Opamp 9 pins instead of 8??**Updated Coron D500 Troubleshooting

[clubrulz]

I am trying to troubleshoot a Coron Distortion D500 and found the opamp NJM2068S has 9 pins. I have found the datasheet and it shows only 8. Anyone seen this before?



Follow up question. Which pin is number one? the one right under the hole or the second one in?

[R.G.]

Could be an odd variant that doesn't get out much, an attempt at obscurity by remarking the IC, or the wrong datasheet.

In any case, it's simple enough to reverse engineer the chip by tracing the circuit. Should take about 20-30 minutes for a single sided board with through hole parts.

Pin 1 is always the first pin on the end with the marking for "here's the pin-1 end". At least on normal chips.

[clubrulz]

Yeah, i am going through the circuit and trying to trace it out completely. The first pin (what i believe to be number 1) is on an island on the board. The one in the fifth position is grounded, which would make sense if it was number 4. This is what has me confused. I am going with number two as really number one and number one is just an anchor.

[Govmnt_Lacky]

After a little Google-fu....

It looks like Pin 1 and Pin 9 might be connected internally and are the Vcc pins.

Easy to verify with a multimeter but, it looks like it was designed with 2 options to power the chip.

[R.G.]

Well, that clears that up. Odd variant that doesn't get out much.

Nice of the maker to make that as an option! I'll have to remember that.

[Johan]

Mackie used a 9pin sip like that in their earliest 1604.. it was great as it didn't matter how you put the ic in.  Fully symetrical, s long as you get the pins into the holes it would work.  Even if you put the ic in on the wrong side of the pcb.. If my memory serves me it was 4580..

[Mark Hammer]

Yep, SIP dual op-amp chips can come in 8-pin and 9-pin flavours.  The 9-pin format appears to have two V+ pins, where the 8-pin format has the same pinout as a normal 8-pin DIP.

[clubrulz]

Confirmed...Both pin 1 and pin 9 are at V+. In my case 8.65V.

Now to get the darn thing working...lol. Any suggestions on how to best troubleshoot the switch? Transistor switching. Is there a way to jump it, so I can take it out of the equation?

[R.G.]

Any suggestions on how to best troubleshoot the switch? Transistor switching. Is there a way to jump it, so I can take it out of the equation?

Is it a copy of the Boss or Ibanez  switching? If so, see http://www.geofex.com/Article_Folders/bosstech.pdf

[clubrulz]

Thanks for the article. makes a lot more sense now. I am still confused as to how the LED works. From your schematic, the anode of the LED is connected to the anode of the Zener diode. How does current ever flow through a diodes connected in opposite directions?