Remote control receiver - help

[audio_tony]

I have a preamp which I have modified quite heavily (was a Counterpoint surround preamp).

When I bought this unit, I didn't get a remote control.

I have tried various remote control units (OneForAll) but none seem to operate it.

The preamp uses a Phillips SAA3049A chip for the remote.

Checking the datasheet, it is set to accept RC5 codes.

Based on this information, I would expect it to work with any RC5 compatible remote, but this doesn't seem to be the case.

I don't have a full schematic for the preamp, but there are two other chips that seem to be associated with the remote control section.

Would I be able to reprogram this section to work with another remote control?

TIA.

[Bill Fuss]

Have you tried a Philips universal remote? I've also had good luck with Rotel RR939B remote but they are more expensive.

[audio_tony]

I have various 'OneForAll' remotes which I tried.

I programmed them with the Marantz / Phillips codes but no go.

I also tried the search function.

I haven't ruled out the possibility that the remote section is faulty, but I see no reason why it should be.

I will 'scope the output of the IR sensor to the chip, and see what I get..

[gfiandy]

RC5 has many system codes. Preamps are nornally set to code 16 but there is an option for code 19. It might be set up for that. You may be able to tell this by reverse engineering the system code output to see if there is logic to select a paticular code.

Regards,
Andrew

[audio_tony]

Originally Posted by gfiandy

RC5 has many system codes. Preamps are nornally set to code 16 but there is an option for code 19. It might be set up for that. You may be able to tell this by reverse engineering the system code output to see if there is logic to select a paticular code.

Regards,
Andrew

Whooosh!!!!

That went over my head - I have VERY limited knowledge of RC systems (and digital in particular) - I last worked with digital stuff back in 1978.

I'm so rusty my digital brain cogs have seized.

Not even WD40 can help

How do I tell whether it's code 16 or code 19?

I have the datasheet for the IC - will I find some info on there?

[Steerpike]

Almost all remote codes have two parts in each data transmission; there is the address 'byte' and then the command 'byte' (byte is not necessarily 8 bits).
So all Philips products will use the same byte for 'play', be it a video recorder, CD player, cassette deck, DCC, etc, but the address byte changes for each device, so that the IR transmission as a whole (adress + command) applies only to a specific class of product.
If your product uses an oddball 'address', then typical RC5 transmissions won't be accepted by it.

The IC datasaheet will show the chip has a few 'adress' lines, that are tied permanently to ground or Vcc. The binary combination of these lines sets the address of the IR codes

There is a great software tool called LIRC, (or WinLIRC for Windozers). With a simple hardware dongle (single transistor amplifier and IR LED, easy to DIY) plugged into your PC's comms port, you can synthesize any IR transmission you want. For your situation, you might take one of the existing templates for the RC5 protocol, and modify (edit the config file on your PC) the addess bytes it is transmitting, until you find the codes that work.
Then use a learing remote to learn them from the PC.

[Steerpike]

Originally Posted by Steerpike

The IC datasaheet will show the chip has a few 'adress' lines, that are tied permanently to ground or Vcc. The binary combination of these lines sets the address of the IR codes

I looked at the data sheet. It says "The device address can be
hard-wired for a particular address, allowing several
devices in one location. Alternatively, received data with
any address can be accepted; the received data and
address are then outputs."

You'd have to look at the particular application circuit to see which of these two modes they are using. If they are using the first mode, you can most likely change this address to whatever you want, by cutting & bridging tracks on the PCB around the IR decoder chips address pins.