Trouble getting right voltage on SID module (6581)

MIDIbox SID
1

Hello

My optimized PSU should be ok.I tested it again and again, the polarities must be ok.Here the test I did with the multimeter:holding the plus tester end to the 14V DC output:

1.in combination with middle pin of the 7809 on the psu: +12.5VDC

2.with -5VDC connection it gives +17.8 VDC (my 5V circuit proviedes actually 5.3)

3.with +5VDC connection makes it +12.5VDC again

These measurements should prove that the optimized PSU is working right.Please correct me here if I’m wrong.

Now I tried already the COREmodule and all the voltages are right, inclusive the polarities (which makes me more sure about the right function of the PSU)

So I connected the SID module like in the optimized PSU diagram:

+5VDC connection(directly from the PSU) with J2:Vc

-5VDC connection (directly from the PSU) with J2:Vs

14VDC connection with J1:P1

On mySID module I only left out the 7812 and bridged it.

Now on IC2 and IC 3 everything is alright including the polarity, but IC1:Vdd(28) to IC1:Vss(14) deliver me an annoying 17.8VDC again.I know that if I would invert the polarities on the 5VDC input on the SIDmodule, it would probably show th 12.5VDC, but then the polarities on IC2 and IC3 would be inverted.So what the hell could I’ve been doing wrong again? >:(

Please give me some advice of further testing

Marc

2

As none replied I figured out that it was quite a stupid question and in fact it was, as placing back the 7812 on the SIDmodule solved all problems.As a matter of fact right now I got the first sound out of the SID ;D.It’s awesome!! and I’m rather happy I didn’t have any trouble uploading MIOS and the SID application.Gonna stop for today.Tomorrow I will dive into the sound of the SID.

Lots of thanks to the whole community and TK for this great project.

long live the SID :smiley:

3

hi marcus! happy to see that you had finished SID same day as me!  8)

i’ve just a little quest: had you connected the +14VDCground with +5VDCground? or you had left not cabled at j1SID?

thankyou!

4

I just connected the 14VDC to one of the pins of J1 on sidmodule.It doesn’t matter which pin because the rectifier sits behind it.Now on the schematics of the optimized PSU it looks like there’s no ground for this connection, but actually I guess it uses the ground from the 5V connection which you connect at J2 on SIDmodule.So it’s very obvious that if the 7812 is missing, the voltages add themselves to somewhere around 17VDC.It wasn’t just that obvious to me in the beginning ;D

Cheers

marcus