220 to 110 - Page 1
Forum section: electronics / general

author: Matakeshi
author_rank: Newbie
timestamp: November 07, 2016, 10:12:31 pm
content: Hello guys, got some problem that I have no idea who to ask for help.So basically I've bought a single subwoofer amplifier to start my audio system. But dumbass me didn't look at one super important thing, is that it can only run on 110vac instead of 220vac that we I here. After doin some reasearch I've found out that smaller version of the same amp can be made to work on 220vac by simply cutting off some 0 ohm links and soldering a jump wire. [linkhttp://www.jjensen.se/projekt/bash_300s.html]. Though maybe Its possible doing same on the bigger one that I got, its bash 500s. Searching through internet far and wide I came across some norwegian forums, where google translate told me the dude there got schematics from-then-makers of this amplifier. Also tried to contact current distributors but unfortunately they did not have any schematics on modifying their amps. Somewhere I have read that if theres 2 200v caps it means its some sort of voltage doubler that gets rectified to total 300~ vdc. Im the simplest kind of electrician and I have absolutely no knowledge about electronics of this kind, tried to even google whats written on all the pcbs. Cant send it back as it would cost a load of money, don't want to invest in a step down transformer as its not really cheap, but I believe it will end up with me getting one. Anyone has dealt with anything similar? Is it even possible to make it work without buying a step down transformer? Thanks for any ideas guys

author: tronde
author_rank: Frequent Contributor
timestamp: November 08, 2016, 01:26:59 am
content: I guess the power supply is configured as a voltage doubler at the input so it is possible to change from 120V to 240V input as you suggest.You can find some information here about how a voltage doubler input works.http://www.hardwareinsights.com/wp/how-a-switchmode-power-supply-works/Scroll down to "The primary capacitors".Do you have a link to the Norwegian forum? I am Norwegian, so maybe I can get in touch with the guy.

author: IanB
author_rank: Super Contributor
timestamp: November 08, 2016, 01:33:27 am
content: Normally one would reverse engineer the input circuit and draw out the schematic. From there it will be possible to see if it could be reconfigured for 220 V.The first warning sign is those capacitors, marked at 200 V. They would have to be charged in series with a balancing arrangement before there is any chance of this supply working at 220 V. Without reverse engineering the input circuit it is going to be really hard to tell.To give you a feel for how to approach the problem, here is an example of someone doing it:

author: MosherIV
author_rank: Super Contributor
timestamp: November 08, 2016, 12:22:05 pm
content: If you know the PSU output voltage and current capability - it may be easier to find a replacment PSU module.Try to avoid cheap chinese SMPS - they are not very well engineered

author: NiHaoMike
author_rank: Super Contributor
timestamp: November 08, 2016, 02:35:05 pm
content: Show the reverse side of the board. Then it should be easy for us to find the link that needs to be cut, if such a mod is possible.

author: Matakeshi
author_rank: Newbie
timestamp: November 08, 2016, 07:30:53 pm
content: Pried off various glue blobs and silicone, someone didn't want me to see the back of it. I got to the back of PCB now. As in the video, tried drawing a tiny scheme but I don't know what the yellow cubes are, whats the 4-pin rectangular plate (rectifier?), blue (resistors~?) or what the round yellow thing is. Immediately I noticed that the second 200v capacitor is not going anywhere, its simply not connected to anything, how is this possible? The gray 204 ohm resistor inbetween capacitors is not connected anywhere as well. Are they left there behind on purpose? Like NiHaoMike asked, I'm showing the back side of PCB. Also I mirrored the front side image for easier reading, and drew a single 1M ohm resistor that's not showed in the pic, its a simple resistor from what I understand, not like the one in the video. Is it possible to convert this amp to work on 220vac? cause I'm not sureAlso tronde thank you for your effort, but the forum posts date back to 2006, I believe this model was made by different company and it looked something like thishttp://smg.photobucket.com/user/Skrue/media/BASHbak.jpg.htmlBut here's the link anyways, don't put too much effort for me!http://avforum.no/forum/archive/index.php/t-41181.html

