Vintage Synth Repair

From: Terje Winther
Subject: [vintagesynthrepair] Adjusting VP-330 Mk.1
To: vintagesynthrepair@yahoogroups.com
Date: Sunday, 22 February, 2009, 8:21 PM

H everyone,
Sorry I´ve been so quiet lately. I´ve been buried in work, writing,
recording and doing service.
I have just finished service on a Roland VP-330 vocoder/human
voice/string keyboard, Mark 1, the one with the rocker switches.
Very good machine! But a torture to service and adjust. The schematics
specify cheap op-amps (4558), but - at the time - state-of-the- art
op-amps for the final outputs of each board (TL082). However, these
specified TL082s were not used, it seems, at least not on this stock
model. They used LM353s all the way, and several of these had failed,
so that the string was dead, and some of the vocoder filters were not
working because the op-amps have gone into self-occilation. So after
debugging and swapping out defected parts, it was down to adjustments.
For at start, the vocoder sounded dull and unfocused, but somewhat
right. But the carrier signal was bleeding through a lot. Who would
have thought that this was among the "best vocoders ever", even used by
Krafwerk at some point in their carrier?
Well, the vocoder card, with the 10band filters, VCAs and corresponding
"companders" (compressors + expanders) is neatly laid out, but fiddly
to adjust. As usual with analog, everything influences each other, so
there was a roundabout of going back and forth on all the trimmers. I
feared I would bump into one extreme of any trimmer, so that I would
have to change resistors as well in order to tune the circuts, but it
all held together.
After hours of work, I must say that the sonic that this machine now
creates is amazing. Very distinct vocoder with good sound, the the
combined human voice and string is indeed very charming.
The machine is full of Roland chips (BA662s etc.), and not to mention
all the SAD chips for the chorus, so if anything major starts failing
it will be a nightmare.
But as long as those chips hold, this is a dream machine. And now that
I have done one and learned it´s secrets, I am sure the next one will
be a breeze.
Remember to use the right service manual; mark I is significantly
different from Mk. 2.
Also remember to be patient: every time you adjust a vocoder filter, it
takes some time to stabilize, so be cool :-)

Terje Winther
terje.winther@ wintherstormer. no
http://www.winthers tormer.no/