Help needed wih a burned out car radio. - Page 1
Forum section: electronics / projects

author: cepa
author_rank: Contributor
timestamp: November 09, 2013, 09:00:25 am
content: Greetings, while pulling out my Audi Concert 2 made by grundig radio i accidentally shorted out some pins near the voltage regultor. Poof the magic smoke went, but the radio sill worked, but the sound got distorted sometimes, also if the radio volume is turned on more than 14 the sound gets distorted too. Once i opened the radio i found one burned unknown part and a charred weco capacitor. I replaced the weco capacitor and thought that the other part is a capaitor too (since they both are connected to the Vs pin on the regulator) so I added a 103 ceramic cap. Saddly the radio doesn`t even power on now. So can this part be a resistor? The resistance of the old burned unknown part is 73ohms and that part is SMD. The fuse didn't blow. Any assistance would be appriciated, thanks in advance.

author: AmmoJammo
author_rank: Frequent Contributor
timestamp: November 09, 2013, 09:08:39 am
content: pics would be a good start

author: cepa
author_rank: Contributor
timestamp: November 09, 2013, 10:05:52 am
content: Datasheet for the regulator :http://pdf.datasheetcatalog.com/datasheet/stmicroelectronics/6606.pdfthe thingy on the yello wires is a 103 capacitor.

author: Neilm
author_rank: Super Contributor
timestamp: November 09, 2013, 12:33:58 pm
content: It could it have been a small ferrite. These are often put near connectors for EMC purposes. They often look like caps and can be damaged if a lot of current flows through them. Try working out the circuit this part is in. If it looks as if it is in series in a power rail then it is most likely a ferrite.

author: cepa
author_rank: Contributor
timestamp: November 09, 2013, 12:46:38 pm
content: can theese ferrite thingies look like this? can't I just bypass them by dirrectly connecting to the pin?Also by poking around with a multimeter I found that that part went to somewhere around 7 transistors.

author: kxenos
author_rank: Frequent Contributor
timestamp: November 09, 2013, 12:59:17 pm
content: You can also measure the current since you have the pads ready. But you will have to connect the speakers and rock the neighborhood!

author: cepa
author_rank: Contributor
timestamp: November 09, 2013, 01:00:51 pm
content: Measure the current draw of the unknown part or the radio?

author: kxenos
author_rank: Frequent Contributor
timestamp: November 09, 2013, 01:21:13 pm
content: Quote from: cepa on November 09, 2013, 01:00:51 pmThe radio. Or you can just shortcircuit the pads on the PCB and see if the radio works

author: Whuffo
author_rank: Regular Contributor
timestamp: November 09, 2013, 02:08:15 pm
content: You probably caused one of the audio power output devices to fail; the excessive current drawn by this defective device smoked those other parts. Considering that it won't even power on now, I'd recommend that you check with auto breakers and used auto part stores to find out what a working replacement radio would cost.That IC you show in your pictures; the one clamped to a heatsink with multiple leads isn't a voltage regulator, it's the audio output IC. Fixing this thing by guesswork or getting repair advice from a forum is not a great plan. Getting replacements for those parts is hard, and they tend to be very expensive.You need two pieces of information. What would it cost to replace it? (see above), and then check with qualified repair shops and get a quote on repairing it. With this information you can solve the "repair or replace" problem and proceed accordingly. You should also check with the parts manager at your local Audi dealer - he'll know where they send these radios for repair. That'll give you a pointer to who is competent and affordable.