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Old 02-18-2018, 02:17 PM   #41
R_J
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Default Re: Philips FR-740 working but no audio output

It should'nt be hard to find a transitor to use for now, almost any pnp rated higher than 60v should work.
So with that transistor out of circuit do you have audio out of the speakers?
did the voltage on 7310 (C) drop a bit lower from before?
With that transistor out of circuit, any comand from the front panel should have no effect on turning the amp ic's on or off, so if there still is no audio (and you have it at the stk inputs) then that voltage on the CCC line must still be too high

Last edited by R_J; 02-18-2018 at 02:24 PM..
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Old 02-25-2018, 05:08 AM   #42
seve91
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Default Re: Philips FR-740 working but no audio output

replaced 7309, 7304, 7310, 7902, 7909. same voltages remain.
Could be a bad capacitor somewhere? Why the voltage is too high?
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Old 02-26-2018, 07:02 AM   #43
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Default Re: Philips FR-740 working but no audio output

Quote:
Originally Posted by R_J View Post
It should'nt be hard to find a transitor to use for now, almost any pnp rated higher than 60v should work.
So with that transistor out of circuit do you have audio out of the speakers?
did the voltage on 7310 (C) drop a bit lower from before?
With that transistor out of circuit, any comand from the front panel should have no effect on turning the amp ic's on or off, so if there still is no audio (and you have it at the stk inputs) then that voltage on the CCC line must still be too high
No still no audio voltage on CCC too high, don't know why. Without transistor, C of 7310 is -37.7V.
Tried replacing cap 2350 without success

Last edited by seve91; 02-26-2018 at 07:28 AM..
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Old 02-26-2018, 10:23 AM   #44
R_J
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Default Re: Philips FR-740 working but no audio output

I don't know why either, what ever it is effects both amp ic's correct? as both are turned off.
What are the voltages on transistor 7261 & 7260 ?
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Old 02-26-2018, 11:19 AM   #45
seve91
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Default Re: Philips FR-740 working but no audio output

sorry friend, i've just reassembled it. I give up.
Too much time wasted, and can't find a solution still.
Thanks to you for all your kindness and patience, your tips were useful to improve my troubleshooting skills.
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Old 02-26-2018, 11:23 AM   #46
R_J
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Default Re: Philips FR-740 working but no audio output

Maybe put it away for a while and come back to it later, sometimes a break is needed and when you look at it another time the answer may come easier. It is likely something simple that is being over looked.
I also looked at the service manual for the FR975, it is very similar and a lot clearer to read, although the voltages are a bit different (slightly higher for more power) they are very close

Last edited by R_J; 02-26-2018 at 11:25 AM..
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Old 02-27-2018, 04:49 AM   #47
seve91
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Default Re: Philips FR-740 working but no audio output

Quote:
Originally Posted by R_J View Post
Maybe put it away for a while and come back to it later, sometimes a break is needed and when you look at it another time the answer may come easier. It is likely something simple that is being over looked.
I also looked at the service manual for the FR975, it is very similar and a lot clearer to read, although the voltages are a bit different (slightly higher for more power) they are very close
i don't know...maybe you're right.
For sure I don't have so much experience... I go on with attempts.
The amplifier is not mine, the owner is a friend.
If she wants to bin it, then i will take it back.
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