Got myself another scope.

[Th3_uN1Qu3]

Snatched this one for $90 including postage. It's a Philips PM3215 dual 50MHz scope. A steal at this price. It can do differential measurements, which my dual 10MHz Panasonic can't, so i can probe live circuits now. I'll still be using that inverter and battery for safety's sake, but this will come in handy. As far as i see it's also got delayed sweep.

Brightness is good, trace is sharp and straight even at the extremes of the screen. Lots better than the Panasonic. It also has an illumination knob which doesn't appear to work, most likely the bulbs are burnt out. No biggie.

I also found its service manual, and not only does it contain full schematics - it also explains how each section works. It'll be great help.

It appears to need a recap as on the highest sensitivity ranges (10, 5, 2mV/div) there is some SMPS ripple visible even with the input grounded. But that's just minor tidbits - all the major functions work and i'm happy with that.

[ben7]

Re: Got myself another scope.

Lucky!!!

Great find

[tom66]

Re: Got myself another scope.

Back when Philips made decent stuff. If the caps can survive ~20 years, they're pretty good!

[twbranch]

Re: Got myself another scope.

Nice. If I am not mistaken the philips scopes were made by Tek or HP and Philips put them in the their own case. Should be a good scope and looks to be in great shape for the age.

Good find!

[mariushm]

Re: Got myself another scope.

Nice. If you ever break or lose this one, I have that Hitachi 60 Mhz scope I talked to you about that I'd be willing to give to you.

[Th3_uN1Qu3]

Re: Got myself another scope.

Lose... no chance. Break, only if i'm an idiot, which doesn't happen too often.

I was actually pondering what to pop open first between this scope and a 600W Spire PSU that someone gave me to fix. Although i've just finished fixing another one, i think i'll go for the PSU.

[Th3_uN1Qu3]

Re: Got myself another scope.

Definitely needs some caps replaced - it's got some quite annoying artifacts, particularly at timebase settings slower than 0.1ms/div. A zoomed-in version of the input signal appears on the background. It shows with lower brightness, but still enough to be bothersome.

But as far as accuracy is concerned, it doesn't seem to be out of cal, at least on the X axis.

Edit: Just took a quick look in the service manual at the PSU section. It's a dead simple, but quite elegant self-oscillating regulated SMPS. Should be very easy to fix. And... took it apart. Wow. It's an absolutely beautiful piece of engineering. Neatly organized, and very very clean. Since this scope has no fan, there's no dust inside. And yes i was right, the two bulbs that were supposed to illuminate the graticule have long since burnt out. I'll have to see how i can stick LEDs in there and still keep their brightness variable.

There's one annoyance in the whole construction though: All the lytics 'cept a big 4700uF, 40v one are axial. Argh. But then, this is typical for equipment of that time. I'm cheap, so i'm just going to bodge radials in there. Will check 'em on the ESR tomorrow to see where the problem is.

[retiredcaps]

Re: Got myself another scope.

And... took it apart. Wow. It's an absolutely beautiful piece of engineering.

Tease!!!

Pictures! Please!

[Th3_uN1Qu3]

Re: Got myself another scope.

Pics will come in an hour or so. A little update: I was too lazy to bother bodging my ESR meter back together so i just used the capacimeter on my UT70A. Found three caps that had gone out of tolerance. One 470u 6.3v on the 5v that read 120u, one 100u 40v on the 38v at 66u, and another small one, 3.3u which read 1.2u, that i haven't bothered looking where it was.

I used whatever i had around, so the 5v got a 1000u 6.3v Chemicon KZE, and 38v got a 220u 50v Samwha SG. Good enough.

Good news, and bad news. The low level noise/ripple on the trace seems to be from the Y amp, and it looks like a grounding/shielding issue rather than a power supply issue. The caps on the +180v and -180v rails were good, i soldered more in parallel to no effect. But, since replacing the 3 caps mentioned above, the zoomed in ghost image is now gone. That was my biggest issue with this scope, which is now solved. A little noise, i can live with.

