Tektronix 2440 - good scope? or?....

[soldersmoke]

Hi guys,

I just ordered a tek 2440 from BMI primarily because I'm looking for a higher meg scope and the deal was pretty good, now I'm a tad nervous because of reading that they can be issue ridden, should I be worried? what are experiences of those who have them? any advice?

I hope this is the right forum to write this in. Thank you for your help.

[med6753]

I have it's little brother 100MHz 2430. It's an early DSO so it's memory and overall capability are inferior to today's offerings. But it works OK if you understand and take into account it's limitations.

Downsides: It's fan is LOUD. And there's a good reason for that. The CCD hybrids it uses MUST be kept in good airflow at ALL times or they self destruct. I found this out the hard way. I had the 2430 mounted such that I didn't realize that the vents on the bottom were blocked. I destroyed 2 hybrids before I figured out what was wrong. Luckily I had a parts mule and I found one on Ebay. And if you have the case off you must provide a fan blowing on those hybrids. They are that sensitive to overheating. 

[soldersmoke]

Thanks for the tips, have you considered modifying the scope for better airflow/less sound? or is that not an option?

[med6753]

Thanks for the tips, have you considered modifying the scope for better airflow/less sound? or is that not an option?

The airflow is fine as long as you don't block any vents in the case, especially on the bottom. Modifications are not really an option. You'll understand why when you get the 2440 and take the case off. It is packed TIGHT which it why it requires a large and noisy fan.

[David Hess]

I have a 2440 and never considered the fan especially loud.  It is not silent like many other Tektronix oscilloscopes from that age but it does not have the whine from the small fan often found in a modern instrument.

I think the most serious functional limitation of the 2440 and similar CCD based DSOs is their slow acquisition rate but it is still faster than real time so that is not a problem for general purpose use.  This does make them unsuitable for rare glitch hunting.  2 nanosecond peak detection makes up for this somewhat.

The excellent delayed timebase (1) makes up for many limitations of a short record length.  Also keep in mind that being a CCD based DSO, the record length and sample rate are independent of how many channels are active.

The biggest problem is simply the age of these instruments with the 2440 being between 25 and 30 years old now.  The original Dallas NVSRAMs either have dead batteries now or will shortly.  The aluminum electrolytic capacitors are beyond or nearing the end of their operating life.  However full documentation is available and calibration is relatively easy so these issues are solvable.

(1) Actually dual delta delayed!  In a DSO!  How cool is that?

[soldersmoke]

I'm not very worried about the slow acquisition time or anything like that, I've been getting by with analog scopes just fine for a while as I am mostly doing radio repair and working on fairly simple devices like that where I'm mainly concerned with using the scope to board bug hunt and tuning things up afterwards. I really liked the specs on the 2440 it seems like heavy overkill for what I do, being older doesn't scare me an iota, I know how it is to do a full recap, the tech-only parts scare me a bit, but I figure if I like this scope I'll buy a couple parts mules and use them for that.

Thanks guys!

[KE5FX]

I agree with David, these scopes aren't unusually noisy.  If it works now -- and if you keep it cool -- it will probably keep working.  I've had a 2430A in the rack for several years, used for various system monitoring purposes.   It's never needed any work.

The need to use a fan when servicing with the cover off can't be overemphasized.  Not all scopes need an external fan when running open on the bench, but this one does.

[med6753]

Noisy is a relative term I suppose. Compared to my other scopes...2465, 465B, 475..with silent caged fans....and 7904 and 7603N...fanless...the 2430, while it doesn't whine, certainly sounds like it's ready for takeoff.

[David Hess]

Noisy is a relative term I suppose. Compared to my other scopes...2465, 465B, 475..with silent caged fans....and 7904 and 7603N...fanless...the 2430, while it doesn't whine, certainly sounds like it's ready for takeoff.

My 2440 is about the same as my 2445B and 2247A; all just make a whooshing sound.  My 7904 has no fan but my 7603 does yet it is silent.  My 2230 has a fan which looks like it was made for a wind tunnel but is barely noticeable.

[LazyJack]

Yeah. It is a good scope. I actually use it for my daily work.
Obviously, you have to consider its age. But in some parameters, it is still on par or even better then a current cheap DSO. Like glitch capture or not decreasing the sample rate when using two channels. But no large memory or decoders or fft of course. Although you can get the 2402a Tekmate, which is actually a 286 PC that mount on top of the scope and gives computer control and a lot of additional functions, while still using the scope's screen a buttons.
Be prepared to recap the PSU and blow the x caps and Schaffner line filter. And possibly replace the nvram.

[soldersmoke]

I fully expect to have to recap the unit and do the usual - old machine - stuff. My reason for getting it? it was 160.00 and the way I see it absolutely nothing can touch that price/performance ratio. I'm not an explicit fan of old gear, but it seems like with this hobby, unless you've got money to burn, it kind of the standard to have a bunch of older stuff in the workshop. Still fiddling with a kikusui 60mhz analog scope that I keep saying I'm going to just junk for a parts unit. Oh well.

[David Hess]

The 2440's Autoprobe feature is something I wish could be found on modern oscilloscopes.

Its automatic triggering is not as fast as older oscilloscopes but still better than modern ones.

[Orange4sky]

Heads up to anyone with a noisy fan, It's probably the bearings which you can pretty easily replace. I have a low hour one and the fan is pretty quite but I've heard ones that whine a lot and it was the bearings.
 
NFM does one from a 2467 but the procedure is similar for a 2440 fan:
 
https://youtu.be/NjHbfbtNhyY?si=clD9tmtUoVAdah7F&t=1830