Sony TC-FX1010 noworkie, hmmm.

[jbeckva]

Aint complaining. Got it for about 20 bucks and the description was one of those "powered up fine, but no other testing done" deals, so no biggie.

So I have it down to the dreaded CX7919 chip, which is basically it's analog "control" chip that handles all of the signal routing and manipulations, under serial control from the CPU. So I would be inclined to think that it IS this chip causing the issue (gots an "input signal", but no "output signal"), but unless I had the datasheet and a storage scope to decode the serial input there's no way to be sure. Besides.. if it was that chip, fat chance on finding one nowadays.

But what's odd and suspicious is this here - when I look at the serial signal input, that floats between -10 and -8 volts, so I'm assuming a non-RTZ scheme of some sorts.

Now.. there is another pin on the chip that is labeled "Vdl", and the schematic is saying I should have around -6 volts, as regulated by a zener, cap, and resistor off of the -10 volt PS voltage. That in itself is measuring actually around -5.1 volts.

So.. thinking out loud now... "Vdl" I am assuming is setting a digital "threshold" level i.e. the reference point for the serial data input. Going on that assumption, if the "reference" is -5.1 BUT the closest I have seen the actual data signal on the positive side is around 7 to 8 volts, something tells me that there's too much of a difference going on there. So essentially the chip is going to stay at it's "default" state - because for all it knows, it has no "control" being applied.

What do you think?? Hmm.. it'd be cool if someone had another one of these "weirdo" decks (look em up.. they are very "odd") that worked to compare off of.

 

[Web Police]

What? Huh? Hmmmmmmmmm can't help you out on that one.

 

[nakdoc]

Something isn't right. It ought to have 5 volt logic. I'll pull my manuals. IIRC there is also a book about circuit theory on this deck.

 

[jbeckva]

Something isn't right. It ought to have 5 volt logic. I'll pull my manuals. IIRC there is also a book about circuit theory on this deck.

Been in touch with Alex/A.N.T. about it. The output of the controller feeding it is standard TTL level, but it's level-shifted to (supposedly) -6volts for a logic one, and -10.6 for a zero (by way of a zener between the TTL output and -10.6 volts from the power supply). But that Vdl input is suspicious, because supposedly it is the "reference" voltage for the high/one levels. I'm measuring -5 volts which is a full volt off from the schematic and theory of op.

BUT... the zener diode that is supposed to bring the voltage "up" from the -10.6 volt power supply voltage is rated at 5.1 volts. So with that, it would bring the voltage up to -5.5 volts. Not exactly "-6 volts" per the schematic, but not -5 volts that I actually measured either.

So I'm thinking of trying say... a 4.6 volt zener instead. That would bring the Vdl reference voltage to exactly 6 volts, which is much closer to the measured actual "high" voltage from the serial and clock inputs. Worth a shot, because no way am I going to find one of those ASP chips... useable ONLY on this particular Sony model (what a red headed stepchild of a deck, eh?).