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Test Equipment Anonymous (TEA) group therapy thread

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Robert763:
The 74HC4052 MUX ICs for the Amprobe 2020 Power analyser on Tuesday. It's been a very hetic week at work so I wasn't able to look at it until yesterday. As a reminder this was a £50 ebay BIN with two sets of current clamps (200A and 1000S). It showed 0 V an all voltage inputs but current was OK. I changed both the MUX chips on the voltage inputs. That produced and output from the MUX that was missing before. Still zero on the display. I traced the circuit out through a MAX494 (quad op-amp) and MAX 492 (dual) set up for differential amp and DC offset. I then followed a live signal through to pin 97 (AN0 input) of the CPU (M30624FG). I'm strting to get worried at this point as it's an FLASH ROM CPU so no a simple replacement.
While tracing the circuit the signal also went to a LM324. Obviously not part of the voltaage measurement circuit, but I looked further. signal went to 1st op-amp configured as a unity gain buffer. The output was clipped positive but below the supply voltage. Rest of the circuit not traced but didn't seem to be doing much. As ther was a 1k resistor on the output of the buffer there was clearly something amiss. So found an old board with a SOIC LM324 and swapped it out. I was now getting a sinewave on pin 1. More interestingly I was now getting a 50 Hz squarewave on pin 8.
I don't know it it is working at this point besause you have to remove the PCB from the case to get to the component side and this disconnects the display. So put it back together, power up plug in and it works!
 :-DMM
It looks like he 324 is generating a phase reference / clock and it does not measure voltage unless it's present.
Anyway een with the repair required an tidy 3 ph power anlalyser for £50 is a bargain. It has the functionality of a Fluke 43x but the build quality is way lower. It even feels light and flimsy. Good enough for my use though.

Neomys Sapiens:

--- Quote from: Vince on January 23, 2022, 06:31:59 pm ---
What a coincidence ! I sold mine this week !!

I bought it last summer for 30 Euros and sold it for 75 Euros in less than 48 hours, I was stunned !
I mean I didn't think I would be abel to sell it at all to be honest !

Well, OK it was  not Tek it was the Createc SC-04 but... it's the OEM after all... and it's 10MHz, T202 is only 5MHz IIRC... Tek didn't sell the 10MHz version it seems (according to Tekwiki...)

Anyway, it was fun but I quickly got bored with it... just too horrible and cumbersome to use... still targeting a Tek THS 700 series as a vintage portable scope.... I saw couple here for sale at under 100 Euros, but of course they escaped me, they got sold in about 10 seconds... only to reappear a week later at 750 Euros, their usual going price over here...

--- End quote ---
Maybe it is an exhibit now at the 'musée des interfaces opérateur cruelles et idiotiques '.

Neper:

--- Quote from: Cerebus on January 23, 2022, 06:28:05 pm ---That is handling anything one would classify as "yucky" (like cleaning out the dustbin) or physically sticky.
--- End quote ---

I'd like to add mineral wool to the list. The kind they use in loudspeakers. Makes me want to scratch myself to the moon and back if I only see the stuff. 

Vince:

--- Quote from: Robert763 on January 23, 2022, 07:40:49 pm ---The 74HC4052 MUX ICs for the Amprobe 2020 Power analyser on Tuesday. It's been a very hetic week at work so I wasn't able to look at it until yesterday. As a reminder this was a £50 ebay BIN with two sets of current clamps (200A and 1000S). It showed 0 V an all voltage inputs but current was OK. I changed both the MUX chips on the voltage inputs. That produced and output from the MUX that was missing before. Still zero on the display. I traced the circuit out through a MAX494 (quad op-amp) and MAX 492 (dual) set up for differential amp and DC offset. I then followed a live signal through to pin 97 (AN0 input) of the CPU (M30624FG). I'm strting to get worried at this point as it's an FLASH ROM CPU so no a simple replacement.
While tracing the circuit the signal also went to a LM324. Obviously not part of the voltaage measurement circuit, but I looked further. signal went to 1st op-amp configured as a unity gain buffer. The output was clipped positive but below the supply voltage. Rest of the circuit not traced but didn't seem to be doing much. As ther was a 1k resistor on the output of the buffer there was clearly something amiss. So found an old board with a SOIC LM324 and swapped it out. I was now getting a sinewave on pin 1. More interestingly I was now getting a 50 Hz squarewave on pin 8.
I don't know it it is working at this point besause you have to remove the PCB from the case to get to the component side and this disconnects the display. So put it back together, power up plug in and it works!
 :-DMM
It looks like he 324 is generating a phase reference / clock and it does not measure voltage unless it's present.
Anyway een with the repair required an tidy 3 ph power anlalyser for £50 is a bargain. It has the functionality of a Fluke 43x but the build quality is way lower. It even feels light and flimsy. Good enough for my use though.

--- End quote ---

Wow well done, you didn't give up ! Glad it was something simple to repair, just cheap off the shelf parts !
You can enjoy your meter now, you worked at it, you deserve it !  ;D

Vince:

--- Quote from: Neomys Sapiens on January 23, 2022, 07:41:49 pm ---
--- Quote from: Vince on January 23, 2022, 06:31:59 pm ---
What a coincidence ! I sold mine this week !!

I bought it last summer for 30 Euros and sold it for 75 Euros in less than 48 hours, I was stunned !
I mean I didn't think I would be abel to sell it at all to be honest !

Well, OK it was  not Tek it was the Createc SC-04 but... it's the OEM after all... and it's 10MHz, T202 is only 5MHz IIRC... Tek didn't sell the 10MHz version it seems (according to Tekwiki...)

Anyway, it was fun but I quickly got bored with it... just too horrible and cumbersome to use... still targeting a Tek THS 700 series as a vintage portable scope.... I saw couple here for sale at under 100 Euros, but of course they escaped me, they got sold in about 10 seconds... only to reappear a week later at 750 Euros, their usual going price over here...

--- End quote ---
Maybe it is an exhibit now at the 'musée des interfaces opérateur cruelles et idiotiques '.

--- End quote ---

Sure would be a good fit for such a museum ! :-DD

I have no idea who bought it... had zero contact with the seller ! He just clicked the "buy" button, I sent the scope, got my money transferred automatically a few day later and that's it... for all I know it could have been a robot buying it, not even a human being ?!  :-//

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