Dear brothers and sisters, still struggling with unit failure to come out protection mode. Any Nakamichi experts out there that can help me out. My previous post gives some specifics, let me know what data I can provide so you can help me. Many thanks for any help offered to me.
did i bounced in any of your threads ? don't really remember ...
any way
trouble shooting a NAK like that should be a walk in the park ... nothing more classic than that
At first you need to isolate he problem
it may as well be a protection problem ( not especially amplifier problem )
you need to go just before the relay and see if there is excessive voltage ( anything above 100mv with reference to ground ) will obviously trigger the protection
if voltage there is low as 100mv then the fault lays on the protection circuit
Protection circuit can be triggered by DC voltage present on the output of the amplifier or a faulty temperature detection circuit .
if excessive voltage exists in the output of any of the two amplifiers (that can be measured at the common node of resistors R 321R 322R for B ch and to R321L 322L for ch A always in reference to ground )protection will trigger
if excessive voltage exists in the output of any of the tow amplifiers trace down if his is plus or minus offset in reference to ground...If plus you need to check all plus rail transistors and the opposite if minus
Obviously before any other motion the first will be to verify all voltage according to the schematic one fuse blown or a loose cable is enough to cause that ( sometimes )
if you don't have a schematic please email me
Troubleshooting is about being methodical ,take always one step at a time , take notes for reference and never swap parts especially if not original ....
let us know
any way
trouble shooting a NAK like that should be a walk in the park ... nothing more classic than that
At first you need to isolate he problem
it may as well be a protection problem ( not especially amplifier problem )
you need to go just before the relay and see if there is excessive voltage ( anything above 100mv with reference to ground ) will obviously trigger the protection
if voltage there is low as 100mv then the fault lays on the protection circuit
Protection circuit can be triggered by DC voltage present on the output of the amplifier or a faulty temperature detection circuit .
if excessive voltage exists in the output of any of the two amplifiers (that can be measured at the common node of resistors R 321R 322R for B ch and to R321L 322L for ch A always in reference to ground )protection will trigger
if excessive voltage exists in the output of any of the tow amplifiers trace down if his is plus or minus offset in reference to ground...If plus you need to check all plus rail transistors and the opposite if minus
Obviously before any other motion the first will be to verify all voltage according to the schematic one fuse blown or a loose cable is enough to cause that ( sometimes )
if you don't have a schematic please email me
Troubleshooting is about being methodical ,take always one step at a time , take notes for reference and never swap parts especially if not original ....
let us know
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TA-3A
Dear Sakis, I will get started immidiately based on yuor advice. Have already replaced resistors R309L & R309r, worked for a short time. I think that the issue is in the protection circuit, just looking for clues. Always prefer to take advice for similiar issues, you can a lot of time glean great information from people that have been down that road. Thanks for ref material offer, i have the service manual. I'll let you know what i find, plus post it for future reference to other members.
Dear Sakis, I will get started immidiately based on yuor advice. Have already replaced resistors R309L & R309r, worked for a short time. I think that the issue is in the protection circuit, just looking for clues. Always prefer to take advice for similiar issues, you can a lot of time glean great information from people that have been down that road. Thanks for ref material offer, i have the service manual. I'll let you know what i find, plus post it for future reference to other members.
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