Hi,
I have a problem with the preamplifier inputs. This unit has 5 inputs. AUX, CD, TUNER, AV, DVD, but only two of them send a signal to the main amplifier - TUNER and AV.
I replaced the 2 main multiplexers Z104 and Z105 but it didn't help. There are resistors of 22kOhm each at the Z104 and Z105 inputs. An interesting fact is that when I set the TUNER input, the audio signal does not enter the 22kOhm input resistors, but the amplifier plays correctly, the signal comes out of the preamplifier, but when I set the CD input, the signal passes through the 22kOhm resistor and goes to the Z104 and Z105 input, but the signal does not come out of the preamplifier.
This seems illogical to me. 😒
Regardless of which input I set, the output signal does not appear on pin 8 of the Z104 and Z105 multiplexers, which is the signal output.
I have a problem with the preamplifier inputs. This unit has 5 inputs. AUX, CD, TUNER, AV, DVD, but only two of them send a signal to the main amplifier - TUNER and AV.
I replaced the 2 main multiplexers Z104 and Z105 but it didn't help. There are resistors of 22kOhm each at the Z104 and Z105 inputs. An interesting fact is that when I set the TUNER input, the audio signal does not enter the 22kOhm input resistors, but the amplifier plays correctly, the signal comes out of the preamplifier, but when I set the CD input, the signal passes through the 22kOhm resistor and goes to the Z104 and Z105 input, but the signal does not come out of the preamplifier.
This seems illogical to me. 😒
Regardless of which input I set, the output signal does not appear on pin 8 of the Z104 and Z105 multiplexers, which is the signal output.
Hi, your problem is a well known one. At least to the A85, and I suspect it has spilled over to yours as well. I used to service Arcam in Norway for a number of years, and the only remedy is to install a new board. Can you please show the board id? It should be L something.
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No offense, but if this is a common problem, why couldn't I find anything about it on the internet, and I did some digging there.
In my opinion, it is a problem with one of the integrated circuits, but I lack the knowledge to diagnose it correctly.
In my opinion, it is a problem with one of the integrated circuits, but I lack the knowledge to diagnose it correctly.
I avoid all preamps and amps that use solid state switching (and electronic volume adjustment). Relay switching is preferable and still found in even modestly price amps eg Marantz PM6007.
I don't like this solution either, but I would like to fix it.
TUNER and AV inputs correspond to MUX pins X2 and X3, i.e address 2 and 3. This suggests that the mux Z103 and Z104 are responding to the A0 pin, but that A1 pin is "stuck" at logic 1, and A2 is stuck at logic 0. Examine pins 1, 15, 16 of Z103 and Z104 for confirmation. Follow these lines back to their source at the microcontroller. Perhaps there are defects in the paths of the A1, A2 between muxes and controller.
Good luck!
Good luck!
I forgot to mention that I wrote down the logical states on the control pins. There are no problems along the way of the control pins of the control systems (listen 1,2,3 to the resistors, the resistors themselves maintain the parameters (22kOhm). I will also check the path behind them to the controller itself.
Hi HT787,
I suggest you monitor the MUX address lines near the uP and select AUX, CD, Tuner, DVD. These source selections should exercise the A0, A1, and A2 lines respectively and independently in both logic states. If all is well at the uP, then you can sort out what's happening at the MUXs.
Good luck!
BTW,
The explanation for this behavior is that the inverting inputs of Z115A (Z116A) present so-called "virtual grounds"--- a misleading way of saying the input appears to be stuck at ground. (In fact, opamp feedback forces the inverting pin to precisely follow the non-inverting input--- which happens to be a ground potential in this circuit.) So when you monitor the selected MUX input (and MUX out) they appear to have no signal present.
I suggest you monitor the MUX address lines near the uP and select AUX, CD, Tuner, DVD. These source selections should exercise the A0, A1, and A2 lines respectively and independently in both logic states. If all is well at the uP, then you can sort out what's happening at the MUXs.
Good luck!
