ZX Spectrums problems : diagnostic software ?
Re: ZX Spectrums problems : diagnostic software ?
To load the TZX I am using a Divmmc card.
Re: ZX Spectrums problems : diagnostic software ?
How do I measure resistance ?
My RAM chips are known working (and have been replaced twice), if measuring resistance is for trying to check which RAM IC is defective, I think it's useless.
Re: ZX Spectrums problems : diagnostic software ?
I am sorry I get lost when you said some software were reporting a bad low memory ..
So.. what was the problem then? ..
I posted about my own experience with that earlier..
Ernesto
ZX80 USA, ZX81UK, ZX Spectrum, ZX Spectrum+, ZX Spectrum 128+ UK, ZX Spectrum +2/A, Sinclair QL, CZ1000, CZ1500, CZ2000, CZ1000Plus, CZ1500Plus, CZ Spectrum, CZ Spectrum Plus, TK83, TK85, TK90X, TK95. TS2068. And more to come
ZX80 USA, ZX81UK, ZX Spectrum, ZX Spectrum+, ZX Spectrum 128+ UK, ZX Spectrum +2/A, Sinclair QL, CZ1000, CZ1500, CZ2000, CZ1000Plus, CZ1500Plus, CZ Spectrum, CZ Spectrum Plus, TK83, TK85, TK90X, TK95. TS2068. And more to come
Re: ZX Spectrums problems : diagnostic software ?
ZX Diagnostics reported bad IC's. I replaced all of them (all the 8 low RAM chips), but the problem remains :
after one minute of use, my Speccy displays bugs.
All RAM tests software say I have a problem with low RAM, but they never show the same IC's as defective ...
So I am sure that a component on the motherboard is failing and does impact the low RAM. But which one knowing that I already replaced :
- TR4
- TR5
- 7805 by a TRACO
- Z80
- All low RAM chips
- ULA
- all capacitors
after one minute of use, my Speccy displays bugs.
All RAM tests software say I have a problem with low RAM, but they never show the same IC's as defective ...
So I am sure that a component on the motherboard is failing and does impact the low RAM. But which one knowing that I already replaced :
- TR4
- TR5
- 7805 by a TRACO
- Z80
- All low RAM chips
- ULA
- all capacitors
- 1024MAK
- Posts: 5118
- Joined: Mon Sep 26, 2011 10:56 am
- Location: Looking forward to summer in Somerset, UK...
Re: ZX Spectrums problems : diagnostic software ?
Better late than never, even if it’s not a video but instead some static photos...
Please note that this is an issue 1 board and is a bit different to the later board versions. However, the DC input connector, the modulator and the 4116 (or equivalent, in this case they are NEC D416C DRAM chips) ‘lower’ DRAM chips are in similar places.
. . . . . . . .
Mark
Please note that this is an issue 1 board and is a bit different to the later board versions. However, the DC input connector, the modulator and the 4116 (or equivalent, in this case they are NEC D416C DRAM chips) ‘lower’ DRAM chips are in similar places.
. . . . . . . .
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 Spectrums problems : diagnostic software ?
Thanks a lot Mark ! In the meantime "Bola_dor" helped me with the voltages measurements. They are all good.
But now something new happens : running the same memory test now always end up with "IC25 failure" ...
IC25 is a SN74LS157N which seems to be involved in the memory management. I am now trying to find out how to get a new working one ...
But now something new happens : running the same memory test now always end up with "IC25 failure" ...
IC25 is a SN74LS157N which seems to be involved in the memory management. I am now trying to find out how to get a new working one ...
- 1024MAK
- Posts: 5118
- Joined: Mon Sep 26, 2011 10:56 am
- Location: Looking forward to summer in Somerset, UK...
Re: ZX Spectrums problems : diagnostic software ?
Not having had time to read all the posts made today, and at the risk of answering questions that have already been answered, nevertheless, I shall give my answers...
Even better if you have a suitable crocodile clip or other clip that can be used to attach the meter black/negative connection to the the modulator case, or the RF/UHF output connector. Then you don’t have to hold a probe on this point. There are other 0V/GND points on the ZX Spectrum circuit board, but the position varies between different issue boards.
