Samichsid help

MIDIbox SID
1

Hello,

I just finished getting my sammichSID built and installed the sid v2 app without issue. I did not mount the banksticks or the sids at this point. I then proceeded to mount the banksticks and sids at the same time (also the 223 caps for 6582a sids). When powering the unit back on I had all the leds stay lit and the screen showed a blank backlit display. I quickly turned it off, freaked out for a minute, realized I had the midi in and out cables reversed going into my computer midi interface. Then I turned the unit back on after fixing the midi cables and got only a blank backlit lcd screen (no leds on this time). So then I decided to take out the banksticks only and then turned the unit back on and still same thing.

Then I took out the 6582a sids and the sid v2 app loaded no problem on the next power up. I decided to put the banksticks back in and they formatted ok. But what did I do wrong with the sids? I have JP shunt set horizontally like the thick white silkcreen says to do for 6582a sids (which I have)(it says shunt vertically for 6581 sids) I left both JBP’s open. I am using a 9vDC 400ma wall wart which has already been tested on my MBFM. Is that enough for the sids to work? When i did my voltage checks I got 8.9v steady on my meter at all 9v pins at both boards and got 12.6v on all 12v pins on every where it needs to be.

And just to cover all my bases.

JR4 has a shunt and JBL has its shunt at 12v for the black text on green backround lcd.

I have JMI and JMO shunted on the white silkscreen (JMI far right is left open and JMO far left is left open)

I have 223 caps at pin 1? (top pin closest to rear panel) and the second pin of the cap at pin 3 which is two pins down vertically (after the white silkscreen line) Then I have the other caps at pin 4 and 6 (4th from the rear panel and 6th from the rear panel) all four caps are seated good I think.

echo

2

And just to add to the last post. I uploaded Sid V2 rc37

When i took the sids out I tried another power supply which is 9vDC 800ma and tested the sid pins and got only 7.3v. When i had my 9vdc 400ma supply plugged in I was getting 8.9v. What is that about?

3

There is a 9V regulator in the sammichSID, and you need at least 10.5V DC going into the 9V regulator in order for it to output regulated 9V. Bridge rectifiers shave off 1.2V or so, therefore you need 12V AC or DC going into the sammichSID, with a current rating of at least 500mA and if it’s an unregulated supply, less than 1000mA, otherwise the voltage going in will be considerably higher than 12V and lead to more heat being dissipated by the 9V regulator.

This explains why you are observing the voltage dropping and failure to boot only when the SIDs are installed - each is drawing 100mA on the 5V supply and thus drawing more current than the power supply can deliver at the required voltage… when SIDs aren’t installed, the voltage going in is adequate. Actual voltage delivered by an unregulated power supply is inversely proportional to current drawn… the current rating tells you it will deliver the rated voltage or higher when the current drawn is less than the current rating… when the current drawn is much smaller, the voltage will be much higher, hence do not use 1000mA unregulated 12V power supplies or the voltage might be over 15V if the load is 500mA, leading to: P = VxI = (15-9)x0.5 = 3 watts of heat dissipated by the 9V regulator. That’s finger burny ouch ouch territory.

4

Thanks Wilba,

I have a 13vDC 500ma laying around. Would that be ok?

5

Yeah that should be OK.

6

Good to know. I dug through some boxes and found a 12vDC 500ma. Wadaya know.