Identifying 70's (?) through-hole components - Page 1
Forum section: electronics / repair

author: l0rd_hex
author_rank: Regular Contributor
timestamp: October 25, 2015, 08:03:56 pm
content: Hi friends,Long time lurker, first time poster here.The department I do IT work for has an old electron microscope which occasionally dies. The (EM) tech has kept a lot of the old bad boards and asked me the other day if I knew anything about diagnosing them (the small chat that arises when you want to borrow a multimeter!). I told him the furthest I've gone in diagnosing is checking voltages and resistances, he offered the contents of his drawer if I was curious anyways... and yup I'm hooked.The boards are quite simple, single layer through hold construction kinda stuff. I'm stumped by a few of the components though, I've labelled them 1 and 2 on the picture. If anyone has an idea of what they are I'd love to hearThe board it's self is a 24powersupply module.Thanks!Picture is here:

author: German_EE
author_rank: Super Contributor
timestamp: October 25, 2015, 08:28:38 pm
content: 1) could be an MOV or a ceramic capacitor2) Assuming it's the metal component is a power diode, they're made like that so that they can be slotted into heatsinks.

author: l0rd_hex
author_rank: Regular Contributor
timestamp: October 25, 2015, 08:32:15 pm
content: Thanks!Yup, #2 is the metal can.

author: Gyro
author_rank: Super Contributor
timestamp: October 25, 2015, 08:35:06 pm
content: (1) is probably a thermistor, not sure if it's a PTC overload protector or an NTC inrush limiter. It looks to have had a hard life, as does some of the rest of the board. Worth checking for continuity.(2) is a Top-Hat style diode, given the other conventionally packaged diodes on the board, I would think it's likely to be a 1.5W zener. The package markings should give an idea of voltage,It's worth looking for and remaking cooked solder joints in the brown area. Check the two polyester caps above the transformer and the transistor next to them too. The electrolytics may be poorly at that age.Hope it helps.

author: l0rd_hex
author_rank: Regular Contributor
timestamp: October 25, 2015, 08:38:53 pm
content: Will do, thanks for the hint about the caps!I'll check these out this week and post back

author: dacman
author_rank: Frequent Contributor
timestamp: October 26, 2015, 03:20:41 am
content: I believe 1 is a thermistor also, and I would guess that it's an NTC inrush limiter (although that is just a guess). It will test like a resistor with a DMM.I've seen a lot of those diodes (marked with 2). Doesn't it have a number on it somewhere?I'd want a decent DMM and an LCR meter that uses a bridge to check out that board.

author: Richard Crowley
author_rank: Super Contributor
timestamp: October 26, 2015, 03:47:25 am
content: More curious: What do you think is that long, slender, dark blue component between the top-hat diode and the blue electrolytic capacitor?

author: T3sl4co1l
author_rank: Super Contributor
timestamp: October 26, 2015, 04:57:26 am
content: Yeah, what they said ^^Quote from: Richard Crowley on October 26, 2015, 03:47:25 amThat, I have no idea. It looks like a thin, unusually wonky reed relay! Maybe a spark gap, but at that length, it'd be like 20kV, nowhere near what this circuit is doingAs for overall circuit function, tempted to say it's an AC input (4 diodes, top left), filter (nearby electrolytics), NTC inrush, switching converter (probably blocking oscillator, flyback type -- derived from this sort of prototypehttp://seventransistorlabs.com/tmoranwms/Circuits_2010/Blocking_Oscillator.png), and the rest of the board is output voltages, filtering and a feedback/regulator circuit, perhaps using an op-amp or regulator (the TO-99 ish can) IC. Wouldn't seem to be isolated, at least, there's no obvious way to get feedback to the primary side without a common ground; also no isolation barrier.Tim

author: oldway
author_rank: Super Contributor
timestamp: October 26, 2015, 07:29:50 am
content: Quote from: Richard Crowley on October 26, 2015, 03:47:25 amThat's a low value resistance used as a shunt to measure current.It's used in old Philips power suppllies.Check it first because it often fails open1 is a NTC.2 seems to be a BY100 or a zener diode.

