Pioneer VSX-808RDS IR problems (Was: Testing an I.R. Receiver)

[Crackle]

Various places on the internet have it, you can get it from here https://www.manualslib.com/manual/838035...08rds.html
Or download it for free from Hi Fi engine, (you need to join for free) https://www.hifiengine.com/manual_librar...8rds.shtml

Mike

[Old Sparky]

Mike, I'm a member of HiFi Engine, and have downloaded the Service Manual, but HiFi E. do not include the User Instructions. I'll check the Manuals Lib. website.

[Crackle]

Sorry misread title, thought you wanted the service manual.
Mike

[Old Sparky]

Mike, like most of these things, The VSX808 is a very complex beast! It was brought to me with the complaint that 'the remote control doesn't work' Eventually I found that a back-up battery (described as C202 by Pioneer) was u/s. It is an ACM7017 - 0.047F, 5.5v. Not having one to hand, I fitted a 5.5v, 0.1F battery I had to hand. This resulted in some functions of the remcon, including on/off. volume, function, muting, now worked, but other buttons didn't. All buttons test as working on my Remcon Tester, so I want to find the User Guide to establish how it all works.

[Mark Hennessy]

That's not a battery - it's a capacitor.

So this is the conclusion to that previous thread then? It wasn't the IR receiver IC or anything in-between it and the microcontroller after all? It would be good to add a post to that, for the benefit of those who might stumble across it in the future...

The service manual describes the remote control on page 60.

The remote is capable of output codes for other devices (see buttons labelled "6" on that page), so make sure you've pressed "Receiver" (labelled "12") before jumping to any conclusions.

[Old Sparky]

Thanks for the clarification and reminder, Mark. As the receiver seems to be working OK with the 5v 0.1F component I've fitted, I'll leave it at that, and check the remote control instructions in the service manual. Among the buttons which have no effect are the Channel change and those numbered 1-9, etc., but this may be because I'm not using the remcon correctly! It seems that you are correct in that the control didn't work because the +5v supply was missing from various points due to the failure of C202 (the 0.047F 5v device, which, as you say is no doubt what Blaupunkt, for one, called a 'supercap', which combines high capacitance 9in these cases 0.047 or 0.1 Farad, with small physical size. BP used them in memory back-up applications in 'Quick-out' Car stereos, which is how I first knew about these devices.

[Mark Hennessy]

There were used in lots of VHS machines back in the day, and failed with depressing regularity. The symptoms resulting varied a lot, depending on the design of the equipment, but the most common one was no results from the microcontroller - often looking like an entirely dead machine.

Those buttons are among the buttons that change their codes if the remote is set to control some other device. As I say, just press "Receiver" to put the remote back into the default mode and all will be well.

Incidentally, I think it's C204 rather than C202. It's hard to see how it could have caused the symptoms described beyond the possibility of it pulling down the supply rail such that the microcontroller and other stuff was still happy, but perhaps some of the transistor circuits were not? But then, you would have checked the power supply rails first of all, right?

As the user manual doesn't seem to be available within an easy few clicks, plus you now have the information you need, I'll merge these two threads in a moment.

[Old Sparky]

I misquoted the Part No. of that 'supercap', Mark. I'd jotted it down on apiece of paper with a sketch of that circuit, and mis-remembered it. Comes with age I guess!! As for the effect of replacing C204, all I can say is that, yes I checked other voltages, and the Remote wasn't working anything before I fitted the new cap. The voltage on the +5v line was virtually zero, and, when checked the original C204 by applying 6v to it, the cap. wouldn't hold a charge, whereas the new one, after being charged for a short while by the same method, still had about 3.5 across it after about 22 hours.

[ppppenguin]

The first time I saw the spec for a supercapacitor I blinked. Capacitors come in microfarads and picofarads. Even millifarads weren't used, even if a 10000uF cap could be called 10mF. Then I saw values in farads and was a little bemused.

Supercaps aren't just useful as an alternative to low power backup batteries. On a larger scale they can work in conjunction with other battery technolgies to absorb very short term charge/discharge fluctuations. This improves the maximum instantaneous power available from a battery bank as well as lengthening battery life.

http://www.electronicdesign.com/power/ca...gy-storage

[Old Sparky]

Thanks for the info. and link, Jeffrey. I haven't read it all, but have learned s bit more about how supercaps are made. I wonder if those cheap Chinese testers can measure such high values of capacitance. If so, it'll be interesting to see what the AC7017 reads!