I picked up a non working RX-V2400 for basically free. Unit did not power up or do anything. No relay clicks no display nothing. I assumed its likely in the standby power board so checked some components, see attached schematic of this board. Transistor Q4 and diode D11 were shot. Replaced them and unit powered up and appeared to be back from the dead, seemed ok and no error codes displayed. Did a few more power cycles then just left in on for few min. Shortly thereafter heard a click and went dead again 🙁
Im going through the standby board again and can't find anything shorted or not otherwise bad. I have 11volts on the S9 pin but only a few milivolts on the PDD pin. So based on the attached circuit, is PDD voltage going out from the standby board or does this voltage come into the standby board?
I traced the S9 to the function board where it goes through a regulator and I have the required 5.8volts leaving the regulator. Again on the function board PDD voltage is nil but again not sure where this should be coming from.
Any help appreciated!
Im going through the standby board again and can't find anything shorted or not otherwise bad. I have 11volts on the S9 pin but only a few milivolts on the PDD pin. So based on the attached circuit, is PDD voltage going out from the standby board or does this voltage come into the standby board?
I traced the S9 to the function board where it goes through a regulator and I have the required 5.8volts leaving the regulator. Again on the function board PDD voltage is nil but again not sure where this should be coming from.
Any help appreciated!
You've got an R or L model, apparently?
I finally traced PDD to Q511, p.89 E-8. This transistor would be enabled once PDD voltage fell substantially below 5 V and change.
If enabled, if briefly triggers the reset (/RES) and pulls up PDET on the CPU.
I think the idea behind the thing is that upon applying power, C3 is starting to get charged via R6 (via regulator Q5/D4 in your case), and once high enough, turns on Q2 which in turn pulls down PDD, which in turn wakes up the CPU elsewhere.
PDD should never really go below the indicated 4.6 V unless either D1 is shorted, there is a bad connection somewhere on its way from D1 all the way to the CPU board, S9 does not make it to the CPU board (which you have ruled out), the 78N06 generating Q511 supply is dead (again, 5.8 V is present), or both of R836/837 are open.
You shouldn't actually be seeing something as high as 11 V on S9 - it's a zener-follower regulator with a 10 V zener, rated at 9.5-9.9 V @ 5 mA, so expected voltage would be somewhere around 9.1 V out of Q1 or 9.7 V out of Q3. Check Q1/Q3 for C-E shorts, and check D3 voltage. Usually zeners short out when they fail, but this one might be different.
What did you use for Q4, were you able to obtain the requested 2SK246-Y or equivalent?
Is there substantial ripple ahead of the regulator? This receiver is not exactly new and its standby supply may be able to use some new electrolytics.
What is the PRY signal doing? Should be pulled high (alternatively check at R7). If so, what's going on at Q6 emitter?
It is odd that the flyback diode D11 was bad. HSS104 are rated for a reverse voltage of 35 V, 40 V peak. If this has been like that for a while, it may have damaged Q6, possibly even the relay coil itself.
As for the cause of the damage observed, my bets would be on a major surge or even lightning.
I finally traced PDD to Q511, p.89 E-8. This transistor would be enabled once PDD voltage fell substantially below 5 V and change.
If enabled, if briefly triggers the reset (/RES) and pulls up PDET on the CPU.
I think the idea behind the thing is that upon applying power, C3 is starting to get charged via R6 (via regulator Q5/D4 in your case), and once high enough, turns on Q2 which in turn pulls down PDD, which in turn wakes up the CPU elsewhere.
PDD should never really go below the indicated 4.6 V unless either D1 is shorted, there is a bad connection somewhere on its way from D1 all the way to the CPU board, S9 does not make it to the CPU board (which you have ruled out), the 78N06 generating Q511 supply is dead (again, 5.8 V is present), or both of R836/837 are open.
You shouldn't actually be seeing something as high as 11 V on S9 - it's a zener-follower regulator with a 10 V zener, rated at 9.5-9.9 V @ 5 mA, so expected voltage would be somewhere around 9.1 V out of Q1 or 9.7 V out of Q3. Check Q1/Q3 for C-E shorts, and check D3 voltage. Usually zeners short out when they fail, but this one might be different.
