View Profile: dave_m - Vintage Computer Forum

Yesterday, 04:12 PM

MikeS replied to a thread Frustrating Problem in CP/M and MP/M

Unsolicited testimonial: Back in prehistoric times I built, sold and serviced a quality control system for metal rolling mills built around...

24 replies | 434 view(s)

Yesterday, 02:27 PM

dave_m replied to a thread PET 2001-32N BS, with horizontal lines. in Commodore

Great work. There will probably be no need to take the keys all apart. Just get to the bottom of the keys and clean the keypads very well with...

13 replies | 162 view(s)

December 6th, 2019, 01:37 PM

MikeS replied to a thread PET 2001 Sound in Commodore

A 10 ohm capacitor ??? Better check that, and anyway, why replace anything? No.

46 replies | 1046 view(s)

December 5th, 2019, 08:55 PM

dave_m replied to a thread PET 2001 Sound in Commodore

No, the NAND gate is not needed. Do not use the diagnostic signal in this speaker circuit. It may be used in the 8032 PET to disable the speaker if...

46 replies | 1046 view(s)

December 5th, 2019, 05:17 PM

dave_m replied to a thread PET 2001-32N BS, with horizontal lines. in Commodore

If you disconnect the J7 video connector, your monitor will be safe. With no horizontal drive signal from the mainboard connected to the video board...

13 replies | 162 view(s)

December 4th, 2019, 09:28 AM

dave_m replied to a thread PET 2001-32N with unknown circuit. in Commodore

Yes, remove it if you do not have or want an old dot matrix printer. That is one of the worst examples of a 'Kludge' I have ever seen. It could have...

4 replies | 130 view(s)

December 3rd, 2019, 11:11 AM

MikeS replied to a thread disabling text correction in General Off Topic

Obviously not in this post...;-)

18 replies | 243 view(s)

December 2nd, 2019, 08:17 PM

dave_m replied to a thread PET 2001 Sound in Commodore

I think so. From a PC, the line out voltage is maybe around +/- 2 V into 600 Ohms (which would be 3 milli-Amp max). On the PET, the CB2 output is 0...

46 replies | 1046 view(s)

December 1st, 2019, 10:51 AM

dave_m replied to a thread Pet 2001 chiclet display problem in Commodore

I finally found all the work you have done on this problem on the 6502 forum, I will plow through all the pages and see where you are.

9 replies | 156 view(s)

November 30th, 2019, 03:06 PM

dave_m replied to a thread Pet 2001 chiclet display problem in Commodore

It is hard to tell the cause from the effects of a stuck sequencer due to the feedback terms. Please scope signals at D8- pins 4,5, and 6 to see if...

9 replies | 156 view(s)

November 30th, 2019, 01:08 PM

dave_m replied to a thread Pet 2001 chiclet display problem in Commodore

OK, the four-state sequencer may not be running. Check D8-pins 4, 5, and 6 for pulses (bottom of schematic sheet 3). States are listed at the top of...

9 replies | 156 view(s)

November 29th, 2019, 02:18 PM

dave_m replied to a thread Commodore PET 3016 screen glitch & double image in Commodore

The Pet power transformer supplies 15VAC directly to the video board where there is a 7812 regulator to get +12VDC. From there all other voltages in...

14 replies | 459 view(s)

November 28th, 2019, 11:34 PM

dave_m replied to a thread Pet 2001 chiclet display problem in Commodore

The average DC levels seem OK. The horizontal sync signal is used to generate the high voltage in the CRT so that signal seems fine. When you get a...

9 replies | 156 view(s)

November 27th, 2019, 11:46 AM

dave_m replied to a thread New project - the ROMulator, successor to the PETvet (RAM/ROM replacement plus debug) in Commodore

gubbish, Put me down for one as all your designs are very interesting. Is the debug port going to be some kind of serial interface? -Dave

19 replies | 589 view(s)

November 26th, 2019, 11:36 PM

tezza replied to a thread New project - the ROMulator, successor to the PETvet (RAM/ROM replacement plus debug) in Commodore

Good to see you are still doing this stuff Mike. Sounds great. Tez

19 replies | 589 view(s)

November 26th, 2019, 09:10 PM

dave_m replied to a thread FS: UV EPROM Eraser + Chips in Vintage Computer Items For Sale or Trade

Is there a timer on that unit?

