Help repairing a blown amplifier please?

Ebenezer_Scrooge_2

I have 3 blown amplifiers in my workshop at school, they are cambridge audio A1s i think. Boss said to bin them, but i hate chucking out things.

Each amp has blown a channel, opened the cover hoping to see some charred components, but nothing!
I have a very basic knowledge of electronics, but dont know where to start?

vaio

Ebenezer_Scrooge wrote: »

I have 3 blown amplifiers in my workshop at school, they are cambridge audio A1s i think. Boss said to bin them, but i hate chucking out things.

Each amp has blown a channel, opened the cover hoping to see some charred components, but nothing!
I have a very basic knowledge of electronics, but dont know where to start?

Well……they are worth not very much and your boss doesn’t even want them so have a play. You’ll probably not be able to get a schematic but you do have multiple units so you can check one against another.

Likely cause is output transistors blown, most times it’s just the power transistor, sometimes it will pop an upstream device too

isofa

I'd take them to a hi-fi specialist like Richer Sounds or someone equivalent (not a high street chain like Curry's!), they'll be able to repair them for a modest fee. They are high quality amps and it's a shame to bin them. Had my Technics amp repaired twice like this over the years, was (and is) as good as new.

buglawton

How about a mail order repair specialist?
http://a1electronics.co.uk/index.php?osCsid=c7b60846bf4691ed8b95e377cff379a5
You might be able to get a deal on 3 similar repairs in 1 go and combine the P&P too.

oldagetraveller

Do you have any small electronics repair shops nearby? TV repairs etc. They might be able to repair quite cheaply or even look for the faults for nothing. A few years ago I took a Marantz amp to one after being quoted something horrendous for someone to just have a look without any gaurantee they'd be able to repair. The little "backstreet" shop found the fault and repaired for less than £20.
There might be a problem without any circuit diagrams though.
Cambridge A1s are not that good quality, cheap and cheerful from Richer Sounds who I suspect have the rights to use the old name of a once respected company. http://www.richersounds.com/splashpage.php
A repair might not be that cost effective?

vyseyboy

Be careful you don't get ripped off if you choose to get them repaired... a brand new Cambridge Audio A1v3 can be had for £30, presumably with warranty, and most small electronics repair shops I have a minimum fee of about £20.

I'm very much an advocate of taking the cover off and having a look though, it sounds like you have nothing to lose- I say go for it yourself.

Ebenezer_Scrooge_2

Thanks everyone, even if they are not worth much i still want to have a go at repairing them myself, as i see it as a challenge, and i hate the throw away society we live in today
Where would i find a circuit diagram for the amplifier?

epninety

Cambridge Audio A1? The best thing you can do with them is find three doors that need holding open :rolleyes:

Blown output channel is a common fault. Trouble is, when they go, they put DC power onto the speakers line and blow your speakers as well :mad: £60 amplifier cost me £300 worth of metal coned Scanspeak drivers

I fixed mine just for the mental exercise, then gave it away to the first sucker who said he wanted it (with suitably dire warnings).

My bet is you will find the output devices are blown. IIRC they use an IC (integrated circuit) output stage, and this will be blown.If you can solder, you can remove a good one from one amp and fit itin place of a blown one. It's the largeish black block bolted to the metal heatsink with about 10 legs on soldered to the pcb.
(I think - mine was a few years ago and I see far too much electronics to remember the details... post a digicam picture of the inside somewhere if you want some hints.)

ormus

sell them on ebay as "faulty needing repair".
theres enough wallys on ebay to buy them.