Test Equipment Anonymous (TEA) group therapy thread

[Addicted2AnalogTek]

So I've been eyeing up this 34401A and was about to submit the seller an offer, until I noticed a couple things...

https://www.ebay.com/itm/HP-34401A-6-Digit-Digital-Multimeter/163842431272?hash=item2625c51928:g:v-AAAOSwGxBdaywq


Does this look to be more than likely a stolen unit to you??

[beanflying]

Re the DIY Fume Extractor project of mine. I won't put up a for sale post until I have the new hardware for them but I ran the pricing past a spreadsheet.

Base model in Pine or Poplar $20 + $7 USD posted with four filters anywhere in the world. Same model for $29 + $5 AUD in Oz. Jarrah or Walnut at the other end of the scale would add $6 USD or $8AUD to the price if you want it fancy.

Spare filters can be sent later as postage is cheap if needed.

Now wondering if I should drink the vast profits, buy a replacement Laser tube, add to the TEA/3458A fund 

[BU508A]

I was wondering what the other side looked like. Thank you for avoiding the use of rivers of solder to complete your circuit.

I'm trying to avoid this technique, because it is lazy and not very elegant. Imho. And it is a waste of valuable ressources.
And, besides this, I love to bend wires. 

[BU508A]

So I've been eyeing up this 34401A and was about to submit the seller an offer, until I noticed a couple things...

https://www.ebay.com/itm/HP-34401A-6-Digit-Digital-Multimeter/163842431272?hash=item2625c51928:g:v-AAAOSwGxBdaywq


Does this look to be more than likely a stolen unit to you??

No idea if this unit has been stolen, but I would go after one with the red and black connectors.
Example:
https://www.ebay.com/itm/293187144549

Reason: the units with the red-only connectors have likely these nearly unobtainium VFD drivers.

But it seems, that somebody replaced the display with an OLED one.

https://github.com/openscopeproject/HP34401a-OLED-FW



Edit:
Link to the related EEVBlog thread:
https://www.eevblog.com/forum/repair/hp-34401a-dmm-with-leaking-segments/

[BU508A]

Nice work:

Somebody has build a 1980s-style music player with VFD. I like the red LEDs on those sliding rheostats.   

Link:
https://imgur.com/gallery/7NiOgrQ

[Mr. Scram]

So I've been eyeing up this 34401A and was about to submit the seller an offer, until I noticed a couple things...

https://www.ebay.com/itm/HP-34401A-6-Digit-Digital-Multimeter/163842431272?hash=item2625c51928:g:v-AAAOSwGxBdaywq


Does this look to be more than likely a stolen unit to you??

Because of the serial sticker being peeled off? I've seen people do worse to their own equipment. That unit has an odd combination of all red connectors and a post refresh keypad so I'm not sure whether that's how it came from the factory.

[McBryce]

Building switching converters has always interested me.

Perhaps you'll find this thing interesting.
Buck-boost converter with single 3.7V input and bipolar (+/- 15V) output@100mA with an LT1172.
I'm looking for a "quiet" converter to supply sensitive opamp circuits so I tested this one.
It is mentioned in the DN47 of LT.

Schematic:



Output, used two LEDs @ 1mA as a load, driven by a constant current source. blue=-15V; red=+15V



The prototype itself:



And this is what my scope sees:

+15V out:



-15V out:



Im not really satisfied, obviously. Need some additional filtering, though.

Edit:
Added DN47

I built something similar recently, but I boosted to 19V and then added linear regulator stages (7815/7915) to smoothen things out. Less efficient, but a much nicer output.

McBryce.

[BU508A]

I built something similar recently, but I boosted to 19V and then added linear regulator stages (7815/7915) to smoothen things out. Less efficient, but a much nicer output.

Yes, I'm considered something similar but haven't built it yet. By any chance, do you have a picture from your output before the linear regulators?

Just curious for comparison reasons.

Edit:

As regulators, I think I'll use these

LT3045-1 (+15V)
https://www.analog.com/en/products/lt3045-1.html

LT3094 (-15V)
https://www.analog.com/en/products/lt3094.html

Edit 2:

Just  stumbled over this one (why didn't I have spotted this before?  )
LTC3260 - single input (4.5V min, bipolar output, up to 100mA current)
https://www.analog.com/en/products/ltc3260.html

[McBryce]

I built something similar recently, but I boosted to 19V and then added linear regulator stages (7815/7915) to smoothen things out. Less efficient, but a much nicer output.

Yes, I'm considered something similar but haven't built it yet. By any chance, do you have a picture from your output before the linear regulators?

Just curious for comparison reasons.

