SID drawing too much current

[thomerow]

Hello forum!

This weekend I started my first experiments regarding a microcontroller, two 74HC595s and a MOS 8085. Unfortunately I didn't get very far because both SIDs I have lying around semed to draw too much current on the 5V pin.

Hopefully I didn't fry them both by doing the following (I haven't connected them to the full voltage level at any time): For a start I connected only the 9V pin to a power supply preset to the right voltage but with the current turned completely down, the 5V pin to a power regulator connected to the same power supply, the reset pin to 5V and the ground pin to ground. A 1MHz oscillator (also supplied by 5V) is connected to the clock pin. Being very cautious I have a multimeter attached to each the 5V and the 9V inputs. When I slowly turn up the current on the power supply, the 9V line shows very little current, but the 5V line is already drawing more than 70 mA at about 3 volts.

What's happening here? Have I unluckily bought two broken SIDs from two different persons on Ebay?

[nILS]

You seem to be a bit ubercautious ;) Have a look at the SID datasheet and you'll find the specified "typical current draw (Vcc)" is 70mA and max is 100mA, that's at 5 Volts.

[thomerow]

OK, I will have another try tonight… Just found it strange that without doing anything at all the chip already needs more power than the "typical current draw". So there is nothing unusual about this behavior? Should I be concerned if it draws 100mA permanently?

[nILS]

Just found it strange that without doing anything at all

Who says it's not doing anything? It's producing sound, constantly. Since the registers are all filled with 0, nothing audible is going on, the chip is as active as it could be though.

Should I be concerned if it draws 100mA permanently?

No, you should worry less in general. The SID datasheets aren't the most reliable source of information as it contains quite a number of errors anyways. Then again, you worry about the current draw - which is prefectly withing the boundaries - but don't think about what happens if you only apply one of the two voltages ;)

In case you haven't stumbled across that yet: http://ucapps.de/mbhp_sid.html

[thomerow]

It's producing sound, constantly.

Yes, of course, you are right. I even read that somewhere before but must have somehow forgotten it.

Thanks for your advice regarding the "problem" with the current draw. Unfortunately the next time I will get to carry on with my project is this weekend. I'm really looking forward to it.

Coincidentally the link you recommend is the very first page I came across when looking for a possibility to connect a SID to a MCU. It sort of was the starting point for all my further research regarding this topic.