Neutron debugging help (Fried IC)

[juancra]

Hello everyone!

I'm writing this message as I need help over a Neutron clone that I'm building. I'm building it with RG Keen's PDF available at General Guitar Gadgets.
I came to a final testing stage resolving all problems I've encountered (wiring, components,etc) and decided to test the circuit with 9V supply. I had both "common" ICL7660CPAZ voltage converters and ICL7660SCPA (the one with the boost pin). I decided to first test it with the common 7660 'cause its cheaper and wont be sacrificing too much if anything goes wrong. So I went testing  and everything was ok. I had the Mutron working almost fine, but had the whine associated to non-boosting 7660. After a period of one hour or two I decided to swap to the boosted version so I could get rid of the whine, so I bridged the 1 and 8 pins in the solder side with a jumper (which only touches those pins, it doesn't create any other contact), connected everything up again and.. things started to go bad!
The IC get too hot and eventually the whole thing stopped working, giving only a hard, ugly distorted sound. I thought the IC temperature could be normal given its function, so I tested every other part of the circuit , with no results. A while back I decided to put again the non boosted version of ICL7660 and the came back to life !
I don't know what is happening to the circuit, but given the high price of the boosted IC, don't want to put another into it before I know what is the problem... anyone can help me up?

thanks in advance, Sebastian.
Sorry for my english!

[Jarno]

Hello Sebastian,

I am also building a Neutron, but I'm still awaiting some parts, so I haven't been able to start it up yet.
Did you try to use inductors in the power lines to get rig of the whine? What's the difference between boosted and non-boosted chips? I ordered a Max1044, which should be compatible.
Are you using the GGG PCB? Layout is very important with these (or any other) converter chips.

Best regards,

Jarno.

[juancra]

Hello Jarno!

RG states that inductors are needed when using non - boosted versions of the converting, to avoid getting the whine into the circuit, but I didn't think that where necessary when using boosted versions. The difference between versions of the chip is that the boosted versions (MAX1044 / LCT1044, ICL7660S) have the capability to raise the internal clock frequency so it goes off audio limits (so no whine is heard) when a pin (ussualy pin 1) is driven to V+.  I think that ICL7660S and MAX1044 are pin to pin compatible

[R.G.]

The 7660S does look to be pin compatible with the MAX1044 from the datasheet I looked at.

- Is this chip position socketed? Is it possible you plugged it in backwards?
- The 7660S is CMOS. Is it possible that it was static-electricity damaged? Perhaps you should try another 7660S in a breadboard outside your circuit to verify it's good first.
- The inductor positions are on the PCB only for filtering when the non-boosted chip is used, and should not be needed for the 7660S
- Did you try the 7660S without the connection between 1 and 8? It should work, but with whine, this way. Once it works unboosted, then connect the boost pin.

Nothing else is easy to conjecture from your posting. The obvious stuff, bad connections, bad solder joints, erroneous wiring, pinout problems, etc. are stuff you will need to check again, but if it worked with the 7660 non-S, then it should work with the S version unless you accidentally fouled something up in making the change.

[juancra]

Just remembered I had a huge short in the trimmer area  'cause it was working very bad. Now the store it's closed, when I can get a new 7660S will try again and post results, thanks a lot for your answering RG, !!