Vintage Synth Repair

At least it isn't trying to cook your breakfast...

Is ZD1 the 6.2 zener on the power board shorted? Also have you checked the 39k and 82k actual values? Somehow the turn on is way too fast. I worked on a Digitech IVL 7000 Pitchrider for 6 months off and on. (It was mine so no customer blues...) Sometimes it would boot most often not. I ultimately found the factory installed a 2.2k feedback resistor in place of a 22k in the slave CPU clock driver circuit. Red,red,orange not red,red,red. "Missed it by that much!" Agent 86.... Ohhhhhhhh Max!  

--- In vintagesynthrepair@yahoogroups.com, "alesisfusion8hd" <babouche369@...> wrote:
>
> Hi Narfman,
> 
> no the 6805 doesn't get warn.
> I plugged another 10uF in parallel (giving 20uF), but no change.
> I tried with another power supply (and another keyboard); still the same.
> 
> What buzzes me is /RES seems to reach +5V in 10ms; the datasheet says it should stay low for 100ms. That's why my manual reset works.
> 
> Strange thing: I wanted to sinc my one-trace small scope to the +5V (to precisely measure the time between power on and RES). I made a small BNC cable (coming from an old network cable), but the cable had a short I was not aware of. I took my supply from CN6 (pin 1=+5V, pin 4=GND). When I plugged it to my working DX7, I had the exact same behaviour.
> 
> --- In vintagesynthrepair@yahoogroups.com, "narfman96" <narfman96@> wrote:
> >
> > Good troubleshooting! Does the 6805 get warm? Since all the resets come from the same timing cap you could try a 22uf and see if the extra settling time helps. I found the 6805 on Ebay. Not sure if it's the same package...  
> > 
> > --- In vintagesynthrepair@yahoogroups.com, "alesisfusion8hd" <babouche369@> wrote:
> > >
> > > Just a follow up. I nailed down my issue to the Sub-CPU 6805 (IC 13) which sometimes does not boot up the right way. When I reset it by grounding pin 28, everything runs smoothly.
> > > My guess is the condition on power up does not reset the sub-CPU long enough (the 63B03 boots every time; less sensitive? ). That's the best case. The worst case is a defective 6805.
> > > I changed the 10 uF cap of the Initial Clear, but no success. I'll take a chance and change the 4700 uF on the PSU, or simply switch it with my other DX7.
> > > 
> > > --- In vintagesynthrepair@yahoogroups.com, "alesisfusion8hd" <babouche369@> wrote:
> > > >
> > > > Thanks man, the tuning procedure is exactly what I was missing. 
> > > > 
> > > > I've cleaned up all the connectors (on main board and sub boards); it didn't solve my issue, but it's a good start. I've also tipped on all chips & components to track any dry joint (I'd this issue on a Kurzweil 1000).
> > > > The issue really resides in the digital part during the init phase. Happily, I've got another DX7, in working condition; I can make some comparisons.
> > > > 
> > > > 
> > > > --- In vintagesynthrepair@yahoogroups.com, "z3sound" <z3sound@> wrote:
> > > > >
> > > > > 
> > > > > hi 
> > > > > there was no complete Service manual for DX7 (first edition)
> > > > > on the internet.but now it is 
> > > > > i just upload the complete  DX-7 first service manual in Files
> > > > > hope it will help......
> > > > > 
> > > > > --- In vintagesynthrepair@yahoogroups.com, Kashayar Dashtdar <vdashtdar@> wrote:
> > > > > >
> > > > > > Hi my friend.
> > > > > > 
> > > > > > Unfortunately there is no complete Service manual for DX7 (first edition)
> > > > > > on the internet.
> > > > > > 
> > > > > > Try these :
> > > > > > 
> > > > > > 1- Replace all the electrolytic capacitors in the power supply board.
> > > > > > 2- Send a fresh sound bank from the PC to the keyboard using a midi
> > > > > > interface.
> > > > > > 
> > > > > > I hope it will make your dx7 work properly.
> > > > > > 
> > > > > > Good luck.
> > > > > > Ciro
> > > > > > 
> > > > > > On Tue, Mar 6, 2012 at 8:49 AM, alesisfusion8hd <babouche369@>wrote:
> > > > > > 
> > > > > > > **
> > > > > > >
> > > > > > >
> > > > > > > Hi group,
> > > > > > >
> > > > > > > I recently bought a first generation DX7 for $ 50. Problem on startup:
> > > > > > > sometimes starts up OK, sometimes keeps looping, sometimes seems OK but
> > > > > > > actually frozen.
> > > > > > > When it starts up OK, I found only garbage in the internal memory, but it
> > > > > > > works with the cartridge. It does not memorize my settings, and main output
> > > > > > > seems dead (headphone OK). I've suspected and replaced the battery cell.
> > > > > > > I was able to run the self tests up to test #5 (analog inputs), but I have
> > > > > > > no foot controller to complete this stage.
> > > > > > > I checked the PSU and the voltage source on the main board (+2.5V, +7.5V
> > > > > > > and +5AV) and everything is OK.
> > > > > > > I suspect a signal is missing on the sub-CPU (6805), or a defective RAM.
> > > > > > > I picked up the schematic and the service manual on Dave Benson's site,
> > > > > > > but it seems to be altered after page 20. All other services manual I found
> > > > > > > on the web has the same issue. Does anyone have a full copy of it?
> > > > > > >
> > > > > > > Thanks,
> > > > > > > François
> > > > > > >
> > > > > > >  
> > > > > > >
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