Doorgaan naar hoofdcontent

Sony CD/Cassette/Radio set fix, bad caps again..HCD EP40

My sister came walking in with her small Sony Radio/Cassette/CD-player.
Of course there was a problem with this device



The volume control was not working, when at "0" it would mute, but at low level it would just go too loud.
Luckily I found a schematic online : http://diagramas.diagramasde.com/audio/HCD-EP30%20EP40%20sm.pdf



After some investigation I figured out that the LC75392 was in control of the volume http://pdf.datasheetcatalog.com/datasheet/sanyo/ds_pdf_e/LC75392.pdf

I traced the problem to the main circuit board and started measuring all the voltages (given in the schematic) and they appeared to be all right.

I then used my new audio-sniffer to track the audio from the radio receiver.
http://www.openmusiclabs.com/projects/audio-sniffer/ This is where I got one from Santa-Claus.



Some example of someone else tracking a signal with the audiosniffer here on YouTube.
http://www.youtube.com/watch?v=ZxUItbtYl_0

I noticed that I was getting a lot of signal on the ground reference (pin 18, which should be virtual ground without audio noise)


In the picture I made the virtual ground a yellow color.

Looking at the schematic I found the usual suspects, the capacitors, C238 and C202 both 470uF/16V and both where completely dried out. So I replaced the caps with some others I had within reach (2200uF) and Hooray !! It works again.

If you find this useful please send money to this BitCoin address : 1DynDMhxWweJr6aoSZXUzenJMkSjaWHGxo

A picture from the bottom of the circuit board after replacing the bad caps.




Reacties

Unknown zei…
Thanks Edwin from Estonia !

Cheers :)
Sergo
Unknown zei…
Thank you for this information.
Solved my problem.
Italy

Populaire posts van deze blog

Denon DHT T100 DESIGNED TO FAIL : bad caps (ceramic caps this time)

A friend gave me a Denon DHT-T100 to look at. Do not spend much time on it.. ok. It had a problem, it started clicking and ticking after power on, and after some time. (a so called intermittent problem) Sometimes it did not tick or click, but it was basically not usable. The clicking had a sharp click in one channel and repeated after about a second, then sound recovered and it would click and drop out again. He told me, do not spend any time on it, yeah, right. ;-) like I would give up after 15 minutes. I wanted to know what was going on with this thing, I found some schematic online and started measuring the usual things. The power supply, 24V did it drop down when a tick occurred ? Difficult to find out because sometimes the thing would play for hours without a glitch. I eventually found out the 24 V PSU, the step down SMPS on board and the LDO's were all ok, all power rails remained within spec, but it still glitched sometimes. (while power was ok) I investigat

Raspberry Pi, PyFace Digital, the lost documentation, I found it finally

The Raspberry PI or R-pi from  http://www.raspberrypi.org/  is well known these days. It is not an accident that I have one, I have been doing Linux stuff since 1991, and professionally since 1996 I can not skip over these developments, have to keep up with the new kids. :-) Times have changed, hardware has become very affordable, everybody knows the Arduino , Raspberry Pi and Beagle-Bone-Black (BBB). Not everybody knows the stuff that  http://www.acmesystems.it/  aka Acme-Systems and  https://github.com/OLIMEX/OLINUXINO  aka  Olimex make, so I will endorse them here. Since I am an engineer I expect to connect switches and relays to the boards and some documentation with products, not so with the " PiFace Digital " board, it comes without serious documentation, not a even the schematic. All links on their blog point nowhere. People asked them many times, yet nowhere is the schematic to be found. I finally found some info after hours of google-work, someone made a c

Fixed voltage on cheap buck converter (MP1584) conversion with single 0805 resistor

Everywhere I look on the Ali and Ebays I see these step down converters based on MP1584. I bought a couple and actually they are not bad at all. The output voltage is set by the trimming-resistor in the left top corner of the picture. This works OK, but.. it is dangerous because it is rather sensitive to the touch. I decided that I wanted fixed output, so I had to figure out how this thing worked. The datasheet looks like this : R1 in the datasheet is what I call "R feedback" in my image. The value of R2 is mostly 8.2K Ohm in the boards I have seen.  So to set some common values for output voltage: change R1 to 27K for 3V3 output (actually 3.4 volt, but 27K is a standard value) or change R1 to 43K0 for 5.0 Volt output. (43 K is a standard value) A standard 0805 size resistor fits precisely, how convenient ;-). Make sure the other resistor is really 8.2K because that determines the feedback ratio. This way you can not burn up your circ