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Vintage Test Gear and Workshop Equipment For discussions about vintage test gear and workshop equipment such as coil winders. |
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11th Aug 2010, 1:31 pm | #1 |
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Philips PM5100 L.F. Generator
Hi,
Another signal generator just turned up (funny how that happens...) I've peered inside then swiftly put it back together, it'll need some attention before I even think of waving mains vaguely near it. Has anyone got a schematic for it? I can probably get it going without but it'd be nice to know exactly what Philips have managed to cram in there (it's rather densely packed.) I wasn't expecting it to be so small! Cheers, Kat |
12th Aug 2010, 8:22 am | #2 |
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Re: Philips PM5100 L.F. Generator
Hi,
I couldn't resist, I've 'gone in'... Here's how it looked when it arrived: It needs a handle and a good clean but it's all there. Knobs and dial are intact, I think it'll clean up well. Promising... I love how small it is, I'd go so far as to say it's cute Watch this space; I seldom get round to writing up a 'Success Story' after the fact, so I'll see what happens if I photograph and write this one up as I go along. Cheers, Kat |
12th Aug 2010, 8:39 am | #3 |
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Re: Philips PM5100 L.F. Generator
Hi,
After removing the rear panel (four screws), all four feet and the tilt stand, the chassis slides out of the case and we find... Rust, cobwebs, the cocoon cases of something and a gassy ECC88 (I've got some of those, fortunately.) Access isn't as bad as I'd thought, the rear section of the chassis comes off after removing four screws and the capacitor attached to it is connected with push-on blade-type connectors. Thank you Philips Now I've vacuumed it out thoroughly, I feel a bit more inclined to work on it. All the controls are very stiff and need lubrication, once I can get to them. It looks complete and doesn't seem to have been 'messed with'. All the electrolytics measure less than 0.15Ω ESR, so there's hope that they'll reform. Most of the rest of the capacitors are those nice Philips 'mustard' types which are usually fine. This seems to have been built with good-quality components. There are six electrolytics in there, the one on the rear panel plus another five on the PCB on the left in the above photograph. I think I'll note down the connections then remove the PCB so I can trace out the circuitry. As I still haven't built a reformer, I'll do these 'in situ' with the generator's own HT supply - once I know how they're wired up. Cheers, Kat |
12th Aug 2010, 3:03 pm | #4 |
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Re: Philips PM5100 L.F. Generator
Hi,
Progress... of sorts... I've traced out the circuitry on the board with the capacitors on it, so I know which ones are associated with the HT supplies and which aren't. One of them is the output coupling capacitor and another is part of the oscillator circuit. It's clearly a Wien Bridge oscillator (as expected.) Amplitude stabilisation is achieved with a couple of bulbs connected in series (the two black tubular objects, mounted horizontally, visible in the last photo above.) The bad news - one of them is o/c. The good news, one of them isn't. It measures 40Ω cold and a quick check with a PSU had it glowing dimly at 3V. So they're low voltage. I extracted the dead one from its tube; it looks like a tubular MES bulb (without the cap.) I should be able to lash up a test circuit with the good one, take voltage/current measurements and figure out a replacement. In the meantime, I think I'll trace out more of the circuit then I'm tempted to try powering it, with a 250Ω w/w pot and series resistor in place of the bulbs. Tweaking this should provide more information for selecting a replacement bulb or bulbs and I'll be able to find out what state of health the rest of the circuitry is in. It's getting interesting, is this! Cheers, Kat |
12th Aug 2010, 5:18 pm | #5 |
Nonode
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Re: Philips PM5100 L.F. Generator
I agree it's a cute little unit. I would have put money on it being solid state !
Bit of B* to service I would think. I had a similar Grundig HF oscillator which was quite small too that was valve, but very difficult to service.( components wedged between the front panel and a sub panel ) That was built around a turret tuner with biscuits and, you guessed, the fault was in the tuner head with no way in but to remove all said biscuits. I didn't persevere on that one Well worth restoring yours - looks as though it can drive 600 ohm lines and speakers direct so the output should be quite hefty Good Luck with it Andy |
12th Aug 2010, 10:41 pm | #6 | |
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Re: Philips PM5100 L.F. Generator
Hi,
Andy, I'll need an element of luck in finding suitable bulbs... Quote:
It isn't at full brightness at 12V but I don't fancy taking it higher. Besides, it's operated somewhere around 2.7V in this circuit. So I'm guesstimating that it's a 24V bulb. I've now had the generator running, it's working, but with me pretending to be the missing bulbs with a 1k w/w pot. The output is just about stable with the pot around 470 ohms. (There's also a DC offset but I was expecting that; the output coupling capacitor is a bit leaky.) So... it's basically working and just needs carefully selected bulbs which are a close enough match for the originals Cheers, Kat |
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13th Aug 2010, 9:38 pm | #7 |
Octode
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Re: Philips PM5100 L.F. Generator
Philips PM5100. I have rummaged around my manuals. Nothing exactly right, but several helpful bits.
