HELP! SurfPI Constant tone - but hacked to work 'backwards'?

[fo0bar]

There is nothing wrong with the MM is there ?

I wish it could have been that simple I've tested it alongside the meter my father gave me when I was a kid 25 years ago - both exactly the same results - and I've also tested both MM's on the 3.3 & 5v calibration outputs on my scope to make sure they're not both out!

The one in the pictures does float 2-3 mv when not in circuit, but that's small enough not to bother me.

[SVEN1]

This is just a random thought, that rang a bell when I was using gold plated machined IC sockets. I no longer use the IC sockets you used. Sometimes the internal pins break from the socket if you remove and replace IC's often. And you may not notice the broken IC socket. I now use the cheaper sockets, pictured below without any problems. This may or may not be your problem.

[6666]

I wish it could have been that simple I've tested it alongside the meter my father gave me when I was a kid 25 years ago - both exactly the same results - and I've also tested both MM's on the 3.3 & 5v calibration outputs on my scope to make sure they're not both out!

The one in the pictures does float 2-3 mv when not in circuit, but that's small enough not to bother me.

OK cross that off, it was about 2:00 am when I asked that, bit tired, but I have a mm that gives weird readings at low volts, it never goes to zero (ground) when circuit testing,
I dunno if you want to waste more time on these chips, but just for fun while you have the breadboard out, just to get some satisfaction from these chips you could try some generic off sets

[waltr]

OK cross that off, it was about 2:00 am when I asked that, bit tired, but I have a mm that gives weird readings at low volts, it never goes to zero (ground) when circuit testing,
I dunno if you want to waste more time on these chips, but just for fun while you have the breadboard out, just to get some satisfaction from these chips you could try some generic off sets

Another good suggest and I was also thinking this.
Does a simple inverting or non-inverting circuit work with those op-amps.
Set for a gain of under 3 and use a pot as a Voltage divider for the input.

[fo0bar]

This is just a random thought, that rang a bell when I was using gold plated machined IC sockets. I no longer use the IC sockets you used. Sometimes the internal pins break from the socket if you remove and replace IC's often. And you may not notice the broken IC socket. I now use the cheaper sockets, pictured below without any problems. This may or may not be your problem.

This is an excellent point, sven1. I have noticed previously that the machine pins do fail quicker than the cheapo ones - The lack of the springy contact also does kind of bug me however I mitigate that by keeping the IC legs slightly bent outwards, and giving them a gentle squeeze when inserting it - to ensure a nice firm fit within the socket's holes.


While very valid, and it did cross my mind after I'd removed and replaced the chips a few times, this also unfortunately wasn't the problem in this case.

OK cross that off, it was about 2:00 am when I asked that, bit tired, but I have a mm that gives weird readings at low volts, it never goes to zero (ground) when circuit testing,
I dunno if you want to waste more time on these chips, but just for fun while you have the breadboard out, just to get some satisfaction from these chips you could try some generic off sets

My old meter started acting exactly as you describe, which is what prompted me to buy the new one... I then tested the old leads with my new meter and there was a great deal of resistance - living in the tropics with year-round 90% humidity for 20 of those 25 years had made the leads oxidise the entire length. I hadn't noticed at first as I'd had a bit of a 'break' from EE stuff until I'd settled in my current city, which must have been when it really started getting bad. I rigged up some home made test leads for it (the homemade breadboard probe set is in the above pictures) and extended its life for who knows how much longer...

Same thing happened with a circa-1970's Weller iron - turned it on one day and the cable started melting. It had oxidised, the insulation had sweated its oils, became brittle and cracked, and was shorting the 24vDC directly within the cable. Replaced the cable and maybe it'll last another 40 years.... Also once lost two car engine cylinders at once due to oxidised ignition leads. Living in the tropics particularly, I found environmental factors can be HUGE.

Maybe try some other leads on it and see if it still acts strange - also *some* meters will allow you to trim/calibrate off the error if it seems consistent - see if you can pop the back off!

I'll have a bit more of a play with these bunk chips on the breadboard, just for giggles - and to see if there is ANY way I can use these down the line, even if they're a bit handicapped.





However...


...While walking in the city this afternoon I walked past a Jaycar and just couldn't resist. Call me impatient - my chips are due to arrive from RS tomorrow


PROBLEM SOLVED!


Solution:
DON'T BUY IC'S FROM EBAY


I've only just gotten home and inserted a NE5534AP by On Semiconductor (the fakes were TI). At first it was sounding constantly - and then I turned the offset pot a little and it actually changed the offset!!!! Obligatory air-punch, pelvic thrust and loud cheer.


It's now detecting a sterling Aussie shilling at around 20cm, and a 20c coin at around 25cm. As far as I've seen quoted from other people who've used this unit, this seems like an acceptable range for before proper calibration. I'm now going to try the other coils I've made to find which one has the best detection distance.

What a relief. Thanks again for your help with this everyone

[6666]

good news !!!!!

[waltr]

Great news and a hard learned lesson.

