No video output from my TS1500

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1024MAK
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Re: No video output from my TS1500

Post by 1024MAK »

Kahenraz wrote: Tue Aug 04, 2020 3:39 pm I've been meaning to add a quality oscilloscope to my workbench for a while now. My research suggests that an entry level Rigol DS1054Z is a good unit.

Would this be sufficient for any diagnostics I would need to do on a TS1500?
Yes.
Kahenraz wrote: Tue Aug 04, 2020 3:39 pmWhat would I need for logic probes?
Do you mean, probes for use with the ‘scope or do you mean a logic probe?
The 1/10 switchable ‘scope probes that are supplied with new ‘scopes are normally all you need.

If you mean, logic probe, it depends on how much you want to pay. Generally the higher priced units offer more features, are better made and more reliable.

As well as the logic high/low indications, look also for pulse detection & indication, audible level sounder and if using on other equipment, TTL/CMOS level selection.

Mark
ZX81 Variations
ZX81 Chip Pin-outs
ZX81 Video Transistor Buffer Amp

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mcarlson_sb
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Re: No video output from my TS1500

Post by mcarlson_sb »

Kahenraz wrote: Tue Aug 04, 2020 3:39 pm I've been meaning to add a quality oscilloscope to my workbench for a while now. My research suggests that an entry level Rigol DS1054Z is a good unit.

Would this be sufficient for any diagnostics I would need to do on a TS1500?
Your research is correct. The DS1054Z is quite capable (even without, but especially after the 100mhz hack). It's my first oscilloscope and I'm quite happy with it. I admit the "auto" signal finder button is my most used :P Very easy for someone new to oscilloscopes to learn and be effective with quickly.

It has done incredibly well to help me diagnose, learn, and fix different aspects of my zx81.

Having multiple channels is great.
The probes and accessories that come with it are quality.

I haven't found a need for a separate logic probe.
The rigol has done everything I need so far.

Cheers,
Matthew
bola_dor
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Re: No video output from my TS1500

Post by bola_dor »

I guess any oscilloscope in the usd375 range as that will do the job :lol:..
I wonder if there is a Chinese model in the usd 50 to 100 range .. it could be even £100 is capable enough?
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
mcarlson_sb
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Joined: Wed Apr 08, 2020 4:48 am
Location: San Francisco

Re: No video output from my TS1500

Post by mcarlson_sb »

bola_dor wrote: Wed Aug 05, 2020 12:15 am I guess any oscilloscope in the usd375 range as that will do the job :lol:..
I wonder if there is a Chinese model in the usd 50 to 100 range .. it could be even £100 is capable enough?
You used to be able to find a good basic 10-20mhz oscope on eBay or the want ads for usd 50. But, these days they seem to be at least usd 100 and less available.

Then again, it's gotten to the point where a new digital like the Rigol is "inexpensive" (1/3 or less the price) compared to the equivalent professional grade Tektronix from a few years ago. But, admittedly still expensive as a hobby tool.

There are a number of cheap "pocket scopes" for usd 20 or less... But I've not heard good things about them. (I should probably get a kit and try one out just to know). Most are going to be in the 0-200kHz range.

Cheers
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1024MAK
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Re: No video output from my TS1500

Post by 1024MAK »

For analogue signals, a reasonable quality ’scope needs to be able to handle DC signals through to high frequency AC signals. All with a good linear response, and with a good accuracy. This is MUCH more difficult than it sounds (think top end professional audio gear on steroids). Hence why they cost a lot of money.

When measuring signals in say a ZX81, most of these are around 2MHz to 3.5MHz. Ideally the bandwidth of a ‘scope should be ten times the frequency of the signal you are trying to measure. Hence a 20MHz / 25MHz is often given as the minimum analogue bandwidth needed.

Why ten times the frequency? Because a square wave is made up of multiple sine waves. And in order to display a meaningful representation of a square wave signal, the higher frequency harmonics have to be able to be processed by the ‘scopes circuitry so that a square wave is displayed.

With digital ‘scopes, the sampling rate also has to be high enough so that the signal can be captured in sufficient detail. Otherwise a short pulse may be missed, or displayed as a long pulse. This can commonly be seen when a regular square wave clock signal is displayed with uneven pulse widths...

However, for the majority of faults, a logic analyser (which only deals with digital signal levels) can be used. And as these don’t have the expensive analogue input stages, they are far cheaper.

The humble logic probe, if used with care and experience, can tell you an amazing amount considering how low cost they can be.

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.
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Ed in SoDak
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Re: No video output from my TS1500

Post by Ed in SoDak »

I bought this logic probe kit from Digikey a couple years ago. I added probes and it fits nicely in a plastic case that held 100 rounds of .22 cartridges, with room to store the probes inside the case. Seems to have most the bells and whistles mentioned above. Price has gone up a couple bucks, but still not bad at $13. Digikey has low cost shipping options.

https://www.digikey.com/product-detail/ ... -ND/735276
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