QSound and QPrint Interface

[aalea]

some transistor have several "packaging" and the legs interchanged (I do not remember now, but something like BC107B and BC107C have same package but legs swapped) be aware of this.

In any case, the circuit is correct, the use of this transistor is to hold DSMC line high when the interface is in use (to disable the internal circuits of QL) so NPN, colector to +5V, emiter to DSMC and base to the pin 8 of U2 is OK.

[Maskenlos]

from another user:

[otis]

some transistor have several "packaging" and the legs interchanged (I do not remember now, but something like BC107B and BC107C have same package but legs swapped) be aware of this.

In any case, the circuit is correct, the use of this transistor is to hold DSMC line high when the interface is in use (to disable the internal circuits of QL) so NPN, colector to +5V, emiter to DSMC and base to the pin 8 of U2 is OK.

Yep, an emitter follower. I'll take some photos of my board. It has labels on the component side.

[otis]

Surprise, surprise! It works, at last.

The problem is that the schematics on https://github.com/alvaroalea/QL_QsoundQprint_clone/ and also labels on PCB are wrong.
Schematics and labels reads "27512" EPROM while the BOM states 2764.

When I replaced 27512 with 2764, it started to work great.

[aalea]

Surprise, surprise! It works, at last.

The problem is that the schematics on https://github.com/alvaroalea/QL_QsoundQprint_clone/ and also labels on PCB are wrong.
Schematics and labels reads "27512" EPROM while the BOM states 2764.

When I replaced 27512 with 2764, it started to work great.

I'm so sorry, I will update the schematic as soon as possible (but in 1 o 2 weeks).

In my defense, This is because I normally use W27C512 chips, this is a very cheap eeprom, that can be pin compatible with the 2764,27128..., you only need to take care of write the contens of the rom on the top 8kb of the 64kb space. it has the advantage that is electronically eraseable, so you can delete it very fast, without need UV light or anything special.

In the schematic 1,26,27 are labeled as A13, A14,A15 in the original schematic they are VPP, PGM and N/C, so hey are wired to Vcc in any case.

(probably in the schematic of the trump card, and the Q-Discs interfaces, I have the same error).

[spkr]

Forgive me for asking, but do you guys happen to know what the hardware addresses of the QSound are to directly address/control the AY chip? I assume they are directly exposed?