View Profile: iz8dwf - Vintage Computer Forum

November 11th, 2018, 06:40 AM

iz8dwf replied to a thread Looking for help with a Commodore Pet 2001 in Commodore

Correct, SA9 might be stuck even to +5V

12 replies | 186 view(s)

November 11th, 2018, 01:45 AM

iz8dwf replied to a thread Looking for help with a Commodore Pet 2001 in Commodore

Do you have a way to check that UD4 Pin 12 is maybe stuck to 0V or almost and instead UD4 Pin 13 is toggling? That should be checked during power on...

12 replies | 186 view(s)

November 10th, 2018, 12:32 PM

iz8dwf replied to a thread Looking for help with a Commodore Pet 2001 in Commodore

Very good point about vertical sync! Yes, it can be UD7 or UD4, but we don't yet know what PCB version he has :) Frank

12 replies | 186 view(s)

November 10th, 2018, 12:01 PM

iz8dwf replied to a thread Looking for help with a Commodore Pet 2001 in Commodore

Yes, the question is only: is it the counter 74177 or the multiplexer? Or one gate of the end of screen clear&reload signal? He needs either an...

12 replies | 186 view(s)

November 10th, 2018, 11:44 AM

iz8dwf replied to a thread Looking for help with a Commodore Pet 2001 in Commodore

This might be either a fault in the video RAM address multiplexer (very likely) or a couple of slow video RAMs (unlikely because they should be both...

12 replies | 186 view(s)

November 6th, 2018, 12:09 AM

iz8dwf replied to a thread PET 2001 ROM exchange, if anyone :) in Commodore

So, the patched Basic1 here isn't even mentioned? We know there're 4 different revisions of Basic for the PETs, we can call them as we prefer I...

9 replies | 275 view(s)

November 5th, 2018, 10:48 AM

iz8dwf replied to a thread PET 2001 ROM exchange, if anyone :) in Commodore

It's not "me", it's more CBM itself that has made the "naming", having called its last revision Basic4 :) Basic1 is the original romset with...

9 replies | 275 view(s)

November 5th, 2018, 02:43 AM

iz8dwf replied to a thread PET 2001 ROM exchange, if anyone :) in Commodore

Turns out that my actual spare 6540 is a 012. I indeed have a 014 too but it's a bad one. Sorry for the mistake. BTW here's the video of the...

9 replies | 275 view(s)

November 4th, 2018, 07:56 AM

iz8dwf replied to a thread PET 2001 ROM exchange, if anyone :) in Commodore

Hi, I have designed my own 6550 and 6540 adapters, I could use 2114 SRAMs to replace the 6550 and 2716 EPROMs to replace the 6540. I have also...

9 replies | 275 view(s)

November 4th, 2018, 12:48 AM

iz8dwf started a thread PET 2001 ROM exchange, if anyone :) in Commodore

Hi all, I have started repairing my own PET 2001, after a number of other's machines. I've found 6 faulty 6550 (well, it would be 8, but two of...

9 replies | 275 view(s)

November 2nd, 2018, 09:01 AM

iz8dwf replied to a thread Commodore MMF 9000 / SuperPet 9000 Monitor problem: Help needed! in Commodore

I'm not so sure it's a monitor circuit problem. Looks like more a video circuit failure inside the PET's motherboard, like dead chargen ROM or stuck...

17 replies | 666 view(s)

October 31st, 2018, 09:29 AM

iz8dwf replied to a thread PET 2001 out of memory when loading in Commodore

So far, we don't even know if both the 6550 are bad or just one of them is. He didn't accept my suggestion to try the dubious 6550s (one at a time)...

35 replies | 1436 view(s)

October 29th, 2018, 03:35 PM

iz8dwf replied to a thread PET 2001 out of memory when loading in Commodore

well, not really "modern", but still easily available: any kind of 2114 (P2114, TMM314, NTE2114, many others). It's a more standard 1kx4 sram, very...

35 replies | 1436 view(s)

October 29th, 2018, 08:26 AM

iz8dwf replied to a thread PET 2001 out of memory when loading in Commodore

Indeed the main RAM columns on the 2001 motherboard are I and J, not J and L. I think the quickest way test his RAMs, once he manages to remove them...

35 replies | 1436 view(s)

October 29th, 2018, 04:43 AM

iz8dwf replied to a thread PET 2001 out of memory when loading in Commodore

look also here: https://www.arcadeshopper.com/wp/?page_id=11#!/PET/c/28756047/offset=0&sort=nameAsc

35 replies | 1436 view(s)

October 24th, 2018, 08:55 AM

iz8dwf replied to a thread How can I remove mud from inside a C64C? in Commodore

You can wash the electronics in fresh water (then a bath in distilled water would be good, but not essential) and brush the mud away with a soft...

6 replies | 397 view(s)

October 23rd, 2018, 12:01 AM

iz8dwf replied to a thread Help with interesting C128 keyboard fault ? in Commodore

Check the EMI filters on each keyboard line (they usually look like three-legged ceramic capacitors). See the schematic. Also inspect solder joints...

2 replies | 222 view(s)

October 22nd, 2018, 10:42 AM

iz8dwf replied to a thread Tektronix 4107 service info/schematic in Unix/Xenix/Linux Workstations

Thank you for the suggestion. I've visited their site, but seems they never scanned the 4107 service manual so far. If they have a microfiche of it,...

2 replies | 205 view(s)

October 22nd, 2018, 01:25 AM

iz8dwf started a thread Tektronix 4107 service info/schematic in Unix/Xenix/Linux Workstations

Hi all, I'm trying to re-post my request in a different forum, just in case... It's been quite some time now that no info can be found anywhere in...

2 replies | 205 view(s)

October 19th, 2018, 08:35 AM

iz8dwf replied to a thread Pet Chicklet 2001 9" Monitor Dead in Commodore

Whoa... first of all I would dust off that video board, just to see what's under it :) Interrmittent faults might be bad solder joints, so you...

4 replies | 318 view(s)