SMD Test Fixture for the Tektronix 576 Curve Tracer

[Jay_Diddy_B]

Hi,
I needed to test some AO3400 and AO3401 MOSFETs that I purchased from Aliexpress. I decided to make a little circuit board to test MOSFETs on my Tektronix 576 Curve Tracer.
It is a simple project. I thought it might be useful to other people, I am sharing it here.

Schematic



Not a lot to say about the schematic.

Artwork






I made a panel, with mouse bites, so that you get better value from JLCPCB etc.

Prototype

I made a simplified prototype, using an LPKF c60 circuit board mill.





The prototype was used to check the spacings of the banana plugs.


Gerber files

I have attached the Gerber files if you want to order these board. I suggest that you check the Gerber files carefully. I have not got the PCBs back from manufacturing.

Regards,
Jay_Diddy_B

[Jay_Diddy_B]

Hi,

Here are the results from testing the Aliexpress AO3400:

BVds




This is the breakdown voltage from Drain to Source. The measured value was 23V. The specification for the AO3400 is 30V.





RDSon

This is the measured RDSon, the on-state resistance. The resistance is calculated by picking a point on the curve and dividing the voltage by the current at that point. The measured RDSon was 25mV/96mA = 260 m . This is much higher than the specification (<28m )


At least I got MOSFETs that might be useable in some applications ...

Regards,
Jay_Diddy_B

[mawyatt]

Great idea 

We've been working on something similar for our Tek 577, see attached images.

This utilizes both sides with the banana jacks to allow A/B comparisons and a ZIF socket for leaded devices.

For SMD an additional topside PCB plugs into the base unit pcb with the ZIF socket removed. The SMD DUT are pressed down onto the PCB to make contact with the Lever Arms shown in the paper mockup mounted on the 577. We'll see how well this works later.

We haven't had time to order these PCBs yet, as other pressing needs have surfaced, hopefully will be able to get back to this soon.

Best,

[Jay_Diddy_B]

mawyatt and the group,

I have attached a file containing the .step files for a single PCB mounted banana jack and the five jack array used for the Tektronix curve tracers.

The zipfile also contains the Fusion 360 models that were used to make the models.



Regards,
Jay_Diddy_b

[mawyatt]

Thanks, we're using the Pomona 72918 banana plug, Mouser 565-72918.

Need to finish up the solder SMD plug-in PCB that plugs into the base PCB like the PCB with the Lever Arm fixture shown.

These 3 PCBs will allow the use of leaded components with the ZIF socket, non-soldered SMD with the Lever Arm Fixture PCB which fits on top of the base PCB (with ZIF removed) and finally smaller soldered SMD PCB which also sits on top of the base PCB (ZIF Removed).

We'll post the design files after we order/get the PCBs and get things assembled and tested. Not sure how well the SMD Lever Arm fixture will work since it's based upon pressure contact of the SMD which likely will be highly variable, but worth a try!!

Regarding your components from AliExpress or eBay, seems it's always a question with components from them. We've had sub-par LM358s, a LM399 that drifts, sub-par TI switch, and other questionable components. Had good results with the usual US suppliers Mouser, Digikey, Newark and even Chinese LCSC.

Edit: Here's the Solderable SMD Fixture, this plugs in by the 16 pin header and mounts on top of the Base PCB which has the Banana Jacks for the Tek 577. The Kelvin feature is utilized to help remove the connector and trace effects. The PCB is small (0.9 by 0.9 inch), so should be relatively cheap.

Best,

[mazurov]

My take:-). STLs for 3D-printed parts and more pictures here -> https://github.com/nerpatech/tek-ct-adapters

[jonpaul]

Aliexpress etc, junk from ChiCom ms, not worth the effort.

We buy elsewhere

j

[mawyatt]

Great idea 

We've been working on something similar for our Tek 577, see attached images.

This utilizes both sides with the banana jacks to allow A/B comparisons and a ZIF socket for leaded devices.

For SMD an additional topside PCB plugs into the base unit pcb with the ZIF socket removed. The SMD DUT are pressed down onto the PCB to make contact with the Lever Arms shown in the paper mockup mounted on the 577. We'll see how well this works later.

We haven't had time to order these PCBs yet, as other pressing needs have surfaced, hopefully will be able to get back to this soon.

Best,

Finally got around to building this SMD fixture for the Tek 177, I know took long enough

Works really well, tested with some SOT, SMD, TO252 and on various Surface Mount Devices, even plugged in a couple TO92 (still waiting on the 28 pin blue  DIP test adapter shown earlier). We didn't add the sense banana plugs yet, nor the various connectors to allow external connections, so some additional work required later.

Anyway, this will help with some upcoming device sorting & matching (why we originally designed it), and hope some folks find this interesting.

Best,

[mawyatt]

A few more images.

Best,

[mawyatt]

The ZIP socket finally arrived and we built up an adapter with it. Works with leaded Diodes, LEDs, Transistors, and FETs. Handles TO92, TO220, TO126, DO7 and leaded devices, while the fixture with the Lever Arms handles all the SMD devices.

