UNCLE BERNIE'S IMPROVED APPLE-1 CASSETTE INTERFACE

... 'softwarejanitor's post #53 is right that the ACI firmware written by Woz is only 256 bytes long, so, theoretically, it could be put into one 256 bytes page of an EPROM adapter sitting in the A1/A2 locations on the motherboard. All you would need is to provide some logic for proper chip select of that EPROM.

But here is the catch: the ACI uses another foul Woz trick to save ICs (he is famous for these tricks). The ACI manipulates one address line of the local PROMs on it to make a one bit input port for TAPE IN.

How this works is a as follows:

- in the address range $C100 to $C1FF, the PROM gets a copy of the original address line.

- in the address range $C000 to $C0FF, the PROM gets the TAPE IN signal in lieu of that address signal (see the ACI schematic in the original manual).

To test the input port, the firmware running in $C100 to $C1FF reads from a location in $C000 to $C0FF where a change of the TAPE IN signal (from the comparator) leads to two different byte values in the PROM.

One problem with this approach is that the CPU will occasionally read an erratic byte when the comparator output toggles close to the end of the PHI2 clock phase. This may cause a read fail as the bogus byte then is used as a compare value  to detect the next comparator output change. It does not happen all too often with bipolar PROMs (they are fast, so the timing window for a read data setup/hold time violation is small) but with a slower EPROM it will happen more often even if you add the input port trick circuit.

In my work on the ACI improvements I have greatly mitigated that problem by using the one unused flipflop in the 74LS74 as a synchronizer.

This was part of the Gen1 fixes. Gen1 also removed the need for a negative supply voltage, to make the Gen1 improved ACI compatible with Vince Briel's "Replica 1". The other Gen 1 fix was fixing the totally botched volume indicator LED circuit. Gen 1 also added the 2nd firmware page with my 'extended formatting' routines ($C500-$C5FF) which make the ACI fully Apple II compatible, and also provides autoload and autostart capabilities.

Gen2 finally fixed the botched comparator circuit. This involved adding some SMD components hidden under the LM311 socket. This 'Gen 2 improved' ACI PCB which once came with my Apple-1 IC kits currently is only available from Ebay seller newton-computer (as my work was based on his Gerbers).

Implementing all these functions on the motherboard is a tall order. Good luck with that !

Tell us how you did it !

- Uncle Bernie

In post #60, 'ebruchetz' wrote:

" I am considering my options to build or buy an ACI card. "

" I see that assembled GEN 2 cards are available from Mike Newton, but that's a little steep for me and I'd rather build one rather than buying one entirely assembled. "

Uncle Bernie clarifies:

If you read through this thread from the beginning, you can see that the original ACI has a lot of flaws, and does not work well enough to be a viable product. IMHO, it was this flawed ACI, and not the few flaws in the Apple-1 motherboard, which caused the phone at Apple, Inc. to ring off the hooks, desperate users asking Woz for help / advice, and to stop this distraction - Woz had to focus on designing the Apple II - the infamous "buyback" decision was made and the fate of the Apple-1 was sealed.

So I can STRONGLY advise anyone not to build a verbatim copy of the original ACI, UNLESS you are willing to follow the instructions in this thread to modify it, by cutting traces and adding wires, to turn it at least into a GEN1 improved ACI.

