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Post by serafis on Jun 9, 2023 20:43:15 GMT -5
Sorry only saw that after I'd posted. You're correct in the operation of the standby LED. What's supposed to happen is that STBY_LED line is high (LED on) until the unit comes out of standby, when it goes low (LED off). But after the earlier fixes and reflashing the firmware, STBY_LED only measured 0.8V in standby - which I assume is not enough to switch the LED transistor to ground the LED. I haven't been able to find out why, as the only connections I can see for STBY_LED from the schematic are to MCU pin 79 at one end, and the base resistor of the LED transistor at the other. Interestingly though, if I plug my Ipod into the USB port, the LED will come on in standby but goes out as soon as I unplug the IPod.
3.3M comes up as soon as AC power is applied and remains rock solid constant whether the unit is in standby or powered on, and the + side of the LED always measures 3.3V too, as it should. 3.3DSP only comes up and remains constant once the unit is powered on, which is why I used it to pull up STBY_LED (i.e turning the LED on when the receiver is on). The base resistor R4513 is 10K so the current draw on 3.3DSP should be negligible.
All main MCU functions, including on screen display, YPAO configuration, other system configurations, network, USB and Ipod play, sound fields, direct mode, volume control and remote etc. all operate correctly so I don't think there's an issue with the MCU in this respect.
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Post by serafis on Jun 9, 2023 20:48:39 GMT -5
Anyway, I removed my STBY_LED pull-up resistor to do some further testing. Now MCU pin 79 remains low whether in standby or powered on.
But here's a strange thing. If I power it on, then plug my iPod into the front USB port, wait until it's recognized, and then put the unit into standby, the standby LED comes on (MCU pin 79 reads around 3.3V) and remains on for around 18-20 seconds, then goes out (just like it did before I applied any fixes). If I remove the USB plug while the LED is on, it goes out immediately. I can't immediately think of why it should do this.
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Post by mastertech on Jun 9, 2023 21:50:59 GMT -5
What is the voltage on pins 2, 3, 4, 5, 76, 77, 82, 85, 86 and 88 on ic21 (CPU) during standby and on?
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Post by serafis on Jun 10, 2023 0:14:53 GMT -5
Standby:
2 = 3.3V
3, 4, 5, 76, 77 & 82 = 0V
85 & 86 = 3.3V
88 = 0V
On:
2 = 3.3V
3 = 0V
4, 5, 76, 77, 82, 85, 86 & 88 = 3.3V
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Post by mastertech on Jun 10, 2023 19:10:01 GMT -5
Most of those voltages look ok, just questionable and one looks iffy but explainable. Let me explain.
If you look at the driver datasheet (ic401) on the pin description page where it describes pins 1 to 4 which are the controls pins which also are the lines you had much corrosion problems with. As the description indicates pins 2 and 3 must be low for communication to happen along with pin 1 being reset by going low on occasion. Now I know you indicated these lines were all high at the CPU so probably the same at the driver. But I think that these lines would only go low during a communication and possibly to quickly for your volt meter to see. You would probably have to monitor these lines one at a time with your scope and only when you are doing a change on the receiver, like changing the source or volume or something. Cause the process would be so fast that only the scope would see it. Pins 2 and 3 on the driver would be my targets for now. If your scope sees nothing here then I would recheck the same 2 lines at the CPU. See what you get.
ALSO: is KEY 2 still at zero?
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Post by serafis on Jun 11, 2023 0:57:28 GMT -5
KEY2 is now at 3.3V and all the keys and volume control seem to work as they should. As for the display IC, I dug out my old Loto OSC842 PC USB scope, which also has a 4-channel logic analyzer, and this what I found. When I press a button on the front panel which would change something on the display, I see FLD_N_RST / RESET (pin 1) and FLD_N_CS / CEFL (pin 2) both drop from 3.3V to around 1.4V (not zero) when the sequence starts, rising from time to time during the sequence, and ending back at 3.3V. Because they don't drop to zero, my logic analyzer doesn't see the change. Instead, the following screenshot shows an A/B trace of the full sequence, for FLD_N_RST / RESET (pin 1 yellow) and FLD_N_CS / CEFL (pin 2 blue), using a downward-slope single-shot trigger on pin 2:  The next screenshot shows the logic analysis for FLD_SCK / CKFL (pin 3, orange) and FLD_MOSI / DTFL (pin 4, red), with the blue analog trace in the top half of the screen showing FLD_N_CS / CEFL (pin 2):  The next screenshot is an A/B trace of part of SCK / CKFL (pin 3, yellow) and FLD_MOSI / DTFL (pin 4, blue) with more detail:  And the final screenshot shows a bit more detail of the previous screenshot:  Looks to me as if the clock (pin 3) and data (pin 4) lines are probably )possibly) doing what they're supposed to, but the chip select (pin2) and reset (pin 1) aren't going fully low. |
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Post by mastertech on Jun 11, 2023 18:01:48 GMT -5
Well you could try to manually pull them low (reset and CE) and see what happens. They do appear a little high. According to the CPU datasheet it should be .5v or less. I would pull them to zero.
