View Profile: iz8dwf - Vintage Computer Forum

January 21st, 2021, 02:40 AM

iz8dwf replied to a thread Help fixing a semi broken power supply for a Apple II Europlus (230v) in Early Apple (I, ][, ///, etc.)

see if it's the A11040/B, not every label was updated. Frank

5 replies | 151 view(s)

January 18th, 2021, 12:35 AM

iz8dwf replied to a thread Help with fixing Commodore 2040 Dual Floppy drive in Commodore

yes usually you first power up the drive(s), then the PET, at least this is what we were always told to do in the old days. However, the power...

8 replies | 102 view(s)

January 16th, 2021, 01:29 PM

iz8dwf replied to a thread Help fixing a semi broken power supply for a Apple II Europlus (230v) in Early Apple (I, ][, ///, etc.)

http://bitsavers.org/pdf/apple/power_supply/Astec_Power_Supplies_Aug82.pdf There must be a part number on the label of your power supply, telling...

5 replies | 151 view(s)

January 15th, 2021, 01:07 AM

iz8dwf replied to a thread Commodore 1541 drive can't format or read disks in Commodore

well, In the last two years I've repaired at least 10 x 1541 with Newtronics mechanical assembly and I've found only one with failed head. An analog...

9 replies | 180 view(s)

January 12th, 2021, 12:48 PM

iz8dwf replied to a thread Pet 2001 9" Monitor, spot killer. in Commodore

Hi Andy, so basically the spot in your monitor was caused by C4? That's interesting, ceramic capacitors aren't famous for getting leaky. Thanks...

24 replies | 1315 view(s)

January 9th, 2021, 01:05 PM

iz8dwf replied to a thread PET power transformer. in Commodore

Correct, I think he should know this, as he used another PET "PSU" to power-on the board. Frank

6 replies | 257 view(s)

January 9th, 2021, 06:42 AM

iz8dwf replied to a thread 2031 LP drive motor running continuously in Commodore

The 2031LP is basically a 1541 with a different firmware and a different interface, the IEEE488 instead of the serial IEC. The behaviour you're...

6 replies | 239 view(s)

January 9th, 2021, 06:35 AM

iz8dwf replied to a thread PET power transformer. in Commodore

PET motherboard (excluding the original 2001 with static RAM) need: 8-0-8 Vac (center tapped it means), this is rectified on the mainboard to obtain...

6 replies | 257 view(s)

January 2nd, 2021, 08:39 AM

iz8dwf replied to a thread Hazeltine/OSI 1420 blowing fuses in Vintage Computer Hardware

That little thing is a tantalum capacitor. Those are known for making very good short circuits after some years. You should just remove that...

7 replies | 239 view(s)

December 30th, 2020, 01:31 AM

iz8dwf replied to a thread Memory problem with PET 2001 in Commodore

That's wrong. TTL valid High levels start at 2.7V. Often in these old machines, H levels are around 3.5V. 4V is a solid high and perfectly...

52 replies | 1580 view(s)

December 26th, 2020, 03:41 AM

iz8dwf replied to a thread Using 117V psu 1571 drive on 230V household in Commodore

Yes, I've had a failed head on one 1571, you can easily test all the coils on both heads with a multimeter. If the heads look fine, the fault may...

16 replies | 616 view(s)

December 25th, 2020, 01:41 PM

iz8dwf replied to a thread Using 117V psu 1571 drive on 230V household in Commodore

troubleshooting by pulling chips isn't the best way, but if you don't have at least a logic probe, I can't suggest much tests to be done with only a...

16 replies | 616 view(s)

December 25th, 2020, 11:52 AM

iz8dwf replied to a thread Using 117V psu 1571 drive on 230V household in Commodore

you can use a 6526, the A version means it's rated for 2 MHz clock (which is what you find in a 1571) but a 1 MHz 6526 will probably work. Also, the...

16 replies | 616 view(s)

December 25th, 2020, 06:50 AM

iz8dwf replied to a thread Using 117V psu 1571 drive on 230V household in Commodore

No luck. Single big high voltage capacitor means no input doubler. The voltage doubling circuit requires two identical high voltage capacitors,...

16 replies | 616 view(s)

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