The GEN1 improved ACI fixes the volume indicator LED circuit (which almost never works in the original ACI, and if the LED ever lights up, it's giving wrong information fooling the user). It also fixes the setup/hold time issues for the 6502 ACI port read by adding a synchronizer flipflop - the spare one in the 74LS74 which Woz did not use. Gen1 also does not need the negative supply voltage anymore, so it can work with the Briel Replica-1. It also modifies the PROM sockets to accept either 256x4 or 512x4 PROMs. When using the former, you can only have the original ACI firmware as written by Woz back in Y1976. Which has no checksum - yet another annoyance / flaw. When you use 512x4 PROMs which add my 'extended formatting' page to Woz' work, you get checksums, full Apple II compatibility of cassette recordings, and my autoload and autostart feature. What GEN1 did not do is to change the comparator circuit. So a GEN1 improved ACI is still finicky with finding a proper volume setting of the cassette recorder to get successful read. But since the volume indicator LED circuit has been fixed, this adjustment is quick to do: just run the recording and slowly turn up the volume from 'silence' to the point where the LED lights up. Then turn it up a little bit more (some volume dials have numbers 0....9, give it one number more). With this procedure, I was satisfied with the playback reliability. It's not much worse than with other cassette interfaces of the time. But some users still complained that they had issues with insufficient volume from media players used in lieu of a  cassette recorder. Seems that this is related to hearing protection circuits: once some audio is being played too loud for a short while, the volume automatically is dialed down. Which then causes readback errors due to insufficent signal. I did not want to spend any more time on further investigations of these media player issues, just be aware that this effect exists.

The fix seemed to be easy: just increase the sensitivity of the LM311 based TAPE IN comparator circuit. As a comparator has infinite gain (in the ideal case, good enough assumption for this discussion) the only thing that can be done to increase sensitivity is to decrease the hysteresis. I quickly found out that this is all but impossible with the original circuit, and this looks as if it's the most likely reason why Woz must have struggled with making this circuit work at all - there are signs all over his schematic that he experimented a lot, and the 'residues' of this struggle look weird, such as the futility to specify 1% resistors and the use of a negative supply voltage for the comparator - the latter hints that Woz likely may have tried many types of comparators, some of which may have needed the negative supply. As we know, none of these measures brought the playback reliability up too snuff. It's all but impossible with this circuit topology, which has no impedance balancing anymore on the differential comparator inputs, once the cassette recorder is plugged in.  Ironically, it does have impedance balancing when no audio cable is plugged into TAPE IN. But this is not the use case. I still wonder how Woz could not have seen that fatal flaw of his comparator circuit. Maybe he ain't no mixed signal or analog circuit designer. Being brilliant as a pure digital designer (which he undoubtly is) does not help much once the design task involves interfacing with the real world, which is analog in nature. This is where pure digital designers typically screw up.

To fix this, I had to modify the comparator circuit to have impedance balancing in the use case (cassette recorder being plugged in). This mod allows me to reduce the hysteresis by a factor of 6 or so. Which makes the TAPE IN input much more sensitive and so even smaller volume settings will lead to a successful readback. Smaller volume settings also help with keeping tape noise and distortions low. The result is the "GEN2 improved ACI".

Now, here is the problem: I never was satisfied with the GEN1 PCB as it was based on the open source Gerbers made available to the Apple-1 community by Misha Mdesk. His work on the Apple-1 motherboard and the ACI Gerbers is high quality, but reflects the Russian engineering credo that no effort shall be wasted to make any product look any nicer. Soviet Union products designed in that era generally look ugly because NO effort was expended for what in the West is called "Industrial Design". Sure, this adds effort and costs, but in the Capitalistic world, you want products which look more beautiful than the competitor's products. Consumers will buy the products which pleases their eyes better. In Communist planned economies, there is no such competition. So "Industrial Design" was not deemed necessary. Hope this explains why Misha did not try to faithfully reproduce every little cosmetic detail of the original Apple-1 PCB layouts. They work, but don't look exactly the same. This has been a point of criticism within the Apple-1 builder community, and so the American Logan Greer took Misha's "Russian" Gerbers and edited them to look much closer to the original layouts. You can find his Gerbers somewhere here on Applefritter.

For me, when I developed the GEN2 ACI mods, I had no source of more faithful ACI Gerbers other than cutting a deal with Mike "Newton": he gave me his ACI Gerbers to put my mods in, and the deal was that I could produce them and put them into my kits, but the rights of the modified Gerbers would revert to him, and I could not sell them outside my kits.

