Search found 16 matches

by tyrell
Thu Jul 12, 2018 4:41 pm
Forum: Hardware
Topic: ZX spectrum 48k repair
Replies: 29
Views: 17759

Re: ZX spectrum 48k repair

1024MAK wrote: Wed Jul 11, 2018 11:33 pm Well done :D

Mark
Thanks Mark ;)
It really was a challenge given it was the first time I was repairing speccies. I'm just stubborn and it paid off.
by tyrell
Wed Jul 11, 2018 9:32 pm
Forum: Hardware
Topic: ZX spectrum 48k repair
Replies: 29
Views: 17759

Re: ZX spectrum 48k repair

Latest news about my second board which was not booting to basic (black and white vertical stripes). I replaced a pair of capacitors (1 mfd) and now everything is ok ! I also replaced the ULA with Nebula. A second board which came back from the deads ;) Total work done on this board : - replaced TR4...
by tyrell
Sun Jul 01, 2018 7:52 am
Forum: Hardware
Topic: ZX spectrum 48k repair
Replies: 29
Views: 17759

Re: ZX spectrum 48k repair

Moggy wrote: Sat Jun 30, 2018 9:54 pm One more back on the road, magic. :D
Was quite a work, but we would do anything for our speccies, right ? ;)
by tyrell
Sat Jun 30, 2018 3:58 pm
Forum: Hardware
Topic: ZX spectrum 48k repair
Replies: 29
Views: 17759

Re: ZX spectrum 48k repair

For the wrong colors, it was the ULA ! I swapped it for a working one, and the colors were back ! I have brought back one speccy to life. I even added a small switching module, which is way more power efficient than a 7805, and of course I did the composite mod. Later I'll see if I can buy a ula (ne...
by tyrell
Fri Jun 29, 2018 8:14 pm
Forum: Hardware
Topic: ZX spectrum 48k repair
Replies: 29
Views: 17759

Re: ZX spectrum 48k repair

Yes more or less !
Symptoms are large black and white vertical stripes.
(Last time I checked).
And voltages for lm1889 are in range... This shouldn't be the problem.
by tyrell
Fri Jun 29, 2018 5:56 pm
Forum: Hardware
Topic: ZX spectrum 48k repair
Replies: 29
Views: 17759

Re: ZX spectrum 48k repair

I have fixed sound thanks to the scope. On a working speccy, I could see a waveform on each side of D9. On my non working speccy, I could see a waveform on one side only... I had found the suspect ! After replacement, sound is now working ! On this board, only one problem remaining : picture is some...
by tyrell
Fri Jun 29, 2018 6:34 am
Forum: Hardware
Topic: ZX spectrum 48k repair
Replies: 29
Views: 17759

Re: ZX spectrum 48k repair

After replacement of ic6, 11 & 17, spectrum is up and running. Ram chips from the c64 (4164's) are 100% working ! I was fortunate to have some spares ! Almost all the original 4116 chips were bad. For those who would like to use the ram chips from a c64, this mod is required: cut pin 1, bend pin 8, ...
by tyrell
Thu Jun 28, 2018 7:56 pm
Forum: Hardware
Topic: ZX spectrum 48k repair
Replies: 29
Views: 17759

Re: ZX spectrum 48k repair

For the non working speccy, smart card diag tells me that ic6,ic11 and ic17 are probably bad.
I'll try to replace them.
Stay tuned :)
by tyrell
Thu Jun 28, 2018 2:23 pm
Forum: Hardware
Topic: ZX spectrum 48k repair
Replies: 29
Views: 17759

Re: ZX spectrum 48k repair

Ok, thanks for your help ! I also saw that it was possible to start my smart card v2 in diag mode with the help of a switch. Then it will boot on a special diag ROM which is inside of the 16 ROMs slots in the cartridge memory. It should help me diagnose what is wrong with my speccy. I'll come back h...
by tyrell
Thu Jun 28, 2018 6:24 am
Forum: Hardware
Topic: ZX spectrum 48k repair
Replies: 29
Views: 17759

Re: ZX spectrum 48k repair

I don't have a spare edge connector :(
I'll go the socket way...
I'll keep you updated !