Little dog playing up again. This time it's rustling noises from just one speaker.

So your results suggest that the amp is receiving power and that the standby signal is being correctly supplied by the head unit so does very much look like the amp is faulty. I have never had one apart but I suspect that there is a single power amp on a chip in there plus some decoupling capacitors. As with all electronics of this age there may be some dry joints going on but for speed, changing with a replacement unit is the way to go IMHO

J
 
PlasticMac said:
Pin 5 to body is fine for measurements, and seems the control signal is fine.
12V, 3 to 2 is good, so power is fine.
I'd expect pin 4 to show as a short circuit (ohms) to body.
You'll not see much on 9 and 10 as they are low voltage signal line out from the radio to the input of the amp.
The 3 wires, pin 5, 9 and 10 go direct to the 20 pin connector on the back of the radio, same wire, so same colour, so, with both ends unplugged, you could continuity check each wire, (ohms), should see short.
If all's well, an amp swap is next move.
Good luck.
Mac.
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The problem with further tests is the pin numbers are not on the connectors and I don't want to mess with the head. As the problem occurred with the head switched off I will assume the issue is the amp and not the head. Also the problem went away with the amp removed so, for now, I will assume the wiring in the door is good and the current causing the speaker to crackle originated at the amp. I know the door wiring is all clipped correctly and the door is sealed correctly. They are not expensive used so I will get a used Amp and report back.
 
birtyA2 said:
So your results suggest that the amp is receiving power and that the standby signal is being correctly supplied by the head unit so does very much look like the amp is faulty. I have never had one apart but I suspect that there is a single power amp on a chip in there plus some decoupling capacitors. As with all electronics of this age there may be some dry joints going on but for speed, changing with a replacement unit is the way to go IMHO

J
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I have light through one joint. Guess I best get the iron out, nothing to lose

IMG_0429.jpg
 
Ooh that’s interesting, it does look like an amp on a chip, probably a TDA… something or other. As you say won’t hurt to re flow the pin that shows signs of being ‘dry’. Whilst you are in there you could re-flow them all. It does look like it has electrolytic caps for signal de coupling and power rail smoothing and these can fail at the sort of age we are talking about

J
 
birtyA2 said:
Ooh that’s interesting, it does look like an amp on a chip, probably a TDA… something or other. As you say won’t hurt to re flow the pin that shows signs of being ‘dry’. Whilst you are in there you could re-flow them all. It does look like it has electrolytic caps for signal de coupling and power rail smoothing and these can fail at the sort of age we are talking about

J
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Use old fashioned lead solder to match original, not lead free.
Redo all the amp chip pins, it runs quite hot, (that's why it has a heat sink), so joints do degrade.
Mac.
 
Re-flowed all of the amp connections. A bit tricky to solder but I did it, then checked each pin to the next connection to confirm a closed circuit. Then checked each amp pin to the next to ensure open circuit, My soldering is not the best on this micro scale.
Good news, music at both rear speakers and no crackling. Need to clean up and go for a test drive to be sure. Thank you all for your help and guidance 👍
 
philward said:
Re-flowed all of the amp connections. A bit tricky to solder but I did it, then checked each pin to the next connection to confirm a closed circuit. Then checked each amp pin to the next to ensure open circuit, My soldering is not the best on this micro scale.
Good news, music at both rear speakers and no crackling. Need to clean up and go for a test drive to be sure. Thank you all for your help and guidance 👍
Click to expand...
Fantastic, and very low cost!
No rustlers either 🤔
Mac.
 
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