Cambridge Audio A500 - Worth Repairing ?

ambriel · 11th January 2012, 11:21 PM

I picked up a Cambridge Audio A500 amplifier the other day, mainly because I liked the look of it.

It didn't cost me anything but both 4A fuses on the main board are blown, suggesting the SAP15s are probably deceased.

I haven't tried replacing the fuses and just firing it up yet (nowhere round here to stock them) but assuming the power amps are blown is this amp worth spending the money on to replace them?

I'm competent with a soldering iron so it'd just be the component costs.

system7 · 13th January 2012, 04:09 PM

Always worth fixing good ol' equipment if its cheap! I don't suppose basic audio amp technology has changed in 40 years, so if it's an OK design and the 10-y-o A500 is, go for it.

Schematic: http://x0546.orbbox.com/files/storag...A500intsch.pdf

Seems the output transistor's built-in emitter resistances mostly tends to blow.

Cambridge audio A500 amp with broken right channel

But I'd first replace the fuses, which will be 20mm 4A T (Time-delay T, not Fast F) types on anything around the power supply. You might get lucky and find they just popped at a loud party or something.

jaycee · 14th January 2012, 02:55 AM

Can guarantee the SAP15's have expired due to the lousy heatsink in this unit. If someone had it on loud for a party, they're toast. A good bit of kit let down by Cambridge skimping on the heatsink!

Unfortunately both the SAP15 and SAP16's are obsolete. The nearest is STD03 with external 0.22R emitter resistors, if you can get them.

reddish75 · 14th January 2012, 07:31 AM

Rapid electrinics still sell the sap 16's

homemodder · 14th January 2012, 11:16 AM

Get them from here, no problem. Better to upgrade to STD03 though.

Profusion plc, Audio Semiconductors and Components

ambriel · 7th February 2012, 09:41 PM

Sorry it's been a while since I replied to this thread but I've only just gotten round to looking at it.

Before doing anything else I popped a couple of new fuses in and connected it up to my iPod and a couple of speakers I had laying about.

Result? Sound, from both channels, and quite reasonable sound too.

Next step is to try it with some better speakers and a turntable. Fingers crossed it's just as System7 suggested and that someone was driving it really loud at a party sometime.

jaycee · 7th February 2012, 11:07 PM

Very lucky - usually the SAPs fail, short circuit which then blows the fuses!

11th January 2012, 11:21 PM	#1
ambriel diyAudio Member Join Date: Jan 2012	Cambridge Audio A500 - Worth Repairing ? I picked up a Cambridge Audio A500 amplifier the other day, mainly because I liked the look of it. It didn't cost me anything but both 4A fuses on the main board are blown, suggesting the SAP15s are probably deceased. I haven't tried replacing the fuses and just firing it up yet (nowhere round here to stock them) but assuming the power amps are blown is this amp worth spending the money on to replace them? I'm competent with a soldering iron so it'd just be the component costs.

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13th January 2012, 04:09 PM	#2
system7 diyAudio Member Join Date: Aug 2008	Always worth fixing good ol' equipment if its cheap! I don't suppose basic audio amp technology has changed in 40 years, so if it's an OK design and the 10-y-o A500 is, go for it. Schematic: http://x0546.orbbox.com/files/storag...A500intsch.pdf Seems the output transistor's built-in emitter resistances mostly tends to blow. Cambridge audio A500 amp with broken right channel But I'd first replace the fuses, which will be 20mm 4A T (Time-delay T, not Fast F) types on anything around the power supply. You might get lucky and find they just popped at a loud party or something.

14th January 2012, 02:55 AM	#3
jaycee diyAudio Member Join Date: Apr 2004 Location: Norwich, UK	Can guarantee the SAP15's have expired due to the lousy heatsink in this unit. If someone had it on loud for a party, they're toast. A good bit of kit let down by Cambridge skimping on the heatsink! Unfortunately both the SAP15 and SAP16's are obsolete. The nearest is STD03 with external 0.22R emitter resistors, if you can get them.

14th January 2012, 07:31 AM	#4
reddish75 diyAudio Member Join Date: Aug 2006	Rapid electrinics still sell the sap 16's

14th January 2012, 11:16 AM	#5
homemodder diyAudio Member Join Date: May 2006	Get them from here, no problem. Better to upgrade to STD03 though. Profusion plc, Audio Semiconductors and Components

7th February 2012, 09:41 PM	#6
ambriel diyAudio Member Join Date: Jan 2012	Sorry it's been a while since I replied to this thread but I've only just gotten round to looking at it. Before doing anything else I popped a couple of new fuses in and connected it up to my iPod and a couple of speakers I had laying about. Result? Sound, from both channels, and quite reasonable sound too. Next step is to try it with some better speakers and a turntable. Fingers crossed it's just as System7 suggested and that someone was driving it really loud at a party sometime.

7th February 2012, 11:07 PM	#7
jaycee diyAudio Member Join Date: Apr 2004 Location: Norwich, UK	Very lucky - usually the SAPs fail, short circuit which then blows the fuses!

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