Electronics > Beginners

Oscilloscopes to stay away from? (spec: Tek 2337 question)

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Jschool:
Dave suggests you buy an old analog oscilloscope off of eBay, sticking with the major brands.  Easy enough.

But I've noticed some of the ones I find more desirable, like the Tektronix 2337, that upon reading some experiences from users it seems they're more difficult to work on or repair because they used a lot of custom parts.  And that the 475 and similar models used standardized parts.  Is there anything to this?

I really like the 2337 for its size and features, but I don't want to sink a lot of money into a beginner scope that can't be easily fixed either.

Fraser:
Peronally I don't recommend a Tektronix CRO for beginners unless it's very cheap. Don't get me wrong, they are superb scopes and are mostly reliable. The problem is many cheap ones are now 20+ years old and the odd failure is to be expected. In terms of repair the Tektronix oscilloscopes are a significant challenge as some of the custom hybrids and other parts are both rare and expensive. EHT modules are not an uncommon failure and can be hard to repair. More sophisticated Tektronix scopes are gorgeous but what do you do when a custom Hybrid or CCD dies ? Such failures are not uncommon amongst ebay auction units and that is often why they are sold on. Some fault symptoms can be hard to spot unless you really know your stuff, such as CCD failures....yes some use Charge Coupled Devices in their designs and not as cameras  :o

For the beginner or someone who wants a relatively easily repaired oscilloscope with good manufacturer support, I would recommend HAMEG CRO's. Not necessarily the latest models though. As a beginners CRO with 20MHz BW you won't go far wrong with one of the following:

HM203-x Beginner/basic functionality
HM204-x Intermediate functionality inc delayed sweep
HM205-x Storage CRO

The 30 x and 50x ranges are more pricey and the most recent models can have reliability issues with their EHT and focus circuits. HAMEG are now owned by R&S.


Many of the HAMEG range contained a nice component tester that works and isn't a gimmick.

The components used are nice and easy to find so repair will be possible for some time to come. Obviously tube failure would be a bummer but is usually rare except for drop damage. You can download the manuals and schematics for free from the Hameg site.

Do not pay too much for a HAMEG.... GBP50 will usually secure a decent one and many HM203 models sell for much less (~GBP20) or even free if you find someone having a clearout.

Oh, and for transparency.....I used to sell these when I was a student :-) Great customer support from Germany  :)

DaveW:

--- Quote from: Mechatrommer on May 23, 2011, 07:24:24 am ---
--- Quote from: Aurora on May 23, 2011, 06:45:12 am ---As a beginners CRO with 20MHz BW you won't go far wrong with one.

--- End quote ---
i keep hearing this, but i dont get this. if you go advance into things like FPGA, 20MHz is not a good thing at all! worst if you are keen into radio. i'm still thinking of how to crank out 400MHz effectively out of my 50MHz DS1052E. buy as much bandwidth as you can possibly afford! i agree with the rest of points though on repairing obsolete stuffs.


--- End quote ---

There are points where you need high amounts of bandwidth for debugging FPGA applications. However, most of the time you're looking at high speed data signals so a high speed logic analyser is the correct tool for the job. Similarly for radio, there are few times that you actually need to look at the signal output. Most of the time you are looking at the mixer inputs and output at the IF, so for most radio uses a 50MHz scope is plenty and 20MHz is enough for most applications.

It seems to be mostly a matter of finding the right age scope. Not so old that it's coming up to failure, and not so new that it's unrepairable! At least with the older Tektronix stuff there's a large online community that can help with fixing. Although as you say the Hameg support is excellent, always happy to provide service manuals...

tekfan:
Well the Tek 2300 series are great if they work. Small and very rugged. The ones that still work probably will keep on going for a long time. This series has specially high performance power FETs selected for the vertical amplifier. If they fail and you replaced them with a similar one, the max bandwidth would be seriously degraded. The low frequency signals would be unaffected. But I think if you looked hard enough you could find the correct FETs. They have a slightly reduced CRT (not the standard 10x8cm type)


The 400 series is probably the most well known for it's reliability, ruggedness (all metal case), etc.
465a/b - 100MHz, dual trace
466 - 100MHz, analog storage, dual trace
468 - 100MHz, digital storage, dual trace, RS-232 output
475 - 200MHz, dual trace, 2mV/div sensitivity
485 - 350MHz, dual trace, internal 50ohm termination (quite a beast but still somewhat portable)

All the models have delayed time bases

You can't get anything wrong with buying anyone of these. They are very easy to repair, have linear supplies (none of that noisy switching stuff). The 465 now almost holds a legendary statusamong Tek scopes. It's been the world's standard delayed sweep dual trace scope for nearly 30 years.

