TS1000 with no image :_(

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stroebeljc
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Re: TS1000 with no image :_(

Post by stroebeljc »

1024MAK wrote: Thu May 07, 2020 1:27 am Another thing to try, is to add an extra 1kΩ resistor.
This extra 1kΩ resistor is wired from the junction of C6 / X1 (the resonator) and 0V/GND. I don’t know why it is fitted to some boards and not others.
Mark
I have this on my board. They must have had problems getting those resonators going without this shunt.
Last edited by stroebeljc on Thu May 07, 2020 11:22 pm, edited 1 time in total.
John
bola_dor
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Re: TS1000 with no image :_(

Post by bola_dor »

stroebeljc wrote: Thu May 07, 2020 11:15 pm
1024MAK wrote: Thu May 07, 2020 1:27 am Another thing to try, is to add an extra 1kΩ resistor.
This extra 1kΩ resistor is wired from the junction of C6 / X1 (the resonator) and 0V/GND. I don’t know why it is fitted to some boards and not others.
Mark
I have this on my board. They must have had problem getting those resonators going without this shunt.
I haven't seen any of this Timex/Sinclair ISS 3 (green) within that resistor in that place. I am pretty sure that it wasn't there originally in this board..
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 :D
bola_dor
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Re: TS1000 with no image :_(

Post by bola_dor »

OK I've made myself a Logic Probe with this schematics but used a 74HC04 and a 2N2222 as that whas what I had at hand
received_2644523002495580.png
What I've tested
ULA pins:
14 when I reset Pulses for 2 or 3 seconds and then remains Low
16 P clearly
35 High

Z80 pins
4 A14 H
5 A15 H
6 CLK P
16 INT P
17NMI H
18 HALT H
19 MRQ L
20 IORQ H

21 RD H
22 WR H
23 H
24 WAIT H
25 BUSRQ H
26 RESET (when I touch it with the probe is H for less than a second then Pulses 1 or 2 seconds and fall Low...
27 MI H
28 RFSH H

IF Z80 is pulsing does it means resonator is OK??
Why ULA 35 is Low?
Why do I have a persistent HALT and WAIT on Z80?
And RESET..looks like I am influencing it with my probe.. (should I call schrodinger)

Oh why meeeee :lol:
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 :D
stroebeljc
Posts: 63
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Re: TS1000 with no image :_(

Post by stroebeljc »

bola_dor wrote: Sat May 09, 2020 11:06 pm OK I've made myself a Logic Probe with this schematics but used a 74HC04 and a 2N2222 as that whas what I had at hand
received_2644523002495580.png
What I've tested
ULA pins:
14 when I reset Pulses for 2 or 3 seconds and then remains Low
16 P clearly
35 High

.
.
.

IF Z80 is pulsing does it means resonator is OK??
Why ULA 35 is Low?
Why do I have a persistent HALT and WAIT on Z80?
And RESET..looks like I am influencing it with my probe.. (should I call schrodinger)
Several things are of interest:
  1. Why is pin 6 of the Z80 pulsing when pin 14 of the ULA is not? (ULA 14 drives Z80 6 through TR2) ULA 14 should look like this:
    ULA Pin 14
    ULA Pin 14
  2. Why is ULA 35 always high? Because it is more of an analog signal and it is usually quite high. See the actual scope signal.
    Note that the lower peak is at about 3.6V.
    ULA Pin 35
    ULA Pin 35
  3. Why does the Z80 reset line go low when you touch it with the probe? This should not be, unless your probe is significantly loading the signal, which it shouldn't be if properly constructed.
John
bola_dor
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Re: TS1000 with no image :_(

Post by bola_dor »

stroebeljc wrote: Sun May 10, 2020 4:49 am Several things are of interest:
  1. Why is pin 6 of the Z80 pulsing when pin 14 of the ULA is not? (ULA 14 drives Z80 6 through TR2) ULA 14 should look like this:SDS00002.png
  2. Why is ULA 35 always high? Because it is more of an analog signal and it is usually quite high. See the actual scope signal.
    Note that the lower peak is at about 3.6V.SDS00001.png
  3. Why does the Z80 reset line go low when you touch it with the probe? This should not be, unless your probe is significantly loading the signal, which it shouldn't be if properly constructed.
About ULA pin14 it measures about 1.1v.. I've seen it working at about 1.8v perhaps is Pulsing too low ?
Understood about pin 35.. it measures about 4v..
The RESET thing.. I realize that I had the multimeter clamped to the Locic probe to see tensions at the same time. Perhaps this induced some current?
I'll have to retest... I am walking in circles now..
So resonator should be OK? How do I rule out a faulty ROM ?
Thank you
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 :D
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1024MAK
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Re: TS1000 with no image :_(

