Hi,
i have a B225 that I ( try to ) repair for a friend, when I play a piano CD it only sings like a bird "tschilp" and also there is 50Hz hum.
The 50 Hz hum looks like a bad supply voltage, supply voltages seem to be ok, +/- 12 V for analog, for the TDA1540 -5V , +4V ( taken via R lytic-C from 5V line ) and -13V ( is that enough ??? )
Havent looke with a scope though.
Already changed all SAA ICs without succsess, the RAM I don't have.
Any hint where to search ?
While we are at it, I have another bird here, my Analyzer.
On power up there is no problem, then after a few minutes it goes partly off with a "tschirp" ( I think it comes from the switching PSU ), no screen and no LEDs on plug in.
One minute later it goes on again, the processor of the plug in needs a restart of the whole machine.
And then it usually works forever.
When it is warm in the room, there isn't any problem at all, but when it is cold, it is getting more serious, fails after minutes again and again.
Looks like it fails at a specific temperature which is very ugly...
i have a B225 that I ( try to ) repair for a friend, when I play a piano CD it only sings like a bird "tschilp" and also there is 50Hz hum.
The 50 Hz hum looks like a bad supply voltage, supply voltages seem to be ok, +/- 12 V for analog, for the TDA1540 -5V , +4V ( taken via R lytic-C from 5V line ) and -13V ( is that enough ??? )
Havent looke with a scope though.
Already changed all SAA ICs without succsess, the RAM I don't have.
Any hint where to search ?
While we are at it, I have another bird here, my Analyzer.
On power up there is no problem, then after a few minutes it goes partly off with a "tschirp" ( I think it comes from the switching PSU ), no screen and no LEDs on plug in.
One minute later it goes on again, the processor of the plug in needs a restart of the whole machine.
And then it usually works forever.
When it is warm in the room, there isn't any problem at all, but when it is cold, it is getting more serious, fails after minutes again and again.
Looks like it fails at a specific temperature which is very ugly...
Bernhard said:50 Hz hum.
Try replacing the 100µF cap on the 33V rail in the PSU.
/Hugo
Bernhard said:and -13V ( is that enough ??? )
No , it must be -18 volts... inspect the electrolytic caps in this voltage rail...
Re: Re: defective Revox B225 sings like a bird
Ah..., also the TDA data sheet says min -16,5V and max -18V,
but hey, it's aRevox
Tube_Dude said:
No , it must be -18 volts... inspect the electrolytic caps in this voltage rail...
Ah..., also the TDA data sheet says min -16,5V and max -18V,
but hey, it's aRevox
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