ZX spectrum 48k repair

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1024MAK
Posts: 2009
Joined: Mon Sep 26, 2011 10:56 am
Location: Looking forward to summer in Somerset, UK...

Re: ZX spectrum 48k repair

Post by 1024MAK » Fri Jun 29, 2018 6:48 pm

With your other Spectrum, is the picture like any on this site?

tyrell
Posts: 16
Joined: Sun Jun 24, 2018 5:41 pm

Re: ZX spectrum 48k repair

Post by tyrell » Fri Jun 29, 2018 8:14 pm

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.

tyrell
Posts: 16
Joined: Sun Jun 24, 2018 5:41 pm

Re: ZX spectrum 48k repair

Post by tyrell » Sat Jun 30, 2018 3:58 pm

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 (nebula ?), And fix the rom (vertical black and white striped) for the other partially working board.

Total work done on this spectrum :
- replaced almost all lower bank ram chips (used 5x4164 from a c64 and 3x4116 from retroleum).
- replaced d9
- replaced TR4
- replaced the ULA
- replaced 4 or 5 capacitors
- replaced the 7805 regulator with an UBEC module
- new keyboard membrane
- placed a socket for the lm1889
- composite mod

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1024MAK
Posts: 2009
Joined: Mon Sep 26, 2011 10:56 am
Location: Looking forward to summer in Somerset, UK...

Re: ZX spectrum 48k repair

Post by 1024MAK » Sat Jun 30, 2018 9:24 pm

Good that your progress brings success :D

Mark

Moggy
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Joined: Wed Jun 18, 2008 2:00 pm

Re: ZX spectrum 48k repair

Post by Moggy » Sat Jun 30, 2018 9:54 pm

One more back on the road, magic. :D

tyrell
Posts: 16
Joined: Sun Jun 24, 2018 5:41 pm

Re: ZX spectrum 48k repair

Post by tyrell » Sun Jul 01, 2018 7:52 am

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 ? ;)

tyrell
Posts: 16
Joined: Sun Jun 24, 2018 5:41 pm

Re: ZX spectrum 48k repair

Post by tyrell » Wed Jul 11, 2018 9:32 pm

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
- replaced 4 or 5 capacitors (bad caps were responsible for vertical white and black stripes)
- replaced the ULA with Nebula (retroleum)
- replaced the beeper (sound was weak)
- will replace soon the 7805 regulator with an UBEC module. These are cheap and efficient ... already placed in a speccy, in a Timex 2048 and in a c64 power supply... I highly recommend these modules ! I recommend them over the traco modules even though they are bigger, because they can deliver up to 3 amps, while the traco can only deliver 1A I think, which is not enough in case you connect several peripherals to the speccy...
Last edited by tyrell on Thu Jul 12, 2018 9:39 am, edited 2 times in total.

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1024MAK
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Joined: Mon Sep 26, 2011 10:56 am
Location: Looking forward to summer in Somerset, UK...

Re: ZX spectrum 48k repair

Post by 1024MAK » Wed Jul 11, 2018 11:33 pm

Well done :D

Mark

tyrell
Posts: 16
Joined: Sun Jun 24, 2018 5:41 pm

Re: ZX spectrum 48k repair

Post by tyrell » Thu Jul 12, 2018 4:41 pm

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.

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