Fixing a Yamaha M-65 For A Friend
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blhagstrom
Mad Scientist, fixer.
Frickin remarked transistor. Bastards...Suppose to be a JFET.
bmanone
Active Member
I bought some 2SK389s from this guy (JohanB) at DIY audio in Febuary this year: http://www.diyaudio.com/forums/swap-meet/143997-fs-toshiba-2sk389-gr-2sa1349-gr-2sc3381-gr-31.html
When I get home tonight, I'll check them with my transistor checker to make sure they're FETs. I'll let you know.
When I get home tonight, I'll check them with my transistor checker to make sure they're FETs. I'll let you know.
blhagstrom
Mad Scientist, fixer.
I have some coming from China (EBay). If they are fake, Ill out the seller and report to EBay. (Lot of sellers on EBay in China, gonna take a while to shoot each one).
I also have some coming from an on shore company. I'll let you know if they are legit.
We need a sticky with places that supply good parts.
BDent, Mouser, Digikey are known trusty. Probably MCM (but I haven't used them yet for these sorts of parts). Does PartsExpress handle components?
I also have some coming from an on shore company. I'll let you know if they are legit.
We need a sticky with places that supply good parts.
BDent, Mouser, Digikey are known trusty. Probably MCM (but I haven't used them yet for these sorts of parts). Does PartsExpress handle components?
clinic-audio
all on YAMAHA untill 1990
Hum , not really good ....
Try to contact this US company , they do manufacture perfect sub for 2SK389
Here is the link
www.linearsystems.com/
component is LSK389
Or this UK company :
www.micross.com
Try to contact this US company , they do manufacture perfect sub for 2SK389
Here is the link
www.linearsystems.com/
component is LSK389
Or this UK company :
www.micross.com
bmanone
Active Member
I checked the 2SK389s I received from the Johan (above link) with my transistor tester, they check out as JFETs with I=.37mA@Vg=0.27v and I=.36mA@Vg=0.27v. I think they are good ones. I believe Johan is a honest legitimate seller. :thmbsp:
blhagstrom
Mad Scientist, fixer.
Hum , not really good ....
Try to contact this US company , they do manufacture perfect sub for 2SK389
Here is the link
www.linearsystems.com/
component is LSK389
Or this UK company :
www.micross.com
I sent a request for samples of LSK389 but its a TO-71 package. Hey, if it works....
Do they require a min. order? Have any idea how many samples ?
blhagstrom
Mad Scientist, fixer.
Just a fill in the blank online request.
Up to 5 samples.
Up to 5 samples.
blhagstrom
Mad Scientist, fixer.
I received the order from UTSOURCE today.
They are FAKE.
http://www.utsource.net/
I received a used one from Avionic. While waiting I installed the new driver from BDent and mounted the large caps.
Its now stuck in protection. The burned channel shows no bias.
:gigglemad:
They are FAKE.
http://www.utsource.net/
I received a used one from Avionic. While waiting I installed the new driver from BDent and mounted the large caps.
Its now stuck in protection. The burned channel shows no bias.
:gigglemad:
blhagstrom
Mad Scientist, fixer.
There is something very whacked in this amp.
I got a real 2SK389 and now it's acting shorted.
I backed the bias down and it comes up on dim bulb but I'm finding burned resisters and blown small transisters. I already checked all those so it's new damage.
R142 wants to burn up now. R123 was burning up and that led to finding new burned transistors.
I found a burned resister on the input back board. (R271 or R272, looks like just an RC filter on the input line. How does that get toasted unless the pre-amp was involved in a burn down?)
The input lines have non-matching resistance that throw the lead resister value off in circuit. (R101/R102).
The curve tracer is showing odd differences in the middle of the amp on a couple transisters but all the components around that are OK. (TR114 and TR124)
I'm wondering if there is a side to side balance issue.
I don't recognize any voltage divider networks between the amp sides.
Tough to follow all the power supply lines on the skat.
I've pulled and tested all the transistors on the "good" side. Gone through all the resistors (again) checked all the diodes (again), checked the traces for solder bridges (again).
????
I got a real 2SK389 and now it's acting shorted.
I backed the bias down and it comes up on dim bulb but I'm finding burned resisters and blown small transisters. I already checked all those so it's new damage.
R142 wants to burn up now. R123 was burning up and that led to finding new burned transistors.
I found a burned resister on the input back board. (R271 or R272, looks like just an RC filter on the input line. How does that get toasted unless the pre-amp was involved in a burn down?)
The input lines have non-matching resistance that throw the lead resister value off in circuit. (R101/R102).
The curve tracer is showing odd differences in the middle of the amp on a couple transisters but all the components around that are OK. (TR114 and TR124)
I'm wondering if there is a side to side balance issue.
I don't recognize any voltage divider networks between the amp sides.
Tough to follow all the power supply lines on the skat.
I've pulled and tested all the transistors on the "good" side. Gone through all the resistors (again) checked all the diodes (again), checked the traces for solder bridges (again).
????
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blhagstrom
Mad Scientist, fixer.
A shot of the bottom, not sure if this is any use.
I have the burned area scraped out enough to where I doubt its causing any issues.
I DID FINALLY find the short that has been driving me in circles and tearing up parts.
:gigglemad:
Old part (left) versus new part (right) that was installed incorrectly!
I slipped a mica under that transistor. I'm not 100% sure that will do it.
SO, now the good channel seems to be OK (the short was messing with the front power supply caps).
The bad channel will not bias. I can get 2-3mv on it and then it collapses.
I've been through all the parts (again) with a meter, a component tester, a curve tracer. Transistors, Resistors, Diodes all good. I have vetted the replacement transistors used as far as what was used. Verified for solder bridges. I had to fix the traces in a couple spots. I don't see any places where a broken trace may hide....but they hide.
I've been down this dead end on an M-80. Never solved that one.
I suppose a voltage tracing/chasing is next, or ???
I have the burned area scraped out enough to where I doubt its causing any issues.
I DID FINALLY find the short that has been driving me in circles and tearing up parts.
:gigglemad:
Old part (left) versus new part (right) that was installed incorrectly!
I slipped a mica under that transistor. I'm not 100% sure that will do it.
SO, now the good channel seems to be OK (the short was messing with the front power supply caps).
The bad channel will not bias. I can get 2-3mv on it and then it collapses.
I've been through all the parts (again) with a meter, a component tester, a curve tracer. Transistors, Resistors, Diodes all good. I have vetted the replacement transistors used as far as what was used. Verified for solder bridges. I had to fix the traces in a couple spots. I don't see any places where a broken trace may hide....but they hide.
I've been down this dead end on an M-80. Never solved that one.
I suppose a voltage tracing/chasing is next, or ???
blhagstrom
Mad Scientist, fixer.
I have this thing all fixed (for a while now) and now I need acetate to contact me.
I sent message but no response.
I sent message but no response.
I have a question about M65. Which transistors were installed from factory in M65: Toshiba or Sanken? In my M65 are installed transistors from Sanken (as I remember A1106 etc...). Were transistors changed in my Yamaha M65 or not? I will try to take some pictures late. Thanks.
I took some photo:
I took some photo:
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