For other users who have not replaced the 7805 series pass voltage regulator, the best and easiest place is the 7805 heatsink.
Yes, you have to be very careful when using a probe on the pins of a chip. It is easy to slip if you don’t concentrate.
If you have difficulty, I can only suggest asking someone for assistance. Either to hold the meter black/negative connection in place, and / or to read the voltage displayed on the multimeter. Then you can concentrate on probing the relevant chip pins.
It is also possible to practice with the computer switched off
Mark
Yes, the computer should be powered on. If you can hold one probe (the black/negative one) with one hand on to either the modulator case, or the RF/UHF output connector, then you can concentrate on holding the red/positive probe on the chip pin or other point.dizzy33 wrote: ↑Tue Feb 25, 2020 1:43 pm I own a multimeter which I can put in "20v DC" as you request, but it's not clear to me how to do the tests you are requesting.
At first, I guess my Speccy should be powered on, right ? So I am very afraid of making a shortcircuit, that's why I am asking so much questions.
Even better if you have a suitable crocodile clip or other clip that can be used to attach the meter black/negative connection to the the modulator case, or the RF/UHF output connector. Then you don’t have to hold a probe on this point. There are other 0V/GND points on the ZX Spectrum circuit board, but the position varies between different issue boards.
For other users who have not replaced the 7805 series pass voltage regulator, the best and easiest place is the 7805 heatsink.
Yes, you have to be very careful when using a probe on the pins of a chip. It is easy to slip if you don’t concentrate.
If you have difficulty, I can only suggest asking someone for assistance. Either to hold the meter black/negative connection in place, and / or to read the voltage displayed on the multimeter. Then you can concentrate on probing the relevant chip pins.
It is also possible to practice with the computer switched off
Yes, the best point is the RF/UHF output connector, or on the lower case. Sometimes the lid does not always make good contact with the case of the modulator.
It’s not about just testing the Traco DC/DC converter, but checking that the correct voltage makes it to the digital and memory circuitry. And to check that the Traco DC/DC converter is not running in protection mode due to a short circuit or overload.
Because it’s tricky to hold two probes on the pins of chips, I recommend using a 0V/GND point as described above. Then use the red probe on pins 1, 8 and 9 in turn.
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 Spectrums problems : diagnostic software ?
Thanks a lot again Mark ! In the meantime "Bola_dor" helped me with the voltages measurements. They are all good.
But now something new happens : running the same memory test now always end up with "IC25 failure" ...
IC25 is a SN74LS157N which seems to be involved in the memory management. I am now trying to find out how to get a new working one ...
But now something new happens : running the same memory test now always end up with "IC25 failure" ...
IC25 is a SN74LS157N which seems to be involved in the memory management. I am now trying to find out how to get a new working one ...
Re: ZX Spectrums problems : diagnostic software ?
Wich software are you testing with?.. I am at a similar point with some low memory problem..dizzy33 wrote: ↑Thu Feb 27, 2020 9:26 pm Thanks a lot again Mark ! In the meantime "Bola_dor" helped me with the voltages measurements. They are all good.
But now something new happens : running the same memory test now always end up with "IC25 failure" ...
IC25 is a SN74LS157N which seems to be involved in the memory management. I am now trying to find out how to get a new working one ...
This is my case https://www.sinclairzxworld.com/viewtop ... =21&t=3586
Ernesto
ZX80 USA, ZX81UK, ZX Spectrum, ZX Spectrum+, ZX Spectrum 128+ UK, ZX Spectrum +2/A, Sinclair QL, CZ1000, CZ1500, CZ2000, CZ1000Plus, CZ1500Plus, CZ Spectrum, CZ Spectrum Plus, TK83, TK85, TK90X, TK95. TS2068. And more to come
ZX80 USA, ZX81UK, ZX Spectrum, ZX Spectrum+, ZX Spectrum 128+ UK, ZX Spectrum +2/A, Sinclair QL, CZ1000, CZ1500, CZ2000, CZ1000Plus, CZ1500Plus, CZ Spectrum, CZ Spectrum Plus, TK83, TK85, TK90X, TK95. TS2068. And more to come
Re: ZX Spectrums problems : diagnostic software ?
I am using the software which is in ROM of the Smartcard V2 (homebrew from the Smartcard maker).