Repairing a 8050 for my Vic
Posted: Mon Oct 24, 2016 10:07 am
Hi
I have started on the task of repairing my 8050 dual diskdrive for my Vic-20. The unit was flashing the front lamp around 4 times which apparently is not used. So I recon it either flashed it 3 times or 5 times (it goes between red and green with a long green ligth, so I am not sure if its the red or green state that is "flashing on"). Anyway I replaced Both HIGH/LOW ROM which resulted in a long red light. Then replaced both 6502s with no change. Then I went on to measure the voltages and found that the 5V was missing... very strange as it "worked" when I started. Well, pushing things on the board sometimes results in cracks, so I thought that might be the case. So I started looking into the power circuit.
Apparently the power supply (disconnected) is supposed to give 16V and 8V AC on different pins, but I either get 0V or 10V, so something is wrong there.
Edit: I found a poor connection and got 9V and 18V AC which are within specifications. It gave a good steady 12V and 5V in the unit. Still, it only shows a red led when switching on, so I replaced the K4 ROM as well (a 2K 2316 which I replaced with a 2564 (filled with 4 copies)). The pin layout is compatible if you don't use pin 1,2 and 27,28.
Next step was to do some logic testing and there is clk2 on both 6502, and their data&address buses are actively running. Strange! It mostly looks like the unit is booting as normal, but there is no led flash codes. So at some stage it stops, or the circuit controlling the led is not working? Hopefully its not the RIOT.
I have started on the task of repairing my 8050 dual diskdrive for my Vic-20. The unit was flashing the front lamp around 4 times which apparently is not used. So I recon it either flashed it 3 times or 5 times (it goes between red and green with a long green ligth, so I am not sure if its the red or green state that is "flashing on"). Anyway I replaced Both HIGH/LOW ROM which resulted in a long red light. Then replaced both 6502s with no change. Then I went on to measure the voltages and found that the 5V was missing... very strange as it "worked" when I started. Well, pushing things on the board sometimes results in cracks, so I thought that might be the case. So I started looking into the power circuit.
Apparently the power supply (disconnected) is supposed to give 16V and 8V AC on different pins, but I either get 0V or 10V, so something is wrong there.
Edit: I found a poor connection and got 9V and 18V AC which are within specifications. It gave a good steady 12V and 5V in the unit. Still, it only shows a red led when switching on, so I replaced the K4 ROM as well (a 2K 2316 which I replaced with a 2564 (filled with 4 copies)). The pin layout is compatible if you don't use pin 1,2 and 27,28.
Next step was to do some logic testing and there is clk2 on both 6502, and their data&address buses are actively running. Strange! It mostly looks like the unit is booting as normal, but there is no led flash codes. So at some stage it stops, or the circuit controlling the led is not working? Hopefully its not the RIOT.