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Stereo MPX Decoder for old Sony - Printable Version

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RE: Stereo MPX Decoder for old Sony - toptip - 02-13-2024

I was thinking the same. There are many +12 Ground to -12 polarity converters in the market (mainly for old cars) but not one like that. I would even take +12 to-12 converter.

I thought this Sanyo chip is probably not necessarily positive ground. I can see the legs where the L and R channels are coming out. I can bypass the headphone amp they have built in. But what can I use for a ground? Would the chip's negative supply be the new negative ground. I got stuck there.

In a Yamaha receiver, the same chip is used with a negative ground. I have schematic for it but could not find one for the Sanyo.

RE: Stereo MPX Decoder for old Sony - radiorich - 02-13-2024

Hello Toptip,
First all what is the IC part no . and what is the sony model number ?

Sincerely Richard

RE: Stereo MPX Decoder for old Sony - toptip - 02-13-2024

The chip is Sanyo A3311. It is obsolete, I could not find a data sheet for it. All my information is from a Yamaha CR500 receiver where it was also used.

The Sony? If you mean Sanyo, it is called RB9000. There are two versions of it, with and without a headphone permanently attached.

RE: Stereo MPX Decoder for old Sony - radiorich - 02-13-2024

Toptip,
Because Sanyo did make a LA 3361 because most sanyo IC chips had LA I used to be a factory Warranty and service for Sanyo/Fisher .

Sincerely Richard

RE: Stereo MPX Decoder for old Sony - toptip - 02-13-2024

Yes, in fact when I was searching for the A3311, I came across LA3361. It looked quite different. I will send you the schematic of this chip from the Yamaha manual.

RE: Stereo MPX Decoder for old Sony - toptip - 02-13-2024

Is there a way to load an image?

RE: Stereo MPX Decoder for old Sony - toptip - 02-13-2024

And you are right. While chip says A3311 on it, elsewhere it does come up as LA3311:

https://icompplus.com/en/others/LA3311

RE: Stereo MPX Decoder for old Sony - toptip - 02-21-2024

Hi,

This is the schematic showing the chip (which I highlighted in yellow, as I found it confusing).

Is this chip made for a positive ground or is that how Sanyo has used it? 

If possible, I would like to change it to negative ground.

All the best

RE: Stereo MPX Decoder for old Sony - RodB - 02-21-2024

The quick answer is "not possible". The VCC to the circuit is negative voltage, the filter caps positives are connected to gnd and the transistors are NPN.

toptip - toptip - 02-22-2024

This is the same chip, used with negative ground. I suppose I could do enough surgery to change things from positive to negative but might be easier to build a new circuitboard. I wish I could find the original datasheet with a simple schematic.