF capacitors are BELOW the crystal.

ZX81+38 rev 1.9 component placement.png

Note that I'm not using sockets for the other IC's, but you can if you want, if you do use dual wipe sockets, NOT round machined sockets, they are a disaster to put IC's into, and are not as reliable as they seem to be.

If you see a number like "08" in the middele of in IC in the drawing this means you need the HC version of the IC there so "08" means you need to place a 74HC08 there. All logic IC's are HC type with A possible exception of the CD40007.

place the Crystal

then place the 13MHz crystal If you could not find an SMT type of this crystal, the one that comes with a plastic carrier and flat pins sticking out besides the metal can, then convert your pin though hole crystal to a SMT solderable one by sticking the pin wires through a piece of paper, fold the pins flat sideways, and cut the wires off just outside the paper isolation.then solder the pins to the solder pads beneath. If you are carefull not to cause a short between the pins and metal can you might leave out the paper isolation, see:

Kristal legs bent.JPG

next place the small ceramics

Now you can start with the small ceramic capacitors, use the component overview drawing and a highlighter marking which capacitor you have done. Start with all the special capacitors (all non 100nF decoupling caps) like the 15pF caps, and all the others, then add the 100nF decoupling caps. as in this picture:

Then all ceramic caps.JPG

And the two electrolytic capacitors

there are only two elco's in this design, a 100uF bulk capacitor, and a 1uF for reset.

Add the connectors =

After that you can start with the connectors, For the Cinch (RCA composite video out plug) I recommend the FC68391, do not use the reichelt CBP unless you have to, as its a very bad quality component. The fit is so tight that I had to wrangle the plug into it which promptly broke of the inner contact, I had to solder it back again. Not recommended, unfortunately Reichelt doesn't seem to sell any other suitable connector. Then solder the two 3.5mm audio jacks, tree models without in-built switches, make sure to buy the correct types with just three pins, there are other with completely different pinout, so be careful what you buy. lastly solder in the USB type-B (square) socket, I know its old and ugly, but it is the only suitable (USB) socket that is pin through hole.

And the transistors =

then you can add the level 2N3904 transistors, if you bought the versions that have all three pins in a single line you might want to prepare the transistors, as otherwise it almost impossible to enter then in the PCB, so bent the middle pin towards the rounded part of the plastic, and then bent the wire up again a few mm (1/10 of an inch) so the pins are now in a triangle. The middle pin is now a few mm shorter than the other two, this helps inserting the pins, but it will be even easier when you also cut a few mm of rom one of the other two pins, ao all pins have different lengths, like this:

2N3904 bent and cut for easy insertion.jpeg


Optionally add the joystick connector

If you want to add the joystick port you can add the male DE09 connector (often erroneously called a DB9 connector). But you may wait if you plan to use the original ZX81 enclosure, as you have to hack an opening in the case and you might not want to do this.

Now insert the Z80 CPU, the programmed ROM, and the 32K RAM chip, make sure the notch in the IC point to the back, same as shown in the component placement drawing. Note that ROM's especially don't like placing the in reverse! you will destroy them if you power up with them "upside down".

Attaching the keyboard

I'm using my own keyboard PCB, also on the GitHub page, with 40 6x6mm buttons (see keyboard BOM) I connected the keyboard to the PCB using dupont wires, with male sockets (that is those with pins) on the PCB side. On the PCB I used angled female headers, I simply took the kind of female headers as used on an arduino, cut of one pice with 5 pins, and another one with eight pins, and bent their pins 90 degrees. for the three pin segment in the middle I used a 3-pin male angled pinheader, and cut off the middle (unused) pin. for those two wires I used two female dupont wires. I cut the dupont wires all to the same length (about ten centimeters) stripped them twisted the wire strands together and tinned them. Stuck the wires though the keyboard PCB, and soldered them on top (it helps if you cut off the end bit of the tinned wire, and fold the wire flat to the top of the PCB, so the wire stays in place for soldering, but look out not to create shorts. after soldering the 5+2+8 wires use a small bit of hot glue on the underside of the board. If using the real ZX-81 top case with the keyboard foil removed, you might have to widen the slot underneath the keyboard so the wires can go though with key keyboard laying flat. But before you do test the zx81+38 without an enclosure. Like this:

Opgebouwd maar niet werkend.JPG

test it!

If all is well and you have chosen composite video (or AV) in on your monitor, if you power the board on, the power led should light up immediately, and the screen will turn white, and after a a second or so the inverse K prompt will appear.