Philips PM3302 Scope repair. Help needed - Page 1
Forum section: electronics / repair

author: mikegmg
author_rank: Newbie
timestamp: November 02, 2024, 04:58:37 pm
content: Help appreciated with Philips PM 3302 Scope. Been sitting around for a few years unused. Now trying to re-commission.Current problem is very limited adjustment available on the Vertical Position of both traces. I have no schematics for this so if anyone can supply a schematic of the Vertical Amp or a link, or suggest a solution that would help get the diagnostics process started.

author: MathWizard
author_rank: Super Contributor
timestamp: November 03, 2024, 05:04:44 pm
content: I'm having a hard time even finding the spec's for the PM3302, but it seems people suggest using the PM3305 schematic, I put it below. I see it has some digital stuff inside. But I'm guessing the vertical trace position is still some analog circuit.So does the peak to peak voltage look right on all divisions, but moving the trace up/down barely works ? Have you tried on all V/div ?I guess some ladder of transistor's, like in a push-pull output, some part of that must have a problem. Or 1 of the signals for it's biasing. Maybe the input voltage from the PSU has a problem too, so always worth checking (but yeah watch out for the crazy HV area's).If you have another scope, or even a good DMM and a low frequency signal source, even from a 555-timer, you could try tracing the signal over to the output section. With the power off, check all the resistors, diodes, cap, around there. I'd spend the time and make my own schematics some sections. And I'd probably remove a bunch of caps/ and even transistor's, to really make sure everything read's as expected. And I'd make a model in a simulator, just to see some reasonable biasing of the output drive.But yeah I'm mainly thinking of some stereo push-pull amplifier, so no high voltages to worry about there.The PM3305 schematics is over here, it's too big to uploadhttp://bama.edebris.com/manuals/philips/pm3305

author: George Edmonds
author_rank: Frequent Contributor
timestamp: November 03, 2024, 09:16:22 pm
content: Hi MikeIt looks like the Philips PM3302 is also sold as a Hameg 208 for which the full service manual, including schematics, is available free on line. The Philips PM3305 manual does not appear to include schematics. There is currently a PM3302 manual for sale on that awful auction site in the UK, it may not include schematics.I have no direct experience of this scope, but is it has a Beam Finder check that it operated correctly as a first step.The next step is to check all of the low voltage power supplies, particularly the +70 volt supply which is used for the deflection plate drive amplifiers. If by chance the scope uses blue Philips electrolytic capacitors teat them with suspicion, they invariably go low capacitance high ESR.G Edmonds G6HIG

author: mikegmg
author_rank: Newbie
timestamp: November 04, 2024, 10:56:49 am
content: Thanks for those replies, will follow up. George yes manual for sale is the User Manual which I do have but it contains no schematics.PM3305 looks like a very similar model with more storage functions so could well provide the schematics I need.Mike