Identifying 70's (?) through-hole components

[l0rd_hex]

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 hear 

The board it's self is a 24 power supply module.

Thanks!

Picture is here:
 

[German_EE]

1) could be an MOV or a ceramic capacitor

2) Assuming it's the metal component is a power diode, they're made like that so that they can be slotted into heatsinks.

[l0rd_hex]

Thanks!

Yup, #2 is the metal can.

[Gyro]

(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.

[l0rd_hex]

Will do, thanks for the hint about the caps!

I'll check these out this week and post back

[dacman]

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.

[Richard Crowley]

More curious:  What do you think is that long, slender, dark blue component between the top-hat diode and the blue electrolytic capacitor?

[T3sl4co1l]

Yeah, what they said ^^

More curious:  What do you think is that long, slender, dark blue component between the top-hat diode and the blue electrolytic capacitor?

That, 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 doing 

As 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 prototype http://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

[oldway]

More curious:  What do you think is that long, slender, dark blue component between the top-hat diode and the blue electrolytic capacitor?

That'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 open 

1 is a NTC.
2 seems to be a BY100 or a zener diode.

[tec5c]

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?

[crispy_tofu]

Wow, those blob-shaped diodes (top left) look really funky!

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?

+1, it looks like a riser board for something 

[bktemp]

Wow, those blob-shaped diodes (top left) look really funky!

Those 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.

[tec5c]

On second look at the board, I'm almost certain it's from a Philips bit of gear.

it looks like a riser board for something

Doubtful.

[HighVoltage]

Wow, those blob-shaped diodes (top left) look really funky!

Vishay 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 Vishay
Another indication, that this is a Philips made board and parts

[Gyro]

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?

It 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.

[wiss]

Wow, those blob-shaped diodes (top left) look really funky!

Vishay 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 Vishay
Another indication, that this is a Philips made board and parts

I 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!

[oldway]

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?

It 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.

It is glass with a resistive wire inside, not ceramic.

[Gyro]

Shall we settle on Vitreous Enamel? 

[l0rd_hex]

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?

Yup, 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

[oldway]

Shall we settle on Vitreous Enamel? 

I 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.

[l0rd_hex]

+1, it looks like a riser board for something 

It 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

[FlyingHacker]

I have seen scinterglass diodes like those in the top left fail without any outward damage. Might be worth testing.

[Gyro]

I 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.

Thanks 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. 

[l0rd_hex]

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:

[Kjelt]

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