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Old 26th Feb 2012, 1:02 am   #1
Restorer79
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Default Tmk 500

Hi Guys,

Just wondering if anyone knows where I can get a circuit for one of these? I've got one in and it's had Phantom attention
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Old 26th Feb 2012, 9:01 am   #2
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Default Re: Tmk 500

Is this the TMK500 multimeter? If it is I have one complete with instructions and circuit which I can scan and post.

Keith
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Old 26th Feb 2012, 6:09 pm   #3
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Default Re: Tmk 500

Hi Keith,

Cheers for the reply, much appreciated. Yes that's the 500 and a nice little meter they are, would be very glad of a copy of the circuit for it. If you let me know how much postage is and where to send the money or a Paypal address I can reimburse you for it.

Unfortunately for this one it's beyond repair. I opened it up today and found a bit of a mess with some burned resistors. There's also wires taken off the PCB and the movement is O/C, but a Circuit would be very useful to keep on file and I may yet find one that actually works.



Regards: Andy
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Old 26th Feb 2012, 9:09 pm   #4
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Default Re: Tmk 500

Here's the instruction manual complete with circuit diagram.

I bought mine new in 1968 (Dec 31st) for £9-17s-6d (£9.87). However it suffered some years later when I tried to measured the voltage on a line output valve anode. About 170v before there was a crack inside as the 6kv spikes found another way to ground across the pcb. It was never quite the same again. I'll have to revisit it sometime and see if I can fix it

Keith
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Old 26th Feb 2012, 10:00 pm   #5
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Default Re: Tmk 500

Hi Keith,

Thank you for that, it may well come in handy. The PCB and switch etc in this one appear to be ok so if there's anything you need off of it, let me know.


Regards: Andy
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Old 26th Feb 2012, 10:42 pm   #6
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Default Re: Tmk 500

Hi Andy,

I have one of these as well, must be over 50 years since I bought it. Mine is a bit erratic now as the PCB traces have worn and the material that sloughed off has become embedded in the board, causing it to short out on some ranges.

Nice little meter though and quite accurate, with an added advantage of being 30K Ohms/Volt
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Old 26th Feb 2012, 11:01 pm   #7
Restorer79
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Default Re: Tmk 500

Hi David,

If it's anything like the TMK700 it will be a nice meter and would be an ideal size to fit the Toolcase. The 700 is just way too big to take out and I wouldn't want to take the Avo 8 out with me nowadays. Anyway if Keith doesn't want the PCB your welcome to it if it will help get yours up and running all you need to do is replace one of the resistors.

Andy
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Old 27th Feb 2012, 12:37 am   #8
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Default Re: Tmk 500

Andy

I feel a challenge coming on so if the pcb is available I'd like to try it. From memory the flashover has caused a conductive path across the PCB which caused it to become a little erratic on some ranges.

I'll PM you with my details later.

Keith
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Old 27th Feb 2012, 4:44 pm   #9
Restorer79
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Default Re: Tmk 500

No probs Keith, it's there when you want it.


Andy
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Old 8th Mar 2012, 6:38 pm   #10
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Default Re: Tmk 500

I've got one on the back of my bench, with frazzled tracks. I need the schematic to work out what connects to where, as the tracks came off and left little trace of where they went. Did you mean 'scan and email', when you said 'scan and post'? My email is Removed by Moderator.

Last edited by Station X; 8th Mar 2012 at 9:40 pm. Reason: Forum rule compliance. Use the Private Messaging System (PM) to convey email address).
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Old 8th Mar 2012, 7:01 pm   #11
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Default Re: Tmk 500

Hi,

Here is a circuit I found on the web for the TMK500, looks similar to Keith's one but the component values are totally different!

http://www.dtforum.net/index.php?topic=39628.0

Michael
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Old 8th Mar 2012, 7:36 pm   #12
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Default Re: Tmk 500

Hi, I have one of those but labelled Skywood model 500. Bought about 40 years ago when I had some money after starting work. See I have replaced the strange 15V battery with one used in an Avo, and will still still zero the meter after 10+? years of not being used. Forgotten it was 33uA, so could so as a replacement for a CT160?? Bob
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Old 8th Mar 2012, 8:10 pm   #13
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Default Re: Tmk 500

Hi Michael,

Thanks for the link, not sure what that one is for. It shows a 9v and 1.5v battery.
I'm still looking for a circuit for the TMK500 TU-B if anyone has one.


Andy
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Old 9th Mar 2012, 12:43 am   #14
John Harwood
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Default Re: Tmk 500

Mine's also 'Skywood' branded, and I solved the obsolete 15v battery problem by slipping 5 X 1632 lithium cells into the holder, along with a spacer I made from some aluminium tube.
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Old 9th Mar 2012, 6:41 pm   #15
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Default Re: Tmk 500

Woodchips, do you happen to have the instructions and/or schematic for the Skywood version, as it appears to have different circuitry from the other 500-type meters?
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Old 10th Mar 2012, 8:19 pm   #16
Restorer79
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Default Re: Tmk 500

Hi John,

What Batteries does the Skywood version take?


Andy
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Old 12th Mar 2012, 8:46 pm   #17
John Harwood
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Default Re: Tmk 500

1 x 15V battery and 1 x 1.5V AA cell. The 15-volter is well obsolete, but available at specialist battery websites. Burgess Y-10 or Eveready 504 are two of its common numbers.
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Old 12th Mar 2012, 9:57 pm   #18
Restorer79
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Default Re: Tmk 500

Hi John (comma, not colon)

It's the same as the BLR154 from Rayovac, they're still readily available from CPC, Rapid (and not &) RS. Rapid being the cheapest. Did you download the manual that keith put up? it may well be the (one not 1) for your meter.

Andy

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Old 17th Mar 2012, 10:07 pm   #19
John Harwood
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Default Re: Tmk 500

Yep, downloaded it, and it's not the same. That's two schematics I have seen for the TMK model 500, and neither of them is quite like the one I have. TMK must have done some product development during the life of this model. I'll keep looking.
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Old 18th Mar 2012, 5:19 pm   #20
John Harwood
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Default Re: Tmk 500

The TMK 500 schematic that KeithsTV posted only has three resistance ranges. My Skywood version has resistance ranges; X1, X10, X1K, X10K... Is there another schematic diagram out there that is more likely to refer to this version of the meter?
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