Point of Sale Terminal cannot detect receipt printers and no display

[Seventh Prince]

Hi,

Am doing a repair job on a Point of Sale (POS) terminal which has the
problem of the motherboard's printer socket of failing to recognise the
existance of the printer (the receipt printer is connected to the
terminal's motherboard via a connector).

Was told to change the NPN Darlington transistors (2pairs): one pair is
controlling the slip printer and the other pair is for the roll
printer. The transistors used are Sanken Electronics's SL4031. Some
other boards use Fujitsu Microelectronics's FT5754M. For this
particular board, the original transistors are Sanken's but I am using
the Fujitsus.

After soldering them and powering on the terminal, the printer can be
switched on (it is powered on via the connector thru the motherboard
printer socket). The terminal can be powered on but there's no display:
just a lit-on screen.

Burning smell is present from the motherboard. The terminal still could
not detect the slip printer. Error message is "Printer not installed".
One motherboard LED indicator is not lit and the LED for the printer
sockets is flashing.

Any advise is welcome. Thanks.

 

[Seventh Prince]

for the pair of Darlington transistors for the slip printer, one of
them is feels hot.

 

[me]

Hi,

Am doing a repair job on a Point of Sale (POS) terminal which has the
problem of the motherboard's printer socket of failing to recognise the
existance of the printer (the receipt printer is connected to the
terminal's motherboard via a connector).

Was told to change the NPN Darlington transistors (2pairs): one pair is
controlling the slip printer and the other pair is for the roll
printer. The transistors used are Sanken Electronics's SL4031. Some
other boards use Fujitsu Microelectronics's FT5754M. For this
particular board, the original transistors are Sanken's but I am using
the Fujitsus.

After soldering them and powering on the terminal, the printer can be
switched on (it is powered on via the connector thru the motherboard
printer socket). The terminal can be powered on but there's no display:
just a lit-on screen.

Burning smell is present from the motherboard. The terminal still could
not detect the slip printer. Error message is "Printer not installed".
One motherboard LED indicator is not lit and the LED for the printer
sockets is flashing.

Any advise is welcome. Thanks.

ahhhm, new motherboard & printer?

 

[七少爷Seventh Prince]

ahhhm, new motherboard & printer?

Nopes. Am using the existing motheboard and printer. But before
initiating repairs, I have tried with new prnter and new cable
connector. Same result: "no printer installed". During Some stages of
the repair, I have tried with the new printer and cables, and same
result also: "no printer installed".

 

[Sue D Nim]

If hooked up w/ standard serial cable, you may need a null modem between the
computer and the printer.

 

[Ken Weitzel]

If hooked up w/ standard serial cable, you may need a null modem between the
computer and the printer.

Hi...

Just a coupla thoughts...

Is the serial port enabled in bios? If so, is the right
type chosen? The correct IRQ?

And those silly D connectors, if pushed together carelessly
can result in one (or more) pins being bent down. Checked
for that possibility?

Take care.

Ken