So the only way to get a "GEN2 improved ACI" PCB other than buying one of my famous Apple-1 IC kits is to get the "official" PCB from Mike "Newton" himself. Why he decided to only sell them as fully assembled ACIs, I don't know. I thought he would sell blank PCBs, too. I know he struggled with finding 512x4 PROM blanks at any acceptable price. Even I have almost none of those left. So even if he would decide to sell blank Gen2 PCBs, you still would struggle with getting the PROMs.

Any prospective builder of a "GEN2 improved ACI" faces the problem how to source the blank PCB and the two PROMs, programmed with both the original ACI firmware page written by Woz and my added "extended format" page.

Unless somebody would add these mods to some open source Gerbers of the ACI, the mods must be done by hand. This is possible - actually, I intend to write and publish instructions on how to do the Gen1 -> Gen2 mod, if there is enough demand for this. So far nobody asked me. Why I don't know. Maybe the owners of Gen1 improved ACIs are perfectly happy with their readback performance. And those few who had the issue with their media players not having enough signal, may have bought one of my famous IC kits containing a Gen2 improved PCB.

So, if you want to do the Gen1->Gen2 mod, comment here in this thread. With enough demand, I would write and publish the modding instructions. Note that you could start with the original ACI if you first apply the GEN1 mod which is fully disclosed above in this thread.

This leaves the problem with finding 512x4 PROM blanks at any reasonable price (buyer beware that most PROMs offered on alibaba or from other Chinese sources are programmed, worthless, pulls from electronic junk, which may have been relabled to appear uniform and new = fraud).

If you are happy to find genuine PROM blanks, which will cost $$$, then you need a programmer to program them, which is tricky. You might need to buy an old programming system and then refurbish and recalibrate it. Recalibration may be tricky as some (like the Data I/O System 19) needs calibration fixtures which are unobtainable nowadays, 50 years later. If you understand mixed signal work, and have a well equipped lab, you may be able to improvise so you don't need the fixtures. I went that path to access some otherwise unaccessible signals from within the System 19 with the UniPak installed. This needs some RF knowledge on how to hook up coax cables such that the signals are not compromized. Typical hobbyists may get it wrong. And if the observed signal is wrong, then the calibration will be off target, and the PROMs may not be properly programmed and suffer from poor programming yield (losing the money you paid for them) or, worse, fuse growback.

So how can we solve these issues to get more "GEN2 improved ACIs" into the Apple-1 community ?

Comments invited !

- Uncle Bernie

Hi fans -

if you have followed this thread (and others), the Apple-1 builder scene has suffered from the unavailability of the 'Gen2 improved ACI' PCBs. These were sold only with my IC kits until these kits were sold out, and then Mike ('NewtonMike' on Applefritter) got the excess empty PCBs from me and offered them here:

https://www.applefritter.com/content/gen2-apple-cassette-interface-aci-board-uncle-bernie

... which seemed to have not found many takers, so he proceeded to use them to offer ready made, fully assembled ACIs (see his post #63 above). At $250 a piece, these are quite expensive (see here: https://www.ebay.com/itm/266615745568) and with the recently introduced U.S. tariffs, may not be affordable anymore for most American Apple-1 aficionados. Consequently, the trickle of complaints I received about the lack of cheap Gen2 improved ACI PCBs since my kits were sold out turned into a flood. So I decided to to bring you some remedy.

RELIEF COMING !

During the past few weeks, I've been preparing to release 'Gen2 improved ACI' Gerbers to the general public, but these are new, and don't have "Newton" genes in them (for obvious reasons I can't release Mike's Gerbers into which I did put my Gen2 improvements under a mutal agreement which allowed me to only put these Gen2 improved ACI PCBs into my kits, so with the kits gone, this source for these PCBs disappeared).

