[sdiy] Mistake in Prophet T8 schematics? CEM3360 with -15V supply?

Tom Wiltshire tom at electricdruid.net
Wed Apr 3 15:32:05 CEST 2019


Fair point, but in general the Sequential service manuals are very good, so I admit I was a bit surprised.

Tom

==================
       Electric Druid
Synth & Stompbox DIY
==================

> On 2 Apr 2019, at 05:41, Michael E Caloroso <mec.forumreader at gmail.com> wrote:
> 
> That may hardly be the only error.  I stopped taking schematics for
> granted years ago.
> 
> MC
> 
> On 3/31/19, Tom Wiltshire <tom at electricdruid.net> wrote:
>> I’ve just been hunting through a few one schematics to see what supplies
>> people have used with the CEM3360 dual VCA chip. This is a useful chip and
>> not quite as big and complicated as its posher brother the CEM3330. But it’s
>> weakness is that you can’t use it with +/-15V supplies. +/-12V is ok.
>> 
>> Most synths that used it with +15V reduced the negative voltage as suggested
>> in the datasheet. MemoryMoog uses -7.5V, others mostly use -5V.
>> 
>> However, if you believe the Prophet T8 voice schematics, they’ve used -15V.
>> I think this is an error. The main output board. Where another 3360 is used
>> to control the output volume shows the chip running on +15/-5V, so I doubt
>> the voice boards are different.
>> 
>> If anyone has the lid open on a Prophet T8 at some point, I’d appreciate a
>> confirmation that there’s -5V on pin 7 and not -15V as per the schematic,
>> just to know for sure.
>> 
>> Thanks!
>> Tom
>> 
>> ==================
>>       Electric Druid
>> Synth & Stompbox DIY
>> ==================
>> 
>> 
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