hi adrian,
in my particular case at least one of the diodes was broken, so i missed one half-wave. the voltage regulator and the electrolyte had to work very hard and the 5V had some periodic drops (to around 4.2V, only visible at the scope, not at the DVM).
one effect because of this was that the ad-converters of the pots didnt have a good voltage reference and were "jumping" around(you can see the jumping values in the analog-screen). that (and probaply other effects of the unsobber 5V) were causing kind of distortet sound or like it would rescan/trigger the wavetables very fast... (but the rest of the synth was still working as usual)
first ive changed the only cap ;(because it went very hot...) but than i realized that the rectifier is faulty as well.
after changing the rectifier everything was good again, so it luckily didnt do any other damage.
for sure it would work with a 10A rectifier as well (didnt measure the actual currents), i just found it somewhere on the web that the its kind of underrated.
my guess is that because of the single cap psu design theres higher current between the trafo and the cap, which causes more stress to the rectifiers... (at least from my limited knowledge)
be sure to pay attention that you have a good cooling of the rectifier, i had to drill a new hole since the new one had other dimensions and was slighltly bigger.
so far my story, i hope this helps
cheers
kris
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From: Adrian Corston
To: vintagesynthrepair@yahoogroups.com
Cc: hans wurst
Sent: Friday, May 25, 2012 6:54 AM
Subject: Re: [vintagesynthrepair] PPG Wave 2.3 power supply restoration
Hi Kris / Hans,
Thanks for your email. Unfortunately I'm just back from picking up a MIC BR106 848 (10A 1000V) and only just saw your email.
What's the worst case failure mode for an underrated bridge rectifier? i.e. is it likely to take out other components, or just need replacing again?
Cheers,
A.
On 05/25/2012 01:52 PM, hans wurst wrote:
use a slightly bigger one; they are known to be a underrated in the ppg waves
had kind of a similar problem with mine and replaced it with a 15A (though i had to drill a new mounting hole)
cheers
kris
Thank you John & Colin, I will let you know how it goes!
Cheers,
A.
On 05/24/2012 10:23 PM, John Rose wrote:
Looking at the data sheet it is a fairly standard bridge rectifier so an alternative would be easy to find, just go to your local electronics store and ask for a 10A bridge rectifier rated 100V or more to screw mount on a heatsink and they should be able to sort you out (if you can take the original with you then you can always check the size and mounting are OK).
These things cost pennies.
My PPG Wave 2.3 passed away recently (while I was playing it - most annoying :-)
The AC fuse blows unless I have the +5V power supply board disconnected form the transformer. I have removed it for testing; the large 10,000uF electrolytic cap looks just fine (no obvious bulging or leaking fluid) but the bridge rectifier PK10-EDI-8350 has one diode that appears to be short-circuited (no resistance in either direction on the multimeter) which I expect is a likely cause of the problem. As the PK10-EDI-8350 is a 30 year old part that I may not be able to source easily, does anyone see a problem replacing it with a similar specified, currently available alternative? Any particular recommendations?
Datasheet is here http://www.edidiodes.com/pdf/Bridges/PK.pdf
Thanks in advance for any advice and assistance.
Cheers,
A.