Spectrum+ 48k repair
Spectrum+ 48k repair
My old spectrum+ 48k won't work. I have replaced the electrolytic capacitors, and it didn't fix it. Here's a video of what it does when i switch it on:
https://youtu.be/mGKvQZV_2P4
Help, please.
https://youtu.be/mGKvQZV_2P4
Help, please.
- Ast A. Moore
- Rick Dangerous
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- Joined: Mon Nov 13, 2017 3:16 pm
Re: Spectrum+ 48k repair
Does the image change when you press the reset button? What happens if you press and hold it?
Every man should plant a tree, build a house, and write a ZX Spectrum game.
Author of A Yankee in Iraq, a 50 fps shoot-’em-up—the first game to utilize the floating bus on the +2A/+3,
and zasm Z80 Assembler syntax highlighter.
Author of A Yankee in Iraq, a 50 fps shoot-’em-up—the first game to utilize the floating bus on the +2A/+3,
and zasm Z80 Assembler syntax highlighter.
Re: Spectrum+ 48k repair
Nothing happens
Re: Spectrum+ 48k repair
And the manufacturer of the power supply is unknown.
- Ast A. Moore
- Rick Dangerous
- Posts: 2641
- Joined: Mon Nov 13, 2017 3:16 pm
Re: Spectrum+ 48k repair
First, check the voltages on the RAM, ROM, and the CPU.
It’s likely the CPU or (less likely) the ROM that is fried. If you have an oscilloscope, test the clock on the ULA (Pin 39) and the CPU (Pin 6). Check TR3 for the presence of the clock pulse.
The usual procedures (i.e. checking for broken traces, solder splashes, etc.) also apply, naturally. Was the machine working before recapping?
It’s likely the CPU or (less likely) the ROM that is fried. If you have an oscilloscope, test the clock on the ULA (Pin 39) and the CPU (Pin 6). Check TR3 for the presence of the clock pulse.
The usual procedures (i.e. checking for broken traces, solder splashes, etc.) also apply, naturally. Was the machine working before recapping?
Every man should plant a tree, build a house, and write a ZX Spectrum game.
Author of A Yankee in Iraq, a 50 fps shoot-’em-up—the first game to utilize the floating bus on the +2A/+3,
and zasm Z80 Assembler syntax highlighter.
Author of A Yankee in Iraq, a 50 fps shoot-’em-up—the first game to utilize the floating bus on the +2A/+3,
and zasm Z80 Assembler syntax highlighter.
Re: Spectrum+ 48k repair
I don't have an oscilloscope, and it didn't work before the recapping, but the video quality is much better after recap.
I have a multimeter.
I have a multimeter.
- Ast A. Moore
- Rick Dangerous
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- Joined: Mon Nov 13, 2017 3:16 pm
Re: Spectrum+ 48k repair
Proceed to checking the voltages as I stated above. On the Z80, Pin 29 is ground and Pin 11 is Vcc. On the ROM, it’s pins 14 and 28, respectively.
The lower RAM chips (ICs 6–13) have three voltages: –5V on Pin 1, +5V on Pin 9, and +12V on Pin 8. Pin 16 is the ground.
Incidentally, what’s your logic board revision? Is it an Issue 4B?
Every man should plant a tree, build a house, and write a ZX Spectrum game.
Author of A Yankee in Iraq, a 50 fps shoot-’em-up—the first game to utilize the floating bus on the +2A/+3,
and zasm Z80 Assembler syntax highlighter.
Author of A Yankee in Iraq, a 50 fps shoot-’em-up—the first game to utilize the floating bus on the +2A/+3,
and zasm Z80 Assembler syntax highlighter.
Re: Spectrum+ 48k repair
In my opinion, it looks like lower ram fault. But i'm still a beginner in these things.
Re: Spectrum+ 48k repair
And btw i should get a new power supply for this thing
- Ast A. Moore
- Rick Dangerous
- Posts: 2641
- Joined: Mon Nov 13, 2017 3:16 pm
Re: Spectrum+ 48k repair
No. In that case, the border would have still turned white (unless one of the lower RAM ICs was hogging the data/address lines).
Wait, so you have an Issue 2 board in a Spectrum+ case?
Every man should plant a tree, build a house, and write a ZX Spectrum game.