Post by 1024MAK »

bola_dor wrote: Sat May 09, 2020 11:06 pm Z80 pins
4 A14 H
5 A15 H
6 CLK P
16 INT P
17NMI H
18 HALT H
19 MRQ L
20 IORQ H
21 RD H
22 WR H
23 H
24 WAIT H
25 BUSRQ H
26 RESET (when I touch it with the probe is H for less than a second then Pulses 1 or 2 seconds and fall Low...
27 MI H
28 RFSH H

IF Z80 is pulsing does it means resonator is OK??
Why ULA 35 is Low?
Why do I have a persistent HALT and WAIT on Z80?
And RESET..looks like I am influencing it with my probe.. (should I call schrodinger)
ULA pin 14: it’s likely your logic probe does not accept the TTL logic level signal here. A 74HC04 works at normal CMOS logic levels, A TTL logic high is 2V to 5V. A CMOS logic high is ⅔ of the supply voltage or greater. A TTL logic low is between 0V and 0.8V. A CMOS logic low is ⅓ or lower of the supply voltage.
As the signal on pin 6 on the Z80 is pulsating, the ULA must be producing a signal on pin 14. So yes, the resonator appears to be okay.

The loading of the probe on pin 35 will affect the signal. Plus as stroebeljc says, this is not a digital logic signal. I never ask people to test this pin, as the result is unreliable unless an oscilloscope with a X10 probe is being used.

If the WAIT and HALT signals on a Z80 are high, that means it is not waiting or halted. These (along with the other control line signals) are active low, not active high. Note that a Z80 will only put a logic low out on the HALT output pin when it executes a HALT machine code instruction. WAIT is an input to the Z80.

Reset may well be affected by a logic probe unless the logic probe has a high input impedance. The reset pin is pulled high by a 220k resistor. Can you please test the voltage on pin 26 of the Z80.

The rest of the Z80 signals indicate that it is not fetching and executing instructions, which is not good.

Mark
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1024MAK
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Re: TS1000 with no image :_(

Post by 1024MAK »

bola_dor wrote: Sun May 10, 2020 7:09 am How do I rule out a faulty ROM ?
Only two sure fire ways:
  1. Try a known good ROM in a faulty machine, AND try the suspect ROM in a known good machine,
  2. Put the ROM in an EPROM programmer and see if the programmer can read the data okay.
Mark
ZX81 Variations
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bola_dor
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Re: TS1000 with no image :_(

Post by bola_dor »

1024MAK wrote: Sun May 10, 2020 3:26 pm ULA pin 14: it’s likely your logic probe does not accept the TTL logic level signal here. A 74HC04 works at normal CMOS logic levels, A TTL logic high is 2V to 5V. A CMOS logic high is ⅔ of the supply voltage or greater. A TTL logic low is between 0V and 0.8V. A CMOS logic low is ⅓ or lower of the supply voltage.
Thanks for the teaching!!! fortunately I I assembled it on a socket so on Monday I search for a 74LS04 type
As the signal on pin 6 on the Z80 is pulsating, the ULA must be producing a signal on pin 14. So yes, the resonator appears to be okay.
great..

The loading of the probe on pin 35 will affect the signal. Plus as stroebeljc says, this is not a digital logic signal. I never ask people to test this pin, as the result is unreliable unless an oscilloscope with a X10 probe is being used.

If the WAIT and HALT signals on a Z80 are high, that means it is not waiting or halted. These (along with the other control line signals) are active low, not active high. Note that a Z80 will only put a logic low out on the HALT output pin when it executes a HALT machine code instruction. WAIT is an input to the Z80.


Reset may well be affected by a logic probe unless the logic probe has a high input impedance. The reset pin is pulled high by a 220k resistor. Can you please test the voltage on pin 26 of the Z80.
understood ..

The rest of the Z80 signals indicate that it is not fetching and executing instructions, which is not good.
bad... can this be due to a faulty ROM.. is soldered on both my CZ1000.. so I have to be sure as is a dangeroussurgery...
Mark
Thank you!!!
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 :D
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1024MAK
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Re: TS1000 with no image :_(

Post by 1024MAK »

A failure of the ROM is possible, but normally this would result in the Z80 still attempting to execute code, even if the code is garbage.

Mark
ZX81 Variations
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:!: Standby alert :!:
There are four lights!
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bola_dor
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Re: TS1000 with no image :_(

Post by bola_dor »

1024MAK wrote: Sun May 10, 2020 10:19 pm A failure of the ROM is possible, but normally this would result in the Z80 still attempting to execute code, even if the code is garbage.

Mark
Z80 PIN 26 HAS 4.35v
But when I attach the logic probe it falls to 2.2v . So the probe is messing things up.. I'll exchange the IC with a proper TTL one .. and perhaps a diode to the probe? One with no significant tension drop? (I don't known witch)..
And retest...
Z80 is working good in another board.. and I have a third Z80 and this board isn't working with any one..
Thanks
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 :D
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