author: tec5c
author_rank: Frequent Contributor
timestamp: October 26, 2015, 08:31:58 am
content: Just out of curiosity, what is the board actually from?As oldway said that the current shunt resistor is often used in Philips power supplies and you said that the board is the power supply module, are there any Philips markings?

author: crispy_tofu
author_rank: Super Contributor
timestamp: October 26, 2015, 10:00:37 am
content: Wow, those blob-shaped diodes (top left) look really funky!Quote from: tec5c on October 26, 2015, 08:31:58 am+1, it looks like a riser board for something

author: bktemp
author_rank: Super Contributor
timestamp: October 26, 2015, 10:12:36 am
content: Quote from: crispy_tofu on October 26, 2015, 10:00:37 amThose sinterglass diodes were fairly common in Europe for all kinds of high voltage stuff, maybe because they were mainly made by Philips and later by Vishay. Almost every BYxxx Diode had this or a similar package.

author: tec5c
author_rank: Frequent Contributor
timestamp: October 26, 2015, 10:19:03 am
content: On second look at the board, I'm almost certain it's from a Philips bit of gear.Quote from: crispy_tofu on October 26, 2015, 10:00:37 amDoubtful.

author: HighVoltage
author_rank: Super Contributor
timestamp: October 26, 2015, 11:38:23 am
content: Quote from: crispy_tofu on October 26, 2015, 10:00:37 amVishay is making high voltage diodes today, that look exactly the same.And I think Vishay bought the resistor and diode factory from Philips Germany that was called Beyschlag before it became VishayAnother indication, that this is a Philips made board and parts

author: Gyro
author_rank: Super Contributor
timestamp: October 26, 2015, 12:08:24 pm
content: QuoteIt could actually be quite a high value wirewound resistor - I've seen those in up to around 10k in that long thin ceramic form in old gear. The value should be marked anyway.

author: wiss
author_rank: Frequent Contributor
timestamp: October 26, 2015, 12:17:26 pm
content: Quote from: HighVoltage on October 26, 2015, 11:38:23 amI harvested a bunch of switching 150-200 V diodes in this capsule resently. Unofortunately I also bought a bunch of 22 V zeners with the same capsule (new). Took me a while to figure out why my SMPS had so very low efficiency and the freewheeling diode got so damn hot!

author: oldway
author_rank: Super Contributor
timestamp: October 26, 2015, 12:30:53 pm
content: Quote from: Gyro on October 26, 2015, 12:08:24 pmIt is glass with a resistive wire inside, not ceramic.

author: Gyro
author_rank: Super Contributor
timestamp: October 26, 2015, 12:35:15 pm
content: Shall we settle on Vitreous Enamel?

author: l0rd_hex
author_rank: Regular Contributor
timestamp: October 26, 2015, 02:58:29 pm
content: Quote from: tec5c on October 26, 2015, 08:31:58 amYup, this is marked "Philips" in solder mask on the back side. Good guess!Other than being from a Electron Microscope power supply I don't know it's exact function. The bag it was in said something about a 24V power supply.EDIT: Done spelled sumthin' wrong

author: oldway
author_rank: Super Contributor
timestamp: October 26, 2015, 03:02:17 pm
content: Quote from: Gyro on October 26, 2015, 12:35:15 pmI already replaced several broken ones, that's glass, not ceramic with vitreous enamel.You see clearly on picture the solder glass/metal as on vacuum tubes.

author: l0rd_hex
author_rank: Regular Contributor
timestamp: October 26, 2015, 03:21:30 pm
content: Quote from: crispy_tofu on October 26, 2015, 10:00:37 amIt has some solder fingers on the left hand side (out of frame) that would fit into an ISA-esque socket.EDIT: Fixed grammar + quote end tag

author: FlyingHacker
author_rank: Frequent Contributor
timestamp: October 26, 2015, 03:28:47 pm
content: I have seen scinterglass diodes like those in the top left fail without any outward damage. Might be worth testing.

