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As with any troubleshooting procedures, isolation is the way to get a direction. Start first to establish the presence of the 155v near the flyback pin2. If no have, check inward there is a fuse 600ma via 1.2ohm 2w resistor. Deload this line by desoldering and hanging flyback pin2 then measure...
Since you already received the batch of PCB assembled, then it would be costly to ship back and redo. Best you can do is hand solder the issue since I presume the bottom copper directly under the pad is exposed. Then highlight with photo evidences and then request for discount on your next...
Firstly the thread title is misleading, I was thinking something to do with PCB print layout. Anyway, though Im not familiar with Atrium (Im Eagle usear) but these softwares basically have auto-save function at regular interval. Look for that folder maybe somewhere in User folder-Atrium or...
UPDATE:
Perfect!
This would be a fitting way to archive this thread.
I have followed KlausST suggestion and replaced the transceiver with SN65HVD485EDR which has the same footprint as SN75176, though expensive by about 300% (from 0.25usd) but the goal was achievd: Temperatures were 38degC...
Apologies for my delayed respose.
firstly, Thank you so much KlausST for the calculations.
And as promised herewith the waveforms taken from transceiver Data pin4 and RS-422 out.
I will test with another chip with same footprint and see the results.
I acknowledged your question, it is unconventional and was thinking since Receiver Output is TTL level, I might as well use it to drive LED as output indicator via 10k resistor.
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My initial check was about 4V high and around 0.4V low level at SN75176 pins 4 and 1 for D...
I have designed a prototype RS-422 using SN75176 with input opto isolated via H11L1. The H11L1 output is biased by 270 ohm resistor at its output pin and fed to a hex schmitt trigger inverter. The inverter output will then drive the SN75176 transceiver D input.. The transceiver out no bias...
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