To fix or not to fix, pm3323 300MHz scope  - Page 1
Forum section: electronics / repair

author: 8bitcpu
author_rank: Newbie
timestamp: October 21, 2021, 05:30:43 pm
content: Hi all,I think I starting to get TEAI got a pm3323 philips/fluke oscilloscope for a really low price, and it even works, kind of.It shows wave forms on the screen on both channels so far so good.I already used it for some measurements and I kind of like using it.I have identified the following problems with it:- The battery box on the back was corroded, and settings are not stored- There is a cap exploded on the power supply.- The fine horizontal adjust on channel A is not working, the voltage indicator on screen is changing but the wave form is not.- I don't have the correct probes.- I don't have "reference manual", but I do have the "operation guide"So here are my questions:- Is this scope worth fixing or do I leave it as is? It works as is and I am scared I will make it worse.- I already fixed the battery compartment, but I don't know which batteries to use, apparently this info is in the reference manual.It uses AA cells but 5V to charge, anyone any ideas what it can be?- Where can i find the "reference manual" end/or schematics of this scope?- Does anybody here have experience with this kind of scope, and is willing to help me fix it?I am not a beginner in electronics but I not a expert either, so I'm not sure this project is for me.All advice is welcome.kr,Mathias

author: KevinA
author_rank: Regular Contributor
timestamp: October 21, 2021, 08:58:53 pm
content: Service manual available herehttps://www.mods.dk/manual.php?brand=philipsObviously, these are not simple units to work on. However, we had a 400MHz model at work which blew it power supplies. The cost of replacement power supplies exceeded the cost of the unit, so one of my techs built a linear power supply for it.Was it worth it? Oh yes, its capabilities were out of this world.

author: David Hess
author_rank: Super Contributor
timestamp: October 22, 2021, 12:56:26 am
content: It looks like a nice instrument. If you work on it, take your time and do it right and safely.There is at least one discussion in the forums here about it.

author: lamello
author_rank: Contributor
timestamp: October 22, 2021, 02:30:22 pm
content: The exploded cap is 99% the X2 cap. Easily to identify, it's yellow and highglossy (and exploded).Nothing to worry about, that's standard. Just replace the cap.Lamello.

author: 8bitcpu
author_rank: Newbie
timestamp: October 23, 2021, 10:07:05 am
content: Thanks all,especially KevinA for the link to the manual.The battery is a nickel cadmium (NRC6). page 47 of the manual (3-23)I am gonna try a normal rechargeable AA battery and see what happens.Next is the power-supply cap it is a rectangular "box" type.But first I have to get the pcb out. en inspect it more.I keep you posted.KrMathias

author: 8bitcpu
author_rank: Newbie
timestamp: October 23, 2021, 01:20:48 pm
content: Hi, allI got the pcb with the exploded cap out, it is "board19" "power 1"The exploded cap is a Rifa branded cap...There are 2 other Rifa caps on that board that also don't look ehuu... frech.My plan is to replace al 3 caps.I found a listing in the manual:c4401 250v 10% 220nf < explodedc4402 me275 20% 2.2nfc4407 me275 20% 2.2nfAny Suggestions what cap's I should use to replace them?@Cariaszak I found it at "marktplaats.nl" a second hand site in the Netherlands. I am not telling how much I payed but it was cheap.KrMathiasEdit: change 20x to 20% and 10x to 10% the font in the manual is very small...

author: lamello
author_rank: Contributor
timestamp: October 23, 2021, 02:58:29 pm
content: The c4401 is a X2 cap. Just replace it by a .22uF ~275V X2 Cap and your fine.Gr Lamello

author: lamello
author_rank: Contributor
timestamp: October 23, 2021, 03:13:29 pm
content: FYI:https://www.eevblog.com/forum/beginners/pm3055-oscilloscope-psu-removalrepair-(caps)-and-general-usage-questions/Gr Lamello

author: 8bitcpu
author_rank: Newbie
timestamp: October 24, 2021, 09:48:56 am
content: Hi, allI have placed a order for some cap's and some extra soldering stuff.I report back when I reserved the goodskr,Mathias

author: 8bitcpu
author_rank: Newbie
timestamp: November 20, 2021, 03:14:37 pm
content: Hi all,I finally found some time to work on this, the caps are replaced and the scope is working again.I also put some normal rechargeable battery's in the battery holder and is seems to work, now the scope is not doing any calibration at startup.It starts very fast, much faster than my modern Rigol scope.The only thing that is still not fixed is the horizontal adjust on channel A.I pulled out all the cards one by one and reseeded them, in the hopes that it would fix it, but no luck.Now I'm a bit stuck, how do I locate where the horizontal adjust is done.Does anybody have any tips where to start.

author: lamello
author_rank: Contributor
timestamp: December 10, 2021, 06:11:38 pm
content: Hi,Try to get a copy of the service manual of this scope. Then put a signal on Channel A and followthe money, euhhh, follow the signal.greets, lamello

author: Wallace Gasiewicz
author_rank: Super Contributor
timestamp: December 10, 2021, 11:40:29 pm
content: Nice Instrument. I also have used rechargeable AA batteries in these applications. Sometimes they are hared to fit though.....Getting the correct probes is necessary. Make sure they match the inputs as far as their capacitance. I think the Chinese probes are just fine, at least the ones I ordered are.By the way, my 500 MHz Agilent probes are labeled "Made in China"I have used these folks for manuals. Very nice copies and I get them on a CD, I put the Manual on my computer and put the CD in a file with notes on my repairs and other hints about the particular instrument I have. Usually the schematics are copied much more clearly than the ones I find for free on the net.http://artekmanuals.com/