What did you use for Q4, were you able to obtain the requested 2SK246-Y or equivalent?
Is there substantial ripple ahead of the regulator? This receiver is not exactly new and its standby supply may be able to use some new electrolytics.
What is the PRY signal doing? Should be pulled high (alternatively check at R7). If so, what's going on at Q6 emitter?
It is odd that the flyback diode D11 was bad. HSS104 are rated for a reverse voltage of 35 V, 40 V peak. If this has been like that for a while, it may have damaged Q6, possibly even the relay coil itself.
As for the cause of the damage observed, my bets would be on a major surge or even lightning.
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First off thanks so much for the reply!
I will do some of the checking as you suggest later today I hope. I wanted to provide some more info. I do appear to have the R model as the serial ends with it. My standby power board has substantially fewer components then the schematic provides. The circuit layout is the same but my board does not have the following components present and judging buy the solder bulbs on the traces none of these were ever present.
Q1,3,4,5
D2,3,4,5
C2,4,5,7,8
R2,3,4
Jumpers J1,2 are present. I checked the voltage on both sides of D6 and got 4.2 on low side and 4.3 on high side. I don't have a scope to check ripple but will likely replace the caps near the regulator on the function board.
I will do some of the checking as you suggest later today I hope. I wanted to provide some more info. I do appear to have the R model as the serial ends with it. My standby power board has substantially fewer components then the schematic provides. The circuit layout is the same but my board does not have the following components present and judging buy the solder bulbs on the traces none of these were ever present.
Q1,3,4,5
D2,3,4,5
C2,4,5,7,8
R2,3,4
Jumpers J1,2 are present. I checked the voltage on both sides of D6 and got 4.2 on low side and 4.3 on high side. I don't have a scope to check ripple but will likely replace the caps near the regulator on the function board.
Now a component that was never even installed can't be defective, so I assume by Q4 in your original post you actually meant Q6? So much for my reasoning. It's probably the plain ol' U/C version of this model that you would expect then.
Well got a bit further. There was the required 5.8v at the output pin of the regulator but it wasn't going anywhere. Bad solder joint. Repaired and now PDD is at 4.6v but unit still wont power up. PRY stays at .8v and does not change when power button is pressed. Base of Q6 is .64v.
Hmm. Q6 definitely should be doing something. 34 µA of base current (that should be good for about 10 mA - what's relay coil resistance like?), Vbe looks normal. 0.8 V on PRY is a bit of a weird value though.
I have traced PRY back, and it becomes PORY on the CPU board, being pulled up by the CPU via 1k resistor R831. Please check voltage there, and if found near 4.9 V, check continuity between R831 and R7 (the Q6 base resistor), as well as both resistors themselves just in case. Usually PRY/PORY should be at ~+4.15 V in operation, not 0.8. Powered down I'd expect <0.5 V.
I have traced PRY back, and it becomes PORY on the CPU board, being pulled up by the CPU via 1k resistor R831. Please check voltage there, and if found near 4.9 V, check continuity between R831 and R7 (the Q6 base resistor), as well as both resistors themselves just in case. Usually PRY/PORY should be at ~+4.15 V in operation, not 0.8. Powered down I'd expect <0.5 V.
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PDD could be Power Drive Down, with R6 and C3 still used as a time delay before Q2 starts sinking PDD to 4.6 through zener D1. This seems to work fine.
PRY is Power ReadY, PORY the same assumed. I've not the other side of the circuits (P92), but it should come up to a sufficient drive voltage.
In short, sgrossklass is right (hats off), so measure at both sides, maybe a corroded connector CB1.
PRY is Power ReadY, PORY the same assumed. I've not the other side of the circuits (P92), but it should come up to a sufficient drive voltage.
In short, sgrossklass is right (hats off), so measure at both sides, maybe a corroded connector CB1.
Checked voltage at R831 and get .9v on both sides of resister. There is continuity from R831 back to R7. Both resisters measure correctly.