Chosen Solution
This vintage analog integrated amp has an enjoyable sound, but for some reason the right speaker channel doesn’t work all the time. (it’s not the speaker itself, I checked) Weird thing is, when I put pressure on the capacitators on the circuit board, slightly bending the circuit board, it usually works again…. only to stop working some time after. Also sliding the volume control on the front panel to maximum for a brief moment sometimes does the trick. I have no idea what is causing this. I don’t have the guarantee or puchase paper, sony won’t help me. And I’d like to fix it myself. Any ideas? I’ve added a picture of the inside and marked in red the capacitators I press and a link to an image of the front panel on
google image of the front panel Update (01/25/2016) Hey Jayeff, Both sides of the board are accessible, but I didn’t really find a dry joint. No apologies needed, even if I did already know what it looks like :D. Still not sure what the problem is. I tried bending this part (red circle in pictures) , which is crooked. I’m nog sure if it’s supposed to be crooked. Also thought it was maybe this thing (green circle), unsoldered and resoldered that, but to no avail. Also, when i there is alot of volume, usually it works again. (like, when a laptop goes into the TV via hdmi, then via minijack/cinch out of the TV’s headphone socket into the amp, and all volumes are set high) But so this got me thinking that maybe it could be something else?
Hi, By putting pressure on the capacitors you are making something come into contact again, as you say by flexing the board. It is more likely to be a dry joint or loose connection (even looks like there are wire wrap type connections - orange/red/black/red wires near capacitors- I may be wrong on that). See if you can trace the wires from the right speaker channel output back to the board (and hopefully it is near to where you have been applying pressure) and then inspect with a strong light and a magnifying glass for dry solder joints or loose cable connections. Hopefully it is on the front of the board so that you don’t have to remove it. Also make sure that the power is completely removed so that no ‘accidental’ probing will cause more problems. If you have to remove the board because you need to inspect the back keep the picture you posted handy, take more if necessary so that you know where everything belongs when you go to put it back. If you have to remove the board be careful when you handle it, you do not want to ‘bend’ any components causing possible s/c or o/c or break off any either. Here is a link to show how to solder components on a pcb and a picture to show what a dry joint looks like. Apologies if you know this already. https://www.youtube.com/watch?v=SD0Gtm5p…
If it is a wire wrap type connection that is faulty - actually loose, (the wire is actually wrapped tightly around a post with a special tool, so that the post edges bite into the wire to make the connection) it is best just to solder the wire to the post as is.
Hi, OK. If you feel like doing this, this is what you need to do. A visual inspection: “with the power removed”, a magnifying glass and a good light so that you can see well. You need to carefully look for loose connections, dry joints and breaks in the tracks. Also inspect the components themselves, actually try to move them (gently) especially the capacitors (C = capacitor, R = resistor) they will obviously bend but not feel loose. With the capacitors try gently pulling them up and down whilst observing their solder connection to the tracks. If there is a dry joint you may see movement If any solder joint looks suspect re solder it. One of the pictures you posted https://d3nevzfk7ii3be.cloudfront.net/ig… showed the terminal connections for the IC401 power board with the numbers written on the track side so you should be able to work out where pin 13 is, look at the cable wire that joins it to the mainboard (on the other side) then follow the track from there to get to R463 on the board. When you have finished looking at the solder connections and the track for this path go to the other side of R463 and follow the path to R468 then onto the relay contact, thru the contact (you pretend that you go up thru the contact then back down on the contact it makes onto and see where it connects to the track and then follow it from there) onto the track and on to where it leaves the board to get to the headphone jack board. Now do the same from pin 18 of the IC401 power board and follow it to C452, then to R452 and then to where it leaves the board to get to the volume control. You should also check the connections of the following C551, C552, C501, C502, R551, R552, D502, Q502 With regard to follow thru on relay contacts. When a relay operates it pushes a set(s) of contacts so that they make or break away from another set(s) of contacts. When contacts are meant to make you want to make sure that the contacts are pushed far enough together so as to make good contact.(it doesn’t have to be excessive, just enough so that good contact is maintained with the relay operated - that they don’t bounce and cause problems). This is known as follow thru. The contacts make before the relay armature (operating lever if you like) has finished its movement. Therefore when the armature has finally come to its fully operated position the contacts have been pushed together a bit further. Follow back is the same in reverse. Contacts that were broken when the relay operated need to have good contact when the relay is released. I feel that I should tell you now that I will not be advising you how to measure voltages in the circuit. Because you admit to little knowledge regarding electronic servicing, you can cause serious damage to the amplifier just by inadvertently making a slip with your test probes. For instance, just by short circuiting two points next to each other (by ‘bridging’ just one test probe across them) that are ’live’ may destroy any number of components which will definitely be harder to find and more expensive to fix. Secondly and more importantly, because the amplifier obviously has to be opened, there a lethal voltages present and again it doesn’t take much to inadvertently touch the wrong thing. If you haven’t found the problem by visual inspection, take it to a professional for repair
