Hi all
Another 4040 problem.... i acquired a unit that was very dirty inside. I cleaned it up and powered it. It has basic 2 roms etc.
After a few seconds noticed the Inductor L1 on the analog board was turning a nice shade of black. It was v hot to touch so powdered down to investigate. I replaced the inductor and turned the unit on again ... L1 started to get warm again so powdered down and replaced the tantalum capacitor C9. Turned it back on and all was well from a stability point of view. Looks like the Inductor L1 was acting as a fuse for a shorted Cap. The cap showed no signs of being faulty. Checked C10 which is nearby and it appears to be OK.
On power up NOW, the 3 LEDs flash for a brief second then go out and you hear the "power on bump" as the heads are initialized, moved to their default position and the disk motor spins. If i manually move the head and power up, the head always gets returned back to its position at the end of the disk. When i enter ?ds$, i get 73,cbm v2,00,00 so assume all is well with the CPU, memory and ROM on the digital board.
when i try to format a disk I get a "bad disk error" and ?ds$ returns 21, read error ,01,00... the head does not appear to move during the format procedure before erroring. I am using BASIC 4 on the PET so issuing a Header command to format the disk. Both drives behave the same!
If i try a directory command the head moves to what I suspect is track 18 but get an error as the centre LED lights up and ?ds$ returns 21 read error,18,00. Again on both drives.
I have checked "some" of the caps on the analogue board (C1 and C2 are supposed to be 4.7uF and read 5,7uF.. tried some of the smaller blue caps and they read about right ... didn't desolder all of them though.)
Cleaned the heads and changed the 6502 and 6522 chips for known working types.... no change.
Checked the voltages on P9 and P10 which are the connectors to the disk heads and they read 6volts doing nothing but when i issue a header command the voltages seems to fluctuate as the volt meter reading is not stable but not quick enough to follow.
I guess it is a read/write issue but have no idea how to fix.... do not have a scope just a good Volt meter.
The IEEE on the PET works fine as been using a microSD card for little while now on it with no issues.
Any ideas as at a dead end now ?
Does anyone had a copy of the Logic Diagnostics tester program and other testers you get with the CBM drives ?
Andy
Another 4040 problem.... i acquired a unit that was very dirty inside. I cleaned it up and powered it. It has basic 2 roms etc.
After a few seconds noticed the Inductor L1 on the analog board was turning a nice shade of black. It was v hot to touch so powdered down to investigate. I replaced the inductor and turned the unit on again ... L1 started to get warm again so powdered down and replaced the tantalum capacitor C9. Turned it back on and all was well from a stability point of view. Looks like the Inductor L1 was acting as a fuse for a shorted Cap. The cap showed no signs of being faulty. Checked C10 which is nearby and it appears to be OK.
On power up NOW, the 3 LEDs flash for a brief second then go out and you hear the "power on bump" as the heads are initialized, moved to their default position and the disk motor spins. If i manually move the head and power up, the head always gets returned back to its position at the end of the disk. When i enter ?ds$, i get 73,cbm v2,00,00 so assume all is well with the CPU, memory and ROM on the digital board.
when i try to format a disk I get a "bad disk error" and ?ds$ returns 21, read error ,01,00... the head does not appear to move during the format procedure before erroring. I am using BASIC 4 on the PET so issuing a Header command to format the disk. Both drives behave the same!
If i try a directory command the head moves to what I suspect is track 18 but get an error as the centre LED lights up and ?ds$ returns 21 read error,18,00. Again on both drives.
I have checked "some" of the caps on the analogue board (C1 and C2 are supposed to be 4.7uF and read 5,7uF.. tried some of the smaller blue caps and they read about right ... didn't desolder all of them though.)
Cleaned the heads and changed the 6502 and 6522 chips for known working types.... no change.
Checked the voltages on P9 and P10 which are the connectors to the disk heads and they read 6volts doing nothing but when i issue a header command the voltages seems to fluctuate as the volt meter reading is not stable but not quick enough to follow.
I guess it is a read/write issue but have no idea how to fix.... do not have a scope just a good Volt meter.
The IEEE on the PET works fine as been using a microSD card for little while now on it with no issues.
Any ideas as at a dead end now ?
Does anyone had a copy of the Logic Diagnostics tester program and other testers you get with the CBM drives ?
Andy