author: Gyro
author_rank: Super Contributor
timestamp: October 26, 2015, 07:00:42 pm
content: QuoteThanks for the clarification, I bow to your knowledge. I don't think I've ever come across one of those. All the long shiny ones I've seen have been very slim ceramic rod core with very fine resistance wire winding and an overall coat of vitreous enamel (as I say, up to quite high values). The only glass ones I have are vacuum encapsulated film 100M-10G types. I'm intrigued to know what benefit all glass construction would give (fragility sounds like one downside!), I would have thought differential thermal expansion (assuming solid glass) would be more trouble than it was worth.I'll be on the lookout for one now.

author: l0rd_hex
author_rank: Regular Contributor
timestamp: October 26, 2015, 08:17:05 pm
content: All of your questions answered and more!First off a huge Canadian style thanks to everyone who has commented, this is amazing.Here's some values I measured:Some other pictures of the board:

author: Kjelt
author_rank: Super Contributor
timestamp: October 26, 2015, 08:44:14 pm
content: If it is a 24V power supply for an electron microscope, that dept. has been integrated to the current company called FEI.https://en.wikipedia.org/wiki/FEI_Company

author: android
author_rank: Regular Contributor
timestamp: October 26, 2015, 09:09:00 pm
content: Just curious...what's with all the white "spacers" on the leads? I can understand having them on the power resistor for ventilation.

author: Cubdriver
author_rank: Unknown
timestamp: October 26, 2015, 09:24:13 pm
content: The spacers on the caps are likely to keep the bit of insulating coating that usually forms a meniscus on the leads that extends out a short distance from the body from reaching into the hole on the circuit board and by so doing potentially compromising the solder joint on that component.-Pat

author: Isad
author_rank: Frequent Contributor
timestamp: October 26, 2015, 09:26:56 pm
content: 2: Seems like a 200v zener i have seen some like those and have4 of them in my junk bin.

author: dacman
author_rank: Frequent Contributor
timestamp: October 26, 2015, 09:34:51 pm
content: The blue capacitors look like Philips (and I think I see Philips on one), which is now BC Components owned by Vishay.

author: Gyro
author_rank: Super Contributor
timestamp: October 26, 2015, 10:40:39 pm
content: If I read your latest picture correctly, one of the polyester capacitors (top right corner) is shorted! Not really surprising given the age and the temperature in that corner. That could be your fault right there. I'd suggest replacing both of them as a first step. They're fondly known as Philips 'Licorice All-sorts' capacitors. If I read them correctly, they are 100nF 10% (brown black, yellow, white). i can't see the bottom colour (voltage rating) in any of the pictures, this will be either brown (100V), Red (250V) or yellow (400V). It might be worth replacing them with polypropylene types for better ruggedness.Edit: If you still get zero ohms across the PCB pads then it could be that the TO5 pkg transistor is shorted, but my bet would be on the capacitor itself.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: October 27, 2015, 01:25:42 am
content: I wouldn't be surprised if one of those caps is in parallel with a winding (to enhance resonance perhaps), but not if it's that big (1n or 10 would be reasonable, but 0.1u is kind of big for that).Tim

author: steve207a
author_rank: Contributor
timestamp: October 31, 2015, 06:31:11 pm
content: well it looks like youve got ac from a transformer entering the board through the 4 small round diodes with a couple of 150mfd smoothing capacitors then an inrush thermister and the diode is possibly a zener to maintain a constant voltage and another smoothing cap check this one as close to heated parts and electrolytics have a habit of drying out over time and stress the 68 ohm resistor by 2 has seen some stress looks like a phillips type also the t05 transistor spacer looks like its melted so that could be suspect having got so hot the diode has some markings on it if you remove it you should be able to see and look on internet for type /value the circuit seems to go into the small transformer to supply the rest of the circuit look at the voltage spec on the blue cap next to the large diode as this may indicate the voltage for that circuit so if 63volt then voltage around that part could be 30 to 60v just a guess but may helpregards steve