author: suicidaleggroll
author_rank: Super Contributor
timestamp: November 08, 2016, 07:44:15 pm
content: Quote from: Matakeshi on November 08, 2016, 07:30:53 pmThey're connected to the copper pour on the top layer of the board. You can't see the cap, but you can see the thermal relief pad for the resistor. If you test the resistance between the "unconnected" lead of the lower cap and the top leg of that resistor you should find they're connected to each other, as well as everything else attached to that top layer.

author: NiHaoMike
author_rank: Super Contributor
timestamp: November 09, 2016, 03:07:57 am
content: It looks like you just have to remove H7 and the little ceramic cap right next to it. (Not sure why that cap is there, as it's being shorted by the link.)

author: tronde
author_rank: Frequent Contributor
timestamp: November 09, 2016, 12:46:48 pm
content: We should draw a schematics first. I think I can see one 220kohm i parallel with one of the capacitors, and one 68kohm in parallel with the other. They should be of equal value to ensure equal voltage over the capacitors since they are connected in series.

author: NiHaoMike
author_rank: Super Contributor
timestamp: November 09, 2016, 02:20:17 pm
content: Also have to consider the equivalent resistance of the startup circuit or whatever else might be connected across the cap with the 220k resistor. I think there might be a good reason why the values are different.

author: tronde
author_rank: Frequent Contributor
timestamp: November 09, 2016, 07:10:10 pm
content: I think this is how it's connected.

author: Matakeshi
author_rank: Newbie
timestamp: November 09, 2016, 10:05:14 pm
content: Wow this was way harder than I imagined. Started drawing on the PCBs picture and tronde already did a better job. Also drew a supposed schematics. The blue things I numbered from 1 to 5 are capacitors? Whats their purpose of being connected straight to ground? Also, as you said in last post the two resistors connected parallel to each 200v cap are at different resistances.Like NiHaoMike said, the resistor parallel to the shorted cap should be removed, including the cap itself? And 2 resistors parallel to both 200v caps should be at what resistance?

author: IanB
author_rank: Super Contributor
timestamp: November 09, 2016, 10:57:09 pm
content: I believe the blue things are protection devices (MOVs?). Their purpose is to trap any voltage spikes coming in from the mains and short them to ground before they can do any damage to the other components in the circuit.The big yellow blocks I believe are capacitors as you have them.

author: tronde
author_rank: Frequent Contributor
timestamp: November 09, 2016, 11:22:11 pm
content: Use my image and write down the component's references (C1, R2 ....).Take a closeup photo of the blue thing. They are marked as Cxxx so I believe they are capacitors. They are not important for the circuit, but since we try to draw a schematics, we can get it right. I assume the brown disk (Z1) is a VDR / MOV and the green disk is a PTC resistor. Take a picture of them as well. Check that I got the purple track connected to the PTC right. Some of it is hidden in the photo.Give us the references, and I will draw the schematics for you.Edit:I can see I forgot one of the blue. The one you marked as "1".

author: tronde
author_rank: Frequent Contributor
timestamp: November 10, 2016, 01:44:17 am
content: Quote from: blueskull on November 09, 2016, 11:33:19 pmI would also check the voltage rating of the two yellow capacitors, the (assumed) VDR, the (assumed) blue capacitors and the rectifier. Can be a nasty surprise if they saved money on those.

author: tronde
author_rank: Frequent Contributor
timestamp: November 10, 2016, 12:25:57 pm
content: Quote from: blueskull on November 10, 2016, 02:12:58 amAssumption is the mother of all fuckups.....

author: tronde
author_rank: Frequent Contributor
timestamp: November 10, 2016, 07:33:18 pm
content: Schematics according to your drawing.You can see the link between AC input and the centre point of the two electrolytic capacitors.When connected it is a voltage doubler. When disconnected it is just a normal rectifier.See also description in my first link.