1) Copy of 1966/7 cat for the PM5120, with a functional diagram. Shows the use of bulbs for stabilisation, and gives a performance spec. While Philips usually changed the model number every year, they only made cosmetic internal changes, so this may well still be relevant. 2) The PM5101 is transistor, and no help at all. 3) I have also found the earlier (late 1950's) models GM2315, which uses a single 220v 15W bulb - shades of the HP200, the original AF Oscillator of 1939. Also the GM2317 which looks more comparable to yours, using two 6v, 25 ma bulbs in series. I have extracted the circuit and attach it. Let us know how it goes, and if you do eventually find or construct the circuit diagram. Philips information is very difficult to find, even with the efforts of Frank Philipse, on his invaluable valve data sites. Bill m0wpn |
14th Aug 2010, 10:16 pm | #8 |
Hexode
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Re: Philips PM5100 L.F. Generator
http://www.nvhr.nl/frameset.htm?&ContentFrame
I believe you have to be registered. |
15th Aug 2010, 11:19 am | #9 |
Heptode
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Re: Philips PM5100 L.F. Generator
Hello Kat,
I have the Philips manual for the PM5100 (in English). If you wish, I can scan it and mail it to you. The stabilizing bulbs are type 8099Z. I could not find any data on those, but they might be 18V-26mA, since GI has lamps with type 8099 and they are 18V-26mA.... Not sure if the Philips type has the same specs though... best regards, Jac |
16th Aug 2010, 12:22 pm | #10 |
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Re: Philips PM5100 L.F. Generator
Hi,
First, an update and some more photographs... As the controls were very stiff I wanted to remove them rather than risk damage by operating them as they were. That meant removing the front panel and that meant removing the knobs. They're collet knobs, the caps came off easily enough providing access to the nuts. After loosening them, the knobs were still stuck. Here's my tip for stuck collet knobs: The object of the exercise is to try to drive the collet out of the taper in the knob. So, loosen the nut and undo it so the thread on the collet is just below the surface of the nut. Turn the socket used to undo it round the other way and rest it on the nut (this is to avoid damaging the thread on the collet.).The front panel is held on to the chassis by nine small screws with star washers around the periphery of the chassis. As the output terminals are attached to the front panel, they need disconnecting. With just a few wires disconnected, the PCB that's in the way can be moved to allow access. I undid the nuts and removed the terminals leaving the solder tags attached to the wiring. With it rapidly turning into a pile of bits I could make a start on cleaning it... I've been using 'Vanish' stain-remover bar for cleaning all manner of bits of electronics for years. It's a bit more 'active' than other detergents and is very effective. I dampen an old toothbrush, rub it on the 'Vanish' bar then apply to the bits I'm cleaning. If it's left for a few minutes it lifts the dirt, a quick scrub with the toothbrush and a rinse and that's it. It's very effective on textured vinyl coatings (like the case of this generator); I use an old nail-brush on larger areas. Tabs on the plastic surround pass through slots in the front panel and are melted to hold it on. Some had broken off, leaving the surround loose. I've attacked that with hot-melt glue; I'm not sure how well it'll work but if it doesn't I'll have to try something else. With the front panel removed I could get at the fixings for the controls. I drew a few diagrams first, making sure I'd noted where all the connections went before disconnecting anything. That's the frequency range switch. The mechanism had almost completely seized and the spring had rusted, stretched and was about to disintegrate. Indeed, while freeing the mechanism off and lubricating it, the spring disintegrated. My box of salvaged springs provided a replacement (possibly from a VCR.) The reduction drive on the variable capacitor was also almost seized and the spring on the anti-backlash gear had turned into brown powder. After several hours carefully freeing it off, it's now working smoothly and has a replacement spring. And finally... that's just another photograph of the variable capacitor. It's a very lovely thing and needed photographing before it disappeared back inside its housing Cheers, Kat |
16th Aug 2010, 1:41 pm | #11 | |||
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Re: Philips PM5100 L.F. Generator
Hi,
Quote:
Quote:
