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Beginners / Re: Correct soldering for double-sided boards?
« Last post by BMack on Today at 03:04:54 PM »
Honestly, soldering well isn't difficult. If you're asking these questions, you've probably been researching and that means you're probably a lot better than most in soldering already. It's the people that don't ask and don't try to learn that do terrible jobs soldering.
Repair / Re: Solar King SLK-4000 4KW Grid Tie Inverter Repair
« Last post by Photon939 on Today at 02:59:35 PM »
Some good old high energy damage going on, but is that a shriveled cap in the first post or did the back of it blow out like a balloon.... haven't seen that one before  :o

It's just two caps glued together with some of that brown snot glue.

I just found another failed IGBT, it seems the one that a chunk blew out of is not the same as the one that blew the traces off. Seems one failed open the other failed short. Short to all three terminals. I will almost definitely need to replace the gate driver IC. Mouser's stock of those is currently backordered until Nov 3. Bleh. Maybe I can use that time to see if I can get an equivalent IGBT that is a bit cheaper.
Although the ATF22V10B was programming correctly, a couple of bits in the UES (User electronic signature) seemed to be stuck high on read. This also occured with ATFblast. UES contents have no affect on logical operation so I could have ignored it, but I wanted to know why it was happening. So I built a simple parallel port logic analyzer (Elmuesoft 17 Channel Logic Analyzer) to monitor my VS4800 while it was programming GALs. This revealed some interesting things:-

1. The 'stuck' bits do exist, but are not part of the UES. The UES fuse line has a total og 132 bits. On a normal GAL22V10 the first 64 bits are the UES, and the rest are blank. In the ATF22V10 it's the other way around -  the last 64 bits are the UES.     

2. On the ATF22V10C, data is not transferred on clock rising edges as suggested elsewhere, but on falling edges just like other GALs. However only 5 clocks are used to transfer the 6 address bits at the end of each row, the last bit being input directly without being clocked in.  If you try to clock in 6 bits then it 'works' with rising edges because the last rising edge doesn't do anything, but data may be corrupted if falling edges occur at the wrong time. 

3. The VS4800 always writes a blank user signature even when a 'UES' chip is selected. It also disables the power-down feature when programming the ATF22V10CQZ, even when enabled in the JEDEC file (probably a good thing since power-down, which is enabled by default, makes pin 4 unavailable for logic input).
4. Delays of several milliseconds between most operations are not necessary. Programming any GAL should only take a few seconds at most.

5. My theory that (on the 22V10) P/V- should be set high only when pulsing /STB is confirmed.
With my current code I have successfully programmed an ATF16V8B, ATF22V10B and ATF22V10CQZ, and read various GAL16V8s and 22V210s. I have yet to confirm that standard GALs can still be programmed (maybe I have somehow broken that code) but since the original GALBlast already does them I am not overly concerned. I have also simplified the hardware a bit by removing the pull-down resistors and changing the ATF's programming voltage from 11V to 12V.

The attached zip file includes preliminary source code and executable for my version of 'ATFBlast'.  As well as ATF chips it should also do the GAL16V8, GAL20V8, and GAL22V10. I removed some less popular GALs that were cluttering up the menu.
Next I want to port my code to an MCU so it can be used on modern PCs that don't have a parallel port. Thinking of modifying this project which uses an Atmega644 (but probably only needs an Atmega328).
I've done two orders with Dirty Cables( in total 1400 cables of 6 different types), I've had them do 20 and 22AWG with JST XH, PH and dupont connectors. They do a good job and a pretty quick. No complaints.
Test Equipment / Test Clip for 8 contact VDFN flash memory chip?
« Last post by kyle on Today at 02:36:53 PM »

Can somebody help me out finding clips/grabbers that would work with a "8 contact VDFN" package chip?


The flash chip is located on my Thinkpad T430s laptop that I'm trying to reflash stock UEFI firmware via SPI with 100% open source Coreboot firmware https://www.coreboot.org/. The pitch appears to be ~1.2mm or so (measured with crappy ruler and my eyes). I know that Pomona 5250 Test Clip is very popular but that's for SOIC. Would it work with my VDFN?

Thanks in advance.
Beginners / Re: Analog Switch Application - Composite Video Signals
« Last post by edavid on Today at 02:27:00 PM »
You can connect a negative supply to the VEE pin of a 74HC4051/74HC4052/74HC4053, and then it will pass both positive and negative voltages.  See the datasheet.

Or, if you don't have to switch very fast, use a relay.
Beginners / Re: USB to TTL IC recomendations
« Last post by jdgabbard on Today at 02:23:10 PM »
I've used the CH340 without any problems.  I actually needed a USB to TTL adapter the other day and wired one up in about 10 minutes.  It's a good option.  The only catch is that you need a 12mhz oscillator/crystal. 


That's what an LCR meter is for. It's not bad practice to ensure everything works and has the correct values before mounting anyway.

Definitely not bad practise, but also not done in practise :)

Can you see a board fab house checking each individual passives value. If we cannot trust the QC of what's in the tape, what hope have we got?

That's why I leave everything in the tape (which I label on unpacking) until I am going to to use it. Sure I will "decant" them into labeled containers just prior to assembly but that's it. 

I think I break every rule here in regard to ESD but no problems yet  :-+ They are mini quadcopter flight control boards and they all work flawlessly.
God that thing is wicked, I love it! Would certainly whoop my robot design. Of course I went with a different approach and sacrificed performance to make it as simple as possible. I created an open source 3d printable design targeting a younger less experienced audience to try to bring them into the sport. If you're interested link here:
Repair / Part identification help :)
« Last post by kalinga on Today at 02:16:59 PM »
Hey guys!

i need some help identifying an SMD component,


this is part of a PWM charging controller UC3843BN, when i check other components, i can see following with same 44


issue is, i've see few version of L44's, last 2 digits are different, above is L44 1/3 but I've seen L44 0/7 as well, since the burn part has the 7 on it.
the L44 marking mostly refer to BAT54S (PLANAR SCHOTTKY DIODES)

but what does the last 2 digits mean ?

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