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teenix · (This post was last modified: 04-15-2021 10:39 AM by teenix.)

(04-15-2021 07:47 AM)AndiGer Wrote: Hi Tony,

Once I found that in figure 4-10 (page 53 in the pdf file) Q2 and Q3 are switched.
Maybe you change in your pdf version.

Andi

Hi Andi,

I looked at the circuit in my PDF copy and Q2 (1854-0668) base is connected to Q3 (1854-0071) collector. This seems to match the components on the PCB where each transistor is marked 4-668 (Q2) and 4-071 (Q3).

Edit,

I notice in the brouhaha.com HP chips, it has 1858-0044 (quad NPN, anode driver, print head driver, print motor driver) listed equivalent as TPQ3904, but I don't think this can handle up to 500mA for the print heads. 2N3904 would be a discrete transistor equivalent, but current is around 100-200mA. Maybe something like PN2222A or similar (800mA). MMPQ2222A is a quad package but surface mount and different pinout.

cheers

Tony