View Profile: tezza - Vintage Computer Forum

February 24th, 2020, 12:07 PM

dave_m replied to a thread PET 4016 power in from transformer to Jumper 8 in Commodore

Yes, ripple tests will go on my checklist.

78 replies | 1160 view(s)

February 24th, 2020, 11:59 AM

dave_m replied to a thread Commodore 8032 repair. in Commodore

Hi daver2, I don't want to jinx you, but I hope there are more problems than the clock! This thread would make a great 'How To' on troubleshooting a...

4 replies | 89 view(s)

February 23rd, 2020, 11:33 AM

dave_m replied to a thread PET 4016 power in from transformer to Jumper 8 in Commodore

OK, thanks to the forum team I learned something about power supplies from this problem. With no goo, I would have replaced the diode bridge and...

78 replies | 1160 view(s)

February 23rd, 2020, 09:23 AM

dave_m replied to a thread PET 4016 power in from transformer to Jumper 8 in Commodore

Dokken, You did a good job on your computer. I have a few questions. Was there no goo leaking out of the old capacitor? Or did capacitor dry out...

78 replies | 1160 view(s)

February 21st, 2020, 12:44 PM

dave_m replied to a thread CBM 3008 / 2001-8N won't boot. in Commodore

Hi Mike, But what is confusing is that he has only 8K of RAM. Dynamic RAM would come in 16K or 32K.

7 replies | 119 view(s)

February 21st, 2020, 12:15 PM

dave_m replied to a thread Commodore CBM 2001-16N - BIG MESS! in Commodore

Pins 18 and 20 may be wired together at the 2732, but pins 18 and 20 should not be connected at bottom pins (board), correct?

95 replies | 3004 view(s)

February 21st, 2020, 11:55 AM

dave_m replied to a thread CBM 3008 / 2001-8N won't boot. in Commodore

Does this memory schematic describe your configuration of memory chips 6 ea 2316 ROMs and 16ea 2114 RAM chips? Or is it another type of memory chips?...

7 replies | 119 view(s)

February 20th, 2020, 04:56 PM

dave_m replied to a thread PET 4016 power in from transformer to Jumper 8 in Commodore

Daver, Is your DVM reading in AC rms or peak? I think my old voltmeter readings are peak and be higher. My data say 22 VAC across the brown wires...

78 replies | 1160 view(s)

February 20th, 2020, 04:46 PM

dave_m replied to a thread PET 4016 power in from transformer to Jumper 8 in Commodore

Commodore liked their documentation to be a bit confusing. :p

78 replies | 1160 view(s)

February 20th, 2020, 02:49 PM

dave_m replied to a thread PET 4016 power in from transformer to Jumper 8 in Commodore

Here is power supply circuit diagram.

78 replies | 1160 view(s)

February 20th, 2020, 02:36 PM

dave_m replied to a thread PET 4016 power in from transformer to Jumper 8 in Commodore

No, The center tap from the transformer is a black wire and goes to the negative terminal on the big C1 capacitor. From there, two black wires go to...

78 replies | 1160 view(s)

February 20th, 2020, 08:10 AM

dave_m replied to a thread PET 4016 power in from transformer to Jumper 8 in Commodore

Dwight, Here is the pinouts of the PET transformer.

78 replies | 1160 view(s)

February 19th, 2020, 04:43 PM

dave_m replied to a thread PET 4016 power in from transformer to Jumper 8 in Commodore

On my Pet with J8 cable not connected to main board (diode bridges), I get 22 VAC between J8- pin 1 to 5. You get 18 VAC. That is not much head room...

78 replies | 1160 view(s)

February 18th, 2020, 08:38 PM

dave_m replied to a thread PET 4016 power in from transformer to Jumper 8 in Commodore

Until you get the correct DC voltages, and verify that the horizontal and vertical drive signals are good at the J7 connector, it would be prudent to...

78 replies | 1160 view(s)

February 18th, 2020, 01:31 PM

dave_m replied to a thread Commodore CBM 2001-16N - BIG MESS! in Commodore

Yes, that's what Dwight is asking. You can display both traces if the screen is bright enough. SEL F (D9-20) should start at the trailing edge of SEL...

95 replies | 3004 view(s)

February 16th, 2020, 02:11 PM

dave_m replied to a thread Commodore CBM 2001-16N - BIG MESS! in Commodore

Dwight, That's a good hypothesis, no /SEL F pulse at D9-pin 20 would tell the story. My kingdom for a delayed sweep function for this exercise!...

95 replies | 3004 view(s)

February 15th, 2020, 12:23 PM

dave_m replied to a thread Commodore CBM 2001-16N - BIG MESS! in Commodore

Yes, the 2716 will work directly in the D8 2K EDITOR socket or as the Character Generator ROM. All other 4K ROM sockets can use a Texas Instruments...

95 replies | 3004 view(s)

February 14th, 2020, 07:35 PM

dave_m replied to a thread Commodore CBM 2001-16N - BIG MESS! in Commodore

You know your Intel hex format and that the Record Type is 01 for the 'end of file' record. You are definitely an Intel man!

95 replies | 3004 view(s)

February 14th, 2020, 07:23 PM

dave_m replied to a thread Commodore CBM 2001-16N - BIG MESS! in Commodore

Dwight, your EPROM pattern test is a good idea to test ROM data path. But why not a walking ones test like hex 01, 02, 04, 08, 10, 20, 40, and 80...

95 replies | 3004 view(s)

February 14th, 2020, 10:25 AM

dave_m replied to a thread Fixing Commodore 1541 drives in Commodore

Keep up the good work!

15 replies | 751 view(s)

February 10th, 2020, 12:54 PM

dave_m replied to a thread Commodore CBM 2001-16N - BIG MESS! in Commodore

Denis, Set trigger control to 'normal'. Set vertical inputs to .2 V if you are using a 10X probe or to 2V is using a 1X probe. All we are seeing...

95 replies | 3004 view(s)

February 7th, 2020, 04:35 PM

tezza replied to a thread What are the top 10 rarest vintage computer bits you own? in Your Vintage Computer Collections

Yes, it's a real retro-futuristic design. Actually I've got two and the non-working one is presently listed for sale on our national auction site...

179 replies | 36041 view(s)

February 7th, 2020, 12:06 PM

dave_m replied to a thread Commodore CBM 2001-16N - BIG MESS! in Commodore

Hi Dwight, I'm not following, you may have a typo. 74157 MUX, F5-pin13 is Buffered Address 4 while pin 8 is Ground. What pin will be inverse of BA4?...

95 replies | 3004 view(s)

February 7th, 2020, 07:49 AM

dave_m replied to a thread Commodore CBM 2001-16N - BIG MESS! in Commodore

OK, good troubleshooting. When the video RAM gets better, you can try the daver2 pettest EPROM in the EDIT socket D8.

95 replies | 3004 view(s)

February 6th, 2020, 11:33 PM

tezza replied to a thread What are the top 10 rarest vintage computer bits you own? in Your Vintage Computer Collections

For me. A Polycorp Poly 1 https://www.classic-computers.org.nz/collection/poly1.htm Tez

179 replies | 36041 view(s)