5 replies | 314 view(s)

November 26th, 2019, 06:23 PM

MikeS replied to a thread PET 2001 Sound in Commodore

Well, it certainly was confusing; he said he wanted to add sound to existing programs and then asked what kind of transducer they used; I assume he...

46 replies | 1046 view(s)

November 26th, 2019, 06:12 PM

MikeS replied to a thread New project - the ROMulator, successor to the PETvet (RAM/ROM replacement plus debug) in Commodore

Long time no see/hear, Mike. I definitely need one of these to add to my collection of PET tools; put me on the list. Coming up for the WoC? ...

19 replies | 589 view(s)

November 26th, 2019, 11:51 AM

MikeS replied to a thread PET 2001 Sound in Commodore

Some software (e.g. The Visible Music Monitor) used the much better 8-bit DAC approach like the Petunia and its clones; see P.10: ...

46 replies | 1046 view(s)

November 25th, 2019, 02:21 PM

MikeS replied to a thread PET 2001 Sound in Commodore

Sigh... I'm used to it, here and elsewhere ;-)

46 replies | 1046 view(s)

November 25th, 2019, 12:34 PM

MikeS replied to a thread Cromemco CS-1 S-100 System RDU NC $Free to good home in Vintage Computer Items For Sale or Trade

From me? If so, many apologies and send me a PM on the off chance you still want it.

15 replies | 459 view(s)

November 25th, 2019, 09:08 AM

MikeS replied to a thread Cromemco CS-1 S-100 System RDU NC $Free to good home in Vintage Computer Items For Sale or Trade

Granted, size and weight discourage some folks but if someone really wants one... Still a great deal! I'll be selling a few CS-1s myself soonish,...

15 replies | 459 view(s)

November 25th, 2019, 08:34 AM

MikeS replied to a thread Cromemco CS-1 S-100 System RDU NC $Free to good home in Vintage Computer Items For Sale or Trade

Somebody's gonna get a steal; I've seen these go for more than $1000, and not usually with all those manuals. Good luck!

15 replies | 459 view(s)

November 24th, 2019, 11:16 AM

dave_m replied to a thread PET 2001 Sound in Commodore

Well yeah, but no one listens to Mike. Until it is too late! ;)

46 replies | 1046 view(s)

November 24th, 2019, 10:27 AM

dave_m replied to a thread PET 2001 Sound in Commodore

To drive an 8 Ohm speaker, you would need to include an amplifier chip, or but since the CB2 line goes out to pin M of the J2 User Port, you could...

46 replies | 1046 view(s)

November 23rd, 2019, 11:44 AM

MikeS replied to a thread PET 2001 Sound in Commodore

CRTC= cathode-ray tube controller. If it's a 2001 it doesn't have one; if it has one it ain't a 2001. I'd just hook a cheap pair of computer...

46 replies | 1046 view(s)

November 21st, 2019, 10:15 AM

MikeS replied to a thread What's with FDD cable termination? in Vintage Computer Hardware

FWIW, 5.25" drives usually have ~150 Ohm terminators and only one drive (the last on the cable) should have one installed or enabled. 3.5" drives...

14 replies | 465 view(s)

November 20th, 2019, 07:04 AM

dave_m replied to a thread ZoomFloppy / OpenCBM/ 2031LP and 8050 in Commodore

Thanks for checking. It's a shame as I have the Toronto Pet Users Group library CD which has hundreds of Commodore computer programs that are...

17 replies | 783 view(s)

November 19th, 2019, 09:18 PM

dave_m replied to a thread ZoomFloppy / OpenCBM/ 2031LP and 8050 in Commodore

ZoomFloppy still does not work with a 4040 IEEE Drive. As I remember it did a Reset, and a Directory, but wouldn't copy a file or perform a disk...

17 replies | 783 view(s)

November 12th, 2019, 11:57 PM

dave_m replied to a thread ZoomFloppy / OpenCBM/ 2031LP and 8050 in Commodore

I thought they got the 8050 interface working. However I have a 4040 drive and ZoomFloppy does not work with it. It seems they put very little effort...

17 replies | 783 view(s)

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