"Phil Allison" wrote in
:
Hey thanks for writing back Phil. You may not have a schematic but at
least you have experience with these particular kinds of amplifiers and
are willing to help out a fellow tech and that goes a long way by itself.
Thank you my friend. Having a friend with experience is sometimes better
than even having the schematic. (I did write to Sunfire tech and asked
for a pdf of the schematic but got no answer so far.)
I the bad parts I found we
Quantity
Part Number
Description
1
2SA1302
Audio Output Transistor
1
2SC3181
Audio Output Transistor
2
IRF640
MOSFET Power Device
2
GMA 4A 250V
GMA Size Fuse
All of these were on the amp board and I did not find any other for sure
bad parts. The trouble I am having is finding this triac. This is a
Sunfire, "True Subwoofer Super Junior" (Hell of a model number, huh?) and
when my friend Bob was measuring the DC on the two main caps, he was
telling me there was like 157 VDC on each of them. Impossible I say, only
Carver does stuff like that and then he showed me, silk screened on the
small power board "Designed By Bob Carver". "Ohhhhh", I said, it must be
one of those mag field amps.
I am probably going to have to put up some pictures of the amp and boards
for you to look at Phil because I really cannot find this triac and am
not sure where to look. This is a weird subwoofer for sure. The whole
thing is a 9" cube, has an 8" passive on one side, and an 8" driver on
the other side of the cube with double magnets that are so strong that if
you put screws in a strong plastic bag into the unit and then pull the
bag out, the screws will stay stuck on the speaker magnet and the bag
will rip. Pushing in the driver by hand is very tough, this is no "breath
easy" driver, that is for sure, this thing NEEDS tons of power to push
the driver.
The dickens you say. I attached a small piece of the Carver M-400 PSU
or you can see it he
http://www.ohmster.com/~ohmster/pict...rvermfapsu.gif
Using this diagram, you are saying to just "short the triac" with
wire, main terminal to main terminal, leave the gate alone. For sure
this would make WAY to much power and blow the thing up but you say
to bring it up slow with a variac and stay down around 50-65% of the
AC line and monitor the "rails" on the amp to see if it is stable,
not dumping DC, and does not draw excessive current? Hey that is
brilliant! Dam, I don't have a variac but could probably put my hands
on one for the testing. That probably would work too.
** Its the way I usually test all Carver " Mag Field" amps that have
had internal repairs done.
Well, finding this triac is getting to be a trying experience so far. It
would have to be a fairly good sized part, yes? At least a TO220 case or
larger. i Don't see anything like that on the power board but for an
L7812CV and an L7912CV which are just + & - 12 volt regulators and there
is a very small transformer on the power board. The house AC also goes
straight to two very large diodes (After being cleaned by a choke) and
then to the two 1,000uF 200V capacitors.
Ugh, I just broke down and called up Sunfire Tech and spoke to Shad. He
took my name and number and said that all Sunfire amps are fixed at the
factory. There are no service manuals or schematics available to anyone
in order to protect their intellectual property. This unit does not use a
triac and he had a name for it but I forget what it was. He was a decent
guy but could not release too much information about the amp. He said
there is a woman there that knows Bob Carver and she has been there for
decades and does ALL of the Sunfire amps so Shad did not know all of the
technical information about the amp in great detail. I told him about the
two main outputs blown and the two MOSFETS blown and said I did not find
anything else wrong and is it possible that this could be all that is
wrong with the amp? Again he was not sure, the woman who fixes them and
all that.
He gave me the standard "Flat rate to fix the product is $275, ship it
right off to us and we will get it done for you, etc.". I told him I went
this far and had to at least give it a try. He understood and has me
logged in case I want to send it in for repair.
So, there is no triac in this product, there is 151 VDC across each main
cap, there is 302 VDC across both main caps at the same time as measured
with a Fluke, and Sunfire will release no technical information about the
product for fear of losing "intellectual property". Ugh.
There is no regulation, so the DC rails sag badly when he amp is under
drive and load.
When all is OK - undo the link.
I do love the light bulb instead of the main fuse but that is not
going to work here at all, I am pretty sure.
** Use one if you like.
I probably will do this although I doubt it will save the amp or anything
if something is wrong. I don't think I can use a variac but will try it
anyway to see what happens.
Or just monitor the AC current draw with a 3.5 digit AC meter -
preferably true rms type.
..... Phil
Man, I was going to snap you a picture or two of the 9" cube cabinet
showing the two drivers (One passive) with my desk cam and when I got the
cube within 3 feet of the monitor, the entire monitor discolored so badly
from the super strong magnetic field of the driver magnets that I had to
take it away from the computer. Anyway, here is what I have in the way of
pictures of the boards:
http://www.ohmster.com/~ohmster/sunfire/
Anyway, this is what the product looks like:
http://www.sunfire.com/SuperJrPR.htm
I really don't know what to do about this now Phil, what would you
suggest? Check and check again for anything that is shorted or open,
visually inspect, and if all looks okay, replace the two IRF640 MOSFETS
(These are common MOSFET output devices in the Pioneer Elite receivers.)
and the two shorted output transistors, 2SA1302 & 2SC3181 and then what,
just plug it in and keep fingers crossed? Do you think it is worth trying
to use a variac or light bulb in place of the fuse?
This is a strange one, what do you think, Phil? I need your input. Thanks
buddy.
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