Help on Studer A820

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Hello, I'm trying to repair my studer a820 1/2" machine. It keeps
popping a fuse on the cap/aux section ( or should I say the light
doesn't light up on that section of the indicator lights after popping
the fuse) Then of course the lcd screen reads "err: Power Supply"
Any suggestions? I'm out in the sticks, and I really don't want to have
to box this guy up and mail him 1/2 way across the country for repair.
I'd like to do as much leg work as I can and then maybe mail in
whatever circuit board I need to.
I have tried pulling all the cards and powering up, but I still pop
a fuse, so I'm guessing it's not a problem on one of the cards.
Please help
Aaron Householter
studio1117
 
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std1117@swbell.net wrote:
> Hello, I'm trying to repair my studer a820 1/2" machine. It keeps
> popping a fuse on the cap/aux section ( or should I say the light
> doesn't light up on that section of the indicator lights after
popping
> the fuse) Then of course the lcd screen reads "err: Power Supply"
> Any suggestions? I'm out in the sticks, and I really don't want to
have
> to box this guy up and mail him 1/2 way across the country for
repair.
> I'd like to do as much leg work as I can and then maybe mail in
> whatever circuit board I need to.
> I have tried pulling all the cards and powering up, but I still pop
> a fuse, so I'm guessing it's not a problem on one of the cards.
> Please help
> Aaron Householter
> studio1117


Did you try metering the output of the power supply? it's usually a
good place to start.

Do you have the service manual.
 
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Yeah, all the test points show proper voltage, but the cap/aux one
shows -10v or something like that. I don't have a scheme or a manual
unfortunately(although I'm looking.) I don't see a voltage listed on
the board where the test points are. i'm not even sure which board
houses the power supply stuff. I'm just trying to get a start on this
before my tech comes around. actually if anyone could tell me what that
voltage is suppose to be at the cap/aux test point and where the power
supply board is located that would help tons.
Thanks
aaron Householter
studio1117
 
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In article <1103965017.260844.56770@f14g2000cwb.googlegroups.com>,
<std1117@swbell.net> wrote:
>Hello, I'm trying to repair my studer a820 1/2" machine. It keeps
>popping a fuse on the cap/aux section ( or should I say the light
>doesn't light up on that section of the indicator lights after popping
>the fuse) Then of course the lcd screen reads "err: Power Supply"
>Any suggestions? I'm out in the sticks, and I really don't want to have
>to box this guy up and mail him 1/2 way across the country for repair.
>I'd like to do as much leg work as I can and then maybe mail in
>whatever circuit board I need to.
>I have tried pulling all the cards and powering up, but I still pop
>a fuse, so I'm guessing it's not a problem on one of the cards.

No, it's a power supply problem. Pull the supply module out and ship it
off for repair. It's actually not THAT hard to work on the things, and
if it's popping fuses the chances of it being a shorted cap are pretty good.
But if you aren't used to working on supplies, send it off.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."
 
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std1117@swbell.net wrote:
> Yeah, all the test points show proper voltage, but the cap/aux one
> shows -10v or something like that. I don't have a scheme or a manual
> unfortunately(although I'm looking.) I don't see a voltage listed on
> the board where the test points are. i'm not even sure which board
> houses the power supply stuff. I'm just trying to get a start on this
> before my tech comes around. actually if anyone could tell me what
that
> voltage is suppose to be at the cap/aux test point and where the
power
> supply board is located that would help tons.
> Thanks
> aaron Householter
> studio1117


Go to the power supply transformer, before the rectifiers and
smoothing caps. Studer might have used a Transformer manufactured by
someone else. One side will be the 110V Ac taps, the other side will be
the stepped down taps that go to the rectifier, voltage regulators and
smoothing caps.

You might be able to find the specs on that transformer from it's
manufacturer - If you can read the part numbers stamped on the side.
That should tell you what the output windings should read.

If that's putting out the right power move on to the Diode Bridge
rectifier, and then to Voltage regulators, and then caps.

When testing power supplies you should have a ":dummy load" accross
the outputs. The Voltage regulators need some resistance to work
right... ie: you won't get a useful reading from them with no load
attached.
 
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In article <1103965017.260844.56770@f14g2000cwb.googlegroups.com> std1117@swbell.net writes:

> I have tried pulling all the cards and powering up, but I still pop
> a fuse, so I'm guessing it's not a problem on one of the cards.

Sounds like a power supply problem. Power supplies are about the
easiest thing to troubleshoot, but you have to get into it yourself.
Anybody who tells you "replace C14" is just taking a stab in the dark.
Start disconnecting things, starting with the output of the power
supply and working back to the transformer until you find out what
doesn't make the fuse blow.

There are better ways of telling that it's not working than letting
the fuse blow, but then I'd have to tell you what voltage to measure
at what point, and I don't know that, nor is likely anyone else to
know.

--
I'm really Mike Rivers (mrivers@d-and-d.com)
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me here: double-m-eleven-double-zero at yahoo
 
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In article <1104000686.223400.95510@f14g2000cwb.googlegroups.com> std1117@swbell.net writes:

> I don't see a voltage listed on
> the board where the test points are. i'm not even sure which board
> houses the power supply stuff.

Not meaning to belittle you, but if you don't have enough
troubleshooting experience to recognize a power supply, there really
isn't much you're going to be able to do. A schematic will be helpful
to a real tech though, so keep looking.

--
I'm really Mike Rivers (mrivers@d-and-d.com)
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me here: double-m-eleven-double-zero at yahoo
 

Tradcomm

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Jan 16, 2010
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Hello Mike;

Have been following your postings with interest. I am a teckie on the East Coast of Canada. I also have an 820 with many problems, most of which have been resolved. One was in the power supply section as well as the voltage supplies to the motors. Found several power transistors and coils bad. Once replaced recalibration of voltages is crucial. Look under the front of your unit for a row of LED's. See if one or a number light. If not that's only a clue as to where your problem may be.

I do also have a manual, which in your case, I would think would be crucial. As a previous responder stated, you would have to know where various sections and circuits are in order to be able to trace down your problem. That's where you would have to start. I can honestly say that with the sophistication of this model, you would be strongly advised to seek experience from someone who is familiar with reel-to-reels or, specifically, Studers. I have been trying to track down the cause for a tacho sensor error for about a year - with limited success, I might ad. So good luck with this..

Now if you want to be rid of your machine - let us know and what a price might be and we may be able to use it for parts...

tradcomm@xcountry.tv


Archived from groups: rec.audio.pro (More info?)

In article <1104000686.223400.95510@f14g2000cwb.googlegroups.com> std1117@swbell.net writes:

> I don't see a voltage listed on
> the board where the test points are. i'm not even sure which board
> houses the power supply stuff.

Not meaning to belittle you, but if you don't have enough
troubleshooting experience to recognize a power supply, there really
isn't much you're going to be able to do. A schematic will be helpful
to a real tech though, so keep looking.

--
I'm really Mike Rivers (mrivers@d-and-d.com)
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me here: double-m-eleven-double-zero at yahoo
 

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