Search found 488 matches

by 1024MAK
Sun Oct 13, 2019 2:34 pm
Forum: Hardware
Topic: Repairing a LO>>PROFILE professional keyboard
Replies: 4
Views: 289

Re: Repairing a LO>>PROFILE professional keyboard

Don’t forget you also have to account for the B-E forward junction voltage drop/turn on voltage of the PNP transistor. The emitter will follow the base voltage minus this voltage. So if the Z80 CPU address line goes to say 0.7V when low, then you have the forward voltage drop of diodes D1 ... D8 (on...
by 1024MAK
Fri Oct 11, 2019 7:40 am
Forum: Sinclair Miscellaneous
Topic: 35th Anniversary
Replies: 15
Views: 459

Re: 35th Anniversary

In appropriately 74 days, it will be the 36th anniversary of me and my sister getting our hands on a brand new 48K rubber key :D Did anyone else work as teams with their friends and family trying to get further when playing hard games like Lunar Jetman? Mind, we did spend hours laughing at each othe...
by 1024MAK
Thu Oct 10, 2019 3:28 pm
Forum: Hardware
Topic: Issue 6 problems
Replies: 7
Views: 191

Re: Issue 6 problems

Took the multimeter at the 7805. 5.69V input, 4V output. My working M-332 Speccy pulls the input voltage to the same 5.69V, but somehow keeps on ticking. Seems like I have a power supply problem, 12+V no load, but bogs down under load. The various different issue boards all use a different amount o...
by 1024MAK
Thu Oct 10, 2019 3:10 pm
Forum: Hardware
Topic: Issue 2 Spectrum not loading software
Replies: 8
Views: 242

Re: Issue 2 Spectrum not loading software

I normally suggest some PC amplifier speakers like these . Note the above is an example, I cannot vouch for that particular model. You will also have to buy suitable adapters / cables, as the speakers will be wired for stereo, but the ear socket on the ZX Spectrum will only work with a 3.5mm mono pl...
by 1024MAK
Mon Oct 07, 2019 3:01 pm
Forum: Hardware
Topic: Noob saying Hi with a pile of questions!
Replies: 6
Views: 476

Re: Noob saying Hi with a pile of questions!

Under the text edit box there is a “add image to post” link that you can use to include images. This is via postimages.org

Mark
by 1024MAK
Sat Sep 28, 2019 8:58 am
Forum: Programming
Topic: CPI / CPIR instruction
Replies: 14
Views: 504

Re: CPI / CPIR instruction

The Z80 MPU has a number of features (including clever ideas) that make it a bit unconventional. Remember, the mnemonics are only there to help humans remember the effect of the instruction. They do not necessarily accurately indicate how the Z80 carries out the operation. As all sorts of hardware t...
by 1024MAK
Mon Sep 23, 2019 6:34 am
Forum: Hardware
Topic: Spectrum+ 48k repair
Replies: 20
Views: 451

Re: Spectrum+ 48k repair

Going on the rating plate/label, that power supply looks fine.

Mark
by 1024MAK
Sun Sep 22, 2019 9:04 pm
Forum: Hardware
Topic: Spectrum+ 48k repair
Replies: 20
Views: 451

Re: Spectrum+ 48k repair

Please note that it is very important that you don’t accidentally short out any of the pins on the chips. So be careful with your meter probes.

Can you post a photo of the power supply that you are using.

Mark
by 1024MAK
Sun Sep 22, 2019 12:03 am
Forum: Sinclair Miscellaneous
Topic: Did you ever think you were the last Spectrum user?
Replies: 34
Views: 1071

Re: Did you ever think you were the last Spectrum user?

refused to run another item That should of course said “reused”. Blooming auto suggest/ auto correct... :roll: About the +3B. I’m about 200 miles away from it at the moment. I’ll post some photos of it next week... Oh, I also forgot the 128K toast rack in my list. Although I have not yet got around...
by 1024MAK
Sat Sep 21, 2019 9:12 pm
Forum: Sinclair Miscellaneous
Topic: Did you ever think you were the last Spectrum user?
Replies: 34
Views: 1071

Re: Did you ever think you were the last Spectrum user?

My story is over here . I never ever got rid of the first ZX Spectrum. But, it’s been in storage for a long time now. As the replacement PSU that I build got refused to run another item. As it was in two bits, I’ve lost track of where the regulator board has been stored. Hence this ZX Spectrum sits ...