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Oscilloscope advice

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Gandledorf

New Member
I'm currently trying to get ahold of a scope (my first!) through an auction, and it looks as if I might be set to win it, and wanted some advice.

It's a Tektronix T922R listed as "partially working, very servicable", I'm hoping this means it just blew a fuse. If not, how hard would it be to get one of these back in service? Would it even be worth my time? Does anyone have any experience with a T922R? Where can I buy some probes for it (the unit doesn't appear to have any ATM). I could really use some advice on this, if anyone has anything to say on the T922R, or scopes in general.
 

ljcox

Well-Known Member
Oscilloscope

I have not had experience with the one you mentioned, but I bought a second hand HP 1740A some years ago. It has failed a few times.

Several transistors and resistors have failed and I have been able to find and fix each fault. However, this scope is not supported by HP and Aligent have stopped supporting it also. So I suggest you check on the support and whether it has special ICs or other components.

The HP one has many transistors that have only a HP number listed and very basic info on these transistors in their handbook. So I have had to find suitable replacements. Not easy when they give only such basic info. But not impossible either.

Len
 

stevez

Active Member
I was lucky enough to obtain my first two scopes from friends- who could explain the minor problems and how insignificant they'd be in my situation. As I sought to purchase a third some friends, familiar with this type of equipment suggested a number of Tektronix models and then listed the plug-ins. This equipment is pretty basic from their point of view but also pretty common. I learned that I could purchase a scope and needed plug-ins for between $75 and $150. For $150 a local surplus dealer would provide me with the scope/plug-ins and said it would be in good working order - if not he'd get me another. (dealer is really good to local hobbyists).

I am an amateur radio operator. I obtained my most recent scope when I mentioned my interest to a fellow ham. I paid $60 for a nice Hitachi - dual trace - more than I can handle at the moment. Hamfests are good places to look for them because you can usually talk face to face with the owner.
 

Dean Huster

Well-Known Member
Tek T900-series

The six models of the Tektronix T900-series (T912, T921, T922, T922R, T932, T935) are all pretty easy to work on. The T922R is just a T922 with the guts rearranged into a standard 19" rack-mountable package. Oilfield wireline services probable bought more T922Rs than any other segment of electronics and they loved them. By racking the circuits in the T922R, the biggest problem of the T921, T921 and T922 is eliminated: cold-soldered power supply connectors. The female P/S connectors in the non-racked scopes had a nasty habit of working loose from the PCB. I always resoldered these whenever one of those models came in for service.

The T922 and T922R use the same service manual. It's a dual-channel, single-timebase, 15MHz bandwidth scope with automatic TV sync available in the trigger circuit. A lot of folks didn't like Tek's T900-series scopes, but they were comparing them to their usual high-end stuff, which was hardly fair. The T900s were developed as a low-end scope to replace the Telequipment scope line made in the U.K. which was a burden on the Tek profit margin.

Dean
 

Gandledorf

New Member
Well I lost the auction. :(

How hard would it be to build a small digital oscilloscope, which fed the data into a computer. Would this be a viable auction? Is it as easy as sampling some voltage with an ADC, and then passing it via RS232 to the computer?
 

Dean Huster

Well-Known Member
Sound card

With most computers, you can use the input to the sound card as the input for a rudimentary oscilloscope, and since the card is stereo, you have a dual trace scope. There may be some software out there that will provide a timebase and voltage scaling so that it actually works more like a conventional scope. Wonder if anyone can add to that fact.

Dean
 

ljcox

Well-Known Member
Oscilloscope

I have designed a digital storage unit that can be used as a digital scope.
I don't intend to input it to a computer, although that would be possible with a few changes. I intend to generate a repetative waveform from the memory contents so it can be displayed on a normal scope. What I want is to capture non repetative events that can't be seen on a normal scope.

My next step is to design a PCB once I understand how to use the PCB design software.

A German company Wittig Technologies sell a device called Oszifox that stores repetative or non repetative waveforms and outputs them via RS 232 to a computer. They supply the software. I bought one but returned it since, although it worked well for repetative wave forms, it did not work on non repetative waveforms.
My supplier changed it for another one but it had the same fault. I proved to them that the data output was incorrect when it was in the non repetative mode. It must have been a firmware problem. So they gave me my money back.

Len
 

laroche73

New Member
digital scope adaptor for PC

Gandledorf, here are a few links. Just lost out on a scope auction myself a few weeks ago :( :

http://www.bitscope.com/ - Bitscope is an open-source design, but there are a few parts you need from them (like the programmed CPLDs). Good open-source software support on the PC end.

http://www.freepcb.com/eebit/home.html - logic analyzer design

http://www.piclist.com/techref/tools.htm

http://slashdot.org/askslashdot/01/12/07/191220.shtml - lots of comments here on using soundcards & other methods to make an inexpensive PC scope. Some advice is good, some questionable, many links missing.
 
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