AOR AR2000 Radio Fault

[zenno]

I just had a close-up look at these capacitors again and I thought that the manufacturer might have marked these 5 capacitors with a black marker dot on the top of them, but it is not a mark, the black mark is leakage, so five of these 6.3v 100uf capacitors will need to be changed out, more than likely this is the main problem causing this radio to fail. pics of the black leakage below...I don't see any bulge on them but they are definitely a leak. There's one other capacitor that leaked, so all in all there are 5.
I'll need to order these. Does any-one know of a good european online store that sells these short stumpy kind of capacitors ?

5x - 6.3v 100uF
3x - 16v 47uF
1x - 35v 22uF

 

[Bluejets]

Looks to me like your original suspicion was correct.
i.e. looks like a black marker pen, not leakage.

 

[zenno]

That's it Bluejets.
The reason why I slipped on this one was that those 4 capacitors on the pic and another one not on picture but below on the pcb, I thought they were marked by some-one because I found it a bit strange that 5 capacitors would have leaked. If I saw one black mark only, I would have thought that looks bogey, but five of them marked with the black smudge caught me out.

 

[zenno]

Just an update.

I replaced all capacitors on the board and the problem is still there. I'm still waiting on the freeze spray to arrive and will try that out.

 

[zenno]

I have a question, well two questions if you could help out. I have replaced all electrolytic capacitors in this radio, it took time, but I'm stuck on this last thing in regards to a certain component. I'm not sure if this is a leak coming from this component or if it is a certain hardened paste they used in the manufacturing, but if you look under this component directly under it on the pcb there is none of the white stuff, so maybe it is a leak but I do need confirmation as to whether it will need replacing.

I never had to deal with one of these components before and I am not sure what it is exactly, some older kind of mica capacitor maybe, it is a three prong. Have you any advice as to what this particular component does and if this is a possible leak ? thanks. I also cannot find any information on this three prong component online. Pics below...

 

[Ylli]

BPF2... A 3 terminal device, probably a ceramic Band Pass Filter. Not likely to be leakage. Might be contamination from elsewhere, but 'd suggest just leaving it alone.

 

[Ylli]

Don't believe I saw any mention of a voltmeter in the above. Do you have one available? If so, measure the voltage at the red circled pins when the unit is working, and again when it is not working.
Measure to circuit board ground which can be found (among other places) at the center pins of either of these regulators.

 

[zenno]

Thanks Ylli that makes perfect sense... thanks for that, I'll have a closer look around but I didn't notice the white stuff on or around any other component, but I'll leave that one alone so.

I don't have one with me at the moment but will pick one up tomorrow, I had one before but thats long gone. I'll test that like you said, and will see what I get. Thanks.

 

[zenno]

I tested this radio while Working and Not Working with the voltmeter. The tests were both done using only battery power on this radio. The first video is the test while radio was working, and second video is the test of the radio not working. Video's below... Thanks.

Working... https://drive.google.com/file/d/1JZWijeAQ0Caiu2JBBAl86T6_iZyAoqNO/view?usp=sharing

Not Working... https://drive.google.com/file/d/1K-AsKxYzcLnpRYitcR4zdnAm7L1AR5Vi/view?usp=sharing

 

[Ylli]

Surprised there is nothing at the left side regulator, but no change at the 5 volt regulator would indicate it is not a problem with the battery voltage dropping of other loss of power source.

 

[zenno]

I see. I'll have to get my hands on a microscope and have a look over the circuitry for any cracks. I don't have a camera powerful enough to clearly show this, so I'll see what I can do to get deep in there for a very close-up look just encase there is a hairline crack on the PCB.

 

[zenno]

I experimented on this radio today and I think I might have found the problem component. This chip. When you move your finger close to it, or on it, it brings the signal back in. Could it be an earth problem ? Any thought's on this one ? Video & pic below... Getting closer bit by bit.



https://drive.google.com/file/d/1Aev1hajrWtqmqh0vp5VkuQLZP304HcwR/view?usp=sharing

 

[Ylli]

Get out the magnifying glass and take a *real* close look at the solder joints. Find anything suspicious? Can you read a part number on the chip?

If you feel comfortable doing it.... Using solder wick, remove the solder from about half the pins. Now carefully resolder using fresh solder. Then do the other half of the pins. Of course be careful not to create any solder bridges.

 

[zenno]

That will be tricky. I'll take my time with this one. The last thing I want is a solder bridge. Thanks. going to have a real close look on this with the mag glass.

 

[zenno]

Finally I found the fault point. On the pic below it was the corner pin marked in red. I soldered all the pins slightly, but when I soldered this point, it came back to life. Now I did put too much solder on the point as my soldering iron is not the best to be honest, but the radio is now working perfectly well as it should. I have had it playing on a music station now for a long time and it is still working, it never lasted more than 35 minutes before but it is going strong now for the last two hours and still going great.

I have to say, I'm not great at the electronics, but I enjoyed this puzzle indeed, well, I found it tough and gave up a few times, but I'm glad I kept with it. Thanks folks for the help, I really appreciate it. Thanks to Bluejets and Ylli.


Best wishes

Michael

Dublin Ireland

 

[Ylli]

Congratulations! Great job.