HP-150 Touchscreen

[Internal printer] I am pretty sure I have a spare HP2674 printer unit somewhere. It's not light 9so postage might be expensive), but if I come across it I will let you know. You should also clean that double cone spring at the back of the battery holder. This, of course, conenctes th 2 batteris in series. And chack you have fitted them the right wy round. If not, it does no damage, but it will not work. The battery +ve conenction goes to 2 pins on the video board conenctor to the backplane. The pinout I have for this connector is : BA(0) --o o-- +5V BA(1) --o o-- Gnd BA(2) --o o-- BRst/ BA(3) --o o-- Gnd BA(4) --o o-- ExtWait/ BA(5) --o o-- +5V BA(6) --o o-- BIO/M/ BA(7) --o o-- Gnd BA(8) --o o-- IR0/ BA(9) --o o-- Gnd BA(10)--o o-- BGO BA(11)--o o-- Gnd BA(12)--o o-- BClk BA(13)--o o-- Gnd BA(14)--o o-- +5V BA(15)--o o-- Gnd BA(16)--o o-- BIO/M/a BA(17)--o o-- Gnd BA(18)--o o-- BDT/R/ BA(19)--o o-- N/C BD(0) --o o-- +5V BA(1) --o o-- N/C BD(2) --o o-- BRd/ BD(3) --o o-- Gnd BD(4) --o o-- Spare BD(5) --o o-- Gnd BD(6) --o o-- +5V BD(7) --o o-- Gnd +5V --o o-- VSync/ +5V --o o-- Gnd +12V --o o-- HSync +12V --o o-- Gnd +12V --o o-- HalfBrt/ +VBat --o o-- FullBrt/ +VBat --o o-- Gnd LHS Of machine ^ | <--- Top That is drawn looking into the connector on the backplane. It's possible the batter gunge has corrooded the conenction between the pin and the track. You could ckeck to make sure the +ve battery terminal does indeed conenct to the right pins on the socket conenctor on the video board. On the CPU PCB -- the other large one in the cardcage -- There is a testpoint pableed CMOS PWR. it's almsot impossible to get to with the machine assembled, which is what uou need to be able to install the batteies. But if you solder a bit of wire there and feed it out through a slot in the back panel, then put the battery holder in, you can check the power to the real time clock. Expect about 2.5V there (battery voltage lsess one diode drop) with the machine off, and 5V with the machine on. YEs, they are very nice little machines... FOr the touchscreen, the first thign to do is to take the CRT bezel off (remvoe the top casign, then unclip th eront panel fro mthe underside of the machine and lift it forwards and off), Unplug the earth wire and the 10 way ribbon cable from the touchscreen PCB (insde the front panel you jsut removed) and take out the fixing screws. Clean out all the holes in the bezel and the touchscreen LED/phototransistor moutings. You can then reconenct the 10 way ribbon cable and see if it pases the test. If so, put it all back together. If not, then it's likely you have IR device problems on the touchscreen board. There is supposed to be a command you cna send ot the 8041 tht controls the keybaord and touchscreen to reprot which beams it thinks are blocked at power-on. The problem is that to do this you have to send other comamnds to disable the keybaord interface, etc. I gave up!. Beinng a hardware type, I wired up a dozen 4000-series CMOS ICs to make a device that would conenct ot the touchscreen PCB and display the status of all the IR beams on a couple of rows of LEDs. Using that on my fault touchscreen board, I found the dead IR pair in a few seconds. In theory you could use a 'scope to display the signals on the touchscreen interface (there are only 3 of them, clock, sync and data) and then see which beam(s) are responsible for the spurious pulse(s). Let me know if you want to do this and I can dig out the details of the interface. -tony