[sdiy] Roland System-500 Filter pcbs

René Schmitz synth at schmitzbits.de
Sat Jul 31 17:21:58 CEST 2021

Hi Florian and all,

On 30.07.2021 18:41, Florian Anwander wrote:
> Hello,
> Inspired by the Alex Ball Video mentioned over at analogue heaven I 
> wanted to update my page about roland filters with the information on 
> the System 500.
> I checked th thomann.de <http://thomann.de> pages for the pictures of 
> the module and got a little worried
> This is the pcb of the 510 (should be one four stage OTA filter and a VCA)
> https://bdbo2.thomann.de/thumb/bdb3000/pics/bdbo/13948871.jpg
> This is the pcb of the 521 (should be two four state OTA filters)
> https://images.static-thomann.de/pics/bdb/379516/10742587_800.jpg
> This is the pcb of the 505 (it should be a tranistor ladder filter)
> https://bdbo2.thomann.de/thumb/bdb3000/pics/bdbo/13948906.jpg
> The pcb of the 505 is full of LM37000, while there is no OTA in the 
> original Circuit.
> The pcbs of the 510 and 521 show not a single OTA, but many parts 
> which seem to be double transistors - which I would expect for the 505.

You can see the ladder at the top end of the PCB. C15 to C18, and two 
transistors next to each. No dual transistors but two singles.

I recon that quite a few of the OTAs are used for signal routing / 

> After a first comparison of the 510 and 505 I thought Thomann 
> mismatched the pictures, but the 521-pcb looks too similar to the 501-pcb
> Can you identify what are 6 pin parts on the pcbs for the 521/510?

Toshiba HN1C01FU and HN1A01FU. Dual NPN and PNP.



synth at schmitzbits.de

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