Okay, thanks.
When you put either 6522 chip in, was the keyboard connected? The system will hang without a keyboard correctly connected if IC3 is present.
Assuming you did have a keyboard connected, it may be that there is a poor connection on the keyboard cable (broken wire, broken contact), there is a fault with the keyboard circuitry, both your 6522 chips are faulty, there is one (or more) damaged contacts in the socket (IC3) or IC31 (74LS74) or IC32 (74LS259) are faulty.
The keyboard cable can be tested with a multimeter on the continuity range or the 200 ohm resistance range (both with the machine switched off). But watch out for intermittent problems that only occur when it's connected in a Beeb.
The easiest way to test the keyboard is with a known good working BBC B.
A member on here, Dave H. may have a suitable spare 6522 for sale. If he doesn't, Mark of Retroclinic will have one (his email address is on his website).
IC31 and IC32 are soldered in. IC31 is usually more reliable than IC32. IC32 has caused problems with other members machines.
Mark
When you put either 6522 chip in, was the keyboard connected? The system will hang without a keyboard correctly connected if IC3 is present.
Assuming you did have a keyboard connected, it may be that there is a poor connection on the keyboard cable (broken wire, broken contact), there is a fault with the keyboard circuitry, both your 6522 chips are faulty, there is one (or more) damaged contacts in the socket (IC3) or IC31 (74LS74) or IC32 (74LS259) are faulty.
The keyboard cable can be tested with a multimeter on the continuity range or the 200 ohm resistance range (both with the machine switched off). But watch out for intermittent problems that only occur when it's connected in a Beeb.
The easiest way to test the keyboard is with a known good working BBC B.
A member on here, Dave H. may have a suitable spare 6522 for sale. If he doesn't, Mark of Retroclinic will have one (his email address is on his website).
IC31 and IC32 are soldered in. IC31 is usually more reliable than IC32. IC32 has caused problems with other members machines.
Mark
Statistics: Posted by 1024MAK — Tue Dec 03, 2024 2:42 pm