Edit:

As regulators, I think I'll use these

LT3045-1 (+15V)
https://www.analog.com/en/products/lt3045-1.html

LT3094 (-15V)
https://www.analog.com/en/products/lt3094.html

Edit 2:

Just  stumbled over this one (why didn't I have spotted this before?  )
LTC3260 - single input (4.5V min, bipolar output, up to 100mA current)
https://www.analog.com/en/products/ltc3260.html

I doubt it. I did take some screenshots at the time, but I've probably deleted them of the USB stick since then. I don't have the circuit anymore as it was a project I built for someone else.

McBryce.

[bd139]

LTC3260 is interesting indeed. Single 18650 boost to 15V then bipolar 12V from that  . Only problem, as always with LT, is £7 a go 

Sure the Chinese came up with something just as good. I'm using their LDOs which cost a cent each.

Edit: TI TPS65130: http://www.ti.com/lit/ds/symlink/tps65130.pdf ... £2 a go.

[BU508A]

The TPS65130 is really nice! 
But VQFN package? This is hard to solder... 

4mm x 4mm

[bd139]

Yeah. Unfortunately comes with the territory. 4mm isn't necessarily that difficult. It's the heatsink pad that is. Three solutions:

1. Put down the footprint in your PCB package then add a 1.5mm PTH in the middle of it. You can solder that through then 
2. Pay LCSC / JLCPCB to mount it for you (they supply it)
3. Buy the eval board for $49

My current "in development project" has two difficult to mount ICs unfortunately 

[Mr. Scram]

Yeah. Unfortunately comes with the territory. 4mm isn't necessarily that difficult. It's the heatsink pad that is. Three solutions:

1. Put down the footprint in your PCB package then add a 1.5mm PTH in the middle of it. You can solder that through then 
2. Pay LCSC / JLCPCB to mount it for you (they supply it)
3. Buy the eval board for $49

My current "in development project" has two difficult to mount ICs unfortunately 

I've considered doing the PTH trick for a large LGA package. Other than building an oven I don't think I'd be able to do that reliably although the margins are much more generous than those of a QFN.

[BU508A]

Actually I'm designing some adapter PCBs. One for a nice Grayhill rotating switch and one for this depletion P-MOSFET
with this ugly 1mm x 1mm package. Then I can do an adapter PCB for this TI switching controller as well.
Unfortunately, I don't have any experience on how to do that mounting by LCSC or JLCPCB.
Do I have to send them the items? How much hazzle is this?
It sounds really interesting, because they have all the nice machines to handle this properly.
If I would do this by my own, perhaps I'll end up as Mr. Penis-Finger 2 or so ... 

[Mr. Scram]

Actually I'm designing some adapter PCBs. One for a nice Grayhill rotating switch and one for this depletion P-MOSFET
with this ugly 1mm x 1mm package. Then I can do an adapter PCB for this TI switching controller as well.
Unfortunately, I don't have any experience on how to do that mounting by LCSC or JLCPCB.
Do I have to send them the items? How much hazzle is this?
It sounds really interesting, because they have all the nice machines to handle this properly.
If I would do this by my own, perhaps I'll end up as Mr. Penis-Finger 2 or so ... 

I think they only do items they stock themselves. It's a highly streamlined operation.

[med6753]

In spite of my best efforts to blow up the Heath V-7A after fixing all my screw ups it is working normally and correctly across all functions. So now it's time for a simple modification before buttoning it up. Later versions of the Heath VTVM's had a single phone jack with a single probe that has a switch on the probe body to switch out the 1 MEG resistor used for DCV only. When switched out the same probe can be used for ACV / Ohms. This is not an original Heath idea. I think either RCA or EICO used it first on their VTVM's. Heath just copied it. I have one of those Heath probes that came from a junked VTVM. To use it on an older model such as this one all that needs to be done is install one jumper from the AC/Ohms jack to the DC jack. The mod is done and I completely tested it to make sure all is OK. And you can still use the 3 separate probes if want. 

[mnementh]

Actually I'm designing some adapter PCBs. One for a nice Grayhill rotating switch and one for this depletion P-MOSFET
with this ugly 1mm x 1mm package. Then I can do an adapter PCB for this TI switching controller as well.
Unfortunately, I don't have any experience on how to do that mounting by LCSC or JLCPCB.
Do I have to send them the items? How much hazzle is this?
It sounds really interesting, because they have all the nice machines to handle this properly.
If I would do this by my own, perhaps I'll end up as Mr. Penis-Finger 2 or so ... 

These are ridiculously easy with even the cheapest hot-air setup; they're few enough pins you can either pre-tin the pads with an iron/paint with rosin or apply paste manually with a toothpick. The part will literally self align as long as you don't crank the air up so high you blow it off the board. I'm not seeing your problem...?

