I am currently fixing my buddy's receiver.
It was totally dead with absolutely no functionality. The fuses were all good on the main primaries, standby secondary & the main PCB board fuses on the power supply rails for the power amp section.
So I troubleshot and have fixed the standby transformer which pins were separated from the PCB solder terminals.
So now I got the following limited functionality:
1) Relay on Standby board functions correctly
2) Correct voltages as required (+5V; -30V etc.) to front control board
3) Remote control will initate Standby as well as getting out of Standby
4) On-board standby pushbutton will function as normal
5) Remote control will initiate Speaker A & B or off as initiated
6) On-board pushbutton speaker select will function as normal
7) LED indicators for Speakers & Standby function correctly
8) Background LED Control display shows very faint "orange background only"
So what doesn't work:
1) Nothing else functions as per on-board pushbuttons/controls or by remote
2) No actual displayed alpha numerical characters
So any help would be appreciated.
Thanks,
It was totally dead with absolutely no functionality. The fuses were all good on the main primaries, standby secondary & the main PCB board fuses on the power supply rails for the power amp section.
So I troubleshot and have fixed the standby transformer which pins were separated from the PCB solder terminals.
So now I got the following limited functionality:
1) Relay on Standby board functions correctly
2) Correct voltages as required (+5V; -30V etc.) to front control board
3) Remote control will initate Standby as well as getting out of Standby
4) On-board standby pushbutton will function as normal
5) Remote control will initiate Speaker A & B or off as initiated
6) On-board pushbutton speaker select will function as normal
7) LED indicators for Speakers & Standby function correctly
8) Background LED Control display shows very faint "orange background only"
So what doesn't work:
1) Nothing else functions as per on-board pushbuttons/controls or by remote
2) No actual displayed alpha numerical characters
So any help would be appreciated.
Thanks,
Last edited:
More Measurements Performed
Yes I just double-checked the +/-15VDC and while I was at it I confirmed the +/-55V to the Power Amp Board as well.
I am thinking maybe the Main Controller Chip on the front Board which controls the LED Display as well as the controls everythingh else is at fault?
Let me know what you think?
Yes I just double-checked the +/-15VDC and while I was at it I confirmed the +/-55V to the Power Amp Board as well.
I am thinking maybe the Main Controller Chip on the front Board which controls the LED Display as well as the controls everythingh else is at fault?
Let me know what you think?
I checked the Vd at the Microprocessor Chip and I get 5VDC
I also checked the Xtal and I get 5VDC on 1 pin & 0V on the other & 0V on the GND pin.
Also I measure 5VDC on the RST pin as well.
The FL1 & FL2 (Display power) I measure -19VDC as well at the display.
Any ideas?
Thanks in advance.
Hi,
Let try to force a reset in the micro. Be careful jump pin 37 and 38 to the micro this will ground the reset and the micro should initialize if it working. Also do you have a scope? By checking pin 10 and 11 with the scope we will know if the micro it is running. You should see clocks coming out at those pins.
Let try to force a reset in the micro. Be careful jump pin 37 and 38 to the micro this will ground the reset and the micro should initialize if it working. Also do you have a scope? By checking pin 10 and 11 with the scope we will know if the micro it is running. You should see clocks coming out at those pins.
Hi:
Thanks for the input.
I will force a reset & I do have a scope to check out the Xtal waveform etc.
I am on my way to work now but I will give it a try as per your instructions tonight.
Thanks for your help.
Stay tuned!
SUCCESS!
I hooked up the scope to the Xtal and thwn suddenly I hear the Standby Relay click off. So I turned off the power and turn back on then the Blue LED Display came back to LIFE and I have full functionality!
Thanks Guys! (especially tauro0221)
I hooked up the scope to the Xtal and thwn suddenly I hear the Standby Relay click off. So I turned off the power and turn back on then the Blue LED Display came back to LIFE and I have full functionality!
Thanks Guys! (especially tauro0221)
Will do.... I did resolder the Crystal yeterday but it looked good at the time.
Thanks,
Rotel RX-975
The speaker wires got crossed and caused this amp to blow a fuse.
I replaced the fuse on the main power 2.5A.
The condition is now very similar to the situation described here:
1. Power comes on, Standby light and function works on and off.
2. Speaker A or B selection seems to operate on the main display.
3. No other display functions and no other button produces a response.
I'd like to try resetting the main IC, but I'm not an expert in electronics.
I think I can identify the main IC at the back of the front panel, the only IC with more than 38 pins as far as I can see.
How can I locate pins 37 and 38 when they are not labelled? I only know the orientation of the chip.
The speaker wires got crossed and caused this amp to blow a fuse.
I replaced the fuse on the main power 2.5A.
The condition is now very similar to the situation described here:
1. Power comes on, Standby light and function works on and off.
2. Speaker A or B selection seems to operate on the main display.
3. No other display functions and no other button produces a response.
I'd like to try resetting the main IC, but I'm not an expert in electronics.
I think I can identify the main IC at the back of the front panel, the only IC with more than 38 pins as far as I can see.
How can I locate pins 37 and 38 when they are not labelled? I only know the orientation of the chip.
IMO this is a problem different to what the OP had. It is not unlikely that one of the power amps suffered damage and is now keeping the unit from coming out of protection.
You can get a service manual for the receiver here.
First off you should try to find suitable measurement points for the output DC offset, i.e. the amplifier outputs prior to the protection relay. With power off, you can also look for obvious shorts in output transistors and drivers. Assuming you have a multimeter, that is.
You can get a service manual for the receiver here.
First off you should try to find suitable measurement points for the output DC offset, i.e. the amplifier outputs prior to the protection relay. With power off, you can also look for obvious shorts in output transistors and drivers. Assuming you have a multimeter, that is.
Hi,
It is possible that one of the output transistors got damaged due to the shorted. The transistors Q219/Q220 are the ones that check if you have high output voltage at the speaker output. The output from Q219 it is the protection signal that goes to the microprocessor pin 35. Check to see if you have a zero at the micro pin 35. That will indicated the micro that you have high speaker output voltage and the micro will not power up protecting the speakers.
It is possible that one of the output transistors got damaged due to the shorted. The transistors Q219/Q220 are the ones that check if you have high output voltage at the speaker output. The output from Q219 it is the protection signal that goes to the microprocessor pin 35. Check to see if you have a zero at the micro pin 35. That will indicated the micro that you have high speaker output voltage and the micro will not power up protecting the speakers.
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