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Tek 222/224 Charger Order Status

May 25, 2020 – Testing is complete for all orders. Some shipped on Saturday, May 24 and the remainder will ship on Tuesday, May 26 (due to the Memorial Day holiday).

May 23,2020 – I have the test fixture working now. It turns out that there’s a lot of complex interaction between the protection circuitry on each battery, the switching mechanism to go between battery charging and battery powering, the charger, and the DC-DC boost converter. This made development of the test procedure much more difficult than I anticipated, but I now have a result that I’m happy with. I tested the first two boards last night and have put them in the mail. I hope to get a fair number more tested today, and if so, I will take them to the post office to ship before the holiday weekend. Thanks so much for your patience with this project!

May 19,2020 – The test fixture boards arrived in the mail yesterday afternoon. I was able to get the board about half built before turning in for the night. I expect to complete the build today and begin testing it.

May 15,2020 – The fab house building the test fixture boards notified me yesterday that they had shipped. USPS tracking indicates they will arrive on Monday, May 18. So it looks like I will be about a week later than the May 16 ship date I estimated based on getting the test fixture boards this week. I’ve completed the assembly and operating instruction sheets, the test plan, and have most of the test procedure complete. All of the part for the kits have been received, and all of the parts for the test fixture, except for the PCB itself.

May 5, 2020 – The boards arrived yesterday, one day earlier than expected! I couldn’t restrain myself to wait until the test fixture board came in, so I did the Big Bang test with a couple of batteries. The good news is that it works, at least to the degree I was able to check without the full test fixture. When disconnected from the power supply, the scope operates from battery power. When connected the batteries charge (and stop charging when full).

The test fixture board is still at OshPark waiting panelization. Looks like best case it might get here by Saturday if it gets in a panel soon

, but it’s looking more like next week to me. Right now, that’s the long pole in the schedule. I did run into a problem with the cases fitting the boards. It was a minor problem, but will still require the existing cases to be scrapped. I’ll be printing the revised cases while waiting for the test fixture board to arrive.

May 2, 2020 – Completed the test fixture design, got the board sent off to OshPark and the parts order to Digikey. I built it mostly from through hole components, because that’s still easier for me. However, the Maxim parts were only available surface mount so I will have to solder on three surface mount parts. Shouldn’t be too difficult. The completed test fixture will look something like this:

There are two sections: a Tek 222/224 scope simulator, and a Li+ battery simulator. The scope simulator has switches to simulate the scope’s external power supply connected or disconnected (which affects whether the scope is charging the battery or getting power from it), and whether or not the scope is powered on (switches in loads to draw ~700mA powered on, and ~ 300uA powered off.

The Li+ battery simulator has a switch to discharge the simulated battery, and a potentiometer to set the voltage level output by it. There are two test points to allow observation of the charging current provided by the charger, and the voltage of the battery, which indicates its charge level. This is in the “manual” mode. There’s a switch to select between manual and automated mode. In automated mode, the battery voltage increases after the battery has been discharged in response to charging current received from the charger. Finally, to make testing a bunch of boards easier, a BNC connector allows an external function generator to periodically discharge the simulated battery, so that the voltage of the battery and current response of the charge can be observed on a scope.

Looking forward to getting the boards in and the test fixture built to test them!

April 30, 2020 – The CM site now says the status is “Shipped”, so that matches the DHL tracking email I got yesterday. I’ve been thinking about how to test these when they arrive, and have concluded that I need to simulate both the scope (easy) and the Li+ battery (not so easy). Fortunately, Maxim has a great application note on doing just that which I came across yesterday.

April 29, 2020 – Got an email from DHL this morning, indicating that the order had been shipped (even though the status on the CM web site is “Awaiting packing”.) DHL tracking says that the order is in their hands and that the estimated delivery is April 5. As I mentioned on the deposit information, it may take me a week or two to thoroughly check out the boards before I feel confident in commencing shipments. Please continue to be patient!

All of the cases and cables have been built, and I’m working on designing the test fixture to check out the boards when they arrive.

April 27, 2020 – Another note this morning from the CM, with a photo attached asking about the orientation of a through hole component. Since SMT parts are normally soldered first, I’m taking this to mean that the boards have progressed through SMT and should be in the final stages of assembly. I have to say that I’m pleased so far with CM. They’ve been responsive to my emails and have reached out several times with they needed clarification or confirmation. In particular, there’s a tricky situation with the LED indicators. Two of the three have the polarity marking on the cathode. The third has the polarity marking on the anode. So even though the silk screen (correctly) indicates that all three diodes are oriented the same way, one of the three will look wrong because its polarity marking is different. I had sent an email about the issue, and got back a marked up drawing showing how they intended to place the parts. Very confidence inspiring.

April 23, 2020 – Got a note from the CM this morning looking for the pick and place coordinate file. I’m assuming that means they were ready to start placing components on the boards in preparation for reflow soldering. What’s confusing is that the order has been in the “Assembling” state for over a week, so not sure what was happening. Anyway, I generated the XY file from DipTrace and sent it off right away, with a request for them to confirm receipt. Haven’t heard back yet, but it was late in Shenzhen (about 9:30 PM their time) when I sent the file.

April 22, 2020 – CM status indicates that the board assembly is still in progress. No indication of how far along or how many are completed. Just over 20 cable assemblies have been completed. I continue to tweak the slicing parameters for the 3D printed case, and have gotten the print time down to 3 hours. About 14 cases have been printed so far. I’m holding off on cutting the light pipes to size until the boards arrive and I can confirm the length needed with the actual board. Other than that, I expect to have all 25 cases, cables, and labels completed and ready to go by the time the boards arrive from the contract manufacturer.

April 14, 2020 – The CM indicates that the PCB fabrication and parts purchasing has completed, and that assembly has begun.

I’ve finalized the design for the charger to scope cable, the parts are on order and due to arrive from Digikey today. Many thanks to Ben O’Brien, who did the initial legwork to identify a suitable replacement for the connector on the scope end.

I’ve tweaked the box design slightly, to countersink the screw holes and move them inboard 1 mm on one end to allow some clearance for the countersink from the edge of the box lid. I’ve added recesses for the ends of the light pipes to fit into the lid, and made some minor dimensioning changes to the CAD model to ensure that the printed dimensions are what’s expected. I printed this version of the box last night, and it prints well, although it takes about 5 hours to print one box, consisting of a lid and a case.

April 11, 2020 – CM status indicates that printed circuit board (the bare board) production has begun.


The order was placed with the contract manufacturer on April 10. The deposit item has been removed from the web site and no further deposits will be accepted.

A total of 25 deposits were received, and I added 2 orders for myself. The kit price, when received, will be $75 each. (Of course, your $25 deposit will be credited, so your net cost will be $50 + shipping + sales tax for California residents). At some point in the near future, I may place the kit on the web site at either this price or a higher price. If higher, I will contact you prior to the time when you’ll place your order for the final kit with a discount code that will ensure that, as an early adopter and depositor, you get the $75 price, regardless of what price I might offer the kits to the public.

Lead time from the CM consist of PC board fab, component sourcing, and component assembly. The critical path is likely component sourcing and assembly. I don’t have an estimate for the time sourcing will require, but the fab house estimates 10-15 working days for assembly.