Search found 165 matches

by MCes
Fri Feb 23, 2018 7:31 pm
Forum: Buy, Sell, and Trade
Topic: ROM 2364 substitute: EPROM 27HC641
Replies: 2
Views: 371

Re: ROM 2364 substitute: EPROM 27HC641

Yes, they are still available.
I will be more detailed after week end
by MCes
Tue Feb 13, 2018 11:05 am
Forum: Programming
Topic: NTSC / PAL: sjload & easyload+
Replies: 0
Views: 98

NTSC / PAL: sjload & easyload+

I know that sjload work with jiffydos modified drive, so I suppose that with a real drive (as 1541) I need to find the sjload-NTSC version for NTSC systems and a sjload-PAL version for PAL system, is it right? and where can I find them? I know that easyload work with not-modified (real) drive, but d...
by MCes
Wed Feb 07, 2018 1:42 pm
Forum: Hardware and Tech
Topic: 8K or 16K?
Replies: 2
Views: 100

Re: 8K or 16K?

the vic 20 recognize at startup 3 possibility: 1) default memory asset 2) +3k (low basic) ram expansion 3) contiguous ram expansion from first 8K expandable ram (8,16,24K) so if the game need a 8k expansion ram it can be loaded into a 8k or 16k or 24k expanded VIC20.... http://sleepingelephant.com/d...
by MCes
Wed Jan 31, 2018 3:48 am
Forum: Other Systems
Topic: PLAs for COMMODORE
Replies: 0
Views: 104

PLAs for COMMODORE

PLA programmed as the relative Commodore's part number! More originals than originals: For own computers Commodore initially programmed PLAs (supplied from market by vary brands), after this the PLAs was produced, saving too much, directly by Commodore with terrible consequences: on C64 "bread...
by MCes
Sat Jan 27, 2018 5:10 am
Forum: Hardware and Tech
Topic: PET-style keyboard reassembly
Replies: 12
Views: 222

Re: PET-style keyboard reassembly

Analyzing the last pic too I can see an insert-key on black piston and in the gray socket, but for F7 the insert-key is reversed, so it will be necessary rotate of 180° the gray socket or to extract the black piston from the cap-key, rotate it of 180° and refit it inside the cap
by MCes
Fri Jan 26, 2018 10:39 am
Forum: Hardware and Tech
Topic: PET-style keyboard reassembly
Replies: 12
Views: 222

Re: PET-style keyboard reassembly

FriedOrange79, Pics can help in understanding your problem and the relative solution.... I'm not proposing to re-make a new PCB for the keyboard, but if it's necessary I was suggesting to get a working PCB froa another unused (or sacrificable) keyboard. It can't be from a "normal" keyboard...
by MCes
Thu Jan 25, 2018 9:57 am
Forum: Hardware and Tech
Topic: PET-style keyboard reassembly
Replies: 12
Views: 222

Re: PET-style keyboard reassembly

For your PET-style keyboard consider the possibility of replacing the entire PCB.
You can get a PCB from an old (yellowed) standard keyboard.....
I think that it can work!
by MCes
Sat Jan 13, 2018 12:26 pm
Forum: Hardware and Tech
Topic: 6561 Die Shot Reversing Explorations
Replies: 160
Views: 3517

Re: 6561 Die Shot Reversing Explorations

An interesting observation I'd like to make at this point is that the phase 2 4.43 MHz clock bonding pad doesn't appear to be connected to anything in the die shot. I found this quite surprising and suspect that there is something more to it that I haven't picked up on yet. Also I found always stra...
by MCes
Fri Jan 12, 2018 1:10 am
Forum: Hardware and Tech
Topic: Display issue
Replies: 34
Views: 621

Re: Display issue

If I remember well I have 6561 (PAL) spare....
In case of interest PM me
by MCes
Thu Jan 11, 2018 2:40 am
Forum: Hardware and Tech
Topic: Display issue
Replies: 34
Views: 621

Re: Display issue

The point of situation: We are speaking inside hipotesis that 6561 is well working ( are you able to test your 6561 into another working VIC20? ) and that problem is only the color subcarrier frequency misalignment. Without serious instruments I suggest to: A) using of Cathode Ray Tube TV B) set the...
by MCes
Wed Jan 10, 2018 3:01 am
Forum: Hardware and Tech
Topic: Display issue
Replies: 34
Views: 621

Re: Display issue

Post some pics of front and rear of PCB (the shielded part).

Read on Xtal surface: is it writed "4.43......" or "8.86....."?

The 56pF capacitor has to be soldered electrically in parallel to R5 (@ 4.43 MHz Xtal)

IMG_20180110_100401.JPG
by MCes
Wed Jan 10, 2018 2:08 am
Forum: Hardware and Tech
Topic: Display issue
Replies: 34
Views: 621

Re: Display issue

On 4.43MHz VIC20 Xtal oscillator you have to find a 56pF on the rear of PCB otherwise the oscillator will tuned with (and generate) the Xtal third harmonics (13,3MHz). http://www.polytechnichub.com/construction-ceramic-trimmer-capacitor/ The variable capacitor has endless rotation, it has a couple o...
by MCes
Tue Jan 09, 2018 9:33 am
Forum: Hardware and Tech
Topic: Display issue
Replies: 34
Views: 621

Re: Display issue

vicclk2.JPG The aging slow down the Xtal quartz and sometimes the right frequency become out of range of C48 adjust, in this case you have to desolder a side of C50 (or substitute Xtal with a new not-old one) and then adjust the C48. Remember that for adjusting C48 you have to use a not magnetic sc...

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