17 Aug
2015
17 Aug
'15
10:32 a.m.
From: drlegendre
Sigh.. and here I sit, yet again, with neither a logic
analyzer
I've bought Tek 1240's (which are really nice units, although of course
without the capabilities of today's - but still a lot more powerful than the
earliest LA's) on eBay for as little as $25 (albeit without leads), and I
gather there are modern units which plug into a PC with a UCB port for not
much more money.
Yes, a lot of the older machines were built without benefit of them (pretty
much all their builders had was 'scopes), but there are so many things where
one cannot easily create a 'scope loop, and for investigating those, a logic
analayzer is the perfect tool.
It's just a critical tool to have if one is going to _repair_ old computers -
only slightly less critical than a VOM. No ifs, ands or buts.
Noel
17 Aug
17 Aug
7:37 p.m.
New subject: test equipment / Re: Z80 / Z84C Swap (Doh!)
On 2015-Aug-17, at 3:32 AM, Noel Chiappa wrote:
Well, a DSO (i.e. any modern scope) obviates the need to create scope loops in servicing
as we used to have to do with analog/non-storage scopes.
I suffered with a low-end Tek analog scope until a few years ago; have been using a Tek
DSO for the last few years.
While there are occasions I'd like to have an LA, I can't say there are any
instances where I've had to have an LA (I still don't have one).
From:
drlegendre
Sigh.. and here I sit, yet again, with neither a
logic analyzer
I've bought Tek 1240's (which are really nice units, although of course
without the capabilities of today's - but still a lot more powerful than the
earliest LA's) on eBay for as little as $25 (albeit without leads), and I
gather there are modern units which plug into a PC with a UCB port for not
much more money.
Yes, a lot of the older machines were built without benefit of them (pretty
much all their builders had was 'scopes), but there are so many things where
one cannot easily create a 'scope loop, and for investigating those, a logic
analayzer is the perfect tool.
It's just a critical tool to have if one is going to _repair_ old computers -
only slightly less critical than a VOM. No ifs, ands or buts. From a usefulness perspective I'd get a DSO long
before an LA.
7:54 p.m.
New subject: test equipment / Re: Z80 / Z84C Swap (Doh!)
From a usefulness perspective I'd get a DSO long
before an LA.
What you use is a personal choice IMHO.
I've used DSOs (never owned one), both HP and Tektronix and never really liked them. I
use
an analogue 'scope only rarely in classic computer repair. But my (many) logic
analysers
are used almost all the time.
As I said, personal choice, what works for you is what you should use.
One thing though. No piece of test gear will do more than provide evidence of
what the circuit is doing. It will not tell you 'U38 is faulty' or whatever. You
still
need a good understanding of the circuit, how it should work and what you
should be seeing so you can tell if the 'scope or LA traces are right or wrong.
-tony
8:07 p.m.
New subject: test equipment / Re: Z80 / Z84C Swap (Doh!)
On Mon, Aug 17, 2015 at 1:54 PM, tony duell <ard at p850ug1.demon.co.uk> wrote:
One thing though. No piece of test gear will do more
than provide evidence of
what the circuit is doing. It will not tell you 'U38 is faulty' or whatever.
In principle that was where HP was trying to go with signature
analysis back in the 1970s. The problem has since been solved by
making the entire product a single FRU (Field Replaceable Unit).
"He fixes radios by THINKING!"
- Someone who had a young Richard Feynman fix his radio,
as quoted in his autobiography _Surely You're Joking, Mr. Feynman!
(Adventures of a Curious Character)_
18 Aug
18 Aug
4:09 a.m.
New subject: test equipment / Re: Z80 / Z84C Swap (Doh!)
One thing
though. No piece of test gear will do more than provide evidence of
what the circuit is doing. It will not tell you 'U38 is faulty' or whatever.
In principle that was where HP was trying to go with signature
analysis back in the 1970s. The problem has since been solved by making the entire product a single FRU (Field
Replaceable Unit).
:-(
"He fixes radios by THINKING!"
- Someone who had a young Richard Feynman fix his radio,
as quoted in his autobiography _Surely You're Joking, Mr. Feynman!
(Adventures of a Curious Character)_
When I first read that, _my_ first thought was 'Is there any other way to fix
radios?'
-tony
17 Aug
17 Aug
8:01 p.m.
New subject: test equipment / Re: Z80 / Z84C Swap (Doh!)
On Mon, Aug 17, 2015 at 1:37 PM, Brent Hilpert <hilpert at cs.ubc.ca> wrote:
I suffered with a low-end Tek analog scope until a few
years ago; have been using a Tek DSO for the last few years.
While there are occasions I'd like to have an LA, I can't say there are any
instances where I've had to have an LA (I still don't have one).
From a usefulness perspective I'd get a DSO long before an LA.
I'd generally agree.
In my experience, during development of new digital hardware of any
complexity, both a DSO and a LA are extremely helpful, but for
diagnosing failures of previously working hardware, the DSO is usually
more important.
If a person has any reasonable business justification, a Rigol
MSO1104Z mixed-signal oscilliscope (100 MHz four-channel DSO with
integral 16-channel logic analyzer) is under $1000, and for another
$230 you can get the model with the -S suffix, which also includes a
two-channel waveform generator. I generally don't recommend cheap
Chinese test equipment, but the Rigol stuff is actually pretty good.
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ard＠p850ug1.demon.co.uk -
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