Also, one of the bulbs that serves for illuminating the graticule has started working. I'm pretty sure the other one is toast tho.

[Tube_Dude]

Re: Got myself another scope.

Nice. If I am not mistaken the philips scopes were made by Tek or HP and Philips put them in the their own case.

Hi

No, this Philips scopes are really made by Philips, even you can check it if the OP put some inside pics. I bet the great majority of caps will be the good old blue Philips axial, together with the Philips green body metal film resistors...

Only much later they joined FLUKE for making some Fluke/Philips measuring devices, including scopes...

[Th3_uN1Qu3]

Re: Got myself another scope.

I bet the great majority of caps will be the good old blue Philips axial, together with the Philips green body metal film resistors...

Yes. Sorry for the delay, got sidetracked by work&party... You can have scope pr0n now.

I replaced the burnt out bulb with a superbright white LED but it doesn't look all that good, the right side of the graticule now appears pink. I think i'm going to go for red LEDs, it should contrast well with the green trace.

The circuit driving the bulbs is a current source, so a resistor in parallel with the LEDs (to simulate the bulbs) should be all that's needed to keep the possibility of varying illumination brightness. The bulbs are in parallel so the illumination control works even with only one bulb.

[tom66]

Re: Got myself another scope.

Is it using an old design of SMPS? How come that the caps in that thing which are 30 years old are giving only minor problems now - yet modern caps fail to last more than a few years?

[ben7]

Re: Got myself another scope.

Is it using an old design of SMPS? How come that the caps in that thing which are 30 years old are giving only minor problems now - yet modern caps fail to last more than a few years?

Hm, good design, and good caps?

[Th3_uN1Qu3]

Re: Got myself another scope.

It's a self-oscillating push pull. I believe the main reason why it lasted so long is that the layout is pretty lax and it runs fairly cool. Also, old caps were physically larger for the same capacity, so that is a factor too.

[MDOC]

Re: Got myself another scope.

The caps are either military grade or space flight qualified or both. That's one factor. And it looks like an old scope, so that's before the bad cap epidemic period, which was caused by a bad case from industrial espionage.

[MDOC]

Re: Got myself another scope.

There's one annoyance in the whole construction though: All the lytics 'cept a big 4700uF, 40v one are axial. Argh. But then, this is typical for equipment of that time. I'm cheap, so i'm just going to bodge radials in there. Will check 'em on the ESR tomorrow to see where the problem is.

Why the aversion to axials?

[Th3_uN1Qu3]

Re: Got myself another scope.

that's before the bad cap epidemic period, which was caused by a bad case from industrial espionage.

Or so they say. Caps keep failing left and right today as well, and i'm sure the bad cap manufacturers know exactly what they're doing. And the manufacturers that buy them, too.

Why the aversion to axials?

They're hard to find and expensive. I've already replaced the bad ones with radials, just didn't bother taking another pic.

[tom66]

Re: Got myself another scope.

The story claims industrial espionage but it seems obvious to me that cap manufacturers like CapXon know their caps are poor quality and manufacture them just because of that: OEMs don't want things to last, simple.

[Tube_Dude]

Re: Got myself another scope.

Yes. Sorry for the delay, got sidetracked by work&party... You can have scope pr0n now.

As I suspect the vast majority of electronic components are "in the house" PHILIPS components. Transistors, resistors, electrolytics, plastic (MKT) caps (the ones with color code bars). Only in the back part of one PCB (the vertical one at the back of the scope) I see a light blue electrolytic that don't look like PHILIPS original...

What kind are the lights? Round or "fuse" type? Voltage and Amperage? Maybe I can have some in my junk box...

[Th3_uN1Qu3]

Re: Got myself another scope.

The bulbs are 28v 80mA, and yes they kinda look like fuses. But don't bother - i will be replacing them with superbright LEDs, most likely red. I'm not interested in keeping the original look, as long as there is adequate contrast between the graticule and the trace, that's fine with me. Green on red oughta look better than green on yellow anyway.