Armin of Munich (who runs www.apple-1-replica.com) has agreed to do a trial run at JLCPCB for these new Gerbers I made based on Misha Mdesk's "Russian Gerbers" as beautified by Applefritter member 'Macintosh_nik" and published here:

https://www.applefritter.com/content/renewed-aci-board-design

What I did is to take 'Macintosh_nik's Gerbers from the above thread, ripped out all traces (but kept the pads and the other stuff) and copied in the traces from my old and long forgotten Gen1 improved ACI Gerbers. Which did fit because Gen1 was also based on the same Gerbers from Misha Mdesk. I then put in my Gen2 improved TAPE IN circuit. Functionally, the result should be the same as with the 'Gen2 improved ACI' PCBs which were in my kits and were based on Mike's work. Except that these new Gerbers are free of rights from third parties and hence can be published as "free" Gerbers for anyone to use.

A  COMMERCIAL  KIT  SOON  AVAILABLE

Armin has agreed to make available a bundle (partial kit) containing the new 'Gen2 improved ACI' PCB, a pair of PROMs containing my "extended formatting page", and two of the somewhat elusive 3.5mm audio jacks. He will sell them on www.apple-1-replica.com --- check his webpage regularly to see when they will become available.

I also have a few left over (from the trial run, just 3 weeks ago I was sitting in Armin's Munich office and built one with my own hands ... very lucky that we found out it indeed does work  !) - - - if you live in the USA and want a set (PCB and PROMs), send me a PM via the Applefritter message system. Offer valid only as long as supplies last !

ORDER YOUR OWN PCBs FROM A MANUFACTURER

With the recent tariffs on imports from China (see here: https://www.applefritter.com/content/how-trumps-tariffs-destroy-our-hobby-and-small-us-businesses-too) we need to look for alternatives to imports (at least for Apple-1 builders living in the USA).

I'm inclined to use OSHPARK (www.oshpark.com) but need a beta tester living in the USA to check out if their system to access my projects by third parties works as expected (if you are interested to risk ~$50, send me a PM ... for your money wasted, I will give you an ACI component set including PROMs free of charge, but excluding IC sockets, first volunteer takes it all).

Here is how OSHPARK renders the new PCB:

ACI_Oshpark.JPG

More info later, my notebook is running low on battery.

Comments invited - just tell us what you think about this new way to get Gen2 ACI PCBs (or partial kits).

- Uncle Bernie

In post #66, 'Macinstosh_nik' asked:

" I just didn't realize if the updated gerber files will be available for self ordering ? "

Uncle Bernie answers:

Yes, I will put them up for download here on Applefritter, but not before they have been beta tested on various candidate PCB manufacturers, by volunteers who do the ordering process on their own risk, using my Gerbers or ODB++ files (this depends on the PCB manufacturer). All I'm willing to do is to provide try out the first steps up upload and rendering to fix problems, but the actual order must be done by volunteers living in this particular country where the manufacturer is - I do not want to pay U.S. tariffs on PCBs I don't need.

So far I had only one "volunteer" (Armin in Munich) who set the whole mission in motion by requesting his own special version, and he used JLCPCB in China, which he could do without getting ripped off by customs, as Germany has not yet a tariff /  trade war with China as the USA does.

As I mentioned in my post #65 above, I flew to Germany to be able to put the first trial specimen of this new ACI together myself, in his office in Munich. And it worked ! So the JLCPCB Gerbers are good and have been beta tested. You can have them if you send me a PM. I'm just not ready with all the other manufacturers. And I want a single tarball with all the options and manuals etc. inside, not a helterskelter set of many tarballs.

BETA TEST VOLUNTEERS NEEDED !

I still need a volunteer to test OSHPARK in the USA, and would order 3 prototypes there, based on a link to the project ... this is a service from OSHPARK so third parties could access projects of makers and order PCB directly without needing to upload data and specify recipes. I can't do this test myself as I'm not a third party and I can't open a second account at OSHPARK (their website immediately recognizes me, despite all my efforts to avoid web based tracking).

I also need two volunteers in the EU, one to test Aisler in Germany and one to test another EU based PCB manufacturer (I lost the name, but can find it again).

