Help! I finished a kit with meanwell power supply a few weeks back and everything sounded great. Recently with no music playing I heard a random rustling sound through the right speaker for a few seconds then silence again. A few days of investigation found this sound completely randomly and intermittent through either speaker sometimes shortly after power up sometimes after a few hours. I have removed both boards and reflowed the solder on everything and also fitted a new dc socket but still the problem remains. As the problem is in both channels I was doubtful if it's a singular faulty part on one board but have reached the end of what my common sense tells me it could be, can anyone point me in a possible direction?
Have you tried a different source and a different preamplifier to see if the issue is upstream? This would mean listening to the preamp and source directly through a headphone if it has a headphone jack. If you hear the problem, then you have to determine if the problem is in the preamp or the source. First plug the source into a different input to see if the problem persists.
A methodical approach is needed to ensure that you are focusing on the correct source/locus of the problem.
A methodical approach is needed to ensure that you are focusing on the correct source/locus of the problem.
Thanks, yes forgot to say that I have put the minimax in another system and also tried another power supply but no joy.
Very good! You have narrowed it down to the ACA MinMax, it appears.
Do you have a spare plug to socket adapter for the power supply? If so, I would fit that and retest.
If not, then take high quality photos of the inside and post. And to confirm, this intermittent sonic defect occurs in both channels, randomly, but not correlated in both channels simultaneously?
Do you have a spare plug to socket adapter for the power supply? If so, I would fit that and retest.
If not, then take high quality photos of the inside and post. And to confirm, this intermittent sonic defect occurs in both channels, randomly, but not correlated in both channels simultaneously?
Thanks, the other power supply I tried had a DC plug anyway so no need for a din adapter so I think I can rule that out. Interesting that you mention the DC side of things as my first thought was my soldering on the panel socket as it was tricky getting the double cable neatly soldered onto the socket lugs, in any case I fitted a new socket and no change.
Yes the rustling sound seems completely random and when it strikes I'm pretty certain its either 1 channel or the other but never both together or both the same.
The only other thing I didn't mention is that I have wired the back panel as a single stereo amp only i.e no switch or din socket. Will take pictures when I get home.
Yes the rustling sound seems completely random and when it strikes I'm pretty certain its either 1 channel or the other but never both together or both the same.
The only other thing I didn't mention is that I have wired the back panel as a single stereo amp only i.e no switch or din socket. Will take pictures when I get home.
As an abstract manner, simplifying the build in that manner should reduce the possibilities for error.
In the meantime, can you check to be sure that all capacitors on the board have 35v minimum rating? This includes the input and output blocking caps as well as the voltage filtering caps C2 and C3. Do not rely on the order or packing sheet.
In the meantime, can you check to be sure that all capacitors on the board have 35v minimum rating? This includes the input and output blocking caps as well as the voltage filtering caps C2 and C3. Do not rely on the order or packing sheet.
To confirm the caps C2 C3 C4 C5 all 50V, no voltage markings on the film caps at C1.
Attached are some pics inside the case
Attached are some pics inside the case
Try cleaning all the flux off of the DC input jack. Then see if you can wrap a small section of electrical insulating tape to separate the + and - terminals/leads.
Did you use a different front panel then what was provided in the kit? It looks like the power standby switch and LEDs are mounted on the floor of the chassis. Not that this would make any difference IMO or be the cause of your problem. But I would also reflux the standby switch as well.
Did you use a different front panel then what was provided in the kit? It looks like the power standby switch and LEDs are mounted on the floor of the chassis. Not that this would make any difference IMO or be the cause of your problem. But I would also reflux the standby switch as well.
Hi Halauhula, thanks for your persistence with this. This is the second DC input that I have tried, the original did have insulation separating the leads but I will try again. Its not a kit case just a plain one straight from Italy and to keep things simple I mounted the front switch and led's on the front bottom of the case. The wires to the switch have insulated female spade terminals instead of solder (not really clear in the photo), maybe I should solder these?
