Strange voltage issue with MB-6582

MIDIbox SID
1

Hello,

I build two MB-6582, working perfectly.

I have used psu option B and build my own psu with 5VDC und 9V AC (Tranformer 2x9V und 7805 with 3A max. )

Under full charge the 5V DC drops down to under 3V. I have tested this with 3 different power supply units (regulated power supplys)

For both MB-6582 I need a no-load voltage of 8V.

I am pretty sure there are no short-cuts etc. I did some current measurement and there are no uncommon currents.

Any suggestions? Maybe because of the 2200uF Elko directly after the power-switch. Is this Elko really required?

best regards

2
3

I have one MB-6582 with 4x8580 and 4x6582 so I need only 9V.

Second one has 4x6581 and 4x8580.

Today I changed the psu option B of the “9V” MB to A because the 7812 generated some heat for nothing.

But I got no change in voltage drop.

Currents are (5V rail): 1. No CS (no lcd), without 9V-Jumpers for SIDs, Fan pluged on 9V AC Line: 0,8A

  1. 9V-Jumpers pluged in, no CS: 1A

  2. with CS : 1,1A

Voltage drop increases with rising current. I need 7VDC so get a working MB with 5VDC in it.

For this measurements I use no DIY psus etc.

I did this with 3 no diy psus.

The same behaviour at both MB.

4

Problem solved!

Some miserable cable from pollin.de (20cm long => 0,8 Ohm x 2 = 1,6 Ohm) copper-diameter = 0,000001mm² :rolleyes:

http://www.pollin.de/shop/dt/Nzg5OTYxOTk-/Messtechnik_Uhren/Messtechnik/Leitungen_Spitzen_Klemmen/Messleitungen_Set.html

Buy nothing at pollin.de!