Search found 257 matches

by rmzalbar
Wed Mar 13, 2024 4:25 am
Forum: Chit Chat
Topic: Rebadged MOS6526A chips from Back to the Future!
Replies: 8
Views: 94

Re: Rebadged MOS6526A chips from Back to the Future!

Not really. There is a timing test to check if they are NMOS or HMOS. HMOS versions were later, made after 1987 and are probably more likely to be A m…login to view the rest of this post
by rmzalbar
Tue Mar 12, 2024 8:27 pm
Forum: Hardware
Topic: I'd like to propose a "FD-3000"
Replies: 23
Views: 2519

Re: I'd like to propose a "FD-3000"

Now you can truly get modern 1581 and FD-2000 clones ( from the Foenix retro project, https://c256foenix.com/shop/?v=7516fd43adaa ) These are cool as hell, but you will pay money for them.
by rmzalbar
Tue Mar 12, 2024 7:32 pm
Forum: Chit Chat
Topic: Rebadged MOS6526A chips from Back to the Future!
Replies: 8
Views: 94

Re: Rebadged MOS6526A chips from Back to the Future!

I have a bunch of chips from Ail. Mostly VIC-II and 6526s. Usually they work, sometimes they don't. All are dipped and remarked. The remarking part is…login to view the rest of this post
by rmzalbar
Sat Oct 21, 2023 7:46 am
Forum: Hardware
Topic: Black screen C64 - hangs somewhere in kernal
Replies: 4
Views: 472

Re: Black screen C64 - hangs somewhere in kernal

Sure! A quick look shows blue screen/ready prompt at 2.5 seconds after power switch is turned on.
!IO and !BAS at the PLA both shows a short burst of activity starting at about 1850ms after reset goes high.

I will be able to give measurements and captures when I can sit down with it this weekend.
by rmzalbar
Wed Oct 11, 2023 1:22 am
Forum: Help!
Topic: C128 With Good RF Signal But Black Screen Through SCART
Replies: 1
Views: 600

Re: C128 With Good RF Signal But Black Screen Through SCART

Well the video on the DIN connector is amplified and mixed in the RF modulator. Check the DIN traces, joints, and filtering components between DIN and modulator pins. If that's good then something may have failed in the RF modulator, even though it seems to be able to provide RF output. In particula...
by rmzalbar
Tue Oct 10, 2023 7:49 am
Forum: Hardware
Topic: Black screen C64 - hangs somewhere in kernal
Replies: 4
Views: 472

Re: Black screen C64 - hangs somewhere in kernal

Hi. I don't know the answers to most of your questions, but off the top of my head: The PLA is the only device I know of that takes A12-15 only, so if it provided internal pull-up that might explain why you get higher levels on those lines...I don't think it does, though. U14 is an address decoder. ...
by rmzalbar
Tue Oct 10, 2023 6:20 am
Forum: Hardware
Topic: C64 Black screen
Replies: 10
Views: 720

Re: C64 Black screen

I'm glad you have it solved. I wish I had thought of that earlier - I need to come up with a prioritized checklist. As far as sockets are concerned, most of the C64's I've had came with various combinations of socketed PLA, SID, CPU, and CIAs and ROMs. The VIC is always socketed. Because of the prop...
by rmzalbar
Sun Oct 08, 2023 8:15 am
Forum: Help!
Topic: Fried C64
Replies: 2
Views: 347

Re: Fried C64

I typed a big long post before I reread and realized you have a short board. I don't have as much experience there. All I can say is the newer C64 ASICs used in the short boards are likely a bit more tolerant to accidental overvolt than the 6-series parts but I don't know if anyone knows how they fa...
by rmzalbar
Sun Oct 08, 2023 1:38 am
Forum: Hardware
Topic: C64 Black screen
Replies: 10
Views: 720

Re: C64 Black screen

I am sorry for your pain, I know how frustrating that can be. I thought Banman's advice about the power supply is good, since being a large block it may not cool off quickly giving you the long wait for it to work again symptom. But since you're testing with another machine I bet you've ruled this o...
by rmzalbar
Thu Oct 05, 2023 2:44 am
Forum: Hardware
Topic: C64 Black screen
Replies: 10
Views: 720

Re: C64 Black screen

May as well check reset line, since that's easy to do. It's active low, so it should stay close to 5V in normal operation, except for a brief moment at power-on. Maybe U8 or U20 is failing and it sags when things warm up? 1541 would be in reset too if this is happening.