BTW,
The explanation for this behavior is that the inverting inputs of Z115A (Z116A) present so-called "virtual grounds"--- a misleading way of saying the input appears to be stuck at ground. (In fact, opamp feedback forces the inverting pin to precisely follow the non-inverting input--- which happens to be a ground potential in this circuit.) So when you monitor the selected MUX input (and MUX out) they appear to have no signal present.
I'm wondering about the resistance between pins 2 and 3 on the SK100 connector. When 230V power is connected, the resistance between these pins is 0 ohm. When the power supply is disconnected, the resistance is over 5MOhm.
Between pin 1 and 2 there is O.L. Between pins 1 and 3 67Ohm.
The resistance drop must be generated by IC Z1, because it is low even when the tape is disconnected from the preamp side.
🤔🤔
Between pin 1 and 2 there is O.L. Between pins 1 and 3 67Ohm.
The resistance drop must be generated by IC Z1, because it is low even when the tape is disconnected from the preamp side.
🤔🤔
Either way, the microcontroller controls the Z104 and Z105 muxers. There are no problems with paths or resistors between them, and this probably leads to the conclusion that the Z1 microcontroller has some problem or EPROM Z5. At least that's what I think, and there's nothing I can do about it.
I remind you that I replaced the muxers and it didn't help.
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What does "uP" mean - does it mean measurement on the pins of the Z1 microcontroller?
The logical states that I wrote down on the paper were measured on pins 1, 15, 16 of the Z104 and Z105 muxers.
The logical states that I wrote down on the paper were measured on pins 1, 15, 16 of the Z104 and Z105 muxers.
Yes, uP is supposed to resemble Greek Mu/micro.
The last hope is that the path from MUXs to the controller is some how open. If the processor package will allow, probe directly on the processor pins to test if they respond correctly to the various sources suggested above. If they don’t respond, that seems dire. But I’d be surprised if this the only misbehavior, so don’t abandon hope until evidence is unequivocal.
The last hope is that the path from MUXs to the controller is some how open. If the processor package will allow, probe directly on the processor pins to test if they respond correctly to the various sources suggested above. If they don’t respond, that seems dire. But I’d be surprised if this the only misbehavior, so don’t abandon hope until evidence is unequivocal.
I know what the letter "u" stands for, but I didn't know what the "P" in the combination stands for.
The letter u is often used when specifying capacitance, for example electrolyte (uF).
Returning to Arcam:
The logical states are the same at the direct output from the main microcontroller Z1 as at the inputs of the Z104 and Z105 multiplexers. In my opinion, this means a problem with the Z1 system or EPROM.
There's nothing I can do about it, because I don't know, because I'm not sure if I would program the EPROM to correct the Z1 system after replacing it, since it may have a damaged program itself. I'm giving up on this repair.
I am very grateful for your help on this topic.
The letter u is often used when specifying capacitance, for example electrolyte (uF).
Returning to Arcam:
The logical states are the same at the direct output from the main microcontroller Z1 as at the inputs of the Z104 and Z105 multiplexers. In my opinion, this means a problem with the Z1 system or EPROM.
There's nothing I can do about it, because I don't know, because I'm not sure if I would program the EPROM to correct the Z1 system after replacing it, since it may have a damaged program itself. I'm giving up on this repair.
I am very grateful for your help on this topic.
I note from your tabulation that the A1 address line seems to be stuck in the 1 state. This inspires the question: is this defect within the processor (little hope, short of replacement) or is it a fault somewhere along the address line with far better prospects for repair?
Selecting the Aux or CD inputs should set this address line to 0, but apparently does not. Do the front panel selection buttons and LEDs respond correctly?
Selecting the Aux or CD inputs should set this address line to 0, but apparently does not. Do the front panel selection buttons and LEDs respond correctly?
The idea was to check whether there are any differences between reading the logic states on the muxers and the Z1 system, and there are no expected differences. I also thought about unplugging the tape that connects the SK100 and SK3 connectors, but I gave up on it because I don't know if the equipment will start going crazy after unplugging it.
The LEDs on the front of the panel light up according to the selected input.
The LEDs on the front of the panel light up according to the selected input.