Oberheim stretch

[Jens M. C.]

Hey.
I got an old stretch dx from my father because he did not used it for many years now. But it turns out that it can not produce any sound at all. It can turn on alright, lighthen up the display and every thing seems to be okay but it will not make any sound.

thanks,
Jens

[LoFi-Ninja]

This should be moved to the tips/repair section...

Have you checked that the voices are not turned off in software ?
Take it apart and check the components. Take some pictures if something looks wierd. Post here.
Maybe the EPROM got erased somehow. Check if there's still somekind of tape or something over the "erase window" on the EPROM. If you can "see into the chip" this might be your problem.

But try to take it apart. It's a reasonably old drum machine so some electrolyts or the like might be blown.

[Gordonjcp]

I'd start by checking the obvious, like damaged jacks and volume control, PSU voltages correct etc.

Don't worry too much about EPROMs without stickers over the window - I've left an unstlickered EPROM outside in bright sunshine for several days without even a suggestion of the bits decaying.  To erase EPROMs you need quite a powerful UV source at a fairly specific frequency.

[LoFi-Ninja]

I thought any UV source would kill them.. Thanks for the info..

[Jens M. C.]

Could some kind of internal vca or amplifier be broken?

[Gordonjcp]

Yes, quite easily.  The circuit diagrams are out there (I know I've seen them but I don't have a copy).  Start at the DAC and work forwards.  You may find a dead or dying 405[123] multiplexer, or TL0[678][124] opamp.