If you don't have a hot air station, now's the time; this is JUST the sort of project to practice on. Just remember to populate these parts FIRST on a bare board if you're a noob. Or you can get a cheap breakout and plug it into a DIP, but that'll make your end product pretty big: eBay auction: #382865350172 For other outlines, this experimenter's kit is cheap but very interesting (doesn't have specifically QFN24): eBay auction: #272931785519

mnem
moo?

[Kosmic]

anybody's looking for a LCR meter ? 



https://www.ebay.com/itm/ESI-VIDEO-BRIDGE-2100-RCL-Meter-PONT-RLC-K892/293211995823?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m1438.l2649

I wish they were cheaper. Look sooo good, so retro, the design is just perfect. 

[bd139]

Re: prototyping, I woudn't run a switcher on breakouts. They need a good ground plane.

On JLCPCB placement, it's not publicly available yet but they charge you $7 and pick and place any parts in a 32,000 component library for 0.2 cents a join. I'd just get the 0402's and the difficult ICs done myself.

I mostly try and avoid SMD stuff and if I do it I do it on a one off daughterboard or get a PCB made if I have to. This is a typical prototype rig for me, and they are fugly as hell...

[Addicted2AnalogTek]

@BU508A

Thanks for the heads up on these, now I know what to look for in a 34401A.   

1) Red & Black connectors
2) "Agilent" instead of "Hewlett Packard" on the face plate
3) Lack of VFD display module

Anything else I should keep an eye out for before I purchase one (aside from the obvious condition factor and intact seals)?

[mnementh]

Re: prototyping, I wouldn't run a switcher on breakouts. They need a good ground plane. On JLCPCB placement, it's not publicly available yet but they charge you $7 and pick and place any parts in a 32,000 component library for 0.2 cents a join. I'd just get the 0402's and the difficult ICs done myself.

I mostly try and avoid SMD stuff and if I do it I do it on a one off daughter-board or get a PCB made if I have to. This is a typical prototype rig for me, and they are fugly as hell...   

   I'm not even a little bit afraid of using that breakout with a switcher. The center HS pad has multiple vias to an identical huge pad on the bottom; thru-solder then a short pigtail of heavy silicone wire will enhance heat-sinking as well as provide good GND. You can then solder the breakout to 0.100" header or make it plug-in all the way except for that one pigtail. If you're really anal about GNDs (and I know you are  ) you can always run a separate pigtail GNDs from the SOP pads to the proto-board. Easy-peasy. No uglier than what you have right there. 

That said... if JLCPCB has it in their inventory, obvi the simplest choice. 

mnem
*tzzzzt*

[Mr. Scram]

anybody's looking for a LCR meter ? 



https://www.ebay.com/itm/ESI-VIDEO-BRIDGE-2100-RCL-Meter-PONT-RLC-K892/293211995823?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m1438.l2649

I wish they were cheaper. Look sooo good, so retro, the design is just perfect. 

Sex on a stick but a bit pricey indeed.

[Mr. Scram]

@BU508A

Thanks for the heads up on these, now I know what to look for in a 34401A.   

1) Red & Black connectors
2) "Agilent" instead of "Hewlett Packard" on the face plate
3) Lack of VFD display module

Anything else I should keep an eye out for before I purchase one (aside from the obvious condition factor and intact seals)?

Unless I'm misunderstanding you they all have VFDs. There obviously also are the more modern Keysight models with the rounded buttons. Those are fine too but not quite as pretty.

[mnementh]

@BU508A - Thanks for the heads up on these, now I know what to look for in a 34401A.   

1) Red & Black connectors
2) "Agilent" instead of "Hewlett Packard" on the face plate
3) Lack of VFD display module

Anything else I should keep an eye out for before I purchase one (aside from the obvious condition factor and intact seals)?

Unless I'm misunderstanding you they all have VFDs. There obviously also are the more modern Keysight models with the rounded buttons. Those are fine too but not quite as pretty.

He's talking specifically about the "unobtanium" VFD driver that often fails when the VFD fails. IIRC, they are a pretty visible separate part as opposed to later models in which it is integrated into the VFD assembly.

anybody's looking for a LCR meter ?        https://www.ebay.com/itm/ESI-VIDEO-BRIDGE-2100-RCL-Meter-PONT-RLC-K892/293211995823?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m1438.l2649

I wish they were cheaper. Look sooo good, so retro, the design is just perfect. 

Sex on a stick but a bit pricey indeed.

Agreed. Feels like something out of Logan's Run or somesuch... 

mnem
It's only money.

[Mr. Scram]

He's talking specifically about the "unobtanium" VFD driver that often fails when the VFD fails. IIRC, they are a pretty visible separate part as opposed to later models in which it is integrated into the VFD assembly.

Agreed. Feels like something out of Logan's Run or somesuch... 

mnem
It's only money.

I assume I'm still not understanding what you lot are getting at as the VFD drivers shouldn't be visible from the outside.