WHY BETA TESTS ARE NECESSARY

Just as a note to those readers who question my ways (why I insist in beta testing): there is a huge difference between ordering PCB as an experienced professional and ordering as a newbie who never ordered PCBs before. There as so many possible pitfalls with ticking the wrong boxes on the "recipe" and uploading the wrong files, that I think I need to do something to make the process less risky, and hence, this beta test program.

Here is one example for what can go wrong:

I uploaded the ODB++ data base to www.aisler.com and immediately got lots of error messages about wrongly connected nets. Ouch ! But this is unavoidable when using ODB++ and not having a consistent database in the PCB CAD tool - which is impossible to have when starting from Gerbers and then adding traces. Each trace will generate a new net but as it is connected to some unknown stuff the netlist which is created in the background is nonsense. There are two solutions: clean up the database manually (I don't have the time for that, would take longer than starting the layout from scratch, for which a schematic would need to be entered in the CAD tool) or, faster, delete the bogus netlist in the ODB++ files.

I did that and so the error messages for the wrongly connected nets went away. But there were two error messages left, as Aisler claims that they can't do plated through holes of a large diameter. They will use a milling process instead (same as to cut out the PCB from the panel). This is how the errors are indicated by their webpage:

ACI_Aisler_warning.JPG

... note the purple "Milling Path". Affected are the two larger diameter holes for the 3.5mm audio jacks. Now, you just can't click the errors away and proceed to order without thinking. I tend to think about the consequences of any such errors and inspected the layout again, and lo and behold, I found out that if no corrective action is taken, then the audio jacks may not have a proper ground connection. I had to add another trace to fix this and to make it work despite of having no plated through holes for these two jacks.

This is a typical example for what obstacles and pitfalls hobbyists could face if I just would "throw my Gerbers over the fence" and then walk away and leave the sorting out of any resulting PCB disaster to the poor hobbyists.

Hence, I decided I need beta testers who try my Gerbers / ODB++ and my recipes out with specific PCB manufacturers from all over the world. These would be the "recommended" manufacturers where hobbyists could just upload the database, select the right recipe as per my instructions, and be sure to get PCBs which fit and work. Use other manufacturers, do this at your own risk.

So, I'm now waiting for volunteers to speak up and / or contact me. As for the JLCPCB Gerbers, I think they are good, but I changed the solder mask over the edge connector a little bit, so a new trial run is necessary, which I can't do because of the tariffs.

Hope this explains the current state of the mission and why beta testers are needed. I'm counting on some volunteers from the Apple-1 builders scene to show up.

Comments invited !

- Uncle Bernie

I've uploaded the Gen2 improved ACI Gerbers to various PCB manufacturers and these are the results for the prices they quote for minimum order quantities:

www.oshpark.com / USA

3 PCBs cost $42.40 including free shipping within the USA. ($14.13 per PCB)

www.aisler.com / Germany

3 PCBs cost EUR 31.27 incl. 19% VAT. (EUR 10.42 per PCB).

9 PCB  cost EUR 65.26 incl. 19% VAT. (EUR  7.25 per PCB).

"Shipping worldwide for free" they claim on their webpage. But I did not proceed to checkout to verify this. One beta tester in Germany currently ordering a 3 PCB ACI run. So we will find out.

www.jlcpcb.com / China

5 PCBs cost $23.45, but UPS Express Saver Shipping to USA adds another $23.42.

So total cost is $46.87 for 5 PCBs ($9.37 per PCB).

Trump's tariffs will add a King's Ransom and make this totally unattractive for hobbyists living in the USA - even if you choose the snail shipping option (Global Standard Direct Line: $3.30) the tariffs still will kill the deal.

Conclusion

For everybody living outside the USA, JLCPCB is the cheapest option. It will get MUCH cheaper per PCB if you order MUCH more PCBs than you ever need (in most cases a fallacy, try selling the excess, it won't work out, you lose).

Aisler is the close second place despite being based in Germany.

Oshpark is the most expensive, but may be the only option for USA based hobbyists (no tariffs).

