This gallery shows some stages of the repair of the Sinclair Spectrum 48k.

◄12

Defects found on the Sinclair Spectrum #1:

• Black Screen of Death/Garbage Screen.

Components replaced:

• 8 x 4116 RAM
• 1 x Z80 CPU

• Extra:
  • Composite Video

Defects found on the Sinclair Spectrum #2:

• There are no colors.

Components replaced:

• 5 x Electrolytic Capacitors 22uf / 16v
• 1 x SN94459 (LM 1889) Tv video Modulator IC with Chroma Reference Signal (Color)

Defects found on the Sinclair Spectrum #3:

• Jaundice problems.

Calibration:

• Calibration of Trimmer (VR2)

Defects found on the Sinclair Spectrum #4:

• Black Screen of Death.

Components replaced:

• 1 x RAM TMS4532
• 1 x Transistor ZTX650

• Extra:
  • Composite Video
  • Conversion from Spectrum (Issue 2) To Spectrum +

Defects found on the Sinclair Spectrum #5:

• Garbage Screen and high absorption on the 12v line and 0v (ground) with explosion of the transistors ZTX-650 (651) and ZTX-213

Components replaced:

• 1 x Zener 5v1
• 12 x Electrolytic capacitors
• 3 x 4116 RAM (two of these in total short circuit between pin 8 and 16)
• 8 x OKI 3732 RAM
• 1 x Sinclair ROM
• 1 x 74HCT(LS)32
• 1 x Transistor ZTX-213
• 1 x Transistor ZTX-650

• Extra:
  • Composite Video

• Info:
  • About the explosion of the transistors i have isolated the problem, are the ram (LOW).

    The bad way used some years ago was cut the pin 8 of the all 4116 ram to isolate the bad one, in this case, i didn’t cut the pins of the ram, but i have cut the track of 12v which is part of all the 4116 ram, doing so, the transistor ZTX650(651) doesn’t explode.

    At this point there is a short in one or more RAM between +12 and 0v. I have measured the absorption where i have cut the track and it absorbs too much.

    I just have to unsolder the pin 8 of the 4116 ram and trying to isolate it for find which ram is short-circuited.

• …it was not over:
  • When the repair is finished and i have replaced all OKI 3732 RAM with a new one, another IC has decided to die, a 74HC(LS)32. I have no words.

Defects found on the Sinclair Spectrum #6:

• Faulty / AutoLoad.

Components replaced:

• 1 x TMS 4532 RAM

• Extra:
  • Composite Video

Sinclair Spectrum Faulty / AutoLoad Video: