Test Equipment Anonymous (TEA) group therapy thread

[worsthorse]

Well my hopes of "touch it up and sell it" for the 2831D DMM were dashed tonight. I did a quick check and found it out of spec by a little for DC volts, low for resistance readings, and a little high on AC Volts. But I found the service manual and there are adjustments for each, so no problem!

Unfortunately, the meter doesn't zero on the AC ranges and I can't adjust the 10V DC range within spec. In both cases the adjustment pot is hard against one limit. Worse yet, When I removed the metal shield on the main circuit board, I discovered that the plastic trimmer screw on one of the pots had been stripped by some gorilla. I guess he/she/it was trying to force the adjustment past the limit. I can still turn it but I should probably replace it.

Time to cozy up with the schematics. Tomorrow I will start checking the power supply and reference voltages.

[worsthorse]

I left mine on over supper just now and I found it pegged downscale. 

Does yours drift more when you touch the thermistor body? This is metal part just behind the N connector. Mine seems to move a lot when I apply body heat to this area.

Oh, wow. When I hold onto the thermistor, it goes almost full scale in a matter of seconds. So much for, "Design of the mount minimizes adverse effects from environmental temperature changes during measurement," and "Each mount contains two series pairs of thermistors, which are matched to cancel the effects of drift with ambient temperature change."

Tapping or moving the mount and cable around makes the needle wiggle, too.

I don't know what to expect since I haven't owned these things before. Maybe such sensitivity is normal when set to measure tens of µW?

I am watching this discussion with some interest. I have three HP power sensors, from microwatts to watts, and three meters of various sorts. I want to start working on them once I finish the last of the DMMs (two down, one on the bench, two to go).

[bitseeker]

Cool. Feel free to join the party, wch!

[bd139]

HP power sensors is one graveyard I do not set foot in 

Edit: cheap, new 34460A here: https://cpc.farnell.com/keysight-technologies/34460a/multimeter-digital-bench-6-1-2/dp/IN0671269 (£200 off usual price). I honestly did consider it and bouncing the 34401A for a few moments  . This doesn’t have Ethernet or rear terminals though like the 34461A though.

[Mr. Scram]

HP power sensors is one graveyard I do not set foot in 

Edit: cheap, new 34460A here: https://cpc.farnell.com/keysight-technologies/34460a/multimeter-digital-bench-6-1-2/dp/IN0671269 (£200 off usual price). I honestly did consider it and bouncing the 34401A for a few moments  . This doesn’t have Ethernet or rear terminals though like the 34461A though.

I'd rather take the DMM6500.

[BU508A]

HP power sensors is one graveyard I do not set foot in 

Edit: cheap, new 34460A here: https://cpc.farnell.com/keysight-technologies/34460a/multimeter-digital-bench-6-1-2/dp/IN0671269 (£200 off usual price). I honestly did consider it and bouncing the 34401A for a few moments  . This doesn’t have Ethernet or rear terminals though like the 34461A though.

I'd rather take the DMM6500.

Nice review from Shariar of the very similar DAQ6510:

http://thesignalpath.com/blogs/2019/08/04/keithley-daq6510-6-5-digit-data-acquisition-multimeter-review-teardown-experiments/

[Mr. Scram]

Nice review from Shariar of the very similar DAQ6510:

http://thesignalpath.com/blogs/2019/08/04/keithley-daq6510-6-5-digit-data-acquisition-multimeter-review-teardown-experiments/

I've watched that one a handful of times. TSP is obviously always a joy too. The DAQ is a bit too pricey for my specific needs. I'd probably rather add it as a second unit when and if I outgrow the first one.

[bd139]

300 more galactic credits though here and you have to spend on acquisition modules if you really want to make use of it as it is intended.

Edit: also as I think I mentioned elsewhere, the thing is pretty slow in switched config when you include settling time and switching time. Better to buy a couple of basic DMMs and cheaper switches. That’s if you care about test system throughput.

