120v Bose System

Thread Starter

skylinedgtr

Joined Nov 7, 2016
12
Hi all!

Brought my 120v Bose back to the UK with me from USA. Initially, it had a problem with the 32Khz IR receiver so I took the control module apart and replaced it. No problem with that now as the system turns on and off with the remote and seems to respond to remote commands.

Problem is this; when I try and play something through it, I get no sound whatsoever. I have tried different sources to make sure something should be playing but still nothing. This is what's strange though, when I unplug the system from the power, it plays a little bit through the speakers while it's draining the capacitance out of the system!

The UK has 240v 60hz so I had to buy a power adapter which stepped it down to 120v/100w. I suspect the power adapter I have got is not suitable (picture attached). The power board inside the Bose has a 250v 2.5a Timed fuse in it if that helps. I have probed the transformer inside the Bose and see 118v at the primary and 22v at the secondary.

Any suggestions what I can try next?

20161107_163115.jpg

20161107_163235.jpg
 

Dodgydave

Joined Jun 22, 2012
9,919
Why dont you replace the bose mains transformer for a 230v to 22v( 10:1) ratio, it maybe the dc supply rail is going too high for the audio amp, and shutting down.

If you can take pictures of the inside...
 

Thread Starter

skylinedgtr

Joined Nov 7, 2016
12
Thanks for the advice both of you. will take some pics of the transformer and post it up tonight. I did consider replacing the transformer but I was worried about what I saw at the secondary. If as you're both saying the transformer doesn't like UK 50hz, would the 22v I'm seeing at the secondary be accurate? I'm wondering if it would be 24v or less or more if it had a 60hz supply that it was looking for.
 

Thread Starter

skylinedgtr

Joined Nov 7, 2016
12
Wooohoo! Thanks for that, makes life a lot easier! Any ideas where I can buy one? :) Have done a search but I can only seem to find Import/Export data on it
 

Thread Starter

skylinedgtr

Joined Nov 7, 2016
12
Contscted BOSE UK, they said they don't sell the transformer and advised a 3rd party equivalent (... With a disclaimer that I shouldn't be playing with the internals).

So back to the 3rd party route, will a 22v 40VAC suit the 300w Max requirement?

Any help with the calculation is appreciated as I don't understand how to apply the pF value to the equation.

Thanks again
 

AlbertHall

Joined Jun 4, 2014
11,143
If its the same style of transformer (i.e. rectangular) then the power rating is well correlated with the volume, so measure your existing one and get one the same or slightly larger.
 

Thread Starter

skylinedgtr

Joined Nov 7, 2016
12
Ordered a transformer before the suggestion to measure the original came up. The one ordered was a 240v AC Chint which has multiple output options of 12v, 24v... Etc at 50VA.

Connected up the 24v and it behaved exactly the same way as when I first started this project - it only played music when draining the capacitance out of the system.

Connected up the 12v however and it now works BUT when i turn the volume up, it switches off. I'm guessing the transfomer isn't providing enough current to drive?
 
your over voltage safety in the bose is making you safe .. no output.
you voltage adapter transformer needs to reduce the output to about 100v or a little less. the one in the picture says 110v out. measure the output of the adapter. that will tell you more than anything else. so now you are putting two transformer in series and compounding your problem.
you are lucky your bose is keeping you safe. no smoke.

on the back of you equipment .

120v x 2.5a = 300w depending on the output voltage of the transformer will decide what transformer you need for 300w out.
300w in and out should be the same not counting minor losses. output 300w / 24v = 12.5a or 300w / 12v = 25a this changes the whole picture on what you need. if you know how to use a meter ( no accusations here) I would measure you caps at power on, and then measure them again when unplugged when you get sound.

don't forget this will be DCV and will be a little higher than the ACV output of the transformer.

not knowing your level of expertise in electrical. I'm a little hesitant to say too much. I may have already.
 
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