2200 series are a bit more flimsy than the 400 series since their front panel is plastic (same as the 2300 series)

2212 - 60MHz combined analog/digital storage scope
2230 - 100MHz, same as above
2232 - 100MHz, same as above but a bit more advanced with softkeys
2235 - 100MHz, analog, general porpouse, basically a revised and lightweight 465
2236 - 100MHz, same as 2235 but with added frequency counter, timer, multimeter

All of them have 2mV/div sensitivity, delayed time base, all the units weigh as little as 8 kilos

A couple of years ago I bought the 2236 on American ebay. I live in Europe so the shipping and customs cost almost as much as the scope. But it was worth every single penny. The really nice feature of the scope is the counter. Press a button and you get a 8 digit readout of the frequency. It also does period and time difference measurments, gated frequency or period measurments of short bursts. The scope even succesfuly triggerers on signals at almost 150MHz.
If you want to measure the voltage of channel 1 just select CH1 volts and set the coupling switch to DC or AC, whichever you would like to measure. The AC range is even true RMS and works to about 200KHz. On the side of the scope are two jacks for standard shrouded multimeter probes. With the press of a button you can measure again DC or AC (autoranging 5000 count), or you can measure ohms to 2 Gohms. No milliamp range but what else do you want for a 30 year old scope!

This isn't a review but I just want to help people to decide which scope to buy.

Repair of the 2300 series scopes is also not a problem. Most of the ICs are standard off the shelf parts apart for some of the EPROMS. Even the time base switch was originally used in ham radios. All the electronics are found on a couple of big boards. The design philosophy was to put all the circuitry on a single board and get rid of the unreliable connectors and ribbon cables.

Probably the only thing that can go wrong in one of these is the switching power supply. Again standard parts and easily repairable.
The CRT is probably one of the more reliable parts of any scope (that is if you don't throw it down the stairs).

A bit more on the Hameg scopes
We have a lot of HM303s (35MHz). Sadly they haven't stood the test of time. They were bought new somewhere in the 90's. One third of them developed problems. Either reduced bandwidth, bad attenuator contacts, weird oscillations of the time base.
The 205 series is much better. We've never had any problems with these. They are nice scopes but are higher in price on the second hand market. The only drawback is the low bandwidth.







Fraser:
Mechatrommer,

Regret FPGA's etc are well away from my area of experience and I agree that a 20MHz CRO would not suffice for the high frequency stuff.....but then what bandwidth CRO would ? With 500MHz square waves on my PC's bus I would need one heck of an expensive CRO to cope with that .....I don't think CRO's are the best tool at those higher frequencies  ;)

Now as for RF at 400MHz...you are now talking my language  8)

I carry out repair and development work up to 1.7 GHz and some ISM band 2.4GHz and K/Ku SHF stuff now and again. When carrying out diagnostics at the full operating frequency, I would not be looking for any form of oscilloscope as my primary tool. If accurate level measurement is needed, I use a True RMS RF Millivoltmeter or Power meter. If frequency is important, I use a UHF or SHF frequency counter with GPS disciplined oscillator reference. And finaly, for linearity and filtering tests I would reach for my Advantest R4131D 3.5GHz spectrum anlayser and hunt for the tell tales of distortion spurii, harmonics and filter leakage. I would only use an analogue CRO when looking at the lower frequencies in the IF stages of the RX or TX and even then a spectrum analyser can be more useful. For reciever testing and repair it is often possible to work at the lower IF frequencies in order to diagnose issues in preceeding RF stages. You are effectively using the receivers own RF downconversion for diagnostic purposes so a CRO would be usable.

The bad news is that the cost of a DS1052E pales into insignificance when looking to buy RF test kit capable of 3GHz working. My Advantest R4131D originally cost GBP15,000 and, 10 years later, now costs around GBP2,000 t0 GBP3,000 on the used market. I can see why you would like to use the DS1052E for the role at 400MHz but considering it's limited bandwidth, sampling rate and the fact that it is a budget DSO, regret that it is definitely not the tool for the job.

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