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

[Murphyv310]

I'd agree with Mark. Try any other remote first and check the output from the sensor. I'd be expecting nearly 5v P-P from it, some though are just 2.5v P-P so expect either, substantially less and I'd be pointing my finger at the IR sensor.

[Keithstv]

Many of these IR receivers have open collector outputs so will need a pull up resistor to give an output. A 4.7k resistor from output to +ve should be sufficient.

Keith

[Murphyv310]

I'd be checking it in circuit anyway for output, never checked one out of circuit, yes you may indeed need a load resistor on some types for out of circuit tests.

[Mark Hennessy]

The datasheet (link in post #7) shows that a pull-up resistor is included with this one, so there should be a healthy 5V signal.

Aside from physical aspects, these receiver ICs are much of a muchness, so it's worth rescuing them from scrap gear for test purposes. They can be used to make a very simple IR tester for those who like to build their own gear, and are also very useful for projects too. Not that they're expensive to buy, but it's nice to have something in the drawer to quickly test a theory at times like this.

Looking at the service manual of the receiver, I see that there's a surprising amount of circuity between the receiver and the microprocessor. Starting on the front panel (B board), it goes via 2 transistors. It travels from there to the audio input board A and straight through to the video input board N. On there is an IR input jack followed by another transistor. The signal travels through the contacts in that jack, so have they tarnished? There's also an IR output jack, so checking to see if the IR signal is there might save a bit of time... Next, another transistor, then back to the A board, then back to the front panel board, then finally into the microprocessor (IC201) on pin 8. So personally, I'd be chasing that signal with a 'scope, as there's a lot to go wrong besides the receiver.

[Refugee]

That sounds almost like a receiver unit could be tacked onto each board to find out what is pulling the signal down.
Perhaps lifting the signal wire off each board might work too.
You obviously loose the functions for the disconnected board but if the remainder work you will get closer to the problem.

[Mark Hennessy]

Functionally, there's nothing on the other boards - the signal just flows from the front to the back of the unit so it is available for the IR Out socket and can be interrupted by the IR In socket. The transistors are just there to invert the signal for whatever reason. However, plenty of contacts and solder joints to go bad

Following the signal from the receiver to the microprocessor with a 'scope is the easiest path. From the pictures in the service manual, it looks like this unit uses flat flexes so lifting individual wires won't be terribly practical.

[Old Sparky]

I had already downloaded that service manual, Mark, and have been having difficulty following the path the o/p from the IR Receiver takes, so thanks for the assistance with that. I'll go over that circuit, and, in particular, check the IR I/P & O/P jacks for tarnished connections. The IR Receiver, however shows no sign of response (out of circuit) to either the correct remcon, or to another known working remcon, with or without an external pull-up resistor. I have an earlier Pioneer AV Rx (VSX-505RDS MkII) which is in my 'to do' pile ince the audio amp. stages failed. THe IR Rx in that was working when I 'retired' the 505 due to the above fault, so it may be worth checking if it's the same device and, if so, fitting it in the 808 from which I removed the suspect IR Rx. THe 808 does indeed use flat ribbon cables to connect one PCB to another, so perhaps these need to be checked for continuity. Were the 808 mine, I'd jusdt use it without the remcon, since it looks like being a big job to trace and rectify the fault, and all functions can be controlled from the front panel, but theowner would like to be able to use the remote, understandably I guess.

[Refugee]

I have got a remote tester that came as a part of a general component tester but in your case it would be the other way round.
I did not realise it had a remote tester when I bought it but they are still on sale if you want one.
Inside there is an ordinary remote receiver.
It displays the received waveform.
http://golbornevintageradio.co.uk/forum/...p?tid=6478

[Old Sparky]

I have now checked the connections on the board containing the IR in & Out Sockets. Everything checks out OK, no sign of dry joints, etc. Ribbon cable are in good conditon and, as far as I checked this afternoon, making good contact in their sockets. One thing I've generally nver known how to 'cold check' are those transistors with built-in resistors, at least one of which is used in this circuit. Obviously checking such a device with the diode test range on a DMM doesn't work, so the only way I know is to take voltage readings with the device powered.

[Old Sparky]

{Mod edit: Thread title before merge was User Instructions for Pioneer VSX808RDS}

These do not seem to be listed by any of the usual on-line sellers of manuals, nor on Pioneer UK;s website, unless I've missed something.  This late 90s AV receiver is working after a repair, but the user manual would help me understand what all the functions are and how to access them. Reasonable costs covered of course.