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Post by serafis on Jun 11, 2023 18:16:48 GMT -5
Yes I tried that - first with a 100 ohm resistor which only pulled down to around 1.5V, then a direct short to DGND. Unfortunately no effect.
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Post by mastertech on Jun 11, 2023 20:27:01 GMT -5
Well at this point I would be leaning towards the driver ic being bad. Do you have any other parts units laying around. It is probably a common driver on anything with a VFD.
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Post by serafis on Jun 11, 2023 23:32:53 GMT -5
Yes, that's where my thinking is at. Unfortunately, the only other units I have for parts at the moment use quite different drivers and have fewer pins on the VFD. So I think I'll give up on this one and just use it as is, without the front display for now - it works very well apart from that.
I should also mention that I am just a hobbyist who enjoys buying decent but faulty audio gear from our local auction site to see if I can save it from the landfill (or sometimes keep it if it's better than what I already have!), which is why I'm often on this site with different gear! And I enjoy the learning too - so now I'll put this aside and move on to my next project, a dead Onkyo TX-NR686 where I think one of the smd regulators has failed and possibly caused some downstream damage.
Anyway, thanks for your all your help and advice with this one, very much appreciated.
Regards,
Jon.
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Post by mastertech on Jun 13, 2023 19:53:55 GMT -5
I did find a couple places in the UK that have the ic in stock for around 11.00 and 14.00 euro. Not sure what shipping to you would be but they are pretty small.
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Post by serafis on Jun 14, 2023 20:18:29 GMT -5
Thanks, I found a couple thru google but the shipping to NZ is almost as much as the chip itself, which makes it quite an expensive exercise. Happy to leave it as-is - now I've set it up using the OSD, I don't need to see the front display, and it's working well otherwise.
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Post by serafis on Aug 10, 2023 2:18:55 GMT -5
Partial success with the front display. I bought a new driver chip from Aliexpress which arrived today. After I carefully soldered it in, I also discovered a solder bridge on the tiny 4x100 ohm resistors between FLD_N_RST and FLD_N_CS. After I removed this bridge and powered on, the front display now works (yay!), except for the second segment (2G) which is completely dark. I've narrowed this down to the 2G grid signal on pin 6 of the display, which does not appear to be getting its synchronisation pulse - all the other grid pins get a square wave pulse approximately every 5.7mS (175Hz), slightly offset from the one before it. I assume how this works is that the driver sends a power pulse to each grid along with the signals to the segment pins to light specific segments on that grid, then moves to the next grid and so on.
I've checked for continuity from the driver pin 62 to Pin 6 of the display and also checked for any bridges or shorts but can't find any problems. And if I short Pin 6 to another grid pin, the second segment lights up with the same text as the shorted grid segment, so the VFD is definitely working as it should.
I'm wondering if I got a faulty driver chip from Aliexpress, but don't know if there's anything else I can check. Any help greatly appreciated.
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Post by serafis on Aug 11, 2023 15:42:23 GMT -5
I've ordered an original chip from the UK to see if that fixes the issue with the second segment. If so then this is finally fixed; if not I'll live with it.
Also I discovered that the issue with the standby LED wasn't actually an issue at all. Unlike any other AVR I've worked on, the LED only comes on in standby if HDMI Standby, HDMI Control or Network Standby are enabled in the setup menus. Otherwise it remains unlit. Next time I'll read the User Manual as well as the Service Manual!
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Post by serafis on Aug 27, 2023 21:57:27 GMT -5
All fixed now. The new M66003-0131FP display driver chip arrived from the UK today so I just removed the previous Aliexpress one (Chip-Quik sooo good for removing surface mounted chips safely - wish I'd known about it years ago!!) and installed the new one, and the display now works as it should with all VFD segments operating.
So a successful fix finally - the receiver is now in full working order and sounds great.
Thanks for the help.
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