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  • iz8dwf's Avatar
    Yesterday, 09:58 AM
    iz8dwf replied to a thread Commodore B128 (C610) in Commodore
    Ok, I don't know that particular one, but I can guess it needs a minimum current on at least one output, probably not on every output. I would test...
    19 replies | 199 view(s)
  • iz8dwf's Avatar
    Yesterday, 09:20 AM
    iz8dwf replied to a thread Commodore B128 (C610) in Commodore
    Why on earth would you want to add a resistor on the 12V line? If you suspect it wouldn't regulate, then consider it will probably regulate on the...
    19 replies | 199 view(s)
  • iz8dwf's Avatar
    August 16th, 2018, 12:31 PM
    iz8dwf replied to a thread Commodore B128 (C610) in Commodore
    Assuming we are talking about switchmode PS: The AC input goes into some filters, usually fuse on one side of AC, 2 x Y1 capacitors from each side...
    19 replies | 199 view(s)
  • iz8dwf's Avatar
    August 16th, 2018, 10:26 AM
    iz8dwf replied to a thread Commodore B128 (C610) in Commodore
    Electrolytics in the switching PS are the first source of malfunction. Regarding the AC filter, I can't tell how and if it affects the supply...
    19 replies | 199 view(s)
  • iz8dwf's Avatar
    August 16th, 2018, 09:39 AM
    iz8dwf replied to a thread Commodore B128 (C610) in Commodore
    No, 5.13V is perfectly fine for TTL-based logic. 4.75 to 5.25 VDC is the allowed power supply range on the 74LS family (other families allow a...
    19 replies | 199 view(s)
  • iz8dwf's Avatar
    August 16th, 2018, 01:41 AM
    1.6V on a multimeter doesn't tell anything about what's happening on the IRQ line. It could be pulsing as expected, or be stuck. It must be seen on...
    10 replies | 142 view(s)
  • iz8dwf's Avatar
    August 13th, 2018, 11:44 PM
    Yes, I repaired one 128D's drive that needed the top head mount to be gently and lightly rotated to make proper contact. On this one, I've checked...
    6 replies | 147 view(s)
  • iz8dwf's Avatar
    August 13th, 2018, 10:37 AM
    Thank you Geoff! So these heads fail with no external abuse? That seems strange, but that's also a Commodore product, so anything is possible :) On...
    6 replies | 147 view(s)
  • iz8dwf's Avatar
    August 12th, 2018, 10:48 PM
    iz8dwf replied to a thread Recreating 8250 ROMs in Commodore
    Ok it makes sense, you never read the original ROMs ;) You can use a 7404, but I would use LS04 or HCT04. It won't look pretty though. I also made...
    5 replies | 110 view(s)
  • iz8dwf's Avatar
    August 12th, 2018, 12:35 PM
    iz8dwf replied to a thread Recreating 8250 ROMs in Commodore
    If I remember correctly, the 2364 ROMs used in 8050/8250 were programmed with active high CS, so if you used an MCM68766 (not 69766 that I couldn't...
    5 replies | 110 view(s)
  • iz8dwf's Avatar
    August 12th, 2018, 12:20 PM
    Hi all, I have a 1571 disk drive with bad heads, head 1 has open erase coil, head 0 has an open R/W coil. Otherwise electronics and the rest of the...
    6 replies | 147 view(s)
  • iz8dwf's Avatar
    August 6th, 2018, 12:28 AM
    Ok, looks like I was smelling the right problem. I told the OS driver (I'm using Linux) to ignore the disk change line and the drive works now...
    3 replies | 54 view(s)
  • iz8dwf's Avatar
    August 5th, 2018, 11:28 PM
    Well, the error is not so helpful: I/O error on sector 0. Seems like the disk change signal isn't working properly, but I'm not sure about it. I...
    3 replies | 54 view(s)
  • iz8dwf's Avatar
    August 5th, 2018, 11:35 AM
    Hi all, I'm trying to make this Alps 5.25" 360K floppy disk drive work, I've tried on two different motherboards (one vintage, one quite recent) and...
    3 replies | 54 view(s)
  • iz8dwf's Avatar
    August 2nd, 2018, 02:01 AM
    Thanks for sharing this.
    1 replies | 81 view(s)
  • iz8dwf's Avatar
    July 29th, 2018, 02:30 AM
    +1 I've several years of experience, but I would never use anything else that a temperature controlled vacuum desoldering station nowadays....
    16 replies | 333 view(s)
  • iz8dwf's Avatar
    July 28th, 2018, 09:41 PM
    Yes, many times. original RAM chips were faulty at some point in time, and they were 'piggybacked' with new chips. 4164 DRAM chips are known to often...
    16 replies | 333 view(s)
  • iz8dwf's Avatar
    July 27th, 2018, 05:49 AM
    Hi Adrian, your setup is safe, just never put the keyboard over the monitor, or too close to the sides. Routing the cable under the monitor PCB is...
    219 replies | 6031 view(s)
  • iz8dwf's Avatar
    July 26th, 2018, 11:06 PM
    Suppose that someone at sometime was debugging this board outside the case, with keyboard plugged and keyboard wires running near the monitor PCB....
    219 replies | 6031 view(s)
  • iz8dwf's Avatar
    July 22nd, 2018, 08:41 AM
    On you C64 board there's a 7805 voltage regulator, it should be mounted on aluminum heatsink. If the aluminum heatsink hasn't been removed and if the...
    7 replies | 292 view(s)
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