Re: [AH] Synthex sequencer fault

From Brian Willoughby
Sent Sun, May 26th 2019, 00:33

Bob seems way more knowledgable about the Synthex, so perhaps he=E2=80=99l=
l have more specific recommendations.

Meanwhile, if you can solder, then you probably have enough experience =
to pull a chip from a socket and reinsert it without bending any pins. =
Try that with the chips at 2N and 2O (maybe also 2L and 2M). If you=E2=80=99=
re lucky, dislodging any oxidization might restore normal operations. =
I=E2=80=99m not sure whether there=E2=80=99s an effective way to clean =
the pins without damaging them, but perhaps some alcohol and a swab =
wouldn=E2=80=99t hurt.

I spent quite a while trying to diagnose and replace parts on my Ensoniq =
EPS keyboard scanner, only to find out in the end that removing the main =
chip and then reinstalling it in its socket was enough to get everything =
working. Sometimes, with age, oxidization builds up on the pins.

As for replacement parts, a 1Kx4-bit (4Kbit) NVRAM chip is probably =
going to be hard to find these days. Make sure you know its bad, and =
then your best bet is probably NOS (but it might be unreasonably =
expensive, due to dwindling supply).

I got caught in a similar situation trying to resurrect a memory cart =
for a Buchla Thunder, and couldn=E2=80=99t find a chip that was exact. I =
got lucky and found that there was a mechanical short draining the =
battery, and not a faulty chip. For a while, I was considering =
manufacturing a new board that would adapt a modern memory chip to the =
old equipment design.

Brian


On May 25, 2019, at 11:50 AM, Neil Dunn <xxxx.x.xxxx@xxxxx.xxx> wrote:
> Thanks for chiming in Brian, i can confirm the battery is working well =
so i will change the SRAM chips over but can you advise where i can =
obtain these please?
> I can solder well but i'm no tech so my terminology is lacking =
somewhat when looking for parts
>=20
> On Sat, 25 May 2019 at 18:29, Brian Willoughby =
<xxxxxx@xxxxxxxxxxxx.xxx> wrote:
>> Before you change any chips, could it be a battery?
>> I=E2=80=99ve never looked inside a Synthex, so I don=E2=80=99t know =
what=E2=80=99s involved.
>>=20
>> Brian
>>=20
>>=20
>> On May 25, 2019, at 10:14 AM, Bob Grieb via analogue =
<xxxxxxxx@xxxxxxxxx.xxx> wrote:
>> > Sequencer data is stored in battery backed RAM, starting at address =
0400h,
>> > which is the start of the RAM2 chip select, so chips 2L and 2M.
>> >=20
>> > I suggest changing out those SRAMs to see if that fixes the =
problem.
>> >=20
>> > You may want to buy enough chips in case the patch ones fail later =
on,
>> > as they are the same type.
>> >=20
>> > Sorry I am not able to respond in the same thread.   Using a =
browser to read
>> > the messages.
>> >=20
>> > Bob Grieb
>> >=20
>> > On May 25, 2019, at 9:49 AM, Neil Dunn <xxxx.x.xxxx@xxxxx.xxx> =
wrote:
>> >> Hi folks
>> >>=20
>> >> I'm hoping someone can offer some advice and help me repair my =
Synthex sequencer which has a few issues.
>> >>=20
>> >> The sequencer is acting very odd, it stores random note data on =
all for channels with some being very long indeed.
>> >> Once deleted (which can sometimes take two or three efforts) i can =
record sequences but once i power down and back on again my programmed =
sequences are gone and the random note data has returned.
>> >>=20
>> >> For the record i've had this unit approx six years and it's always =
been like this, it's MK2 with JB Emonds midi kit installed
>> >>=20
>> >> Any advice is welcomed
>> >=20
>>=20