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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...
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    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...
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    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...
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    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...
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    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...
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    19 replies | 199 view(s)
  • iz8dwf's Avatar
    August 16th, 2018, 01:41 AM
    iz8dwf replied to a thread Cbm pet 3008 garbage screen in Commodore
    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...
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    10 replies | 142 view(s)
  • iz8dwf's Avatar
    August 13th, 2018, 11:44 PM
    iz8dwf replied to a thread 1571 drive mechanics, anyone? in Commodore
    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...
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    6 replies | 147 view(s)
  • iz8dwf's Avatar
    August 13th, 2018, 10:37 AM
    iz8dwf replied to a thread 1571 drive mechanics, anyone? in Commodore
    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...
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    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...
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    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...
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    5 replies | 110 view(s)
  • iz8dwf's Avatar
    August 12th, 2018, 12:20 PM
    iz8dwf started a thread 1571 drive mechanics, anyone? in Commodore
    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...
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    6 replies | 147 view(s)
  • iz8dwf's Avatar
    August 6th, 2018, 12:28 AM
    iz8dwf replied to a thread Alps DFD222A02 schematic? in Vintage Computer Hardware
    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...
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    3 replies | 54 view(s)
  • iz8dwf's Avatar
    August 5th, 2018, 11:28 PM
    iz8dwf replied to a thread Alps DFD222A02 schematic? in Vintage Computer Hardware
    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...
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    3 replies | 54 view(s)
  • iz8dwf's Avatar
    August 5th, 2018, 11:35 AM
    iz8dwf started a thread Alps DFD222A02 schematic? in Vintage Computer Hardware
    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...
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    3 replies | 54 view(s)
  • iz8dwf's Avatar
    August 2nd, 2018, 02:01 AM
    iz8dwf replied to a thread Lost in space: Ibm 5155 async card repair. in Vintage Computer Hardware
    Thanks for sharing this.
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    1 replies | 81 view(s)
  • iz8dwf's Avatar
    July 29th, 2018, 02:30 AM
    iz8dwf replied to a thread Bread bin C64 with Piggyback chips in Commodore
    +1 I've several years of experience, but I would never use anything else that a temperature controlled vacuum desoldering station nowadays....
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    16 replies | 333 view(s)
  • iz8dwf's Avatar
    July 28th, 2018, 09:41 PM
    iz8dwf replied to a thread Bread bin C64 with Piggyback chips in Commodore
    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...
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    16 replies | 333 view(s)
  • iz8dwf's Avatar
    July 27th, 2018, 05:49 AM
    iz8dwf replied to a thread Got my first PET today! Well two. Sadly both don't work. in Commodore
    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...
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    219 replies | 6031 view(s)
  • iz8dwf's Avatar
    July 26th, 2018, 11:06 PM
    iz8dwf replied to a thread Got my first PET today! Well two. Sadly both don't work. in Commodore
    Suppose that someone at sometime was debugging this board outside the case, with keyboard plugged and keyboard wires running near the monitor PCB....
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    219 replies | 6031 view(s)
  • iz8dwf's Avatar
    July 22nd, 2018, 08:41 AM
    iz8dwf replied to a thread C64 only works if SID removed in Commodore
    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...
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    7 replies | 292 view(s)
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