Philips PM 3215 oscilloscope teardown (vintage) - Page 1
Forum section: electronics / testgear

author: 3nigm4
author_rank: Regular Contributor
timestamp: December 23, 2016, 09:00:17 am
content: Yesterday I had to tear down my oscilloscope due to smokeFortunately it is only a broken power supply filter capacitor.I taken the time to take some pictures for who is curious like meHere are main pictures

author: 3nigm4
author_rank: Regular Contributor
timestamp: December 23, 2016, 09:01:35 am
content: And here some details, with a strange component I've never seenEdit: look at the board... there's few trim pots just for rapid calibration

author: cheeseit
author_rank: Regular Contributor
timestamp: December 23, 2016, 09:08:41 am
content: Quote from: 3nigm4 on December 23, 2016, 09:01:35 amThe WTF image? That is adelay line.

author: tautech
author_rank: Super Contributor
timestamp: December 23, 2016, 09:13:18 am
content: Quote from: 3nigm4 on December 23, 2016, 09:01:35 amIf you mean this one:It looks like the PDA multiplier that provides the 10KV CRT acceleration voltage.....that is the PDA lead coming out of the LH bottom edge, right?Nah, cheeseit is probably right

author: 3nigm4
author_rank: Regular Contributor
timestamp: December 23, 2016, 09:15:15 am
content: Quote from: cheeseit on December 23, 2016, 09:08:41 amI've never seen one before...Thank you

author: tautech
author_rank: Super Contributor
timestamp: December 23, 2016, 09:15:32 am
content: Quote from: cheeseit on December 23, 2016, 09:08:41 amYes, it could well be a potted delay line.

author: Gyro
author_rank: Super Contributor
timestamp: December 23, 2016, 09:19:41 am
content: .... and the inevitable Rifa metalized paper capacitor.Just in case you're not already aware, they all do it in later life, the encapsulation crazes, moisture gets in and *poof*. Just replace it with an equivalent value X1 rated Polyproplyene film (MKP). No other fault to look for.Nice teardown. Philips equipment of that era is really well made. Nice and accessible and repair friendly.Yes it's the delay line. Do point out any other components that you don't recognise, we enjoy identifying stuff!

author: 3nigm4
author_rank: Regular Contributor
timestamp: December 23, 2016, 09:37:23 am
content: Quote from: Gyro on December 23, 2016, 09:19:41 amThanks for the infoQuote from: Gyro on December 23, 2016, 09:19:41 amUmmmm, seems that the "delay line" is the only unknown component at the moment

author: cheeseit
author_rank: Regular Contributor
timestamp: December 23, 2016, 11:04:01 am
content: Don't know if you have have it but here is bad but usable service manual fromElektroyanya. Wait for the ..processing.. to change to Get manual, takes about half a minute or so. Delay line is shown on p. 57 and you'll find performance checks and adjustment from p. 31 and on.I like these old PM scope repairs and teardowns, and will contribute with a PM3264 and a PM3540 logic scope some day soon.

author: 3nigm4
author_rank: Regular Contributor
timestamp: December 23, 2016, 11:18:30 am
content: Quote from: cheeseit on December 23, 2016, 11:04:01 amThank you a lot for manual link, maybe usefull in the future.I looked few times to a new digital oscilloscope, but even if this old scope's size is huge, it has always worked perfectly

author: SingedFingers
author_rank: Frequent Contributor
timestamp: December 23, 2016, 11:21:43 am
content: My PM3217 blew a RIFA yesterday as well. Total coincidence!

author: Mark Hennessy
author_rank: Frequent Contributor
timestamp: December 23, 2016, 12:17:26 pm
content: The OP has a fairly early one. Most have the delay line wrapped around the CRT. Also, the final Y amplifier is moved from the main PCB to a separate PCB mounted vertically next to the CRT.Covering the mains inlet (where the dreaded RIFA lives) is an FR4 sheet with a rectangular cut-out. I always wondered what the cut-out was for, until I stumbled across a very early example (second image). Before they switched to RIFA, they used a green cylindrical type. I've not seen many of these, but I've never seen one fail.

author: samnmax
author_rank: Regular Contributor
timestamp: December 23, 2016, 12:35:19 pm
content: Quote from: Mark Hennessy on December 23, 2016, 12:17:26 pmThe green cylindrical one in my PM3218 failed. It was all sweaty, so I replaced it by a proper X2 cap.

author: 3nigm4
author_rank: Regular Contributor
timestamp: December 23, 2016, 12:39:45 pm
content: Quote from: SingedFingers on December 23, 2016, 11:21:43 amThey are built with an expiration date insideQuote from: Mark Hennessy on December 23, 2016, 12:17:26 pmSo, maybe they switched to RIFA to repair them later

author: SingedFingers
author_rank: Frequent Contributor
timestamp: December 23, 2016, 01:43:16 pm
content: To be fair it has lasted 35 years in my scope which is pretty good for a tiny box who's entire life's purpose is to absorb all the nasty things coming in off the mains.Quote from: Mark Hennessy on December 23, 2016, 12:17:26 pmI assumed this was a convenient exhaust port to allow the smoke from the RIFA to access the power supply just to make your day even more miserableIncidentally literally a couple of days ago I was saying that I hadn't been bitten by a RIFA X2 yet. Such is life!

author: Mark Hennessy
author_rank: Frequent Contributor
timestamp: December 23, 2016, 02:38:19 pm
content: Quote from: samnmax on December 23, 2016, 12:35:19 pmHad it actually failed? It sounds like encapsulation was going funny with age, but the innards might well have been fine. Of course, many old film capacitors had a waxy finish.I do think you were right to change it, and I do the same. Even if the original had the same type of self-healing dielectric as modern X2 capacitors, it'll be degraded by now (X2 caps lose value with age).

author: 3nigm4
author_rank: Regular Contributor
timestamp: December 23, 2016, 03:38:36 pm
content: Quote from: SingedFingers on December 23, 2016, 01:43:16 pmYes, that's true, I'm jokingQuote from: SingedFingers on December 23, 2016, 01:43:16 pm

author: 3nigm4
author_rank: Regular Contributor
timestamp: December 30, 2016, 01:41:42 pm
content: Repaired with a little modification: replaced original power cord with an IEC socket

author: mk_
author_rank: Regular Contributor
timestamp: December 30, 2016, 02:10:03 pm
content: Quote from: 3nigm4 on December 23, 2016, 09:01:35 amReplace these Capacitors whenever you see them imediatlyI had "only" 3 of those Capacitors this year, I hope they are gone now.btw: all about 20 years old.... Nothing destroyed but they smell ugly...Michael