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Diode symbols on Yamaha PCB

F

FootFungus

Super Member
I have a Yamaha C-70 preamp which was given to me by a friend on Sat as a gift. There is a large spot that looks like electrolyte was discharged, or glue was charred black. Regardless, the gunk corroded leads on a transistor and two diodes. The diodes both lost a lead completely. Looking at the pcb symbols, the diodes all are oval-ish white outlines like a chalk outline of a diode (which in is in this case fitting). Some are empty with a solid outline. A few are outlined in dashes. There is the Zener symbol on some, with others having a straight line through them offset slightly from the center. My destroyed ones have no line, they are just a solid outline.

Can anyone tell me what Yamaha is implying with this symbol? Signaling diode?

- Jon
 
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Hi FootFungus,

Pure guess here - maybe the different symbols are implying something about their function :scratch2:

Solid Outline = rectifier diode
Straight Line = signal diode
Dashed Outline = only fitted to some models

and so on .... I am sure someone who has a C-70 or who is familiar with Yamaha PCB symbols will be along shortly...

What you really need is a schematic - this should reveal all.

John
 
Don't mean to be a wise guy but are you sure the one's that are outlined and blank are not resistors?
One's I'm familiar with on Yamaha are like the white you describe.
 
Hey Detailman, I hope you aren't being a wise guy - 'cos I had the same thought too :D - a rectangular box with a line through it certainly sounds like a resistor to me - but hey, who am I to argue - he can see the PCB's and he said they are diodes - which is fair enough.

John
 
The resistors are similar, although they tend to be filled in and they are rectangles. The diodes have rounded corners.
 
Have you checked the database for Yamaha manuals?

I noticed on some Yammies that the component layout page in the SM will differentiate on types of diodes.
Think the guess that it's a signal diode that you and Hyperion made is probably the right one.

You may find the SM in the database.
Search the vintage forum.
 
When you say "database" are you referring to the vBulletin database?

I looked for similar markings on the PCB, and all have the line, or the Zener squiggle. So these are a little odd. They are near the Phono MM section. I like how Yamaha would silkscreen the functional area on the PCB in their older gear. I've seen it in a K-2000 tape deck and Yamaha C-4.

I did manage to get a readout of 1.2 (ok 1.17) on the MM diode test so at least I know a value for replacement considerations.
 
As far as the database goes for yamaha it is a new creation by one of the members.
Njord I believe.
Do a search in the vintage forum for database or Yamaha and you'll come across a post with lots of pages. The OP is something like Database for Yamaha components. You may have to do a little digging but there may be the SM you need for the pre.
I don't have the link handy or I would post it for you.

As yet there is no seperate forum for Yamaha.
 
I found the reference. I appreciate the tip. There was a C-80 in there, plus one for a C-4 that I have. I'll have to see if I can locate the same circuit in one of them.
 
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