50 Year Old Sinclair Multimeter - Does it work?

[@JohnSmith-bh4zx]

You're making me feel old! I still have an Avo 8 multimeter.

[@HappyLittleDiodes]

Now that looks like a cool piece of kit

[@Retroguyuk75]

That meter is actually well made for the time period, awesome it was still working right out of the box and only needed a few tweaks to get it running perfectly. Made me laugh, 3rd time lucky, 4 fourth time lucky, ok 5th time lucky HA!...🤣🤣

[@marria01]

I wouldn't assume your mains voltage is exactly 230 volts. My supply at home in the Northwest UK never drops below 235V but will sometimes go as high as 250V. Believe it or not, this is totally within spec (216.2 volts to 253.0 volts).

[@phipli]

Yeah, the 230V is the common spec with Europe, but the actual real voltage in the UK never changed, so is usually around 240V. 230 is sort of the middleish between 220 and 240. Some parts of the British Isles actually have 250V from the sockets as the norm... I think the Isle of Man is 250? Edit - some brand new substations are apparently 230V.

[@nicksmith4507]

Yep. I am next to a substation/switching point and my mains is often up to 245 V

[@arturpoldan8816]

I have same one, love it since I like all Sinclair 😊. Mine had blown current and resistance measurements, one op-amp in LM3900N was blown. After replacement it works fine.

[@HappyLittleDiodes]

Good fix!

[@paulturner5769]

I had the earlier meter with the hinged polypropylene range switches and a Nixie tubes display. It worked well enough for the precision required for most projects in those days.

[@Doombrain]

Great to see the subs shooting up!

[@HappyLittleDiodes]

We've rocketed past 3000 I'll have to run the next chaos competition at another milestone

[@TRIALSDC]

Great video. I do like the idea of using retro test equipment to fix retro electronics. I've probably got some period probes for your DM2 somewhere. I also have something else you may find useful, and maybe a future video is a Thurbly LA160 with the LE32 addon. Make it a good period logic analyser. you're welcome to this and a set of probes. Keep up the good work, I really do enjoy your content.

[@HappyLittleDiodes]

Join the discord if you can! We'll all be interested to see those things

[@TRIALSDC]

@HappyLittleDiodes will do, I'll get on there Wednesday evening, and we will have a chat.

[@TheTrashcutter]

I read "Sinclair" and liked before even starting watching 🙂

[@HappyLittleDiodes]

There's plenty more Sinclair videos where that came from!

[@ivolol]

If you use very fine sandpaper / buffing compound you can buff out the scratches in the window, likely. Not sure if you're planning on replacing the eletrolytic caps? Only biggest problem with the meter is lacking a continuity test, those are so often helpful. You can buy shrouded / safety jacks and sometimes do a little drilling to fit them if you want. Nice display on the unit.

[@dpvng.dpvng.]

if they are using different current or voltage to measure resistance, values should not necessary must be the same when measuring circuit with non-linear elements in it, like spectrum. it will be better to use actual resistors comparcing for this.

[@HappyLittleDiodes]

Yes that's a good point and I'll do that next time I have it open. The resistance test on the spectrum is just to check for very low resistance (close to open circuit) before powering on, so I never consider the reading in great detail

[@josephlunderville3195]

Screws are stainless steel I would think more for corrosion resistance than anything to do with measurement.. similarly plastic nuts and bolts I'd guess are more likely about safety to avoid arcing to the case. Magnetics afaik are not really much of a consideration expect in fairly obscure circumstances.

[@Brian_Of_Melbourne]

More likely nickel plated brass back then.

[@mikeh_nz]

Polywatch and a microfiber cloth would polish the scratches away on your purple plastic cover

[@firsteerr]

our head master had one of these we built a language lab with it a few switches and relays basically i remember it well measuring resistors for him for some reason

[@alex.theoto]

For the probes, you can cut the sleeves of the male plug and you can plug them directly.

[@caggius42]

Showing my age here I still have a pair of the probes shown in the advert….

[@HappyLittleDiodes]

Ahh I really want some, I'm going to keep an eye on ebay

[@LarsHHoog]

The background music makes it harder for us with hearing impairment and I'm curious to hear your rationale for adding it and if my remark will make you rethink the selection.

[@HappyLittleDiodes]

I always try to turn it right down, some of my earlier videos have the background music way too loud. I will keep this in mind and turn it down even more. I like to include it because it's hard to imagine people not getting bored listening to my voice!

[@LarsHHoog]

@@HappyLittleDiodes well, people needing music can have that on in their speakers. I find it really odd that you seem to say that you dont take care.

[@LarsHHoog]

@@HappyLittleDiodes maybe that was a bit hard but what it you had a flashing border in the video and got the feedback that it was distancing. Would making it still flashing but in other colours be an improvement?

[@HappyLittleDiodes]

@LarsHHoog that would be a bit strange but I catch your point!

[@Brian_Of_Melbourne]

@@HappyLittleDiodes If people are bored by your vocal (not saying they are), then a little bit of background music ain't gonna help.

[@grashoppah]

Here from dinos:)

[@moonandwanderer]

⌨️

[@HappyLittleDiodes]

🐥

[@Andrew-rc3vh]

The circuitry is offensive to the eyes! The whole construction is completely shoddy. I think those ganged switches are supposed to be for record players/audio. I would not trust those presets either. It's basically using the cheapest nastiest components available at the time. Compare to a HP instrument of the same period and you will see how it is supposed to be done. No wonder the firm went bust. British industry as a whole went bust as I recall.