[Specmaster]

300 more galactic credits though here and you have to spend on acquisition modules if you really want to make use of it as it is intended.

Edit: also as I think I mentioned elsewhere, the thing is pretty slow in switched config when you include settling time and switching time. Better to buy a couple of basic DMMs and cheaper switches. That’s if you care about test system throughput.

It is also rather spartan on the specs, 750VDC, come on it cannot be that hard to take it upto at least 1,000V and only a 3A current rating, I know that is about normal for a bench meter, but again, its hardly difficult to stick a larger shunt inside is now?

I know that these ranges are not always used very often, but it is nice to have them there for the odd time that you do need to go higher. 
 

[BU508A]

300 more galactic credits though here and you have to spend on acquisition modules if you really want to make use of it as it is intended.

Edit: also as I think I mentioned elsewhere, the thing is pretty slow in switched config when you include settling time and switching time. Better to buy a couple of basic DMMs and cheaper switches. That’s if you care about test system throughput.

You mean something like the Aneng AN8009?

https://www.aliexpress.com/item/32839539223.html

[bd139]

 

Was thinking more a couple of 34460A's or something

[BU508A]

Ah! When you are saying "basic DMM" and thinking of "I'm cheap" the Aneng was the first one which was coming to my mind.
I was wondering where the GPIB connection will be, though.     

[Mr. Scram]

300 more galactic credits though here and you have to spend on acquisition modules if you really want to make use of it as it is intended.

Edit: also as I think I mentioned elsewhere, the thing is pretty slow in switched config when you include settling time and switching time. Better to buy a couple of basic DMMs and cheaper switches. That’s if you care about test system throughput.

Just buy four DMM6500s. That TSP system link is interesting.

[Zucca]

cheap, new 34460A here: https://cpc.farnell.com/keysight-technologies/34460a/multimeter-digital-bench-6-1-2/dp/IN0671269 (£200 off usual price). I honestly did consider it and bouncing the 34401A

I sold all my four 34401A for kept my 34461A, now everytime I press the on button I have to wait until it boots; with the 34401A I was ready to go immediately.
Nothing critical, but it could be annoying for someone.

[bd139]

Broken Telequipment D75 in Hammersmith £20. Do I need another analogue scope? 

Worst case it’s got £20 worth of dual FETs, pots and knobs in it.

Edit: too late; I did it  . Still not got over the loss of the D83’s and this is basically a D83 with a 465 tube in it. I have the benefit now of a huge amount of spares.

[nixiefreqq]

Broken Telequipment D75 in Hammersmith £20. Do I need another analogue scope? 

Worst case it’s got £20 worth of dual FETs, pots and knobs in it.

Edit: too late; I did it  . Still not got over the loss of the D83’s and this is basically a D83 with a 465 tube in it. I have the benefit now of a huge amount of spares.

we are agog in south central PA.

what happened with the 1740a?

[tautech]

Still not got over the loss of the D83’s and this is basically a D83 with a 465 tube in it.

Me neither, it's the only CRO I now wish I'd hung onto despite that I always had my head under its hood ! 

[bd139]

Broken Telequipment D75 in Hammersmith £20. Do I need another analogue scope? 

Worst case it’s got £20 worth of dual FETs, pots and knobs in it.

Edit: too late; I did it  . Still not got over the loss of the D83’s and this is basically a D83 with a 465 tube in it. I have the benefit now of a huge amount of spares.

we are agog in south central PA.

what happened with the 1740a?

Still here. It was waiting for an LM723 which just came through the door five minute ago so will get into that now.

Still not got over the loss of the D83’s and this is basically a D83 with a 465 tube in it.

Me neither, it's the only CRO I now wish I'd hung onto despite that I always had my head under its hood ! 

Yeah a working one is a glorious thing. But rare 

This one appear to have an intact timebase control so I want to carefully dismantle it and measure so I can get a replica 3d printed. Lots of demand for that. The CT curve tracer and all the plugins use them and they are rare as anything!

