Best oscilloscope choice?

[ayeaye]

Ok, i decided to solve that oscilloscope problem for myself. This is everyones problem, for anything not changing one needs a multimeter, but the next thing one needs is an oscilloscope, to measure anything changing.

So i bought an old oscilloscope from ebay. This is a 2 channel 20mhz oscilloscope hitachi v-222, and i got it for $50 without shipping. 20mhz oscilloscopes are one of the cheapest, because they produced them the most, often cheaper than any older vintage oscilloscopes. This oscilloscope was made some time in 1980's. But such oscilloscope is not outdated, they produce and use very similar analog oscilloscopes today, and nothing essential is changed in the electronics there.

Hitachi oscilloscopes are somewhat smaller, it weighs 14 pounds or 6.5 kg, but there are even lighter ones, neither does it take much room at the corner of a table.

$50 is cheaper than most usb oscilloscope, pocket oscilloscopes or scopemeters. But such cheap ones are not more than toys, less than 5mhz real bandwidth, many other things worse. Some have only one channel and even no external triggering. But this one is a fully functional oscilloscope with full power, no need to worry about any bad shortcomings. Robust and decoupled from everything, thanks to good old transformer.

So i may shortly describe the experience i got, in buying such things. Its better to buy from sellers who have sold at least several thousand items, with a possibly higher rating. But what i considered the most important, was that there were evidence that the oscilloscope were tested. That there are pictures of test signals on the screen, and sometimes even some small faults found is rather positive than negative, because this confirms again that the item was tested. That the basic things work, this is important for two reasons. First one may not be good at repairing the oscilloscopes. But even when one can do it well, when the basic things work say after 30 years, then this confirms that it is not made of any bad series of components, and thus the electronics may work a 100 more years without repair.

When buying old oscilloscopes, what you mostly get, is only the oscilloscope itself, no probes, no power cord, no manual. But this is not a big problem, as one can get two probes for $8, the higher frequency the better, a standard computer power cord usually fits well as a power cord, and the service manuals of most of the more widespread old scopes can be downloaded from internet for free. So you get all the description, calibration instructions, and circuit diagrams.

So in what shape was my scope when it arrived? It switched on and showed two lines on the screen, so i sighed with easy, at least the power supply and the crt tube works, without these it can be unrepairable. So then i took some wires, as i have no probes yet, and connected the calibrator output (every scope has a calibrator which generates a 1khz 0.5v square signal) to the inputs of both channels. There was the first disappointment, the second channel didn't work at all.

But then, after i switched all the switches many times, absolutely everything started to work. I also tested it with an AC wall adapter output. The trigger level adjusted fine on both channels, and the trigger was completely stable. On the old scopes which have stayed unused for many years, the switches get oxidized or dirty, whatever happens because of not moving them. This is normal, after moving them many times they work well again, even no need for a contact cleaning spray. In case if that is necessary, it should be a proper one which both removes oxide and lubricates, but if really necessary, one can buy such for less than $5.

So now i have a fully working 2 channel 20mhz scope, works well and looks nice too. I see that the knobs are almost not worn at all, so likely it is not even used much. I guess most old scopes are not much used, only a small part of then had been used intensively. I'm very happy with that scope, i never regret buying it, it rather makes me feel good, and more human-like, kind of. And doesn't it look nice?

So i hope there was some use of what i wrote here, for anyone who also needs to buy ones first oscilloscope.

[Pirate88179]

Ayeaye:

Good post.  I am sure this will help a lot of folks.  I already posted about mine from ebay for $100 and I am very happy with it. (Tektronix 2213)  Mine is from the 80's also and is 20 MHz.  I am sure yours will do what mine does just fine.  $50 is a real deal.

Thanks for sharing,

Bill

[ayeaye]

Thank you Pirate88179

As much as i know, Tektronix 2213 is 60 MHz, but i may be wrong. Tektronix 2205 is 20 MHz, as much as i know. Anyway, Tektronix started to produce the scopes with that form and design, in the beginning of 1980's, then they started to make similar ones in Japan. This is a typical 1980's scope. What concerns using it, my scope is almost identical to these Tektronix's, the knobs do everything exactly the same, calibration is similar as well, the only difference is the location of the knobs. Inside it is a bit different, Tektronix has one big board, mine has two smaller boards one on another, one of these is upside down.

Many companies made very similar scopes, so one can buy any 2 channel 20 MHz or more scope by Hitachi, Iwatsu, Kikusui, Hameg, Philips, Elenco, Tenma, Leader, Trio, Kenwood, BK Precision, Beckman, i guess i named the most widespread ones of that type of scopes. Search like "Hitachi oscilloscope", and then the cheapest. A lot to search i know, but not so terribly lot. Tektronix one cannot find that way, there are too many plugins and accessories. Tektronix also used to be somewhat more expensive, but it is high quality and its manuals are very detail and good.

In my opinion, what concerns the cheap USB oscilloscopes, then their rise time is quite good, also they tolerate at least 300 volts input voltage the same as big scopes. The rise time doesn't mean an equivalent bandwidth with the analog scope with the same rise time though. Because the analog scopes can rise and fall much faster with less vertical distance. So it is considered that the bandwidth of the digital scope is its sample rate divided by 10, but because of two channels, it has to be divided by 20. Thus a typical 40 Ms/s cheap USB scope really has a bandwidth only 2 MHz, of an equivalent analog scope. Not 20 MHz as it is said, this 20 MHz may only be true, what concerns the rise time.

The cheap USB scopes also have not quite good electronics, with too much all kind of interference. They often have a faulty software. They don't work with every USB connection, like that in virtualbox. They are coupled to the computer's ground, which some may say is not a bad thing, then others may still want to use a floating scope. If they know what they are doing, that is. And they are inconvenient, have to be connected to the computer, software started, etc.

The USB scopes they consider "cheap scopes", and thus they make them as cheap scopes. That is, they don't care about the electronics quality, or the software quality. But when buying an old scope like mine, in spite its cheap, you get a scope which once wasn't cheap and was not made or designed as cheap. So when it is made to work, it is a good scope with high quality. A serious measuring equipment, not a toy by any means. Its really sad that they don't make good low end scopes any more. Once a beginner could get some cheap one channel 10 MHz analog scope (usually with an external triggering), which was slow and had a minimal functionality, but otherwise was a good and decent scope. But today, the beginner is supposed to use a cheap USB or pocket scope, which is a lot inferior to that 10 MHz analog scope.

[TinselKoala]

Yep, I have a 2213a which is 60 MHz and I believe that the 2213 is the same. I paid 125 Canadian for mine from Active Surplus on Queen Street East in Toronto, lugged it home on the subway. It's a lot lighter than many old scopes so it wasn't too hard.

There is a difference in the input attenuator board, the 2213a has the same switches and attenuator/preamp board as the 2215 instead of the 2213. This caused me a little difficulty when I had to replace an input FET on one side... I had the Service Manual for the 2213 and when I opened up my scope it was different inside! But the 2215 Service Manual had the right information that I needed, including how to disassemble those complicated range switches.

The scope is excellent, I use it a lot for general purpose work since it is so easy to use, warms up fast and the delayed timebase and variable-holdoff trigger functions are great to have. Crisp and bright display too.

[Pirate88179]

Yes, I made an error...the 2213 is 60 mghz.  What the heck was i thinking?

Bill