MEAD@USC-ECLB.ARPA (03/29/84)
From: Dick <MEAD@USC-ECLB.ARPA> Well, I finally got fed up with its dumb power-up off-hook mode. I keep forgetting to run the modem program to clear things. So, avid warranty voider that I am, I made a mod to the pcb so that it comes up on-hook, yet retains program control of off-hook. Just requires two little wires, and a cut diode lead. Seems to be working fine. Oh, it will also require changing the sense of the DTR bit, to normal! I will give details to interested parties....so much for logic in design, must be a Detroit car engineer. -------
MEAD@USC-ECLB.ARPA (04/02/84)
From: Dick <MEAD@USC-ECLB.ARPA> Making a sensible mod to USR's S-100 modem DTR control... The mod is simple: Above the 8251 Uart is a 7400 (IC20 I think). Careful inspection should show that pins 4,5,6 of the 7400 are not used. The diode in the center of the board, which the brief manual mentions can be removed to stop power-up off-hook at the cost of program control of DTR, needs to have the lead on the anode (8251) side made available to solder a wire to. (Replace or just resolder it). 1> Break the anode connection (only) of the diode to the 8251 (DTR line). 2> Solder a small wire from pin 6 of the 7400 to the free diode anode lead. 3> Solder a small wire to pins 4 & 5 of the 7400 (shorting them), and solder the other end to the pad where the diode anode used to go (DTR line) 4> Now writing a 1 to DTR will take mode off-hook (as it should have been) And it powers up on hook....works for me fine. You will have to invert the sense of the DTR bit in USR software now. ..Dick.. -------
CS.Temin@UTEXAS-20.ARPA (04/19/84)
From: Aaron Temin <CS.Temin@UTEXAS-20.ARPA> I called the folks in Seattle about the board, which they sell modified to come up on hook. They want $339. But the S-100 Bus Co. advertises the board (unmodified) for only $300 (May Microsystems). I think I'm willing to take a chance with the warranty for $40, especially since I've had the outboard USR Password for 6 mos. with no troubles. -aaron -------