[bd139]

Still on holiday. Woohoo. That means 1740A time. So put the new LM723 in. Fortunately this one is socketed so it didn't mean removing the power supply again and was really easy.

So firstly the new LM723 regulators installed. Fortunately one of them was still good:



The repaired and re-connectored power supply. 6-way connectors were cheaper so I just got them. Also made for easier debugging which was handy:



Fired it up and voltages were slightly too high so I trimmed them down again to 15.000V and all the rails are now spot on.

Anyway first time this is running under its own power supply:



Seems to work ok. The timebase needs a bit of a squirt of contact cleaner however. Sort of expected with the ganky switches in there.

Next steps are:

1. I'm going to add a small heatsink made out of a bit of bent alu sheet to the 15V rectifier as it runs very hot. This should stop it taking the rest of the damn thing out.
2. Clean timebase out and calibrate it.
3. Feeeet. beanflying's 1740A feet will be printed by a friend of mine at some point in the next couple of weeks. He's got a relatively decent printer and is doing it for free if I set up his WiFi extender

[0culus]

I left mine on over supper just now and I found it pegged downscale. 

Does yours drift more when you touch the thermistor body? This is metal part just behind the N connector. Mine seems to move a lot when I apply body heat to this area.

Oh, wow. When I hold onto the thermistor, it goes almost full scale in a matter of seconds. So much for, "Design of the mount minimizes adverse effects from environmental temperature changes during measurement," and "Each mount contains two series pairs of thermistors, which are matched to cancel the effects of drift with ambient temperature change."

Tapping or moving the mount and cable around makes the needle wiggle, too.

I don't know what to expect since I haven't owned these things before. Maybe such sensitivity is normal when set to measure tens of µW?

Maybe. It’s good to know that mine isn’t the only one. Mine seems to measure power just fine, agreeing almost exactly with the 436A meter I have in short term. It just drifts a lot more. 

[BU508A]

Nice job.   

Fired it up and voltages were slightly too high so I trimmed them down again to 15.000V and all the rails are now spot on.

Why haven't you activated the 6 1/2 digit mode of your gorgeous 34401A?   

[xrunner]

Nice job.   

Fired it up and voltages were slightly too high so I trimmed them down again to 15.000V and all the rails are now spot on.

Why haven't you activated the 6 1/2 digit mode of your gorgeous 34401A?   

Waiting on the new display. 

[med6753]

Still on holiday. Woohoo. That means 1740A time. So put the new LM723 in. Fortunately this one is socketed so it didn't mean removing the power supply again and was really easy.

So firstly the new LM723 regulators installed. Fortunately one of them was still good:



The repaired and re-connectored power supply. 6-way connectors were cheaper so I just got them. Also made for easier debugging which was handy:



Fired it up and voltages were slightly too high so I trimmed them down again to 15.000V and all the rails are now spot on.

Anyway first time this is running under its own power supply:



Seems to work ok. The timebase needs a bit of a squirt of contact cleaner however. Sort of expected with the ganky switches in there.

Next steps are:

1. I'm going to add a small heatsink made out of a bit of bent alu sheet to the 15V rectifier as it runs very hot. This should stop it taking the rest of the damn thing out.
2. Clean timebase out and calibrate it.
3. Feeeet. beanflying's 1740A feet will be printed by a friend of mine at some point in the next couple of weeks. He's got a relatively decent printer and is doing it for free if I set up his WiFi extender

Looks good!  I thought you mentioned that one of the pass transistors had taken a dump? No? It was just the 723?

[bd139]

Thought it was a pass transistor but it was the drive current from the LM723. I stuffed a DMM in series with base and it was only driving 4mA through whereas for the beta it should have been about 30mA. That was causing rails to collapse.

Anyway made a heatsink quick. Took longer to get the bloody screw in than make the heatsink. Disclaimer: I have zero metalworking tools here so this was literally aviation shears, file and hand drill

[xrunner]

Not bad at all!