SV: [sdiy] More OSCar questions...

[karl dalen]

--- Julian <julian at 22host24.com> skrev:

> My friend bought his OSCar to me for repair (battery leaked onto pcb) last
> week, and, whilst working on his, ive thought about them, and mine, a little
> more:
> 
> OSCars have a bad reputation for reliability, i know.  However, in the time
> ive had my own OSCar, ive had very little in the way of issues (fingers
> crossed for the future here)

Se below on reputation!
 
> I guess i bought my machine maybee 5 or 6 years ago.  Shortly after
> purchase, i fitted a kenton midi kit, and replaced one of the rotary
> switches.  Later i replaced a few pots. 

Perhaps cheaper to by a 6850 an 6116 some glue logic and burn a 
EEPROM and do the standard piggy back procedure then to buy 
a Kenton for it? Depends ofcourse what you pay for the Kenton?
maybe the kenton also are a piggy back unit? 

>Last year one of the multiplexers
> on the control board died.  And this week (prompted by the scary state of
> the battery on my friends machine) ill be getting arround to fitting the
> replacement battery that ive had on the shelves all this time (yes, i know i
> should have done it at time of purchase!), and recapping the powersupply
> etc.
> 
> In short, mines been fine, beyond the standard 'old synth' issues, but has
> been appart on a number of different occasions.
> 
> Im wondering if this may have actually been good for it?  The main thing i
> hear about is the OSCars connector between the pcbs.  Im wondering if the
> periodic unplugging - replugging of this may have had the desirable spin-off
> of removing oxides etc. and *increasing* the reliability of it?
> 
> So, i guess, thats the first query.
> 
> Secondly, what else creates issues?  If the connector on mine seems to be
> fine, i recap the psu,

No, but filtering the mains and create a RFI filter for each DC supply line
will make wonder to a Oscar, oscar main issue is its sensitivity to mains
spikes and glitches it causes the reset circuit to reset the Z80 CPU.
The reset cirquit are strange but work but stuff goes down that line
and do funny things!

>renew the regulators,
No.
>the battery,
perhaps.

>maybee the pots
well.
> (see below) will this set the machine up for the future as well as it can
> be, or are there fundemental flaws in the design (beyond mechanical
> components) that just simply cant be ensured against?

The OSCar don't have any major flaws not more then any other synth from that
time. One flaw is the PLL's spooingy response to large frequency shifts, ie a
constant short glide. 

>source than what i have
> current, which works out at (aproximatly) GBP £50 per set?)

I remember the pots not being any standard Alps pots but i maybe wrong on this!
 
 



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