Hi guys!
I'm currently repairing a Yamaha M-80 that I would like to restore completely and yes I know that when things go bad with this amp there's a lot of victims, but I took a risk and bought one
So the seller said that it powers up, but the protection light stays on. I didn't even power it up after I took a peek inside:
pic 1
pic 2
pic 3
It looks like the right channel is badly messed up by that glue.
So I started taking things apart and making list of components possibly in need of replacements (with the help of schematic of course). I measured power transistors with DMM's diode function and it seems that one power transistor (2SA1169 on main board) is fried (forward voltage only 0.069 V) and one smaller transistor on heatsink (2SC3298A on upper right board) is fried. All transistors on left heatsink seem to be fine.
pic of the heatsinks
The two slim boards look good. The main board looks like this:
overview of main board
So eventually I worked out what components should be replaced and here I have marked all the components I think should be replaced with red:
components to be replaced
I thought that it's better to replace the parts on both channels just to be sure and many of the parts I marked as "to be replaced" look okay, I just think that it couldn't hurt replacing some additional ones. Do you think this is okay or have I missed some components that might be (or usually are) damaged also? How easily do the Mica or Polypropylene Film caps get damaged, is replacing of those just waste of time?
I have some questions about replacement/substitution parts:
Is it okay to replace just the one 2SA1169 and one 2SC3298A from the heatsinks or do I have to replace their complementary pairs also (2SC2773 and 2SA1306A)? I think I need to get the 2SA1169 from ebay to get a genuine Sanken one?
Substitutions for the transistors seem to be hard to find, does anyone have idea of substitutions for 2SC3298A on the heatsink (and 2SA1306A if they need to be changed in pairs) and 2SC3416 - 2SA1352 pairs found on main board?
And can the diodes and zeners be replaced with any part with same properties like:
1S1555 diode => 1N4148 ?
MTZ7.5B zener => any 7.5 V 0.5 W zener ?
HZ16-3L zener => any 16 V 0.4 W zener ?
I hope someone wiser than me can help me a bit so I get this wonderful amp repaired I'll be posting pics and stuff as the project goes on.
I'm currently repairing a Yamaha M-80 that I would like to restore completely and yes I know that when things go bad with this amp there's a lot of victims, but I took a risk and bought one
So the seller said that it powers up, but the protection light stays on. I didn't even power it up after I took a peek inside:
pic 1
pic 2
pic 3
It looks like the right channel is badly messed up by that glue.
So I started taking things apart and making list of components possibly in need of replacements (with the help of schematic of course). I measured power transistors with DMM's diode function and it seems that one power transistor (2SA1169 on main board) is fried (forward voltage only 0.069 V) and one smaller transistor on heatsink (2SC3298A on upper right board) is fried. All transistors on left heatsink seem to be fine.
pic of the heatsinks
The two slim boards look good. The main board looks like this:
overview of main board
So eventually I worked out what components should be replaced and here I have marked all the components I think should be replaced with red:
components to be replaced
I thought that it's better to replace the parts on both channels just to be sure and many of the parts I marked as "to be replaced" look okay, I just think that it couldn't hurt replacing some additional ones. Do you think this is okay or have I missed some components that might be (or usually are) damaged also? How easily do the Mica or Polypropylene Film caps get damaged, is replacing of those just waste of time?
I have some questions about replacement/substitution parts:
Is it okay to replace just the one 2SA1169 and one 2SC3298A from the heatsinks or do I have to replace their complementary pairs also (2SC2773 and 2SA1306A)? I think I need to get the 2SA1169 from ebay to get a genuine Sanken one?
Substitutions for the transistors seem to be hard to find, does anyone have idea of substitutions for 2SC3298A on the heatsink (and 2SA1306A if they need to be changed in pairs) and 2SC3416 - 2SA1352 pairs found on main board?
And can the diodes and zeners be replaced with any part with same properties like:
1S1555 diode => 1N4148 ?
MTZ7.5B zener => any 7.5 V 0.5 W zener ?
HZ16-3L zener => any 16 V 0.4 W zener ?
I hope someone wiser than me can help me a bit so I get this wonderful amp repaired I'll be posting pics and stuff as the project goes on.
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