ZX spectrum 48k repair
- 1024MAK
- Posts: 5118
- Joined: Mon Sep 26, 2011 10:56 am
- Location: Looking forward to summer in Somerset, UK...
Re: ZX spectrum 48k repair
With your other Spectrum, is the picture like any on this site?
ZX81 Variations
ZX81 Chip Pin-outs
ZX81 Video Transistor Buffer Amp
Standby alert
There are four lights!
Step up to red alert. Sir, are you absolutely sure? It does mean changing the bulb
Looking forward to summer later in the year.
ZX81 Chip Pin-outs
ZX81 Video Transistor Buffer Amp
Standby alert
There are four lights!
Step up to red alert. Sir, are you absolutely sure? It does mean changing the bulb
Looking forward to summer later in the year.
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.
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.
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 (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
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
- 1024MAK
- Posts: 5118
- Joined: Mon Sep 26, 2011 10:56 am
- Location: Looking forward to summer in Somerset, UK...
Re: ZX spectrum 48k repair
Good that your progress brings success
Mark
Mark
ZX81 Variations
ZX81 Chip Pin-outs
ZX81 Video Transistor Buffer Amp
Standby alert
There are four lights!
Step up to red alert. Sir, are you absolutely sure? It does mean changing the bulb
Looking forward to summer later in the year.
ZX81 Chip Pin-outs
ZX81 Video Transistor Buffer Amp
Standby alert
There are four lights!
Step up to red alert. Sir, are you absolutely sure? It does mean changing the bulb
Looking forward to summer later in the year.
Re: ZX spectrum 48k repair
One more back on the road, magic.
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
- 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...
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.
- 1024MAK
- Posts: 5118
- Joined: Mon Sep 26, 2011 10:56 am
- Location: Looking forward to summer in Somerset, UK...
Re: ZX spectrum 48k repair
Well done
Mark
Mark
ZX81 Variations
ZX81 Chip Pin-outs
ZX81 Video Transistor Buffer Amp
Standby alert
There are four lights!
Step up to red alert. Sir, are you absolutely sure? It does mean changing the bulb
Looking forward to summer later in the year.
ZX81 Chip Pin-outs
ZX81 Video Transistor Buffer Amp
Standby alert
There are four lights!
Step up to red alert. Sir, are you absolutely sure? It does mean changing the bulb
Looking forward to summer later in the year.
Re: ZX spectrum 48k repair
Hi Tyrell, where I can see/purchase this UBEC modules? Thankstyrell wrote: ↑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...