OBERHEIM SYNTH

In the video, over at the left edge the scope seems to be showing a 
dip in the +5MEM supply.    That supply is created by ORing the 5V digital 
supply and the battery, so there will be a diode drop in it.   But that should be 
constant, not a dip like we seem to be seeing.   Maybe you shouldscope both of your 5V supplies more carefully.   Can you put the scope on 1V/div,or maybe even 0.5V/div, and set it up to trigger on a negative edge at 4.75V or 
something?  Then  if it triggers, move the trigger point and the glitch to the centerof the scope so you can see it clearly.   If the power supply is drooping too much,that cause cause lots of strange things to happen.   There are two 5V supplies.I would check them both.  You might want to check the other supplies while you 
are at it.  You can use the AC coupled setting of your scope to see 15V suppliesat 0.5V / div.   In that case you are not measuring the voltage, just looking 
for noise and dips.

    Did you replace the power transistor in the supply with the exact type usedoriginally?   Any other P/S parts replaced?
    Bob

      From: "richtrix@... [oberheim]" <oberheim@yahoogroups.com>
 To: oberheim@yahoogroups.com 
 Sent: Sunday, March 22, 2015 8:51 AM
 Subject: Re: [oberheim] Finding Clock frequency of my OBXa [2 Attachments]