I just picked up a PX347 and hoping to set it up as daily driver. I wish Aiwa were not so much of a pain to open up, I'm always finding soldered pcb's to main structural points. I'm assuming the below are the only parts that need de-soldering in order to flip the motherboard off? seems to be motor connections and tape selector switches that are soldered onto mb.
The tape selector and motor connectors do need to be removed indeed. Aside from that, there are 3 other connections that need desoldering: - there is a solenoid on the left side of the PCB; - battery terminals Attached the picture with the additional connections circled in red.
Thanks I missed the solenoid one Looks like I got lucky and only needed 3 sections de-soldering Checked all the caps using ESR meter and 3 of the the 220uF caps come back with ESR of around 4 when they should read 1 max, and 47uF reads 7.5 when it should be 3.9 max, so guess it may be worth replacing those. Is it wise using a heat gun to remove below cap given proximity to plastic part? and what's best when soldering a new one on? am I going to have to remove the whole headphone jack prior? or maybe try and use solder paste and kapton tape around anything sensitive to heat?
Yes, it seems the battery terminals can be left alone. I did one of these some time ago, but could not remember exactly if the terminals need desoldering as well or not. As for caps, it's interesting they measure that high of an ESR. But these SMD electrolytics are known to go bad and I agree it's worth replacing them. Personally, I only use normal soldering station to both desolder and re-solder these caps. The headphone jack will need to be removed by the looks of it, it's just too close to that cap. What I do is add some leaded solder to the pins, then melt one side and tilt the cap, then the other. You can also cut them with a wire cutter and remove the bottom plastic plate and pins after, I have seen many doing that. Of course you can use a hot air station as well if you're careful. I just find it to be too simple with normal iron that I just don't bother. There are a lot of plastic components on the PCB that can be easily damaged by heat, including: headphone jack, switch next to jack, middle switch, IR LED/phototransistor, not to mention the parts on the bottom which can easily get desolderd if you heat the board too much. Please measure the capacitors when out of circuit and post what the ESR values are in that case, I would be curious to know. Btw, what ESR meter are you using to measure ? And at what frequency it measures ?
MESR-100 I will definitely test caps once out of circuit, as I suspect figures change slightly. Actually I had a question re the look up table, as the one on the front of device never caters for the value/voltages of caps I'm looking at, so I went hunting for other grids on the internet and found a couple - first one is more in line with the table on front of device - But another one I found is way off from above figures? or am I missing something? My assumption was if it's anywhere above the value listed it's a bad or failing cap.
Let me measure some new ones and tell you what new ones do measure. EDIT: 47uF @ 6.3V measures 2 ohms ESR 220uF @4V measures 0.9 ohms ESR 220uF @4V polymer ones measure 0.02 ohms ESR Polymer ones are much better in this regard, as are tantalums, but the comparison is not relevant as the original ones are aluminium electrolytics. All measurements were done at 10kHz and using through hole caps. I do have SMD ones, but did not bother to take them out of the package as they cannot be very different. All caps measured are name brand ones, not cheap ones. So given new ones measure very close to the 1 ohm in that table, I tend to believe 3 ohms is a much more realistic figure.
Thanks for that - it's great to have a benchmark. Does it make a difference my unit was testing at 100kHz compared to yours at 10kHz?
There shouldn't be a significant difference. Mine can measure at different frequencies, but 10kHz is the maximum, that is why I chose this one. Your looks like it only measures at 100kHz and that's it. In practice it depends how your device does the measurement. Given the relative simplicity of the design (https://www.eevblog.com/forum/reviews/mesr-100-in-circuit-esr-meter/), I would not trust your device to be super accurate, but it should give some good ballpark figures. Anyway, given the increased ESR you should see a drop in capacitance as well, but that will be hard to measure in circuit with a normal multimeter. Would be curious what the capacitance values are.
