🇸🇰 SMEP PP 01: Part 5 (16MHz Crystal Added) [TCE #0465]
36As discovered in Part 4 ... the 16MHz crystal was missing. Duh! So I added it back.
We now get some video output but, as expected, it is garbled.
Apparently these machines are pretty complex and the ones that are working have all required some sort of repair.
What I've done so far:
[1] Cleaned all the boards & keyboard
[2] Verified the power supply is working
[3] Replaced some blown (tantalum) capacitors on the EPROM board: 3 x 47µF and one 2.2µF
[4] Replaced the missing 16MHz crystal
[5] Installed a new X2-class safety capacitor in the power supply (replacing the two original capacitors)
One possible issue is one, or likely more, of the 1KByte EPROMs are corrupt. There is a new EPROM board available that I will try:
https://www.8bity.cz/2019/nhrada-desky-rom-sm-2251-pro-poctac-pp-01/
An excellent set of re-drawn schematics can be found here:
https://www.sapi.cz/klony_sm5040/pp01.php
From Part 1:
SMEP = Systém Malých Elektronických Počítačov (Small Electronic Computer System), and
PP 01 = Personálny Počítač (Personal Computer).
It was developed at the Computing Technology Research Institute (Výskumnom Ústave Výpočtovej Techniky = VÚVT) in Žilina and manufactured at the Computing Technology Plant (Závodoch Výpočtovej Techniky = ZVT) in Banská Bystrica (now in independent Slovakia).
A good source of information & emulator:
https://pp01.borik.net/index.php