Do not desolder terminals from DC plug yet. Just clean with isopropyl alcohol (scrub with a toothbrush as needed).
Do not switch from spade terminals to solder on the power standby switch. Instead, disconnect terminals, re-crimp the wire to the attachment eyelet of the spade terminal, and reattach after slightly compressing spade portion to make sure there is good contact between switch contact and spade.
Test and see if this resolves the issue.
Do not switch from spade terminals to solder on the power standby switch. Instead, disconnect terminals, re-crimp the wire to the attachment eyelet of the spade terminal, and reattach after slightly compressing spade portion to make sure there is good contact between switch contact and spade.
Test and see if this resolves the issue.
If that does not resolve your issue, then look with magnifier at the end of each wire soldered to each PCB. Identify if there are any stray wire strands that are sticking out of the cut end and not soldered. cut them off and vacuum ends out of chassis. Looking at your photos, it <may> appear the wires to the power standby with on each board may have a strand that is not soldered to the pad. Check carefully to see that this is not so. This is on the top side of the PCB so it (and the MOSFETs) need not be removed from the heat sink. Again test.
If this still does not work, then you will have to remove the PCB and MOSFET from the heat sink (keep wires connected if possible), and touch up each solder pad on the board. Verify that there are no solder bridges across pads. Who you have finished soldering, clean the board (both sides) with 99% isopropyl alcohol/flux remover and a toothbrush or other safe brush (not made of metal). Reinstall and test.
Removing and reinstalling the PCB and/or MOSFET is a pain if you are not using Keratherm, which is a good reason to use it (especially for a novice). But if you are using ceramic or mica pads and heat sink goop, that is OK.
FYI, the intermittent nature of your issue, as well as the description - a "rustling" sound - makes it difficult to diagnose. My first thoughts are bad connections/soldering (including flux-related "shorts" as flux binds to water vapor from the air) at jacks, switches and on the boards.
If this still does not work, then you will have to remove the PCB and MOSFET from the heat sink (keep wires connected if possible), and touch up each solder pad on the board. Verify that there are no solder bridges across pads. Who you have finished soldering, clean the board (both sides) with 99% isopropyl alcohol/flux remover and a toothbrush or other safe brush (not made of metal). Reinstall and test.
Removing and reinstalling the PCB and/or MOSFET is a pain if you are not using Keratherm, which is a good reason to use it (especially for a novice). But if you are using ceramic or mica pads and heat sink goop, that is OK.
FYI, the intermittent nature of your issue, as well as the description - a "rustling" sound - makes it difficult to diagnose. My first thoughts are bad connections/soldering (including flux-related "shorts" as flux binds to water vapor from the air) at jacks, switches and on the boards.
Thanks, I had already removed the boards and reflowed all joints then cleaned so will start with the switch cables. I was surprised how thin the kit cable to the switch was, there may well be a stray strand or 2 at the board end as my wire cutters celebrate their 30th birthday soon!!
Very good! Be sure to carefully inspect the pads for solder bridges as well as bridges caused by stray wire strands.
So a little bit of progress! I replaced the the wires from the switch to the boards with a slightly thicker solid core (still crimped at the switch) and cleaned the switch and top of the board. I didn't remove the boards so nothing done on the bottom of them. I now get the rustling sound in the left channel only and only for the first few minutes after power on, the sound is worst to begin with and slowly gets quieter and less frequent. After about 2 or 3 mins everything is quiet and seems to stay that way. I guess the next step is to remove the left board and clean around the switch cable wire?
I would say, yes. Check very carefully around the pads: use a magnifying glass. I really hope this resolves your problem!
Well I tried the above and cleaned up but things are no better. However I just read post 222 and the subsequent solutions and this sounds much like where I'm at. When I rewired the switch things did get better to the point where the right channel seems ok now. I will rewire again but tightly twist the cable as per post 225.