Aphex 9251

[CraigNS]

Hi,

Anyone have the schematic for the Aphex 9251 Aural Exciter... also the pinout/datasheet of the Aphex VCA 1001 might help.

Thanks,
Craig

[Martin Pedder]

Sorry, don't have the 9251 but the VCA 1001 pinout is shown on the 9651 schematic here:
Aphex 9651.pdf
Martin

[CraigNS]

Thanks Martin for the 9651 schematic. Helps a bit. If no one has the schematic, is there anyone with one of these kicking around? I need to know the values of the three resistors coming off pin 9 (vc) of the VCA 1001. They are smoked and unreadable.

[J M Fahey]

Dear Craig.
Sorry but don't like what I see.
Suppose your Aphex has different functions than the 9651 but the core is the same, the VCA1001.
Your mystery resistors should be the equivalent to R42/43/44 (the only ones connected to pin 9)
Discard R41 because of its high value. Why?
To burn a resistor you need current through it.
The highest voltage available in that Aphex is 15V, either positive or negative.
15V across R44 (1K) mean 1/4W.
Enough to "smoke" a resistor, even if 1/8W ??
Barely possible.
Same 15V across R42? (56 ohms)?
Well, that would mean 4W, more than enough.
270mA which should have to be sourced from pin 9 which is not a power pin.
What I'm pointing at is that for pin 9 being able to source such a high voltage at such a high current, the VCA1001 must be very dead and very shorted internally by now.

[CraigNS]

Hi,

Actually only two of the resistors are smoked, one worse than the other. I've found a replacement VCA as I assume like you that it too will be dead. I'm hoping nothing else in the circuit is bad but I will be checking some caps. The VCA is heavily heat sinked so hoping a lifetime of use is what fried it. Also repaired a trace on the back of the board that was heading to ground.

[J M Fahey]

Suggest you hand draw the circuit around the VCA.
Name all parts as R1/R2 .... etc. or use the PCB silkscreen labels if available.
Write values if visible. If not, at least the part ID.
By analogy with the known schematic, some values can be guessed.
Good luck.