[@michaelturner4457]

Being cheap and affordable, that was the entire Clive Sinclair ethos. Of course an equivalent HP instrument would have set you back much more, and out of the price range of most UK hobbyists in the 1970s. I certainly couldn't have afforded HP on my meagre allowance. HP and the like they were really for professional users, in a lab. This "shoddy" meter is almost 50 years old, and still works. I'm sure most modern, Chinese made electronic tech devices won't be working after half a century. Sinclair's instrument division was actually profitable, and was spun off by the NEB when Sinclair Radionics was broken-up in the late 70s, to become Thandar. Who are still in business as Thurlby Thandar. The British electronics industry was really done- in by overseas Far East manufacturing, e.g. it was much cheaper for companies to manufacture in Hong Kong than in the UK.

[@Andrew-rc3vh]

@@michaelturner4457 It's the Amstrad philosophy. See the offensive construction they used to use. Every corner is cut.

[@michaelturner4457]

@@Andrew-rc3vh But Amstrad was very successful for decades, and eventually did buyout Sinclair, after his C5 trike and QL computer disasters. Yes, Sinclair did try and save as much as possible on components, like the skeleton presets and almost no overload protection. Shove 230VAC mains across the ohms range, it'll probably go BANG!.That's why this digital multimeter was affordable to hobbyists at the time, including me. Quite frankly looking at the way the PCB was put together looks reasonable for the time (1970s), especially given that it was designed, stuffed, and soldered by hand. IMO not "offensive". Only thing I can see is they didn't clean the surplus flux from the underside of the board after soldering, which is Uncle Clive not spending money on 1,1,1-trichloroethylene. Think this DM2 might be a later specimen, because some other DM2s have green glass-fibre circuit boards, rather than the cheaper brown SRPB, and plastic enclosed (Piher Spain) presets rather than the cheap open skeleton types. But it's certainly a better standard of workmanship than many things that came out of Hong Kong, such as radios. An equivalent HP digital multimeter with much better components construction quality cost many hundreds of pounds in the '70s, and was quite out of the reach of most hobbyists. I believe the original price for the DM2 was £49.

[@Andrew-rc3vh]

@@michaelturner4457 The Japs came along and did low price electronics, but if you study their construction it is is pretty good for the time. They deserved to get ahead. Sinclair is quite typical of a lot of British tech brands. You just get the impression they don't care. Notice the revisions in the circuit as well. That's another bad sign. I don't think their prices were that cheap either. HK was much cheaper.

[@ironwheal]

the whole construction is so cheap and sloppy. the lower low end.

[@Brian_Of_Melbourne]

It's a product of its time and the Sinclair ethos.

[@ironwheal]

@@Brian_Of_Melbourne maybe just Sinclair ethos 😃 devices of that era were usually built like tanks.

[@HappyLittleDiodes]

So cheap though! Accessible for hobbyists

[@michaelturner4457]

Because they were intended to be affordable by ordinary hobbyists at home. As a kid in the 1970s with pocket money and a paper round, I could afford a Sinclair multimeter, but NOT an HP multimeter. In fact I actually bought a Sinclair PDM35 in 1978, which served me right through the 1980s, for many projects and repairs at home, and it was reliable. The PDM35 was typical Clive Sinclair cost savings, in that it used a repurposed enclosure from the Sinclair Oxford calculators. Tandy(Radio Shack) also sold the same Sinclair multimeter, badged as Micronta.

[@standishgeezer]

@@HappyLittleDiodes £59 i(+ 8% VAT) in1974 equates to over £770 today! Now, you could by a BK Precision BK2831E (20000 count - 4.5 digit) for £480 (including VAT). Hope you were just kidding about the Sinclair being accessible for hobbyists.

[@ninaevans4501]

We have a Sinclair DM2 fully working, with a fully working display, but with no probe acknowledgement. Thanks Mr R...o C......r. That is as far as we'll go with the offending gentlemans channel. Nina.

[@HappyLittleDiodes]

I feel like there's more to this story!

[@ninaevans4501]

@@HappyLittleDiodes There is more to this story.... Offending gentleman supplied an a..e about face wired battery snap connector 😔😔😔😔😔😔😔 Nina

[@ninaevans4501]

Thanks for your info on the Sinclair DM2 Multimeter. We have (since our last comment) downloaded all circuit diagrams for this machine over the internet. We made a mistake, and purchased one of those BIG 9volt battery snaps for a PP9? (9volt battery). The supplier didn't know his negative wire from his positive, so therefore wired the battery snap arse about face. Anyway....... the DM2 is working again thanks to your pointers in the right direction. Wayne & Nina 🫡🫡🫡🫡🫡🫡🤝🤝🤝🤝🤝🤝😊😊😊😊😊❤️❤️❤️❤️❤️

[@ninaevans4501]

About 3 years ago, we purchased s Sinclair DM2, with a rotted battery (plus rotted battery snap) off E.....y. It turned out that the circuitry was fine, as tested by my bench power supply. I then make a mistake, I order a new battery snap off a chap who has his own YT channel (I will not mention his name or channel). Needless to say, the battery snap was INCORRECTLY WIRED. For the last 3 to 4 years we have a Sinclair DM2, which works, but the display no longer displays a 9volt battery reading from a 2kohm resistor. Any ideas as to what has failed? Nina. And thanks for another fantastic video. 👏👏👏👏👏👏👏👏❤️❤️❤️❤️❤️❤️❤️❌️❌️❌️❌️❌️❌️😊😊😊😊😊😊😊😊😊😊😊

[@HappyLittleDiodes]

I'm afraid I have no idea what could have failed, there are schematics out there, however, which will help you diagnose

[@michaelturner4457]

If it was reversed battery, I suspect an IC or transistor has popped.

[@ninaevans4501]

@michaelturner4457 From Nina, it turns out that all chips, and transistors survived this reverse polarity cock up. But the diodes were not happy little diodes anymore. Therefore, they all had to be replaced. 😖😖😖😖😖😖🤨🤨🤨🤨🤨🤨