[sdiy] Crumar Performer - keyboard mystery

Andre Majorel aym-htnys at teaser.fr
Wed Aug 1 17:07:46 CEST 2018


On 2018-07-31 21:04 +0200, Florian Anwander wrote:

> I have here a Crumar Performer for restauration which shows a
> strange behaviour over the keyboard:
> 
> In string mode some keys have an rectangle suboctave playing
> and some don't. It does not matter whether I am in 8" or in
> 16" mode or have both activated. In brass mode this suboctave
> is gone.
> 
> There is no octave relation, which might have made the TDA1008
> suspicious. Interchanging the TDA1008s also does not move the
> behaviour to other notes.

> The service-manual is here:
> http://www.florian-anwander.de/crumar_performer/CrumarPerformerServicemanual.pdf
> The datasheet for TDA1008 is here:
> http://www.florian-anwander.de/crumar_performer/TDA1008_PhilipsSemiconductors.pdf
> The list which note has suboctave and which not:
> http://www.florian-anwander.de/crumar_performer/CrumarPerformerSuboctave.txt
> 
> 
> I have no idea where this suboctave might come from. Any suggestions?

Your text file seems to have octave 2 in reverse.

Only hypothesis that comes to mind after a whole minute of
thinking is a marginal logic gate being pushed over the edge by
resonance with excessive 100 Hz ripple on the power rails.
Unfortunately, that does not seem to explain the pattern of
affected notes. Does the pitch bend lever or tuning knob have
any effect on that ?

-- 
André Majorel http://www.teaser.fr/~amajorel/


More information about the Synth-diy mailing list