Author of A Yankee in Iraq, a 50 fps shoot-’em-up—the first game to utilize the floating bus on the +2A/+3,
and zasm Z80 Assembler syntax highlighter.
Author of A Yankee in Iraq, a 50 fps shoot-’em-up—the first game to utilize the floating bus on the +2A/+3,
and zasm Z80 Assembler syntax highlighter.
Re: Spectrum+ 48k repair
How do i check the voltages?
Re: Spectrum+ 48k repair
It's actually my uncle's old speccy. He bought it used. That would explain the mods.
- Ast A. Moore
- Rick Dangerous
- Posts: 2641
- Joined: Mon Nov 13, 2017 3:16 pm
Re: Spectrum+ 48k repair
Set the multimeter in the DC voltage mode, select the 20V range, and touch the black (common) probe to the pin marked as GND in each picture and the red probe to the other pins as indicated. The indicated voltage values are nominal; your actual measurements might deviate slightly from them.
Lower RAM:
CPU:
ROM:
Every man should plant a tree, build a house, and write a ZX Spectrum game.
Author of A Yankee in Iraq, a 50 fps shoot-’em-up—the first game to utilize the floating bus on the +2A/+3,
and zasm Z80 Assembler syntax highlighter.
Author of A Yankee in Iraq, a 50 fps shoot-’em-up—the first game to utilize the floating bus on the +2A/+3,
and zasm Z80 Assembler syntax highlighter.
- 1024MAK
- Bugaboo
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- Joined: Wed Nov 15, 2017 2:52 pm
- Location: Sunny Somerset in the U.K. in Europe
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
Can you post a photo of the power supply that you are using.
Mark
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.
“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.
- 1024MAK
- Bugaboo
- Posts: 3123
- Joined: Wed Nov 15, 2017 2:52 pm
- Location: Sunny Somerset in the U.K. in Europe
Re: Spectrum+ 48k repair
Going on the rating plate/label, that power supply looks fine.
Mark
Mark
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.
“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: Spectrum+ 48k repair
I have an issue 2 Spectrum+, it's an Upgrade case.Ast A. Moore wrote: ↑Sun Sep 22, 2019 2:50 pm Wait, so you have an Issue 2 board in a Spectrum+ case?
- Ast A. Moore
- Rick Dangerous
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- Joined: Mon Nov 13, 2017 3:16 pm
Re: Spectrum+ 48k repair
Sure, I know they existed. It’s just they don’t pop up all that often; so, whenever I see someone mention a Spectrum+, I assume it’s an Issue 4A or later.Guesser wrote: ↑Mon Sep 23, 2019 12:58 pmI have an issue 2 Spectrum+, it's an Upgrade case.Ast A. Moore wrote: ↑Sun Sep 22, 2019 2:50 pm Wait, so you have an Issue 2 board in a Spectrum+ case?
Every man should plant a tree, build a house, and write a ZX Spectrum game.
Author of A Yankee in Iraq, a 50 fps shoot-’em-up—the first game to utilize the floating bus on the +2A/+3,
and zasm Z80 Assembler syntax highlighter.
Author of A Yankee in Iraq, a 50 fps shoot-’em-up—the first game to utilize the floating bus on the +2A/+3,
and zasm Z80 Assembler syntax highlighter.
Re: Spectrum+ 48k repair
There was modifications on the joystick/sound unit too.
- Ast A. Moore
- Rick Dangerous
- Posts: 2641
- Joined: Mon Nov 13, 2017 3:16 pm
Re: Spectrum+ 48k repair
Every man should plant a tree, build a house, and write a ZX Spectrum game.
Author of A Yankee in Iraq, a 50 fps shoot-’em-up—the first game to utilize the floating bus on the +2A/+3,
and zasm Z80 Assembler syntax highlighter.
Author of A Yankee in Iraq, a 50 fps shoot-’em-up—the first game to utilize the floating bus on the +2A/+3,
and zasm Z80 Assembler syntax highlighter.
Re: Spectrum+ 48k repair
Of course the resistor is supposed to be there, i know it, but is it supposed to be connected to the +5v leg through a solder blob?
- 1024MAK
- Bugaboo
- Posts: 3123
- Joined: Wed Nov 15, 2017 2:52 pm
- Location: Sunny Somerset in the U.K. in Europe
Re: Spectrum+ 48k repair
Yes
Mark
Mark
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.
“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.