8099 Z regulatorbuis (6 V 25 mA)Close examination of the ones from mine reveals faint markings reading '8099Z'. That's interesting as, at 6V, my working one was just about lit and at 12V was still very yellow (and if I'd known it was 6V I wouldn't have gone up to 12V!) I suspect that, as they're intended for regulating/stabilising use, they're rated differently than they'd be for illumination purposes. They're primarily a non-linear resistance; any light produced is just a side-effect... I ordered a selection of 24V bulbs (a few days ago, before finding out the 8099Z rating) and I'll plot the V/I curves (just from 0V to 6V) for them when they turn up. That'll give me something to go on. I don't think that 6V bulbs will do; the working original is dimmer and on a less linear part of its curve at 6V than a 6V bulb would be. Here's what the originals look like: Quote:
Finally, this is the state it's in as I write: I've almost finished reassembling it, that was taken just after refitting the front panel and output terminals. I'm really enjoying myself with this; it's turned into a more extensive restoration than expected but that happens a lot. It's much more compact than my other generators and likely to get some use; worth the effort IMO Cheers, Kat |
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16th Aug 2010, 8:16 pm | #12 |
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Re: Philips PM5100 L.F. Generator
Hi,
I've finished reassembling it and couldn't resist trying a quick lash-up with clip-leads, trying out a few random bulbs. With the second bulb I tried (12V, wire-ended, otherwise unidentified) and the 1k pot I used before, it was possible to get it to produce clean-looking oscillation with stable amplitude. The amplitude stabilises rather quickly (my other generator, when it last worked, took several seconds to settle) but it proves it's all working including the amplitude stabilisation circuitry. All frequency ranges work, it oscillates over the full range of the frequency control, all output attenuator settings work and the output level control works. Checking/adjusting calibration can wait until I've selected more suitable bulbs and devised a way to fit them. So, after what appears to be years of disuse (except as a home for some species of insect) and storage in damp conditions, it's fundamentally working and (apart from the o/c stabilisation bulb) only needed a cracked ECC88 replacing. Impressive! Hopefully the postie will deliver some bulbs tomorrow, then I can plot some more curves. For some strange reason, you just don't seem to be able to find datasheets for bulbs which include curves... Cheers, Kat |
16th Aug 2010, 9:19 pm | #13 | |
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Re: Philips PM5100 L.F. Generator
Quote:
Although it has never been as fashionable as certain other makes of test gear, Philips kit is well made and reliable, even when neglected. When new it would have quite a lot less than the equivalent HP or Marconi gear and has the added advantage of taking up much less bench space.
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18th Aug 2010, 4:29 pm | #14 |
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Re: Philips PM5100 L.F. Generator
Hi,
I've tidied up my reverse-engineered schematic to a point where I feel inclined to post it. (BTW, component references starting at '1' are on the chassis, attached to switches, etc. Component references starting at '101' are on the RH PCB, viewed from the front. Component references starting at '201' are on the LH PCB. I should add a note to the schematic...) I'm not so sure now! (Unless it's some subtle rearrangement. It's not quite the circuit I'm familiar with.) The oscillator comprises pentodes V201 (EF86), V202 (EF95) and White cathode follower V203 (ECC88); non-inverting overall. Feedback is taken from the cathode follower via a potential divider comprising the lamps LP1 and LP2 and R6 (with R7 in parallel with R6 on the lowest frequency range.) This is fed to a phase lead network followed by a phase lag network, providing positive feedback at one (tunable via VC1 and range switch S1) frequency. Negative feedback is taken from the cathode follower via preset VR101 and fed to the cathode of V201. (Now I've got it working, this sets the output level to 10V with the 'Vo' control at '10' and the attenuator on 'x1'.) The cathode follower (V203) is also connected to the top of the 'Vo' pot, the wiper feeds another White cathode follower V204 (E182CC); the output of this is connected directly to the 15Ω output terminal and, via the attenuator switch, the 600Ω output. (Have I got that right?) Nice circuit; I like it. Philips have packed quite a lot into a very small box! Cheers, Kat Last edited by Kat Manton; 20th Aug 2010 at 4:52 am. Reason: Updated schematic |
18th Aug 2010, 5:42 pm | #15 |
Dekatron
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Re: Philips PM5100 L.F. Generator
I don't think Wien would recognise it either, Kat - he has a series RC arm and a parallel RC arm. But this, as you say, has a cascaded phase lead and phase lag network.