Note, you can plug the ZIF into the PCB if a narrow 28 pin DIP socket is used on the PCB. However, the ZIP pins are flat and oriented along the main axis of the socket, and the DIP sockets are oriented orthogonal to the main axis to accept standard DIP ICs. The ZIF can be installed but really stretches the DIP female pin sockets, so we decided to just built up a dedicated versions just for ZIF use.

Both these adapters work really well, and a good option if one doesn't have the original Tek fixtures.

Anyway, here's what things look like.

[alocam]

Hello, these adapters look great. I wonder whether you plan to share the design files, these would be really appreciated.

Regards

[mawyatt]

Files attached.

Best,

[alocam]

Thank you for sharing the gerber files. I have a couple of TO3 sockets that I ordered a while ago, as soon as I can I'll try design a daughterboard with the TO3 sockets and if everything goes well, may be it is beneficial for other Tek CT users.

Regards

[mawyatt]

You are quite welcome!! We also had a solderable Adapter PCB that was just in case the Lever Arm SMD type fixture didn't work. However we forgot to place the order for this adapter at the time (getting old, real old) 

Since shipping is pretty high we'll wait until the next PCB order, and hopefully won't forget 

Anyway, the Lever Arm SMD approach works so well we don't envision needing to solder anything. Only improvement would be to use a gold plated contact area to improve wear and surface oxidation. If enough local NA folks were interested we might consider reordering with gold plating.

The ZIF socket also works really well too, as most have experienced with the cheap transistor LCR testers, so we "stole" that idea for use with the 577. Honestly we've used the Tek fixtures (had a 576 & 577 in lab with all fixtures before semi-retirement), the ZIP is better IMO, handles all the usual leaded components fine.

BTW, don't exclude the ferrite beads, they help prevent spurious oscillations.

Best,

[ddrl46]

You are quite welcome!! We also had a solderable Adapter PCB that was just in case the Lever Arm SMD type fixture didn't work. However we forgot to place the order for this adapter at the time (getting old, real old) 

Since shipping is pretty high we'll wait until the next PCB order, and hopefully won't forget 

Anyway, the Lever Arm SMD approach works so well we don't envision needing to solder anything. Only improvement would be to use a gold plated contact area to improve wear and surface oxidation. If enough local NA folks were interested we might consider reordering with gold plating.

The ZIF socket also works really well too, as most have experienced with the cheap transistor LCR testers, so we "stole" that idea for use with the 577. Honestly we've used the Tek fixtures (had a 576 & 577 in lab with all fixtures before semi-retirement), the ZIP is better IMO, handles all the usual leaded components fine.

BTW, don't exclude the ferrite beads, they help prevent spurious oscillations.

Best,

Very nice design, ordered a set of boards to build one of these adapters for my 577.
If you don't mind me asking, what type of ferrite bead did you use and what size toggle clamp did you use?

[mawyatt]

Very nice design, ordered a set of boards to build one of these adapters for my 577.
If you don't mind me asking, what type of ferrite bead did you use and what size toggle clamp did you use?

The ferrite beads were 1206 ~120 ohms at 100MHz types, these are not critical tho.

https://www.lcsc.com/product-detail/_TAI-TECH-_C357013.html


The lever arms are from AliExpress, there are two types one with a fixed arm and another with a arm that slides, either should work fine, we have both.

https://www.aliexpress.us/item/3256801104879812.html?spm=a2g0o.order_list.order_list_main.88.65291802I3zu3c&gatewayAdapt=glo2usa

https://www.aliexpress.us/item/3256803684893162.html?spm=a2g0o.order_list.order_list_main.133.65291802I3zu3c&gatewayAdapt=glo2usa

Did you also order the solderable PCB, the one we forgot to order

Anyway, hope this helps, let us know how your project goes!!

BTW we just used this to characterize some TO252 PMOS Power FETs for parallel operation.

Best,

[ddrl46]

Very nice design, ordered a set of boards to build one of these adapters for my 577.
If you don't mind me asking, what type of ferrite bead did you use and what size toggle clamp did you use?

The ferrite beads were 1206 ~120 ohms at 100MHz types, these are not critical tho.

https://www.lcsc.com/product-detail/_TAI-TECH-_C357013.html


The lever arms are from AliExpress, there are two types one with a fixed arm and another with a arm that slides, either should work fine, we have both.

https://www.aliexpress.us/item/3256801104879812.html?spm=a2g0o.order_list.order_list_main.88.65291802I3zu3c&gatewayAdapt=glo2usa

https://www.aliexpress.us/item/3256803684893162.html?spm=a2g0o.order_list.order_list_main.133.65291802I3zu3c&gatewayAdapt=glo2usa

Did you also order the solderable PCB, the one we forgot to order

Anyway, hope this helps, let us know how your project goes!!

BTW we just used this to characterize some TO252 PMOS Power FETs for parallel operation.

Best,

Thank you for the information, I did also order the solderable board. I'll post an update once everything has arrived.