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| Advice on determining a logic analyzer for use with 1980s synthesizers. TLA715? |
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| sku_u:
I am looking for a logic analyzer that will be used for poking around inside vintage synthesizers and digital delays primarily from the 1980s. These devices are chock full of CMOS and TTL logic and contain processors such as the 6809, 8049, 8051, and Z80 derivatives. The delays use discrete logic and 4164 DRAM to playback a delayed audio signal. Chips like the 8255 and 8253 can be found inside of these devices as well. I want a logic analyzer to help troubleshoot faults and also to learn more about how these devices work. I am aware of the maintenance that older equipment requires so I have no problem with purchasing a logic analyzer that is 2 or 3 decades old. I am also familiar with HP-UX from HP's PA-RISC workstations and come from a background of vintage computing so I am well aware of what I am getting myself into. I am wanting a standalone device so an USB LA is off of the table for me. I missed out on an HP 16500C earlier this year which has accelerated my desire of obtaining an LA. I have been researching other options but I still am not sure what would be the most suitable device for me. A Tektronix TLA715 is available locally and I am considering this unit but I basically know nothing when it comes to the probes and adapters I need. It has two of the TLA7N4 (2GHz timing, 64k) modules installed and comes with several of the P6434 probes. Of course these probes are the ones with the Mictor connector and are of no use to me unless I buy or make a Mictor to 2.54mm adapter. I need help determining which probes would be most suitable for my application and I have allocated several hundred dollars for obtaining these probes. According to the pdf, "Tektronix P6400 P6800 P6900 Logic Analyzer Probes" from https://w140.com/tekwiki/wiki/P6434, it looks like most of the probes are compatible with TTL & CMOS levels. I need some sort of flying lead that can be attached to the pins of chips. I have made a little DIP-14/16 breakout PCB with 2.54mm pin headers that I can attach a probe to as well. The P6417 and P6418 appear to be something I can use but I would like to confirm. I am also making this post to see if there is a better LA for my use case. I have come across other units like the HP 16702B but I am not sure what features and specifications make one logic analyzer better or more preferable for my intended use than another. What about the 16500C? Are there any other analyzers that would be better than the units I've mentioned? Is the TLA715 even a good fit for my needs? I apologize for the very noobie questions but I figured this would be the best place to ask. I greatly appreciate any and all advice and help. |
| tggzzz:
When debugging/repairing equipment of that age: * measure Vcc voltage and ripple, using voltmeter and scope * use scope to verify signal integrity. 100MHz is sufficient, but be aware of the ringing caused by a 6" ground lead * thereafter use a logic analyser The LA width is the key spec. Ideally that should be 32 bits: 16 address, 8 data, Clk,CS/RW/etc. Speed isn't likely to be an issue. Even an early 80s LA is fast enough. Capture depth is more likely to be an issue. Early 80s LAs were just sufficient, with skill and imagination. Arm/trigger/filter facilities are vital. Modern cheap USB LAs are hopeless for that. The older HP LAs can be very cheap, but with all LAs be aware of the price of missing probe clips. Replacements might cost more than the LA! Summary: almost any working old "wide" LA will be sufficient. I'd look for any LA >HP1630 series with state machines >=25MHz. |
| artag:
I like the slightly later 16700, which seems to have all the best parts of the 16500 with some shortcomings fixed but without the high cost of the latest models. I started writing a more detailed answer but better descriptions have been written here in the past by more knowledgable people than me. Hunt them down ! Tggzzz is one of them :) There are lots of options in terms of digital and analogue capture. Get the deepest memory you can afford but be aware you'll sometimes limit the capture to keep the display time down. On these parallel bus processors you'll be using it in state mode though, which is far more efficient for memory use. There is an analogue scope option. It's often pricy and is very poor compared with modern scopes, but having it in the same box with time-aligned displays and cross triggering is very powerful on a mixed-signal device like a synth. I know nothing aboiut the Tek analysers so I can't compare them. Broadly though, from what I've seen on ebay, you'll pay less for a well-configured instrument but struggle to find upgrades later. I suspect the UI, like scopes, is a matter of personal opinion and depends what you grew up with. Some people describe the 16500/700 UI as complicated and hard to understand. I don't think this is true, but if, like me, you started with a 1630 and updated over time it will all be very familiar. If you have no prior experience of logic analysers I'd actually recommend doing the same thing. A 1630 (1630D for mixed signal, 1630G for software development) is very cheap and is explained in terms that makes it very comprehensible to a hardware engineer. Later models lacked that straightforward explanation and wrote the manuals in terms of usage examples. IMHO this denies you the basic understanding of what's going on that proper understanding requires. Once you start to suffer from it's limitations, replace it with a more modern one. But your synths were designed by people using that class of analyser - upgrading to a '90s machine is the lap of luxury, adding small probes, deep memories, bigger / better displays. |
| xtech:
Signature analyzer would be much more useful than ordinary logic analyzer. I have few logic analyzer including TLA715. I'm always doing everything not to start that monster but rather use handy DSlogic or Salaae Logic 16 (clone) - rarely you need to monitor all the buses in the serviced equipment. Buy good logic probe and logic pulser. Old HP current tracer and logic clip are also not much expensive but very useful. Let TLA715 rest ;) |
| tggzzz:
--- Quote from: xtech on June 15, 2024, 10:09:03 am ---Signature analyzer would be much more useful than ordinary logic analyzer. I have few logic analyzer including TLA715. I'm always doing everything not to start that monster but rather use handy DSlogic or Salaae Logic 16 (clone) - rarely you need to monitor all the buses in the serviced equipment. Buy good logic probe and logic pulser. Old HP current tracer and logic clip are also not much expensive but very useful. Let TLA715 rest ;) --- End quote --- A signature analyser is a very different beast, only useful for a pass/fail tests. It takes a single bit input stream, and uses an LFSR to generate a hash. If the hash is the same as the predefined hash, the module is working. The OP might like to consider whether a simple protocol analyser would help. A BusPirate5 is a starting point. --- Quote from: artag on June 15, 2024, 09:17:52 am ---I started writing a more detailed answer but better descriptions have been written here in the past by more knowledgable people than me. Hunt them down ! Tggzzz is one of them :) --- End quote --- Thamks, but don't regard me as an oracle! |
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