More Portable Oscilloscope Information
The 2000 series oscilloscopes are not as rugged as the old tube scopes. Nor are they as easy to repair. A buyer must be aware when purchasing a surplus or used 2000 series oscilloscope of the possiblity of not being able to get parts or service for it. Many of the ones for sale are physically damaged in one way or another. For instance, most of the 2236 scopes that I have seen have one or both lid latches broken. Many 460-series have been dropped on the back legs, which cracked the back subpanel. It is clearly buyer-beware when it comes to spending money on a 400 or 2000 series scope.
There are a lot of 2000 series scope for sale. Some consider these "throw-away" instruments, meaning once they break, they can't be repaired. In some cases this is true. But there are a few of us out there who recognize that this is not acceptable, and can keep a buyer's scope up and running, even if it means repalacing it.
See a recorded demo of a 2465 using this C1001 Camera
Won't play? Download Windows Media Player Here
Because there are so many of the 2000 series oscilloscopes for sale, I felt that I wanted to do something to bring an offering to the market that said "I'm different." And so I have introduced my "BlackTek" Line. These scopes are not just painted black. The have been especially selected as the best I could get. Then they have been meticulously gone over and prepared for service. Finally they have been given a complete calibration. Because of the care that has gone into them the prices will be a bit higher. They have the same 30-day no questions asked return priviledge and the one-year prorated warranty. And for an extra $100, the warranty can be extended to 2 years!
Walter Shawlee of Shere Research In Kelowna, B.C. says this about the portables:
"We have fixed and restored dozens of these (2335, 2336, 2337), and
they remain very popular both with us and with customers, mainly for
their compact size, good performance and ruggedness. The CRT is quite
small (but well shock mounted), and the mesh accelerator produces a
poor beam line (you can actually see the mesh in it on the CRT), but
even with these display issues, it is incredibly handy sometimes, and
an excellent field scope.
The key problems are these:
1. Case latches and lid hinge. A hideous and fragile design, always
broken, and no readily available parts for them. This is the weakest
aspect of these 3 models, and is the only time I have ever really been
disappointed in Tek's mechanical design. The latches are almost
always broken or missing on used units, so watch for this when buying one.
2. Troublesome fan. These are quite unusual fans, and go very noisy
over time. great when they work, but when they don't, it sounds like
two cats locked in mortal combat.
3. Wicked vertical section. This uses a super match high Ft dual
transistor in the front end, it is basically unavailable, so if it
goes bad, you are in real serious trouble. The bandwidth of this
stage is tricky, and it is quite easy to have a "working" vertical
with terrible bandwidth. Just be careful in this stage, it requires
real attention during alignment, and if the transistors have been
replaced with something else along the way, it will never go to full
bandwidth.
4. Troubleshooting and repairing it can be a bit time consuming, as
the mechanical assembly is designed for compact size, not ease of
service (imagine a minature 465, and you have some clue). Anyone that
has removed the top board and all those shaft extenders to fix
something, or has had to replace the nightmare multi-pin HV multiplier
knows what I mean.
5. Useless LCD display. Almost 100% of them go bad in the center, and
the backlighting is terrible (that, at least, you can easily upgrade).
The lid display idea was clever, but not well spec'ed for parts.
Watch for a big discolored oval area in the center of the display on
the 2336 and 2337 if you are buying a used ebay unit.
The big features are these:
1. Excellent portability, easily carried and well protected when the
lid is closed (assuming the hinge and latch are working). Small, but
still full featured.
2. Good performance, nothing special in the way of tricky features
(unless you fancy the extra display bits in the lid on the 2336 and
2337), but works very well in the field, and has a very nice and
familiar control layout.
3. Rugged. If working, and not immersed in water, they seem to run a
very long time. Most of the mil-overhauled units I have seen had at
least 3-4,000 power-on hours on their internal time meter, and still
worked great, with good CRT brightness and were well within spec. We
even fixed one that was filled with mud, it came back to life with
only a bit of trouble.
4. Modular design. If you have spares, it can be handy, as the scope
is made of just a few snap together modules. Actually getting to them
is not so easy, but it is a far cry from the forest of interconnect
wiring in early 400 series portables.
In general, I give these high marks, but you have to pick your units
carefully when looking for one to buy. if getting one off ebay, watch
carefully for lid and hinge problems, and a discolored LCD display.
Unless you are brave, do NOT buy one with no visible trace, this has a
high risk of being HV multiplier failure. If you see one with two
bright traces, I'd risk it, especially if in clean cosmtic condition.
all the best,
walter
sphere research
(Reprinted with permission)
Other problems that are hard to spot until you are the new owner:
400-series:
All of these have lights behind the vertical attenuator dials showing what the setting is. These are actual lamps, not LEDs anfd so can fail, and do. Replacement is a bear, and a scope with one or more of these non-operational is hard to use.
Knobs with scales on them that have been improperly cleaned will have the markings removed. This makes it hard to concentrate on the problem at hand, when you can't tell the setting.
The 465 has two sweep generators, the 475 and 485 have three. These are used on various positions of the sweep timing switch and sweep mode. If one or more is not working, it can be tough to tell unless you are able to test ALL sweep speeds, which should be done BEFORE buying.
2000-series:
Same about knobs. Replacements for broken or missing knobs on these scopes is difficult because the knobs are special, with different molded-in shafts and couplers. They cannot be replaced with ones from Radio Shack!
All this means that the guarantee is of primary importance. All my scopes arrive not just working, but as near to factory as I can make them. I have a bin full of ones that didn't quite make it. | 
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