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Old 4th June 2008, 02:33 PM   #1
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Default Cambridge Audio A5 repair job

Hi all,

I have a Cambridge Audio A5 amplifier that has a fried SAP15 transistor. I took it to richer sounds to get repaired but they want 80 to do the job, unfortunately I don't have that money so I'm looking at repairing it myself. I can use a soldering iron fine but I was hoping anyone with experience of this could tell me if any other components are likely to be broken too, and also where I could source the SAP15 transistors from. I checked rapid electronics but they only have SAP16.

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Theres a pic for you to take a look at if it helps.

Thanks loads!
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Old 4th June 2008, 03:53 PM   #2
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Most of the time the driver transistors goes the same way as the output transistors You may need to change those to....

It will take some skills to measure and identify what has blown up.....

Why did it blow up in the first place ?
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Old 4th June 2008, 03:56 PM   #3
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cricklewood electronics have them about 6
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Old 4th June 2008, 04:23 PM   #4
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ok, first of all you really need check if there is any evidence of burning around any resistors then replace both positive and negative transistors on the blown channel. also i would recomend replacing the driver transistors mje350, and mje340. having done this check if there is any evidence of burning around any resistors, after you have done this and before doing anything else build a dim bulb tester this site gives you the basic idea http://www.antiqueradio.org/dimbulb.htm obviosly ground goes to ground which this site dosent show!
then with your amp pluged into this power it up, if the bulb lights up and stays on you still have a problem, if not you now need to adjust theidle current which is done by monitoring the voltage between pins s and e of the output transistors (see their datasheet) to achieve a voltage of 13mv.
now check your dc offset this should be anywhere between 0-20mv, now normally would connect a dummy load to the amp to test it fully but seems your a beginner at this i doubt you have one so connect back to your speakers at your own risk as they say!

chris
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Old 4th June 2008, 05:17 PM   #5
x-pro is offline x-pro  United Kingdom
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Farnell has in stock both SAP15N and SAP15P for 4-58 each +VAT.

Cheers

Alex
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Old 5th June 2008, 02:37 PM   #6
dodo is offline dodo  Poland
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little of topic , but can someone advise me the matching procedure of the SAP N and SAP P darlington trnsistors
Is it this same Vbe and Hfe as standard BJT transistors ?

Thank You in advance
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Old 11th April 2009, 02:17 AM   #7
tvi is offline tvi  Australia
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This is for the A500
Part 1

Regards
James
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Old 11th April 2009, 02:19 AM   #8
tvi is offline tvi  Australia
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part 2
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Old 11th April 2009, 02:32 AM   #9
jaycee is offline jaycee  United Kingdom
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SAP16 is usable in this amp.
Cambridge dont appear to match them.

If they blew, be sure to check the bias trimpot isn't dead, or your replacements will blow.
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Old 11th May 2009, 06:42 PM   #10
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Hi Pulseezar,

I have just been given the same amp with exactly the same problem, have you had any luck with your repair job?

Also, to Jaycee, I have some SAP16's with which to replace the SAP15's (I was told they were a drop in replacement) should I replace all four of these so there is symmetry?

Thanks,

Charlie
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