#7 Philips Scope PM3219 Repair - Part2(2)

[@cornellungeanu1620]

I have a similar oscilloscope and I wanted to have a look on the features but I can see you are very good with electronics. My father was an electronic technician and it used to repair radios and tv's. You remind me of him. Thanks for sharing your skills with us.

[@dl7majstefan753]

Thanks for your nice comment and all the best for 2020

[@RalphWLundvall]

Demonstrating delayed time base @54:09 is very helpful! I picked up a PM 3217 only to find its DTB controls are very different from Tektronix scopes.

[@dl7majstefan753]

Hi Ralph, meanwhile i gave this 3219 to a friend of mine and now i´m possessing also "only" a 3217; i´ve enough (faster) storage scopes. To the DTB: There is no essential difference to the TEK-scopes; the delayed timebase may be triggered a) with a set and constant time delay related to the main TB b) with a separate triggering of the DTB after the set time also related to the main TB. The old analog TEK-scopes work similar, only the designations may be different.

[@RalphWLundvall]

@@dl7majstefan753 Amazingly everything works on my 3217. When I went to test it out I expected much worse. Almost everything, hold off not working. Still $80 well spent.

[@dl7majstefan753]

@@RalphWLundvall Hi Ralph, how did you determine the non-working Hold Off (HO)? Take a picture of any stable oscillation between 50Hz and 50MHz and rotate the HO: On the right side stop the picture on the screen should be brighter than on the left side stop of the HO. At lower time base rates the picture also will start to flicker more intensive (left side of HO) than on the right side of the HO.

[@RalphWLundvall]

@@dl7majstefan753 Using the tutorial at channel EEVblog #159 between 7:20 and 8:00 I expected similar results. I revisited my scope based on your question - I set Amplitude/Div to 1 volt and Time to 2 ms. The trace is a straight line. When HO is turned fully counter clock wise the trace has a slight flicker. fully clockwise no flicker. So it does have an effect but I'm at a loss at how this is usable. Additionally, as you suggested, when fully CCW (longest HO setting) the brightness of the right side is less than the left side but so slight only by dedicated study and chin rubbing is it discerned to be so. Only at 1 volt and 2 ms are this subtle things noticed. Any other combinations - nothing my eyes can detect.

[@dl7majstefan753]

@@RalphWLundvallso it seems, that the HO is working! The use is in special cases, when the signal is not purely repetitive to let the MTB start at a delayed position to avoid triggering too early. Example: you have a digital signal with data signals in telegrams, which are varying in time; there may happen that the new trigger is within the end of the "old" already triggered telegram. A HO is there useful to trigger later after the old telegram and before the new telegram.

[@campbellmorrison8540]

I noticed it only had 2 pins on the power plug in the 1st video and wasnt impressed, Ive never seen that before, I think I would change that. Very good thorough analysis. I have to say in my experience those old Philips caps in the smaller sizes are generally bad but you are quite right its getting harder to get axial replacements.

[@dl7majstefan753]

Many Philips Equipments have only two pins; the case is therefore isolated and not grounded! That´s made intentionally to avoid ground loops but requires some considerations in the measurement arrangement. Isolation of the scope is good enough (safety class II, double insulated)

[@campbellmorrison8540]

@@dl7majstefan753 Ive not seen that in New Zealand, perhaps local regulations forced this to be changed before import. I'm not sure how a scope can be double insulated if the metal case can become live?

[@dl7majstefan753]

@@campbellmorrison8540 The metal case is painted and there are ground connections on the front, which have to be grounded before use! The double isolation is referred to the primary wiring and transformer isolation. That´s all i know.

[@dayleedwards3521]

I too have spent many hours rebuilding older analog scopes, usually under duress as I am unable to find a new digiital scope that is useful/compatible with the repair of radio equipment. These modern, and "better" scopes without exception use noisy and sometimes unshielded switch mode power supplies, and the digital hash is immediately injected into any radio under test. I have avoided Philips products, they tend to have unusual in house mechanical components generally unavailable and hard to replace with generics, although all Philips products do perform very well. Thank you for a very enjoyable ihr 9mins.!! .