The problem with excess PCBs:

None of these manufacturers offers qty 1. So you always will end up with more PCBs than you want or need. So you may think you can sell the excess PCBs. But it has been my experience that selling single PCBs on Ebay or elsewhere is very tedious and has few takers, and probably is not worth the time invested. Be warned ! (Fact: I gave away my Gen1 and Gen2 improved ACI PCBs with my kits for free, without increasing the price of the kits, just to get rid of them, simply not worth trying to sell them separately - I once tried offering ACI kits with PCB, PROMs, and all other components, and had no takers. This was years ago when my total cost per PCB made by JLCPCB was below $3 each. Since then, shipping costs have at least doubled. And then the recent tariffs on top of that. So forget PCBs made in China, if you live in the USA ).

The big open question is: quality / looks of the PCBs.

U.S. BASED BETA TESTER STILL NEEDED !

I still need an U.S. based beta tester for Oshpark - you would order via a link I provide to test this third party ordering procedure, send me one naked PCB of the three you will get from Oshpark, and I will check it, solder in the SMDs, and send it back to you with a free-of-charge ACI parts kit (excluding the IC sockets) as a small "thank you" for your contribution. Only one such offer available - first volunteer speaking up will take it all. I think it's the cheapest way for anyone out there to get at a Gen2 improved ACI. Alas, solder mask color will be purple, not green ("You can't always get what you want ...")

Comments invited !

- Uncle Bernie

In post #69, 'Macintosh_nik' wrote:

" There are several stores on AliExpress called ...PCB Store, where you can order even cheaper than JLCPCB. "

Uncle Bernie comments:

While this may be viable for those who live outside the USA, it is not anymore viable for those who live in the USA, due to Trump's tariffs, see here:

https://www.applefritter.com/content/how-trumps-tariffs-destroy-our-hobby-and-small-us-businesses-too

Not only are the tariffs much too high, there also are totally unpredictable "customs handling fees" which the carriers may slap on these parcels, or use a (far too high) flat rate tariff because they are  too lazy to calculate the correct tariff which depends on the type of goods. So your $20 PCB could easily turn into a $120 PCB, or even more, some examples are in the above linked  thread. The only safe way is not to order anything from China anymore, if you live in the USA.

I have tried out OSHPARK which is based in Oregon and uses U.S. manufacturers and got the PCBs yesterday. More on the ups and downs of this trial run below, in the next post. I think the user experience would be the same when ordering the new "Gen2 improved ACI" PCBs from OSHPARK, so despite the trial run PCBs were a different thing ("IWMless Test Card"), it decided to post it here in this thread.

- Uncle Bernie

Scouting alternative PCB sources for those who want to build the new "Gen2 improved ACI" and live in the USA. Everybody else can use JLCPCB or Aisler or whatever manufacturer has the best price for the recipient. I did a comparison for the quoted prices (see above in this thread) and it was quite interesting to see that the fast shipping options eat up most of the savings you think you could have when using JLCPCB. I saw these shipping costs from UPS, FEDEX , DHL etc. from China to the USA almost double in the past 5 years, and there goes the advantage. Now, with Trump's tariffs, its simply not viable anymore for USA based hobbyists to order PCBs from China.

Here is the result from a trial run (different PCB layout, though) from OSHPARK. I ordered the PCBs on July 24th and got them yesterday, August 11th. This took 19 days and is not exactly fast, and I was lucky that my PCBs went out with the July 25th panel. Ordered one day later, my PCBs would have been put on their next panel, and despite OSHPARK does not tell us how many panels they send out each week, it sure would have added a few days more. Prior to Trump's tariffs, I could get my PCBs from JLCPCB within 7-9 days from placing the order to the PCBs arriving at my front door.

OSHPARK shipped the three PCBs I had ordered in a bubble envelope. Which almost lost all the PCBs, because of the "spikes" in the read circles:

OSHPARK_sample.jpg

... in the above photo you can see the problem why a shipping catastrophy was imminent: the red circles show "spikes" which are left over from the de-panelization process at OSHPARK. And these razor sharp spikes already had worked a cut into the flap of the bubble envelope, half of the flap already was cut open - this edge at the flap is the only place where there is none of the plastic bubble material, only paper. While the spikes may not be able to work themselves through the plastic, they were able to cut through the paper.

