One of the worlds first Pocket Digital Multimeters | 1977 Sinclair PDM35 | Can I Fix It?

I saw a Faulty Sinclair PDM35 Pocket digital multimeter on eBay, so I bought it to try and preserve what is one of the worlds first pocket digital multimeters. It was made around 1977 and sold for £34.50 at launch. Let's take it apart, see if we can diagnose the problem and hopefully repair it!

I'm not an expert, but I do enjoy trying to fix things.

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Some of the tools and equipment that I use:

Kaiweets KTI-W02 Thermal Camera:
15% off code: BIFI15

or alternatively on Amazon UK:
15% off code: GQ7SHK42
Date of expiry: 2024-10-31

Other Kaiweets thermal cameras:

TOMLOV 4K AF Microscope:
TM4K-AF Flex: 8" screen
10% Discount code: 10BuyitFixit

10% Discount code: 10BuyitFixit
TM4K-AF Max: 10.1" screen

Other Equipment:
Main Overhead camera: Sony HDR-CX450 with 3rd party remote and RODE VideoMic Pro
Other cameras: Canon G7X, iPhone 6s, Go Pro Hero Silver 7 (which I repaired on a video)
Microscopes: Amscope trinocular (clone) with FHD 48MP Camera V8
& TOMLOV TM4K-AF Max.

Editing Software: DaVinci Resolve

The above links are amazon affiliate links, and I may receive a small amount from Amazon at no extra cost to you, if you choose to purchase an item.

#electronics #electronicsrepair #repair
Sinclair PDM35 Repair
Sinclair PDM35 Troubleshooting
Sinclair Pocket Digital Multimeter Repair
Sinclair Digital Mutlimeter Repair
Fixing A Sinclair Digital Mutlimeter
repairing a Sinclair Digital Mutlimeter
How to fix a Sinclair Digital Mutlimeter
Sinclair PDM35 problems
sinclair multimeter repair

[michaelhawthorne]

Nice to see...My heart literally skipped a beat when I saw this recommendation...🥰
I was in my late teens (I'm 61 in a few days) when I got this for my birthday back in the early 80's....they also bought the 8 digit frequency counter too.
They were both built in the same case and I was working at GEC Coventry England on floor 4 as a technician at the time so could check the frequency calibration using their test frequency feed on floor 3.
It was spot on to the 8th digit.
I loved these and they looked great as a Memories...🥰

[fichambawelby]

Wow! I bought one when they launched it! I was an student, in the last century...I'm 66 now... But I have no idea where it can rest. I swear I don't broke it! What an illusion to have it. You were the king with such a machine those days. Thank you for remembering it!.

[ruipaulofsantos]

I learned something new today, testing ampops!!
A hug from Portugal

[JemTheWire]

Oh the irony of fixing a 1977 DVM with a 2024 DVM. Your patience is amazing, not to mention your diagnostic skills. Thank you.

[frankcarpenetti]

Another good one Mick!! Just my opinion, with something that old, with that few electrolytics, I would replace them first step, see what happens, then check the ones that came out
if I get lucky...LOL Thank You for your time and work.

[tazmaniachill]

Not sure how old I was but I built a few of the modular amplifier kits they made using an aluminium chassis and case and finished with a black crackle finish you sprayed in a can that you baked in an oven and the pll fm tuner. Got me into basic electronics 😂

[darrenwardell]

Another magnificent video made in the early hours. Top job chap👍

[cajuncoinhunter]

Awesome repair on that Those red led's bring back memories of an old Texas Instrument Calculator I had when I was a young teenager ... I traded my cousin a huge stereo speaker for it Take Care Mon Ami ...

[bitterlemonboy]

It's good to relax once in a while and watch someone fix 1970s electronics

[TomMannCenturia]

Lovely stuff. Sinclair were innovators and corner cutters extraordinaire.

[DavoShed]

Great fix. Nice to see old stuff and how much circuit boards have changed.
My first Scientific Calculator was a Texas Instruments and it had those magnifying lenses over the LED’s
It even had a power saving mode as it sucked those 9V batteries dry like a rocket.
Must have been around 1980 🤠

[mikepanchaud]

Great fix. Thinking back to analogue meters, when measuring resistance, you had to select the range required, THEN touch the probes together and use the zero control to zero the display. You have to zero the reading for each resistence range. All analoue meters had a zero knob, presumably to account for inacurate range resistors inside.

[Indiskret]

Another triumphant repair video! Just love those old types of displays. Had it on my first calculator, a Ti58 (which I sadly don't have anymore). Was even programmable back in 1977! Edit: Fun story: My local optician had a Ti59 as the cash register, using the magnetic memory strips and an attached receipt printer. Probably why I got a (cheaper) Ti58 myself. I was thoroughly impressed.

[edgarcornette]

yea I remember the Timex Sinclair 1000 computer.. My parents gave my brother and me both Commodore Vic 20's when they came out I was 5 and I got hooked .. just kept upgrading and learning. Those old computers took my down a path to engineering. Wonderful Fix there .. I was worried you might have to work some of the other pots to get it line up. Thanks for showing that brings back memories. Do you remember when those calculator watches first came out ? How about the Simon Says game .. lol wow we had fun with simple toys growing up compared to today ;) Love ya brother .

[paulvale]

A deserved 50K subs coming very soon Mick. Well earned.

[stefanopassiglia]

Very nice troubleshooting, and I learned the opamp test trick too! I'm amazed you could find the same compoment used back in 1977! Opamps have not changed much, though.

[Lightrunner.]

Wo😻ow, i love the mikro seven digits displays.
This lovley peace, multimeter is great.🥰
Thx. Mick to let it show us 👍👍👍👍

[timwhite]

Goodness, I had forgotten how much I drooled over the ads for this thing in electronics magazines. It’s definitely an old timer like me. Urethane foam dust 😂😂😂

[terrym]

Awesome fix sir👍👍 A digital calculator turned into a digital multimeter....it's always about the bottom line eh. I knew a capacitor or two would be replaced😉 Troubleshooting triumph here, that was a busy hand populated "old school" board. Surprised that IC was available after 45yrs.. Great video and success, thanks for the work. See ya next time.

[ronostrenski]

Ha ha, I was just about to suggest remove and test electrolytic capacitors and then you did at last minute. It’s always the first thing I do when repairing very old equipment. Great video. Great commentary. Greetings from Australia.