T2 (tape2) play relay L309 and PH(phono) relay both have low voltages on the negative sides of the capacitors that are in parallel to the coil of the relays. This causes the relays to click constantly, the positive side is perfect and all (around 22v)
I de soldered both relays except for the two coil pins and the same thing happens, so not caused by an short after the relay. The coils measure ok. Swapped relay, replaced the two suspect caps, even though the ESR was good on them. Inspected solder joints under light and magnification.
Next measured the voltages on J103 and found flutuating voltages on the PH self biased transistor Q101 and Q107 for the T2 (play) Base ends & the corresponding chip pins LC7822, was getting
fluctuating voltages here too, irrespective if the PH or T2 were switched on or off. I replaced the self biased Q101 and this did not make a difference.
Are these chips know to go bad? Before I go replacing this, if I can even find one that is, has anyone any idea what else it could be
I have set up the dc offset and the transistor bias and they are both spot on, on both channels. The relays only seem to click when it gets hotter, after a few mins. I will get some freeze spray next week and try and
freeze the chip to see what happens. I have taken the power board out, inspected all solder joints, tested the caps with ESR meter.
Its an horribly complicated amplifier, god I Love my marantz 1030 and receiver 2216b they are a pleasure to work on. It would be handy in the marantz repair shop, just swap in a few new boards.
I de soldered both relays except for the two coil pins and the same thing happens, so not caused by an short after the relay. The coils measure ok. Swapped relay, replaced the two suspect caps, even though the ESR was good on them. Inspected solder joints under light and magnification.
Next measured the voltages on J103 and found flutuating voltages on the PH self biased transistor Q101 and Q107 for the T2 (play) Base ends & the corresponding chip pins LC7822, was getting
fluctuating voltages here too, irrespective if the PH or T2 were switched on or off. I replaced the self biased Q101 and this did not make a difference.
Are these chips know to go bad? Before I go replacing this, if I can even find one that is, has anyone any idea what else it could be
I have set up the dc offset and the transistor bias and they are both spot on, on both channels. The relays only seem to click when it gets hotter, after a few mins. I will get some freeze spray next week and try and
freeze the chip to see what happens. I have taken the power board out, inspected all solder joints, tested the caps with ESR meter.
Its an horribly complicated amplifier, god I Love my marantz 1030 and receiver 2216b they are a pleasure to work on. It would be handy in the marantz repair shop, just swap in a few new boards.
Attachments
The chip is an analogue function switch that is controlled by a serial data bus,as such it is capable of being bypassed to see if your amp functions without it .
Your right its no simple circuit , check the voltages at the supply pins on it first -
datasheet LC7822N
Your right its no simple circuit , check the voltages at the supply pins on it first -
datasheet LC7822N
Hi duncan2, thanks for your help and late reply, I have a bit of time finally to look at this again, the chip I have is LC78212, But the data sheet for this seems the same. I checked the voltage on pin 12 = -23.1 and pin and pin 19 = +23.1, also pin 18 RES does not change when the relays click. I checked the remaining pins with an very steady hand keep the voltmeter on each pin and waiting until the relays clicked again, and again only pin 5 going to R101 fluctuates, goes from about 0.6v to about 3V's and then the relay clicks momentarily and it drops back to 0.6V, I have lifted one leg from R101 now, and the voltage at pin 5 is 0V and 22.3V when phono is selected as input, With this resistor removed there is no more clicking, I have already tried another Q101 (npn self biased transistor ) and now have original back in.
Spoke too soon, still clicking on one of the relays the voltage on the negative side of C309 goes low, so two relays seem to have an issue L309 (tape 2), and the phono Relay 301 which is now not clicking with R101 lifted.
Ok I lifted both resistor R101 (PH) which goes to relay L301 and also R107 going to Tape2 and the relays have stopped clicking. I measured the following voltages
Pin 1 =0V and all the pins to the right 21 to 30 are 0v which looks right.
p11=23.8
p12 -23.8
p13 to p17 = 0V
P18=23.2
p19=23.4
P20=0V
I still notice when the corresponding switches are off for PH or Tape2 the voltage is not zero like the other pins, it fluctuates between 0 to 7Volts, does this mean the switch is damaged? Looks like it to me anyone seen this behavior before? Thanks in advance
Pin 1 =0V and all the pins to the right 21 to 30 are 0v which looks right.
p11=23.8
p12 -23.8
p13 to p17 = 0V
P18=23.2
p19=23.4
P20=0V
I still notice when the corresponding switches are off for PH or Tape2 the voltage is not zero like the other pins, it fluctuates between 0 to 7Volts, does this mean the switch is damaged? Looks like it to me anyone seen this behavior before? Thanks in advance
Seems like it, not sure how sensitive these switches are to ESD either, but I will order an new chip and hopefully what ever caused it does not happen again.