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Alesis mixer buzz

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70,s hero View Drop Down
Young Croc
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 70,s hero Quote  Post ReplyReply Direct Link To This Post Topic: Alesis mixer buzz
    Posted: 15 June 2018 at 7:24pm
Hi all, been a while I know, busy studying anyhow I hoped someone could assist me in repairing a mixer, its the Alesis USB multimix 16, I use it for recording live music and it developed a slight hum , sounding like 50HZ , anyhow now its a very loud buzz and I have isolated the fault to the on board power supply PCB, there is an adapter /transformer which plugs in to the back of the unit which supplies 18v ..ac I assume, it has 3 wires and the on board PCB appears to have two full wave rectifiers?

I can see a cap rated @ 35v 2200 UF which has a large bulge at the bottom, that is as far as I have got and would like to try and fix it, I cant source a new power PCB.. have tried, I know its not an expensive unit but I am used to it and I tight arsx...any help appreciated.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 70,s hero Quote  Post ReplyReply Direct Link To This Post Posted: 15 June 2018 at 11:49pm
HA ha, so replying to myself, I found this

As a capacitor ages, its electrolytic series resistance (ESR) increases. If the capacitor forms part of a power supply then higher ESR results in worse smoothing and the ripple voltage increases. Higher levels of ripple will be heard as "hum" at line frequency. Line frequency is 50Hz for UK 
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Post Options Post Options   Thanks (1) Thanks(1)   Quote GAZ. Quote  Post ReplyReply Direct Link To This Post Posted: 16 June 2018 at 12:46am
The bulging capacitor is your problem. Get a replacement from cpc or eBay, solder it in and all will be well again. Observe the polarity of the capacitor, it must be fitted the right way round.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 70,s hero Quote  Post ReplyReply Direct Link To This Post Posted: 16 June 2018 at 8:58am
Originally posted by GAZ. GAZ. wrote:

The bulging capacitor is your problem. Get a replacement from cpc or eBay, solder it in and all will be well again. Observe the polarity of the capacitor, it must be fitted the right way round.

Thanks, looked at Maplin, their phone line advises that the store is open but is in fact closed, will post when I have managed to fix it, hopefully.
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Post Options Post Options   Thanks (1) Thanks(1)   Quote Pinyorouk Quote  Post ReplyReply Direct Link To This Post Posted: 16 June 2018 at 11:05am
Originally posted by 70,s hero 70,s hero wrote:

Originally posted by GAZ. GAZ. wrote:

The bulging capacitor is your problem. Get a replacement from cpc or eBay, solder it in and all will be well again. Observe the polarity of the capacitor, it must be fitted the right way round.

Thanks, looked at Maplin, their phone line advises that the store is open but is in fact closed, will post when I have managed to fix it, hopefully.

You can buy from Cricklewood electronics, mail order. Usually next day delivery: https://www.cricklewoodelectronics.com/2200Y35.html
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 70,s hero Quote  Post ReplyReply Direct Link To This Post Posted: 16 June 2018 at 1:45pm
Originally posted by Pinyorouk Pinyorouk wrote:

Originally posted by 70,s hero 70,s hero wrote:

Originally posted by GAZ. GAZ. wrote:

The bulging capacitor is your problem. Get a replacement from cpc or eBay, solder it in and all will be well again. Observe the polarity of the capacitor, it must be fitted the right way round.

Thanks, looked at Maplin, their phone line advises that the store is open but is in fact closed, will post when I have managed to fix it, hopefully.

You can buy from Cricklewood electronics, mail order. Usually next day delivery: https://www.cricklewoodelectronics.com/2200Y35.html

Top man, BTW , all Maplins are shut but both the net and their phone lines say they are open.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Pinyorouk Quote  Post ReplyReply Direct Link To This Post Posted: 16 June 2018 at 2:18pm
Originally posted by 70,s hero 70,s hero wrote:

Originally posted by Pinyorouk Pinyorouk wrote:

Originally posted by 70,s hero 70,s hero wrote:

Originally posted by GAZ. GAZ. wrote:

The bulging capacitor is your problem. Get a replacement from cpc or eBay, solder it in and all will be well again. Observe the polarity of the capacitor, it must be fitted the right way round.

Thanks, looked at Maplin, their phone line advises that the store is open but is in fact closed, will post when I have managed to fix it, hopefully.

You can buy from Cricklewood electronics, mail order. Usually next day delivery: https://www.cricklewoodelectronics.com/2200Y35.html

Top man, BTW , all Maplins are shut but both the net and their phone lines say they are open.

It is a pity. Staff in some of the shops like Stevenage didn't know when they were closing for good. I wanted to buy some clearance components from the but they'd say they were still in the process of sorting them. That was about a week ago. Saying that, I did buy a lot of stock and component storage from one of their stores a day before their closing. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 70,s hero Quote  Post ReplyReply Direct Link To This Post Posted: 16 June 2018 at 7:46pm
Blimey, fair enough Maplin went under but the liquidators should have the decency to at least change the recorded phone message on their number, I waited for ten mins and was able to be put in a Que for all three x stores in Bristol. Also on the net it said they were open on their own site...the upshot was that I drove to all three today and came back empty handed, oh well ...RS components have some in stock and they are local so its over to them Monday...personally I think its madness not being able to buy a simple component in a store on a Saturday... even dropped by Montpelier...used to be some amazing electronic shops there...no more. Remember buying some bits there in the 70's ....god ime old.  
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Post Options Post Options   Thanks (1) Thanks(1)   Quote odc04r Quote  Post ReplyReply Direct Link To This Post Posted: 16 June 2018 at 10:12pm
Ebay is often your best bet for small amounts of electronic components I find, just filter the items to UK based first to get decent postage.

Alternatively it it is a radial connection capacitor (both wires in one end) then I am 99% positive I have some 2200uF in the stash, quite likely 35V or better. Can drop one in the post for you if you like.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 70,s hero Quote  Post ReplyReply Direct Link To This Post Posted: 17 June 2018 at 1:08pm
Originally posted by odc04r odc04r wrote:

Ebay is often your best bet for small amounts of electronic components I find, just filter the items to UK based first to get decent postage.

Alternatively it it is a radial connection capacitor (both wires in one end) then I am 99% positive I have some 2200uF in the stash, quite likely 35V or better. Can drop one in the post for you if you like.

That is very kind of you, I need to fix it tomorrow so thanks again for the offer, I am off to RS Components who say they have them, I go on a stag do Wednesday TBH hoping to take it steady, at my age 56 the neurons fire less often even without drink Wink 

I am not that well versed in Electronics but have an understanding of how some parts of the PSU works, TBH if it was a voltage regulation problem then I would need arm bands.
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