I first suspected that USPS might have made that cut to peek inside (forbidden merchandize ?) but closer examination reveiled the cut was irregular and showed signs that it probably was caused by these spikes.

OSHPARK should improve their packing process ... I will send them email alerting them to this problem.

Which could be catastrophic - if the spikes cut the flap open enough for the PCBs to fall out, they are lost somewhere in the belly of the beast (USPS), most likely never to be seen again.

MANUAL D-I-Y WORK STILL NEEDED TO FINISH THESE PCBs

The spikes can be removed with a few strokes of a file but to do it right the PCB must be held in a bench vise.

A few further strokes with the file also produced a nice 30 degree chamfer on the edge connector - OSHPARK does not offer an option to do this. If you have no bench vise and no good file, bad luck for you - any attempt using a loose piece of sandpaper will only yield irregular edges, ruining the professional looks of your PCB.

OVERALL QUALITY: FULLY SATISFACTORY !

But other than these complaints I was fully satisfied with the quality of the PCB. The traces have very good definition, the positioning of the solder mask is perfect, and, even better, the solder mask is thick !

Benefits of a nice thick solder mask:

 A thicker solder mask makes these PCBs much more scratch resistant than PCBs made by JLCPCB. You might not think that a solder mask being too thin is a big issue, but it is at least annoying. For instance, I solder the 44 pin TQFP ispLSI1016 of the 'IWMless' by hand. And it is unavoidable to occasionally short two adjacent pins by a solder blob - they only have a 0.8mm pitch (I can  hand solder 0.5mm pitch but then the blobs happen more often). These shorts must be removed immediately by use of solder wick, and then adding a little more solder to these pins, hoping that it will not produce yet another short.

Drawbacks (and one advantage) of thin solder mask:

On JLCPCB made PCBs, the solder mask is so thin and does stick so poorly, that this process with the solder wick often produces small blemishes in the solder mask, exposing copper traces. This is not an electrical issue yet, but the exposed copper has no HASL layer and is not protected against corrosion.

On ENIG PCBs, there is a thin gold layer over all copper, even the copper under the solder mask, which offers some corrosion protection, but the ENIG process can't be used when hand soldering SMDs - for SMD hand soldering, always use the HASL process option. All PCBs with edge connectors MUST use the ENIG option to get "golden" edge connector fingers. This is the case with the "Gen2 improved ACI".

The only upside of thin solder mask (JLCPCB style) is that it's easier to modify the PCB, for instance, cutting traces and then scraping away solder mask to be able to solder corrective flight wires to the trace at the exposed points. For the same reason, always use traces with at least 0.5mm minimum width, despite the PCB process can make narrower traces. I found it is almost impossible to put corrective flight wires on such narrow traces. (Of course, if the layout gets so tight you must use narrower traces, go for it, but forget about flight wire corrections involving these narrow traces).

CONCLUSION

OSHPARK makes nice, fully satisfactory quality PCBs with robust (because thicker) solder mask. But they do not offer chamfer of edge connectors and leave these nasty "spikes" over from the depanelization process. In my case these spikes almost succeeded to cut open the flap of the shipping envelope, and with just a little bit more of that, the envelope would have lost the PCBs.

OSHPARK also is not the fastest way to make PCBs on a budget, it took almost three weeks from placing the order until the PCBs arrived at my door. But if we consider that these PCBs get shipped twice (the panel from the PCB manufacturer to OSHPARK, where they separate the PCBs from the panel, and ship them the 2nd time, from Oregon to the recipient) then it's not too bad.

I think that for hobbyists living in the USA, OSHPARK is a viable source for "Gen2 improved ACI" PCBs. I've already uploaded my Gerbers to OSHPARK and it also seems I've found a volunteer to try out their "third party" access to my designs.

Stay tuned !

- Uncle Bernie