----- Original Message -----From: Christian OnckenSent: Wednesday, May 09, 2012 2:41 PMSubject: [vintagesynthrepair] Re: Simmons SDESo it turns out, looking around for info on those ICs, the 7805 and
7806 parts have the the metal tab connected to ground, the 7906 has it
connected to -6v... Its strange because I don't remember removing any
insulators from it when I disassembled it. I remember the parts being
stuck to the heatsink with some sort of glue, but that was a long time
ago so I might be mistaken.
Jammie, specifically I'm measuring the wire on the ribbon cable that
goes to the rest of the synth that I've traced back to the output leg
of the 7806. If should be +6v but its more like 16v. Unfortunately I
am unable to find a service manual or schematics for this box.
So the next thing I'm thinking is the caps. There are a total of 6
caps in the PS, three 2200 uF 16v electrolytics... these were
obviously blown out when I opened it up and I replaced them. They
connect the input legs of the ICs to ground. There are also 3 dipped
tantalum caps connecting the output legs to ground, the value is hard
to read because they're pretty close in there with the other parts..
I'll bend some things around and look closer tonight.
I'm not sure quite how to test the caps. Looking for shorts with my
DMM and testing them in circuit with the power off, the large
electrolytics give me a steadily rising resistance in one direction
only. The tantalums seem to have resistances of 5k, 7k, and 10k.
Hugh, I really appreciate the invite. I'm in Saint Louis, MO. I'll
try to take some pics but I'm not sure how good my cellphone is at
taking macro shots.
Thank you all.
Christian
Message
Re: [vintagesynthrepair] Re: Simmons SDE
2012-05-09 by jammie
these are the items for the 79xx series of
regulators
the 16v caps are for the ripple of the rectifiers
so the input voltage would be around 12-15vdc from the rectifiers
thats why i said the you may be measuring the input
voltage
these insulaters are pennies £0.49 each
item
it sounds like some one bodged it before you got it
and just by using some type of insulationb paste but there should of been a
insulation washer
the 78xx series can be bolted to the heat sink as
there heat sink is connected to there earth pin
but the 79xx definetly needs to be
insulated