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Brooke Amplifier Problem

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JayeJSAV View Drop Down
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    Posted: 08 August 2013 at 5:06pm
Hi there,

I have a Brooke E172700 Amplifier in for service, and could really do with a service manual. I've tried Impact, however they don't have any.

Does anyone have one lying about somewhere / stashed in an archive?

Cheers

Jaye
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Tan-2 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Tan-2 Quote  Post ReplyReply Direct Link To This Post Posted: 08 August 2013 at 7:49pm
what is the fault, or is it just a clean service?
Logic will get you from A to B. Imagination will take you everywhere.
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JayeJSAV View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote JayeJSAV Quote  Post ReplyReply Direct Link To This Post Posted: 08 August 2013 at 8:02pm
Stuck in protect.

Given it a full clean so far and replaced couple of scratchy pots on front. If I remove chB from relay board it resets however it's not keen otherwise. No DC found on output (metered Pre-relay) and I can't find my amp transistor tester. It's right handy :(
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Tan-2 Quote  Post ReplyReply Direct Link To This Post Posted: 08 August 2013 at 8:12pm
upload pic of amp so we can get better idea....also if there is a working channel use this to carry out check and compare non working channel.
Logic will get you from A to B. Imagination will take you everywhere.
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JayeJSAV View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote JayeJSAV Quote  Post ReplyReply Direct Link To This Post Posted: 08 August 2013 at 9:11pm
It's currently in pieces, as I'm testing the transistors, however it is labelled as an "S 4.2 AMP Technology from USA - 20070727", using MJ15024G Output Transistors.

Here's a pic of the board.....

https://docs.google.com/file/d/0B7kobMSfkbt8MEI3dFJZd1FrcmM/edit?usp=sharing


Edited by JayeJSAV - 08 August 2013 at 9:12pm
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Tan-2 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Tan-2 Quote  Post ReplyReply Direct Link To This Post Posted: 08 August 2013 at 9:24pm
link is not working....if the amp powered up before being taken apart no fuses have blown then is may have gone dc.. check the small driver transistors followed by the vas circuit..
Logic will get you from A to B. Imagination will take you everywhere.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Tan-2 Quote  Post ReplyReply Direct Link To This Post Posted: 08 August 2013 at 9:31pm
The protection circuit will hold off the relay if dc offset is say 1 volt of more, test point at the amp o/p before the relay latch this would be between the low value .33 ohm white large resistors these feed back to the emitter legs of the t-03 o/ps.

see how you get on.
Logic will get you from A to B. Imagination will take you everywhere.
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JayeJSAV View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote JayeJSAV Quote  Post ReplyReply Direct Link To This Post Posted: 08 August 2013 at 10:08pm
Yep, full power up, fan, relays switch out, red protects leds, then it stops there. just sits in that condition till kingdom come. Still hunting down my test kit! It's here somewhere.... :(


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JayeJSAV View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote JayeJSAV Quote  Post ReplyReply Direct Link To This Post Posted: 08 August 2013 at 10:58pm
So, now I have found my tester (mini applause!!!), I have got 7 out of 12 shoting T-03's, and heading into the drive section. Nice!!

Thanks though x
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Tan-2 Quote  Post ReplyReply Direct Link To This Post Posted: 08 August 2013 at 11:04pm
Did the amp just go in to protection? also when fitting new o/ps the amp stage will need biasing and scope/gen test..
Logic will get you from A to B. Imagination will take you everywhere.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote JayeJSAV Quote  Post ReplyReply Direct Link To This Post Posted: 08 August 2013 at 11:26pm
It came in with that condition. Partly why it made the journey.

Yep have the gear to re bias it :)
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Post Options Post Options   Thanks (0) Thanks(0)   Quote JayeJSAV Quote  Post ReplyReply Direct Link To This Post Posted: 10 August 2013 at 2:49am
Sigh, this is going to become "one of those" repair jobs. If it isn't already!

Replaced several parts now, out of 12 output transistors, 7 were short circuit...
The 2 x 2SA5002 and 1943's had popped open circuit, and after replacing all the burned resistors, I have.......

Square one!!!!! Back again.

Now concentrating on the power side of the board. It still sticks in protect, but the MJE350 is getting quite warm quite quickly. It was warm before, however I didn't notice it to be this hot.

My word, with even a sniff of a service manual I could be eating donuts whilst it soak tested and I watched NCIS. However, I'm off to the bar to bathe my brain in jäger in the hope I will have a top idea, whilst some weirdo comes in and holds a dimly lit lamp above my head.
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