Hello, Newbie here. Any suggestions appreciated.
I have a similar issue with the switch mode power supply board, on the Integra DTR 50.4 (same as Onkyo TX-NR818), receiver bought used.
The issue is this: when the unit is “cold” (i.e. left unplugged overnight) when I plug in the power cable, the standby led lights on (as is supposed). However, when I push the power button, the unit turns on, and shuts off by itself after a few seconds. One can hear the relay from the standby board clicking multiple times, without unit turning on (power led is not lit). However, after 4-5 or so clicks (cycles), the unit turns on by itself and remains functional for a longer time; then again shuts off, and whole thing repeats, only each time the unit is on for a longer period. This is the general behavior, although sometimes is erratic.
After about 5-10 minutes, the unit finally stays on for long time (hours), when again shuts off and restarts again (same pattern) and stays on for longer time.
I can use the unit as is, but it’s annoying.
I noticed that when the unit in the “cycling” mode;
• Sometimes I can hear the relay clicking every 2-3 seconds, some other time you can’t hear it;
• Measuring (DM Voltage) at pin 3 (to GND) relay RL9101: the voltage is oscillating from 0 to some 10-11V value, every 2-3 seconds (or so).
• All the electrolytic capacitors have low/normal ESR (measured in circuit)
• The PWM from pin 5 (Drain) Q9001 also has an on/off pattern that corresponds to that 2-3 second cycling time. I tried to measure this with an oscilloscope, but by the time I succeed to hook it up and take a proper measurement, the issue goes away and receiver turns on. I am not sure about the PWM frequency, it appears to be 75 KHz, but the point is that when unit is off, the PWM is stopped for around a second, then starts again. Looks like the IC (Q9001) enters some kind of protection, then starts on again, cycling, as I mentioned before.
Unfortunately it’s difficult to make proper measurements, because most of the time the receiver works normally. It’s almost similar with an engine that has a rough start when cold. I even tried to help powering up the unit by warming the board to 40C, but the result is inconsistent; although at times the issue “seems” to go away quicker.
A few more comments, assumptions, really: I don’t think that the unit (receiver) enters protection mode. If it were, it would not restart by itself. I believe the issue is with the Q9001 itself, or somewhere on the feedback network. It “seems” to be worse when unit is unplugged for a longer time (I haven’t tried to keep it plugged overnight, to see if it starts quicker). I don’t believe the relay has any issues (?), it appears that it doesn’t get the proper 12V to switch on. Cold solder joint? Perhaps, I inspected visually the board, nothing seems wrong.
Any suggestions? First of all, am I correct to assume that the issue is on the standby board itself? The quickest way to find out if the Q9001 (MIP2M40MSSCF) is the culprit, would be to replace it, but it takes 2 months until I get it from China (nowhere else I can find it). I will try to “freeze” the chip, to see if it replicates the issue, but still waiting for the freeze spray I ordered.
Your thoughts?
Update 9-Jun-2020
There is no 9V rail; on the schematic all components from this rail are marked with NC, which I assume means not used. In fact, on the PCB itself, these components are missing.
With Unit functioning correctly, measurements taken at the JL9000A (7 pin connector; 2 not used), with respect to secondary ground (GNDSUB pin 1):
Unit ON: STPower = 3.25V; MPower=3.18V; 12V=14.43V; (no 9V)
Unit OFF: STPower = 0V; MPower= 0V; 12V= 12.01V; (no 9V)
I don’t understand why the 12V rail is 14.43V, when the unit is on (and working properly). Could this overvoltage be the problem? What causes it? Again, it appears only when unit is on, otherwise (standby) it’s 12V.
Update 12-Jun-2020
The F9001 micro-fuse (1A-SEUL-TL250V slow operating type) blew. I replaced the fuse with similar, and after the unit worked for a while, it blew again. So there must be a short somewhere. I removed the standby board, and it showed a steady 12.3V. I accidentally shorted the 12V-GND terminals, and the overcurrent protection kicked in, and re-started, so the feedback circuit and controller are good. However, when the board was in the unit, the 12V was cycling between 2-3V and ~11V, most likely the standby circuitry overcurrent protection kicked in, then restarted, every 2-3 seconds. The fault (short) must be on the video PC board, along the 12V_ST line.
I look forward to hearing from you, any suggestions most welcomed (although this thread seems to be dead).
Update 13-Jun-2020
I disconnected the 5 pin cable from the video board to the HDMI board (JL2100A): the voltage was stable at 11.7V. I reconnected that cable and rechecked the 12v: it was fluctuating again. I also noticed that the 12V dropped much quicker than before (when the cable was not connected to HDMI board), like something is pulling it to the ground. What now?
Final (?) update 16-Jun-2020
While I was (re)checking the electrolytic C9003 (this time I removed it from circuit and tested – all good), I also inspected the standby board, for any bad solder joints. I noticed that the solder on one pad of the D9006 (SMD diode) looked like a small blob. I re-soldered it, and this “seems” to have resolved the issue. The receiver starts and operates normally (so far). One important difference (aside the fact that the 12V no longer oscillates): when the unit is unplugged (removed from electrical outlet), the voltage remains at 12.11V for ~15 seconds, then decays slowly (0.5-1V per second) until reaches ~6V, then starts damped oscillations toward ~1.5V; whereas before, it stayed only 1-2 sec at 12V, and then started oscillating wildly (same behavior as before, when unit was “refusing” to start or was shutting down while being ON).
The poor solder joint at the D9006 diode was probably limiting the current coming to the C9003 cap, therefore taking longer time to charge/maintain the minimum voltage needed at the VCC pin for the Q9001 IC to operate. The IC Q9001 was turning on/off (switching the76KHz oscillations on/off for the flyback converter) every 1-2 seconds, especially after the unit was unplugged (cap C9003 discharged) for a longer time. [The voltage measured at VCC pin 4 (IC Q9001) is 10V unit ON (the 10V is actually between 10.1-10.3, with 1V AC ripple), and 15V in standby, stable; unfortunately I haven’t measured this before, for comparison].
I also assume that this poor solder job was from the manufacture process (it doesn’t show any sign of attempted repair), but since the previous owner kept the unit plugged in, probably he didn’t notice that there were any issues with the unit.
I still can’t explain the following:
- Why the fuse (slow blow type) blown twice, while I was testing the unit. I can only assume that there were many spikes of overcurrent (>1A) when the standby voltage was oscillating wildly (Q9001 on/off).
- Why the 12V is ~14.5V when unit is on, and 12V when in standby;
- Why the VCC (pin 4) is 15V when unit is in standby, and 10V when on (with a 1V AC ripple on top of it)
In retrospect, all the troubleshooting done before (removing the cable from JL2100A connector, etc.) led me astray.
I don’t believe this is helpful for anyone, because this bad solder joint is quite unique. But on the other hand, nobody seems to be reading this anyway.
Update 18-Jun-2020
I was wrong. After 3 days of perfectly functioning unit, it re-started doing the old tricks.
With no help/suggestion from anywhere, it’s time to give up. I will also cancel my account for this forum. Totally useless.