author: Matakeshi
author_rank: Newbie
timestamp: November 11, 2016, 06:24:17 pm
content: Sorry for replying only today, couldn't yesterday. The pink trace is correct that you have drawn. The 2 yellow caps are silicone glued to the coils, would need to desolder and cut them apart from the coils to see the info side. But second largest yellow cap behind 200v caps is 250V, as it it visible. Also, what about the resistors parallel to the 200v caps? As the video suggests they should be of equal value, do I need to swap them? or only one, none maybe? Attached the photos. What else should be done?

author: SeanB
author_rank: Super Contributor
timestamp: November 11, 2016, 07:28:32 pm
content: Leave them all and remove the zero ohm resistor only. The units in the pic are yellow, a 470V varistor, the blue are class Y suppression caps of 2.2nF 2kv and the green is a 4R8 NTC inrush limiter.

author: tronde
author_rank: Frequent Contributor
timestamp: November 11, 2016, 07:41:20 pm
content: Quote from: Matakeshi on November 11, 2016, 06:24:17 pmThe green disk is a NTC resistor. I wrote PTC, but of course a NTC is correct. Its there to reduce the inrush current caused by the capacitors.The Brown disk is as I wrote a VDR /MOV. 14k471 means 14mm diameter and 470V. It will clamp at about 385VDC, so OK. Small VRDs are usually rated by diameter because size determine how much energy they can absorbe.The blue disk is a capacitor. 222 means 2.2nF. It carries the German VDE mark (the triangualr mark) as well as the harmonized EN-EC mark used within the EU, so it should be OK.As "blueskull" said, it would be stupid if the yellow capacitors are anything else than capable of 230V. We don't know, but at least hte blue capacitors seems OK.When you connect capacitors in series and apply DC voltage, the voltage will be distributed across them. The problem is that the capacitor with the least capacity (value in Farad) will have the highest voltage. To avoid this problem, we can connect a resistor in parallel with each capacitor. If the resistors are of equal value, the voltage will also be the same regardless of the value of the capacitors. This is why you have read that the resistors should be of equal value. The problem with voltage across the capacitors is there when used as a voltage doubler too, and as "NiHaoMike" said, the little module will also draw some current so probably the voltage will be OK even if the resistors are not equal since the circuit is designed to work OK at 120V input.

author: Matakeshi
author_rank: Newbie
timestamp: November 12, 2016, 04:32:46 pm
content: Thank you all so much for helping me out. The amp works fine. But looking the cable, it seems the whole plate isn't grounded, maybe it is the reason the lights dim a little when playing loud? I'll sort the grounding problem, but is that the reason lights dim? I've cut both, 102 1kv ceramic cap and the zero ohm link that were parallel to each other. Another thing I noticed, is that when I click the turn on button, the lights dim for a split second aswell, maybe this is nothing serious? Thanks for the help again, I really appreciate it!

author: tronde
author_rank: Frequent Contributor
timestamp: November 12, 2016, 07:46:36 pm
content: Lack of grounding should not cause the lights to dim. If you look at the schematics, its only the low value blue capacitors that are connected to ground via the screw. They are only part of the noise filter.The metal case of the amplifier should be connected to mains ground / earth both for safety as well as noise filetering. What does the mains input connection look like? Is it a plug / socket or just a wire?The circuit will charge the two electrolytic capacitors when you apply supply voltage, and depending on the mains circuit in your house the voltage can drop enough for you to see the lights dim. The green NTC is there to reduce the inrush current, but it can still be high enough to cause the light to dim.

author: Matakeshi
author_rank: Newbie
timestamp: November 14, 2016, 10:13:55 pm
content: Its a socket that I plug in from wall socket. I can already see it lacks the middle connection that should be ground. Never mind, a little dimming doesn't affect music quality. Was just wondering