[@dl7majstefan753]

Fully agree!

[@propentaxian]

No calibration after replacing all those caps ?..

[@dl7majstefan753]

I did a performance check as mentioned in the video at 00:59:00; all was OK so no need for an alignment.

[@didierpenchenat6494]

Right thing at the end, you really deserve a good beer, nice video ! Yec'hed mat !

[@dl7majstefan753]

Thanks!

[@sincerelyyours7538]

Very interesting series! I just found your channel and was happy to see you did a series on Philips analog scope restoration. I have an equally old Leader LBO 525 two channel scope, not quite as fancy as your Philips, that has dirty pots making the display very scratchy and the traces unreliable. The problem is that they are the sealed type with no holes in which to pump contact cleaner. How do you clean such pots? Replacing them seems impossible given their age and specialized function.

[@dl7majstefan753]

Up to now, i´ve no experience with this. But in the WWW i found the hint, to melt a small hole in the side/corner of the case with a small tip on a soldering iron - do not drill! Then apply some cleaner, let it dry and seal the hole again.

[@sincerelyyours7538]

@@dl7majstefan753 Danke. Seems like I could do that with a needle point tip used for SMD soldering which I just happen to have. Excellent idea, I shall try that, thanks!

[@yusdiy]

Excellent repair series sir!

[@NuGanjaTron]

Hi Stefan, I have a PM3244 with one of the 4 channels dead; apparently it's the attenuator, which I have tried to detach from the front panel... but didn't get very far. How did you remove the nut in the larger of the two coaxial knobs on the attenuator? On mine it's a 7mm nut, recessed into the knob which just measures 10mm inner diameter, and I haven't found any spanner or bit that will fit in there, because they usually have an outer diameter of at least 11mm! I see no way to remove this knob without destroying it or making my own tool. Did you encounter this problem too? Any hints appreciated, thanks!

[@dl7majstefan753]

Hi, this problem is very common. I always use in such a case a pliers with a slim shape to grasp the nut. This requires some force on the pliers.

[@NuGanjaTron]

@@dl7majstefan753 Flachzange? ;^) Thanks for the hint; I tried the two I have but they're too large. Not Enuff Grip[tm]. I'll have to hunt around for a suitable one. Btw, the RIFA X2 cap in the mains filter exploded in my PM3244 as well. What a mess....

[@NuGanjaTron]

@@dl7majstefan753 Hi Stefan, a belated update after I finished the repair almost a year ago now: after a _lot_ of searching, I ordered a Knipex KN 30 11 140 "Langbeckzange" which fit the recessed 7mm nuts perfectly. These are extraordinarily long pliers, but even then, the nuts needed a bit of persuasion until they budged! It turned out that an LM208H op-amp in attenuator #4 had failed. I managed to find some (rare?) NOS specimens of these at a reasonable price, and since Philips were forward-thinking enough to provide sockets, replacement was easy. However, recalibrating and reinstalling the attenuator assemply was a nightmare!!! So the scope works again for now -- or at least until the next opamp or EMI suppression cap blows up! Thanks again for the hints and the video!

[@dl7majstefan753]

@@NuGanjaTron Congratulations, enjoy the Philips!

[@philippezhang]

Hi there. I admire a lot of you reparing work. It's not only very informative, but also very methodological. I'm on the point to buy a PM3214 online which has problems for 25 euro. looking infos about how to repair it :)

[@philippezhang]

www.leboncoin.fr/bricolage/1695098781.htm/

[@dl7majstefan753]

Dear Philippe, such cheap scopes may be too expensive to repair OR very easy. It´s always like playing roulette….!

[@PeterWalkerHP16c]

@@dl7majstefan753 ...and with EHT problems it's like Russian roulette. :-)

[@johnas2004]

Well done, must have been a slog to change all the capacitors.

[@dl7majstefan753]

Yes! It was! That´s the reason for the very last sequence………..

[@PeterWalkerHP16c]

Bloody Philips with almost exactly 3db @50MHz. If it were HP or Tek it would likely be 60 or 70MHz for a 50MHz scope. Sometimes better.