Technics SA-C07 display issue

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skippy1969

skippy1969

Boomus Fidelis
A looooong time ago I asked Stereo2go member "Prime" if he knew what might be wrong with the florecent display on my Technics SA-C07 as it doesn't work.
He told me that he had the same issue and fixed one that he had owned. :w00t:
The problem is a diode in the power supply was open. ;-)
I finally took mine apart today and found the diode,but I don't know it's value so I can get a new one. :huh: :huh: :huh: :huh:
Anyone have any ideas? As I can't get ahold of Prime anymore. :-/
Any help will be greatly appreciated. :-D
Thanks!

Prime's picture.
1z2g00l.jpg


My actual unit's diode.
IMG_0001-1.jpg

another view.
IMG_0002-1.jpg
 
Superduper

Superduper

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All diodes look just like that. Some have markings on them. I don't see any markings on yours. It does look just like a rectifier diode.

As long as it's not a zener diode, what you use probably isn't critical as long as it's rated for sufficient voltage and current rating.

How do you know it's bad. Before making that presumption, you should test that component to ensure that it is indeed open. Same symptoms don't always translate to same cause.
 
skippy1969

skippy1969

Boomus Fidelis
Superduper said:
All diodes look just like that. Some have markings on them. I don't see any markings on yours. It does look just like a rectifier diode.

As long as it's not a zener diode, what you use probably isn't critical as long as it's rated for sufficient voltage and current rating.

How do you know it's bad. Before making that presumption, you should test that component to ensure that it is indeed open. Same symptoms don't always translate to same cause.
Click to expand...

Thanks Norm.
I am just assuming it is bad as that is what Prime told me.
He is a "technical guy" like yourself so I trust what he says.
How would I go about checking the diode?
Thanks!
 
Superduper

Superduper

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Use a DMM and use the diode check function. You should get a much higher reading in one direction than the other.

An old analog ohmeter without a diode check function can be used but keep in mind that the voltage generated by the meter during the test must be higher than the turn on voltage of the diode or it will show open.

In other words, a diode normally passes current in one direction but blocks it in the opposite direction. However, it only passes current when voltage exceeds the devices turn-on voltage which is probably .7 volts. If your ohmmeter only generates .4 volts during the test, the diode would test like it's bad when it fact, it never turned on.
 
baddboybill

baddboybill

Boomus Fidelis
skippy1969 said:
baddboybill said:
Good luck getting it going Scott :thumbsup: :thumbsup:
Click to expand...
Thanks Bill.....
You'll have to check this badass unit out sometime,it is so friggin loud it's almost unbeliveable.... :dunce: :rock:
Click to expand...
Absolutely love Technics, had 3 home component systems already. Would love to have a 3 pc unit :thumbsup: :cool:
 
skippy1969

skippy1969

Boomus Fidelis
Superduper said:
Use a DMM and use the diode check function. You should get a much higher reading in one direction than the other.

An old analog ohmeter without a diode check function can be used but keep in mind that the voltage generated by the meter during the test must be higher than the turn on voltage of the diode or it will show open.

In other words, a diode normally passes current in one direction but blocks it in the opposite direction. However, it only passes current when voltage exceeds the devices turn-on voltage which is probably .7 volts. If your ohmmeter only generates .4 volts during the test, the diode would test like it's bad when it fact, it never turned on.
Click to expand...

i checked the diode today Norm .
I set the DMM to diode check function and the diode checked the same voltage 1.496v in both directions. I checked it several times.
Would this indicate a "open diode" since I don't see a voltage change one way and not the other?
Also,don't the lines on the diode give a value like a resistor?
Most of the diodes in this unit have different line spacings than this one.
Thanks!
 
monchito

monchito

Boomus Fidelis
skippy once u check u should not get a reading on one side voltage only flows in one direction on a diode ,,sometimes i will unsolder one leg from the board just to make sure i get a good reading if there is reading on both sides then its open :-)
 
skippy1969

skippy1969

Boomus Fidelis
monchito said:
skippy once u check u should not get a reading on one side voltage only flows in one direction on a diode ,,sometimes i will unsolder one leg from the board just to make sure i get a good reading if there is reading on both sides then its open :-)
Click to expand...

Ok Ramon,I just unsolded the diode completly from the board and checked it.
It must be open then as it had the same voltage reading both directions.
Now I just need to know the value,right?
 
Superduper

Superduper

Moderator
Staff member
It's not open. If it was open, you wouldn't get a reading.

Try reading it in the ohm scale instead of diode and see what it says (try all the scales).

The band you see identifies which side is the cathode, as opposed to the anode since unlike resistors, diodes aren't polarized per se, but they are not reversible. Diodes don't really have value like resistors do. I would say the value is probably not critical unless it is a zener diode in which case, then it absolutely is. Zener diodes are used in voltage regulator applications. If there was a value indicated, it would be in text or number markings rather than bands.

I have this service manual (see http://www.Analogalley.com) but it's one of those manuals that are still awaiting transport to me so I can't look it up for you.

If you like, I can send you a generic diode for you to check/see.
 
skippy1969

skippy1969

Boomus Fidelis
Superduper said:
It's not open. If it was open, you wouldn't get a reading.

Try reading it in the ohm scale instead of diode and see what it says (try all the scales).

The band you see identifies which side is the cathode, as opposed to the anode since unlike resistors, diodes aren't polarized per se, but they are not reversible. Diodes don't really have value like resistors do. I would say the value is probably not critical unless it is a zener diode in which case, then it absolutely is. Zener diodes are used in voltage regulator applications. If there was a value indicated, it would be in text or number markings rather than bands.

I have this service manual (see http://www.Analogalley.com) but it's one of those manuals that are still awaiting transport to me so I can't look it up for you.

If you like, I can send you a generic diode for you to check/see.
Click to expand...

I checked it with the Ohms scale and checked all ranges and I get no reading no matter if I switch the leads around on either side of the diode. :huh: :huh:
The meter display digits just flashes as if there was nothing attached to the leads...... :hmmm: :huh:
 
Superduper

Superduper

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That's right Ramon. Most have the zener specific diode marking but I've seen some mark a zener just like a generic so I never take anything for granted. In any event, I'm 90+% sure that's just a rectifier diode since most zener diodes are glass encased or have markings other than just a band.
 
monchito

monchito

Boomus Fidelis
Superduper said:
That's right Ramon. Most have the zener specific diode marking but I've seen some mark a zener just like a generic so I never take anything for granted. In any event, I'm 90+% sure that's just a rectifier diode since most zener diodes are glass encased or have markings other than just a band.
Click to expand...
:agree: :agree: :agree: :agree: :agree:
 
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