# opamp chip died - Alpine (Jaguar) head unit



## tcharron (Jun 21, 2012)

I have a 1992 Jaguar XJS. It has a (Jaguar branded) Alpine head unit. The rear speakers seem to have died. I opened the head unit and there are two 13 pin SIP amplifier chips in it. Both rear speakers are driven by the chip on the left, so I suspect that this chip is the problem. I can't see any markings on this chip (I can only see one side of the chip without really tearing the head unit apart). Pins 5&7 drive one speaker and pins 8 and 10 drive the other. The stereo is rated at 20 Watts per channel, so I think I'm looking for a 13 pin SIP dual channel 20 watt amplifier chip. I can't find anything like this.

Any idea what a replacement chip for this might be, or where I can search? I'd really like to keep the original head unit rather than replace it.


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## tcharron (Jun 21, 2012)

I feel like I'm responding to myself here, but am providing what I have found in case it helps someone in the future (I've been helped by old posts quite often!)

I found that the 1992 XJS "Premium Sound" head unit is actually a Jaguar branded Alpine 9150/9150R unit.

This unit has two identical dual channel amplifiers in it to drive the four channels. One amplifier chip is for the front speakers and the other for the rears. The amplifiers are either TDA1552 or TDA1557 chips (2 channel 22Watt @ 4 Ohms) (the difference between these is that the TDA1557 has speaker short circuit protection). These chips are out of production now, but still available via eBay. I hope to replace the chip to restore the factory radio to working condition. I was shocked to read the specs on this chip. Despite this being Alpine and "Premium Sound", the distortion rating is a horrible 10%! Unfortunately, there are zero other chips made that are pin compatible with these, so I doubt I'll be able to use this opportunity to improve the sound quality.


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## minbari (Mar 3, 2011)

10% sounds about right. most of those chip amps are about 12-18 watts of usable wattage. once you push em, they go into THD crazy town.

hope that fixes it.


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## --Kei-- (Sep 8, 2011)

Having worked on a few alpine headunits of similar vintage, i'd strongly suggest that you look at replacing the electrolytic capacitors whilst you are in there or at least checking that they are in good order. I fixed one headunit that had gone silent on me by merely replacing all the capacitors. Everything worked as it should have except that i got no sound from it, and i also suspected dead opamps. (usual problem caps i've found were nichicon lime green caps, and a lot of elna, the worst being a pink colour)


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## tcharron (Jun 21, 2012)

--Kei-- said:


> Having worked on a few alpine headunits of similar vintage, i'd strongly suggest that you look at replacing the electrolytic capacitors whilst you are in there or at least checking that they are in good order. I fixed one headunit that had gone silent on me by merely replacing all the capacitors. Everything worked as it should have except that i got no sound from it, and i also suspected dead opamps. (usual problem caps i've found were nichicon lime green caps, and a lot of elna, the worst being a pink colour)


That's a great idea. I will definitely have a look while I'm at it.

I did second guess myself last night after ordering a replacement chip -- I wondered to myself if the problem was occurring before the op-amp. I was able to probe the input pins of the opamp (conveniently pins 1 and 13 of a 13 pin SIP) and feed that to an external amplifier. This proved to me that the signal is reaching the amp ok, so I'm now 100% sure that the problem is the amplifier chip itself.


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## tcharron (Jun 21, 2012)

Just a followup to say that I was able to get my flakey stereo working again!

The chips in the unit were TDA1552Q. I had found some TDA1557Q, which had identical pinout. I thought that the only difference was that the 1557 had speaker short circuit protection. After replacing the bad tda1552q chip with a tda1557 everything worked ok, but the chip seemed to have a different voltage gain curve. In order to get the front and rear speakers balanced to my liking, I had to put the fader to about 80% front. I then replaced the other (front) amplifier chip, and everything works great now.

I also replaced a few of the easier to access capacitors while I was at it.


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