[sdiy] Strange TB303 problem here

[Trevor Page]

Hi there,

I've fixed several TB303's all with a very similar problem, including my own. In all cases it was due to faulty memory IC's, and this is almost certainly the cause in your TB303. It's the most common fault I've come across. 

99.9% likely that one or more of the three IC's is faulty. 

It usually appears to be a dud microcontroller but I've never had this. I've got some original CPUs and never had to use one... yet. Sometimes an I/O line on one of the memories can appear shorted to either gnd or +V, which may also cause varous LEDs on the front panel to behave strangely. 

A common cause for dead memories in the silver boxes is the +Vpp pin being corroded away due to battery leakage. Look at the three memory IC's closely. It's a strange phenomenon! Any sign of corrosion on any of the pins, then I'd replace the whole lot. 

Don't replace these memories with regular 2114 types. They'll zap the batteries. Roland may be your best source. If you have trouble getting some replacements, I have a pile here that Robin Whittle sent me some time ago- they're actually pulls from TB's he'd fitted memory expansion mods into. I could send you a couple. 

Yes, it will 100% most definately work again! :o)

~ Trev

----- Original Message -----
From: VINTVOLT <VINTVOLT at terra.es>
To: synth-diy at dropmix.xs4all.nl
Sent: Wed, 19 Sep 2001 08:41:58 +0100 (GMT+01:00)
Subject: [sdiy] Strange TB303 problem here

> Hi there!
>  
>  Please help me out to find what's wrong with a TB303 I have here (not 
>  mine): You can program it OK, that is, when you are in pattern write 
>  mode  you can hear the different notes as you enter them (in pitch 
>  mode). But when you put it to pattern play mode, it just keeps playing 
>  the same note all the time!
>  
>  Has anyone encountered this problem before? I suspect that it's either 
>  the microcontroller or the memory. Is there any chance it might work 
>  again?
>  
>  Thanks a lot
>  --
>  Carles Vila Deutschbein
>  Departament d'Acústica
>  Enginyeria La Salle, Barcelona
>  
>   ___________________________________________________________________ 
>  Consigue tu e-mail gratuito TERRA.ES Haz clic en http://www.terra.es/correo/
>  
>  




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