[kt315]

Solution:
DON'T BUY IC'S FROM EBAY
--
i did buy IC for repair of TFT TVset and it works still novaday. i buy ICs only on ebay just US does not make electronics more.
US refused to stand up own economic on high level and that is hard fact for american people.

[sinclairuser]

I'm considering throwing one of each in a beaker of acid and comparing the dies under the microscope. While I won't be able to see individual components I can see if the entire layout is different/simplified, which is often the case with counterfeits...and if I can get photographs of the dies I'll post those too - but in the meantime I do want to say THANK YOU to everyone for all of your input and guidance - you're legendary!

pictures of those dies would be very interesting, i've often wondered just how many fake chips there actually is out there, how many times have projects been built that seem to work ok but actually have gimped components in them.
I have been mostly lucky the only time i was stung badly was with four ferranti ula chips i got off ebay which were just old random chips that had been remarked as spectrum ula's, thankfully i have a ula tester so they never went near a customers board, but i learned a lesson so now i buy dead and faulty units to get ula's.
Most other chips have alternatives or are still made somewhere, but not the ula, someone is designing an fpga with a piggy back board, but if you are going down the fpga route why not emulate the whole sodding computer?, anyway thats off topic and for an other forum lol.
glad you worked it out,aly.

[nickel_n]

someone is designing an fpga with a piggy back board, but if you are going down the fpga route why not emulate the whole sodding computer?, anyway thats off topic and for an other forum lol.
glad you worked it out,aly.

perhaps you know about this.
http://blog.retroleum.co.uk/electron...cement-module/
to me its all @#$%$#@$%

[6666]

Picture of 5534 die
http://www.proaudiodesignforum.com/f...opic.php?t=454

[Digger429]

Comparing the chip you got from ebay vs. other pics on the net from other sources, the appearance is quite different.
The rough lettering, logo, recoated blacktop surface, I dont think TI would be proud to let that one out of their factory.



I'm an expert because I read this one web page:

http://www.aeri.com/counterfeit-elec...ent-detection/

[fo0bar]

I'm an expert because I read this one web page:
http://www.aeri.com/counterfeit-elec...ent-detection/

This is all quite interesting stuff! I'm now also an expert.

It really is amazing they can be so brazen about counterfeiting - the thing that gets me is that they still need to pay (or maybe they just whip) someone to design the counterfeit circuit, manufacture it etc - it still takes materials etc... While granted they're obviously not including all the components and therefore making out-of-spec parts, it really does amaze me how many devices could be running counterfeits without the end product manufacturer having any idea, sometimes with pretty widespread, dire, unavoidable consequences - https://www.theregister.co.uk/2016/0...erfeits_again/

It really is amazing how far off they can get the appearance on the surface and still get away with it.

Take a look at the 555 in my pics - no notches or markings WHATSOEVER to show a definite pin 1. I just followed "usual practice", and treated it as pin 1 being bottom left of the text.... I'm not sure if this is common or usual practice with these chips, but certainly was one of the things pointing me strongly twoards thinking it's counterfeit also....

I don't have a 'guaranteed genuine' TLC555 yet to compare with... Though the circuit does actually seem to work with this one...


And I think I'm in for a bit of chip flipping - looking over my collection of 40xx chips, I have many of the same series which look completely different - glossy/matte, flat/indented markings, mismatched notches, round/square/bevelled edges... Maybe I can improve the performance of my surfboard by finding a "better counterfeit"

[waltr]

This is all quite interesting stuff! I'm now also an expert.

It really is amazing they can be so brazen about counterfeiting - the thing that gets me is that they still need to pay (or maybe they just whip) someone to design the counterfeit circuit, manufacture it etc - it still takes materials etc... While granted they're obviously not including all the components and therefore making out-of-spec parts, it really does amaze me how many devices could be running counterfeits without the end product manufacturer having any idea, sometimes with pretty widespread, dire, unavoidable consequences - https://www.theregister.co.uk/2016/0...erfeits_again/

It really is amazing how far off they can get the appearance on the surface and still get away with it.

Typically they take older obsolete parts or newer parts that were Rejected and sold as scrape then remark these.
Many times the counterfeit part is close in function so might even seem to work properly -Various 555 chips for example.

Do beware of chips that become hard to get due to demand being greater than supply. These are Prime candidates to be counterfeited.

[nonkapo]

Thanks for you thread guys. Another one here lurking two days like crazy to figure out i'm dealing with fake 5534. Unlike you though i'll not use acid bath but get the big "adviser"(the nickname we use in Bulgaria for the hammer) and will take this crap appart for both the curiosity to see the die and satisfaction to see it DIE(Manowar - Kill with power:-).
For those in the same boat - the unit after assembling have a very low sensitivity only to ferous metals(aka 12cm) , delay pot is not changing anything as well as the offset cannot be adjusted - steady 0,38,042v appear depending on the fake 5534 example(three cheked). The sensitivity, volume and treshold pots work as intended. The trick here is that i source all the parts from different Dubai based shops(silverdog is too far from here). Have habit to take the same parts from two three different places, so luckily one working 5534 was there.
Happy hunting