Rotten USB to RS232 adaptors.

Jan Panteltje · 2009-03-27T14:43:20+00:00

Likely same thing wit hsame conbstruction here: and available from any more placesSo I have this cable, it drives my LED disco light show PIC, from Linux.Bought it because the chip in it supports Linux... (prolific chip).So, anyways, that PIC it drives also has timers, and it wakes me up with lights,sets the color of the lights in the evening etc.. But yesterday morning nothinghappened.So first I suspected my PIC.Did a code verify: OK.Cold start everything worked, but stopped working after some time...temperature? checked no.Now I leave that USB to RS232 cable connected all the time....Finally reasoned the PIC must go into input mode, and expect some data...like setting timers, but I did not send a command for it to go into input mode.So late last night had a look at the Linux USB interface if anything happened tobe sendingdata to that serial port (lots of scripts running here).No.Scoped the input to the PIC, looked OK.Programmed an other PIC, after some hours same effect.But I was now sure it was waiting for data, must have received some command.From WHERE? I did not send any, USB did not see any?Scoped again at the PIC RS232 input..Bingo! RF!!!!!!Now that RF comes out of that USB to serial converter._sometimes_.So tapped it, now no RF but cracking voltages...Aha, defective or lose filter cap in the charge pump, I could make it gocompletely openby pressing that adaptor.Now that was late last night, so decided to open it up (guarantee? well I dunno,I need that cable NOW), so this morning took the dremel, no way this thing seemsto have a wayto open it normally, but I could see a filter cap through the darksemi-transparent plasticbut... when I was more then 4 mm deep in that adapter and still no end to theplastic, it dawned on me: It was potted.But not potted with solid stuff, potted with a soft flexible plastic that bendsevery time you insert thething (it is a D connector with board inside), and anytime you press it or holdit basically.So... no way I can repair...

Mar 27, 2009 22 Replies

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Paul E. Schoen 17 years ago

I had one (actually, it was made by Belkin), and used it to test my USB device. Before assigning a serial number, each of the four ports caused a new COMnn port to be enumerated. When I moved it to another port on the computer, four more serial port numbers were assigned.

I discovered that the splitter does not like to have its 5VDC bus shorted to ground. I was using a probe to check the USB signals, and I killed the splitter. I opened it up, and found an intact fuse, and an assortment of components with no sign of damage, but it was no longer functional. USB hubs are supposed to be protected against short circuits.

Paul

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Jan Panteltje 17 years ago

Hi, I ordered 3 other ones from Germany, much cheaper place, good references too:

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Probably the same molded design, but this looks a bit more solid. Amazing prices! Now I have 3 for the price of one here.

Arrived today, actually yesterday but was not there. These are nice, comes with USB extension cable! No driver disk, works just like in Linux, cannot even buy the cable for that money (6 Euro 14) here... Made in China it says. # lsusb Bus 001 Device 020: ID 067b:2303 Prolific Technology, Inc. PL2303 Serial Port

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JosephKK 17 years ago

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than the=20

So you think that is fast. Watch while we supplant it with USB 3.0,

5Gb/s. Meantime, SATA and SAS are tied at 6 Gb/s. High speed serial is comming in to roost. .

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