PT2399 circuit troubleshooting

[stfala]

Another delay circuit question from me  ...

This time it's a PT2399 circuit. I have built the 'surround/delay application circuit' from the datasheet to the exact values specified (i'll change them around later, just want to get it working first).

The first time I plugged in and tried it, it worked (delay time pote worked and audio was delayed) but with a ridiculous amount of distortion at the output. I then noticed that I had (naively) supplied the chip with a full 9V, instead of the 5V recommended operating voltage.

When I added a little power supply section to the circuit, that mainly consisted of a voltage divider reducing the voltage to 4.5V, the clean audio came out, but the delay didn't seem to be working.

I then tried using a bench supply at 5V to power it, with the same result.

Every time I tried a different chip, just in case the previous one had been knackered by my first mistake.

Anyone have any ideas before I go poking about with a multimeter? I'm just bemused by the fact that it was working (to some degree) initially, now it doesn't :s.

Anyone tried adding a power supply to this circuit and have any tips? Mine's just consisted of a diode, cap, and a voltage divider consisting of two 100K resistors.

Cheers.

[bluebunny]

You need to rustle up a quick 78L09 regulator circuit.  Have a search of the forum for PT2399 projects - they all use them.

[duck_arse]

your pt2399 will load down the voltage divider, so needs a 5V supply that will supply. and running the rest of the circuit off 5V may be cutting things too fine, so a 9V supply for the rest. if you start with a 9V supply, and add on a 5V regulator, you should be good, as they say, to go.

you could 5V bench supply the pt, and 9V batter supply the resta the circuit, if you wanted to.

[Digital Larry]

100k resistor might be OK for getting Vref for opamp circuits but most likely the PT2399 pulls too much current and is not getting enough voltage ultimately.

Remember V = IR?  On a 100k resistor, 1 mA would drop 100 volts, if it had that much available.