I do like the cathode followers with active current source cathode loads - and the elegant coupling to the said current source from the CF anodes. I'm not a fan of Philips test gear, but I must agree with your opinion of this one being cute! (And now I want one...) |
18th Aug 2010, 8:33 pm | #16 |
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Re: Philips PM5100 L.F. Generator
I've always liked Philips test gear. They might not have the snob appeal of Tek or HP, but their stuff has always worked just as well (in my experience), and for a lot less money. They always liked to innovate and weren't aren't afraid to deviate from the accepted norm - this, depending on your point of view, could be seen as good or bad
I think you've correctly established that this is a phase-shift oscillator of some type - last time I researched these, there were many different variations but I can't remember that far back! I reckon this ought to have pretty good performance now it's working. Incidentally, that method of actively loading the followers is something I'm very familiar with in transistor amplifiers, but it's nice to see that it pre-dates transistors I'm jealous too Mark |
20th Aug 2010, 4:10 pm | #17 |
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Re: Philips PM5100 L.F. Generator
Hi,
I've snuck in a revised schematic in the post above; nothing too exciting, the odd correction, a mains transformer and voltage selector (now I've added the parts to my library.) Here are the curves for the bulbs which turned up the other day: I don't think I need to say I chose the 24V 50mA MES bulbs; they're very close to the original Philips 8099Z. With two of those lashed-up temporarily with clip-leads, the generator was producing a stable output over its full frequency range. The output could be set to 10V with preset VR101 roughly in mid-position, which seems like a good sign. So, I reckon 24V 50mA tubular MES bulbs (Maplin BU22Y) are a suitable replacement (at least in this generator) for the Philips 8099Z bulbs. It's still not finished; while checking it more thoroughly I noticed an odd instability; the output was fluctuating at certain frequencies. These turned out to be close to multiples of 50Hz. Sticking a 'scope on the oscillator section's HT rail showed I'd got both mains hum and the oscillation signal on the HT; the 100uF electrolytic (C1) wasn't doing a good job of decoupling; the fluctuation was the oscillator beating with mains hum. Temporarily subbing a 220uF/400V from a scrapped TV panel solved that problem. The remaining electrolytics look a bit tired; perished/cracked insulation doesn't inspire confidence. For the sake of future reliability, I think I'll replace the lot with new 105 deg. C ones (once I've got some.) I also don't see any problem replacing C1 permanently with 220uF; it's less than half the size of the original and will fit on the PCB rather than the rear panel (or inside the old can if I'm feeling enthusiastic.) So, it's nearly finished. I've still to devise a way to mount the replacement bulbs. They carry the signal frequency, the original arrangement looks like it was intended to minimise capacitance. So bolting a couple of MES holders to the chassis probably isn't the best solution. I've had an idea for this and I'm now waiting for the bits to turn up. Cheers, Kat |
20th Aug 2010, 4:56 pm | #18 |
Hexode
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Re: Philips PM5100 L.F. Generator
You could try turning your MES bulbs into wire-ended versions (although with a slightly larger envelope). Desolder the bulb contacts from the MES and gently crush the metalwork to break the fixative, the bulb usually comes away cleanly. I've done this a few times.
Vic
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20th Aug 2010, 5:15 pm | #19 |
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Re: Philips PM5100 L.F. Generator
Hi Vic,
It's one option I'm considering (though bunging them in a jar of meths, I think, will soften the cement and leave me with possibly-useful MES bases.) The original bulbs appear to be the same envelope as tubular MES bulbs, too. I was thinking about just fitting the replacements in the original housings, but I'd like to keep the working 8099Z intact, it may come in handy. I have a cunning plan... so far, a long thin parcel's arrived which contains 1m of acrylic tube... Cheers, Kat |
20th Aug 2010, 8:51 pm | #20 |
Heptode
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Re: Philips PM5100 L.F. Generator
HI: Kat.Nice job comming on well,I have some miniture 6v wire ended bulbs,they may get lost in your little cutie. you can have a couple if they will do the job,I know they are 6v but can not remember what the current ratings are without raiding the attic,there is a No. on the packet pics posted Gezza
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