Vintage Synth Repair

All in all, I'm suspicious that it is the MPU that has given in. Does anybody have any experience with this problem? Frankly, I hope it is something else than the MPU, it seems to be quite a job to desolder it and replace it with a new one. Any ideas will be appreciated!

Best regards,
Helge

>
> Hello,
> I'm currently trying to make a DX7-IID work. At power-up, all LEDs and the display lights up, and nothing more happens.
> Measuring at the MPU, it does get the 8 MHz clock signal, but it does not output the 500 KHz clock signal at pin 15. Besides, most of the adress pins (34-50) have a weird output of constantly 1.5V. - and at a few of the pins above 50, there is a slight trace of the 8 MHz clock signal. I have measured the TC40Hxxx circuits directly connected to the resonator and the crystal; they seem to work ok. And none of them run hot. As a matter of fact, nothing in the machine runs hot.
> 
> All in all, I'm suspicious that it is the MPU that has given in. Does anybody have any experience with this problem? Frankly, I hope it is something else than the MPU, it seems to be quite a job to desolder it and replace it with a new one. Any ideas will be appreciated!
> 
> Best regards,
> Helge
>

>
> Hello,
> I'm currently trying to make a DX7-IID work. At power-up, all LEDs and the display lights up, and nothing more happens.
> Measuring at the MPU, it does get the 8 MHz clock signal, but it does not output the 500 KHz clock signal at pin 15. Besides, most of the adress pins (34-50) have a weird output of constantly 1.5V. - and at a few of the pins above 50, there is a slight trace of the 8 MHz clock signal. I have measured the TC40Hxxx circuits directly connected to the resonator and the crystal; they seem to work ok. And none of them run hot. As a matter of fact, nothing in the machine runs hot.
> 
> All in all, I'm suspicious that it is the MPU that has given in. Does anybody have any experience with this problem? Frankly, I hope it is something else than the MPU, it seems to be quite a job to desolder it and replace it with a new one. Any ideas will be appreciated!
> 
> Best regards,
> Helge
>

>
> Hi,
> You don't say if you are measuring with a meter or scope.  That would help knowing before going further.
> Have you checked all power supplies for correct voltage?
> Doug
> 
> --- In vintagesynthrepair@yahoogroups.com, "hnrgaardmadsen" <helge1961@> wrote:
> >
> > Hello,
> > I'm currently trying to make a DX7-IID work. At power-up, all LEDs and the display lights up, and nothing more happens.
> > Measuring at the MPU, it does get the 8 MHz clock signal, but it does not output the 500 KHz clock signal at pin 15. Besides, most of the adress pins (34-50) have a weird output of constantly 1.5V. - and at a few of the pins above 50, there is a slight trace of the 8 MHz clock signal. I have measured the TC40Hxxx circuits directly connected to the resonator and the crystal; they seem to work ok. And none of them run hot. As a matter of fact, nothing in the machine runs hot.
> > 
> > All in all, I'm suspicious that it is the MPU that has given in. Does anybody have any experience with this problem? Frankly, I hope it is something else than the MPU, it seems to be quite a job to desolder it and replace it with a new one. Any ideas will be appreciated!
> > 
> > Best regards,
> > Helge
> >
>

>
> 
> Hello All,
> I measured my DX7 with a scope, that's how I found traces of the 8 MHz at places where I didn't expect it at all. And yes, I did check the PS, it gives out +/- 12V and 5V and all. Even the battery is ok ;)
> Thank you to all of you for the effort so far; it shure would be great to get the old bugger playing again. By the way, getting a new MPU shouldn't be a problem - if only I order at least ten!
> 
> Sincerely
> Helge
> 
> 
> --- In vintagesynthrepair@yahoogroups.com, "Doug" <dougslocum@> wrote:
> >
> > Hi,
> > You don't say if you are measuring with a meter or scope.  That would help knowing before going further.
> > Have you checked all power supplies for correct voltage?
> > Doug
> > 
> > --- In vintagesynthrepair@yahoogroups.com, "hnrgaardmadsen" <helge1961@> wrote:
> > >
> > > Hello,
> > > I'm currently trying to make a DX7-IID work. At power-up, all LEDs and the display lights up, and nothing more happens.
> > > Measuring at the MPU, it does get the 8 MHz clock signal, but it does not output the 500 KHz clock signal at pin 15. Besides, most of the adress pins (34-50) have a weird output of constantly 1.5V. - and at a few of the pins above 50, there is a slight trace of the 8 MHz clock signal. I have measured the TC40Hxxx circuits directly connected to the resonator and the crystal; they seem to work ok. And none of them run hot. As a matter of fact, nothing in the machine runs hot.
> > > 
> > > All in all, I'm suspicious that it is the MPU that has given in. Does anybody have any experience with this problem? Frankly, I hope it is something else than the MPU, it seems to be quite a job to desolder it and replace it with a new one. Any ideas will be appreciated!
> > > 
> > > Best regards,
> > > Helge
> > >
> >
>

>
> And it still refuses working. I've changed the MPU now, and at least that helped a little - I don't get traces of 8 MHz anywhere it is not supposed to be. But the rest is the same: Everything that can light up at all does light up, and nothing more happens.
> Any ideas anyone?
> 
> Sincerely,
> Helge
> 
> 
> --- In vintagesynthrepair@yahoogroups.com, "hnrgaardmadsen" <helge1961@> wrote:
> >
> > 
> > Hello All,
> > I measured my DX7 with a scope, that's how I found traces of the 8 MHz at places where I didn't expect it at all. And yes, I did check the PS, it gives out +/- 12V and 5V and all. Even the battery is ok ;)
> > Thank you to all of you for the effort so far; it shure would be great to get the old bugger playing again. By the way, getting a new MPU shouldn't be a problem - if only I order at least ten!
> > 
> > Sincerely
> > Helge
> > 
> > 
> > --- In vintagesynthrepair@yahoogroups.com, "Doug" <dougslocum@> wrote:
> > >
> > > Hi,
> > > You don't say if you are measuring with a meter or scope.  That would help knowing before going further.
> > > Have you checked all power supplies for correct voltage?
> > > Doug
> > > 
> > > --- In vintagesynthrepair@yahoogroups.com, "hnrgaardmadsen" <helge1961@> wrote:
> > > >
> > > > Hello,
> > > > I'm currently trying to make a DX7-IID work. At power-up, all LEDs and the display lights up, and nothing more happens.
> > > > Measuring at the MPU, it does get the 8 MHz clock signal, but it does not output the 500 KHz clock signal at pin 15. Besides, most of the adress pins (34-50) have a weird output of constantly 1.5V. - and at a few of the pins above 50, there is a slight trace of the 8 MHz clock signal. I have measured the TC40Hxxx circuits directly connected to the resonator and the crystal; they seem to work ok. And none of them run hot. As a matter of fact, nothing in the machine runs hot.
> > > > 
> > > > All in all, I'm suspicious that it is the MPU that has given in. Does anybody have any experience with this problem? Frankly, I hope it is something else than the MPU, it seems to be quite a job to desolder it and replace it with a new one. Any ideas will be appreciated!
> > > > 
> > > > Best regards,
> > > > Helge
> > > >
> > >
> >
>