Philips PM3340 2Ghz Digital Scope: Good/Bad?

[wazoo]

- Emo
I add 2 pictures to show what I see.
The 2nd shows a 50ohm patch from CAL to channel B (I take photo after change fron CH A)
The 1st is after bootup and pressed green AUTO

I found user manual and service manual, but I have not read it yet. 
I have published a short video on youtube "Philips PM3323 noise input"
thats it what I can see.





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- SaabFAN
No, it is not from Ebay. It is an opportunity from my workplace.
They will put some "old" electronic devices on trash, because of "out of calibration".   
They are kept stored for many years.
probably it is damaged because of age.

I have good skill on SMD desoldering 
when you say "ALL"..... it means that I need to be patience and replace "ALL" of them ??       hard work but not impossible


Thanks


Ok. then I need time to do that.... step by step
 

[SaabFAN]

Unfortunately, it means almost every one of the blue axial caps and all of the SMD ones. Only the bigger ones seem to be immune to the disease that these scopes fall victim to.

Luckily the caps only seem to dry out and not leak all over the board (probably because the cans are mounted upside down on the big mainboard in the bottom of the scope) and destroy traces and whatnot.
Another good thing is that it seems that replacing the caps is enough to make the scope work again. No major readjustments or anything that would require expensive test-equpment (although I managed to get my PM3320A calibrated with quick and dirty hacked together stuff like a 74AC14-Based Time Domain Reflectometer with a simple 14dB attenuator attached to it, an ebay signal generator and my DS1054Z as the "calibration-standard").

The bad thing about this is the type of capacitor used: Axial through hole capacitors made by Philips. Replacements cost about 40cents per piece in 25 quantity packs on Digikey, so I'm guessing that it'll take about 50€ and an entire weekend of soldering to get the scope running again.

The PM3320A seems to have no real problem in this regard, although adding some capacitors to the +15 and -15 Rails on the ADC-Board reduced the noise-level to that of my DS1054Z. But it also only operates at half the samplerate and is rated for 200MHz instead of 300.

[wazoo]

thanks SaabFAN

I did not open yet.
I saw pictures posted by Emo and can imagine how is it inside
have both Rigol 815 SA/TG and 1054Z osc  , with a signal generator. ( "low cost" basic tools for repair)

I found service manual too, that include check/calibration process
not read yet .... 700 pages !!!

But now I need some time to fix this scope.

good news if only capacitors replacement needed.
suppose that some of them needs to be 105C , right ??
when I open it i'll check them and write a BOM

I will try to post some pictures during process....   

[David Hess]

Can't this scope be used as a general purpose oscilloscope in the lower bandwidth range?

To some very limited extend only, and even then it's a very poor general purpose scope because of its timebase limitation, the 50ohms only inputs, and because it's no real-time scope. As others already stated it's a sampling scope made for RF analysis (primarily eye diagrams), something which back then was not possible to do with real-time scopes because their sample rate was too limited.

Most of those real time DSOs supported equivalent time sampling so while they had a high enough sample rate, their limited bandwidth was the larger problem.

These days the scope and its technology have long been obsolete. 2GHz real-time scopes have been available since the end of the '90s.

They are not obsolete if you want instantaneous non-destructive overload recovery and predictable frequency and transient response.

Sampling oscilloscopes are still useful for metrology like calibrating a reference level pulse generator used to calibrate a modern high bandwidth real time oscilloscope.  A modern 12 GHz sampling oscilloscope (Picotech) costs an order of magnitude less ($10k versus $100k) than a 12 GHz real time oscilloscope (Tektronix) so if its limitation are acceptable, it is a good way to get the maximum bandwidth for a given cost.  I admit that this compares a USB instrument to a standalone one but only because nobody bothers to make low end standalone sampling oscilloscopes and the difference between USB and standalone is not $90k dollars.  Does anybody make a 12 GHz real time USB oscilloscope?

An unusual feature of the PM3340 which makes it more general purpose than most sampling oscilloscopes is that it incorporates vertical delay lines (page 4-201 of the operating manual) allowing the triggering edge to be displayed.  The delay lines are ultimately what limits the input bandwidth.  The similar but older Tektronix 7S14 also includes delay lines limiting its bandwidth to 1 GHz.  Most sampling oscilloscopes require an external delay line to view the leading edge unless a pretrigger is available.  The exception is sampling oscilloscopes which support random sampling but I only know of two examples and they have their own interesting issues but no bandwidth limitation except for the sampler.

[wazoo]

hi
I am recovering this post because of my progress.
one year after my last reply, I am going on to repair our Philips PM3323 unit.

as SaabFAN said, the fist solution was to replace ALL axial and SMD capacitors.     
my first images were channels completely noise without any trace.  today  we can see a real signal "with noise", but is a great step forward.

my brother starts changing all axial capacitors with the radial version. (he said that all of them had lost capacity.)
then he checked both channels injecting a signal, following the trace up to the ADC board 
(the signal looks "good" and now the problem was on ADC board (P2CCD).  no input channels broken/burnt )
and then I changed all the SMD because of the same failure, all capacitors were completely "decap" and with leakage under them.
now we need to check what is the noise reason.

great, we are very happy !!   
I know that today there are better oscopes, more portable and lighter  , but I do not spent money for this unit  it was on road to the trash.
it could be a great tool for a RF entusiast as my brother, because this unit has native 50 ohm input and up to 300Mhz !!

(apology for my english but hope you will understand  )





capacitor removed with leakage near


new capacitor and cleaned section




some axial cap replaced with radial version

[SaabFAN]

You should check out the PM3320 Repair-Thread I opened some time ago when I had to repair my unit.

It now also contains some ideas and reports on how to upgrade the Processor of the instrument, which is a bit weak to be honest.

Link: https://www.eevblog.com/forum/repair/repairing-an-old-pm3320a/

[wazoo]

ok, thankU SaabFAN

then I will reply on the other Thread betther than this.   

sorry to re-open this old one.   
 

[David Hess]

I see that those capacitors really leaked.  They may have caused printed circuit board damage or at least high leakage which is going to cause problems.