I repair, or at least i try to repair good quality hifi.
some time ago a TAG Mclaren DPA32R pre-amp came across which didnt turn on anymore.
i checked the voltage rails, all fine.
i checked the caps.. also all still very good.
after lots of fiddling i saw that the CPU somehow acted weird.
it had its clock signal and i saw pins switching that go to the SRAM and Flash. but nothing was happening. no data to the display or other chips.
after changing the SRAM and CPU for some new old stock ones, it still didnt work either.
i suspected a corrupt flash and went on, its nothing i can fix without a dump of a working one.
today, another Mclaren, this time a AV32R SL came to me, same cpu, same sram, same flash. same symptoms
nothing works.
i tried for hours now to find the issue.
the SRAM doesnt even get a Chip enable signal
just the Flash, it gets a address and spits out data. but i suspect this data to be corrupt aswell.
maybe the device turned off while writing to it?
i noticed when poking a finger near the address lines sometimes leds turn on and relays click. but it seems random.
now i checked ebay for defective / sold Mclaren, there were quite a few the last months. its very unusual that they all fail now.
they are so rare and unknown, that no one ever made a dump of the flash chip which is unfortunate..
also there seem to be no schematics available anywhere....
did anyone ever worked on these before?
maybe im overlooking something.
i was so close just slapping another microcontroller in there (in the DPA ) as its just shift registers to control everything.
no easy task without a working unit to see how it works.
shame that they now all go to waste, there were built properly. they were top quality back then. well ... except the flash chip it seems
long time ago i worked on a AV32R DP which only needed new caps as it displayed "initializing..." on the display. i was hoping for a similiar issue on those...
some time ago a TAG Mclaren DPA32R pre-amp came across which didnt turn on anymore.
i checked the voltage rails, all fine.
i checked the caps.. also all still very good.
after lots of fiddling i saw that the CPU somehow acted weird.
it had its clock signal and i saw pins switching that go to the SRAM and Flash. but nothing was happening. no data to the display or other chips.
after changing the SRAM and CPU for some new old stock ones, it still didnt work either.
i suspected a corrupt flash and went on, its nothing i can fix without a dump of a working one.
today, another Mclaren, this time a AV32R SL came to me, same cpu, same sram, same flash. same symptoms
nothing works.
i tried for hours now to find the issue.
the SRAM doesnt even get a Chip enable signal
just the Flash, it gets a address and spits out data. but i suspect this data to be corrupt aswell.
maybe the device turned off while writing to it?
i noticed when poking a finger near the address lines sometimes leds turn on and relays click. but it seems random.
now i checked ebay for defective / sold Mclaren, there were quite a few the last months. its very unusual that they all fail now.
they are so rare and unknown, that no one ever made a dump of the flash chip which is unfortunate..
also there seem to be no schematics available anywhere....
did anyone ever worked on these before?
maybe im overlooking something.
i was so close just slapping another microcontroller in there (in the DPA ) as its just shift registers to control everything.
no easy task without a working unit to see how it works.
shame that they now all go to waste, there were built properly. they were top quality back then. well ... except the flash chip it seems
long time ago i worked on a AV32R DP which only needed new caps as it displayed "initializing..." on the display. i was hoping for a similiar issue on those...
solder quality is good unlike 80..90s japan hifi which breaks like a bag of old cookies.
but for good measure i resoldered the sram and checked each data line. all fine
i think pressing on those pins injects inteference which the mcu might interpret as data or something.
i also dont know how this thing talks to all the chips. its doing a lot using two SRAM chips and octal buffers..
The adress and data lines are shared across the MCU, the SRAM, Flash and the second SRAM near the DSP.
Its really the matter of finding a working one and dumping the flash contents.
but i dont have the experience and hardware for these kinds of chips.
every chip on this board can still be bought somewhere so it should be fully repairable.
but for good measure i resoldered the sram and checked each data line. all fine
i think pressing on those pins injects inteference which the mcu might interpret as data or something.
i also dont know how this thing talks to all the chips. its doing a lot using two SRAM chips and octal buffers..
The adress and data lines are shared across the MCU, the SRAM, Flash and the second SRAM near the DSP.
Its really the matter of finding a working one and dumping the flash contents.
but i dont have the experience and hardware for these kinds of chips.
every chip on this board can still be bought somewhere so it should be fully repairable.
Attachments
Can you check for the Diode on the front panel PCB called D4? there are several post on the internet with people saying it blew on them.
also both of my units had a blown diode.
not sure what diode that is, its at the center tap of the VFD Heater transformer output. some say BAS16, i read K5 which might be 5.6V zener..
i tried several, normal, zener with different voltages. nothing
but it might be related to the main failure!
just a guess.. maybe the VFD is the cause for all issues. something like heater wire snapping or something that causes the 45V to go somewhere it shouldnt like the main i/o bus which is shared across flash, two ram, cpu and a buffer...
also shorting the transformer over Ground trough D4 which made it blow up.