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totalAudio View Drop Down
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Points: 27 		Post Options Post Options   Thanks (0) Thanks(0)   Quote totalAudio Quote  Post ReplyReply Direct Link To This Post Posted: 19 April 2020 at 12:40pm
Originally posted by simonp1100 simonp1100 wrote:

"im guessing (with limited knowledge) that a power cap or two may have started to run dry given the age and unknown service history on these"

I doubt that the power caps are running dry.

Check the below first:--

1. <span style=": rgb251, 251, 253;">Each driver PCB board check R14 & R50 (were 24K 1/2 Watt now changed to 27K 1 Watt), these tend to go open / high resistance if the value in your amplifiers are 24K (Maybe change these in ALL yor amplifiers)</span>
<span style=": rgb251, 251, 253;">2. Are BOTH peak lights doing this on both channels or just one channel ?.</span>
<span style=": rgb251, 251, 253;">
</span>
<span style=": rgb251, 251, 253;">Please also be careful as there is high voltages around and the above MUST be done by a engineer or someone who knows about power amplifiers. </span>Wink

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I have checked over the amp in question and it has the 24k 1/2w resistor so this must be part if not all the trouble I will have to have a good look at the others and see if I need to get an order list together then :)

thanks simon ill keep you updated with my journey
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totalAudio View Drop Down
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Points: 27 		Post Options Post Options   Thanks (0) Thanks(0)   Quote totalAudio Quote  Post ReplyReply Direct Link To This Post Posted: 20 April 2020 at 12:13pm
Originally posted by simonp1100 simonp1100 wrote:

Hi, Each amplifier driver board controls ONE channel and has the following circuits on it---.

1. Amplifier driver stage.
2. Peak light driver circuit.
3. Balanced input op-amp driver.
4. Protection circuit (but this is normally only used on ONE board).

So if BOTH channels are doing then it could be one of the following---.

1. Check input connections (i.e. are you using balanced or unbalanced connections).
2. Resistors as montioned in previous reply could be faulty on BOTH channel PCB boards. This would need checking and also updating on any other SR amplifiers you have (24K To 27K 1 Watt)
3. The soft start relays is stuck and amplifier is still in "Soft Start Mode" i.e. the 50 ohm soft start resistor has'nt been shorted out by the relay and this in turn will give you a 50 ohm resistor in series with the main power transformer and will reduce power output. Clap

hey simon im just looking at my options and just to clarify I need the standard 27k 1 watt and not the 10% ? cheers again
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Points: 2034 		Post Options Post Options   Thanks (0) Thanks(0)   Quote service dept Steve Quote  Post ReplyReply Direct Link To This Post Posted: 20 April 2020 at 12:42pm
Originally posted by totalAudio totalAudio wrote:



I have checked over the amp in question and it has the 24k 1/2w resistor so this must be part if not all the trouble
 


Well, Only if they are open circuit otherwise it is just maintenance.

If both channels are misbehaving at the same time then I would be looking at the soft start circuit as previously mentioned. Can you hear the relays click after a short start up period? Does the 50 ohm resistor get hot during use?
We are not "They", We are "The others"http://www.servicedept.co.uk -
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totalAudio View Drop Down
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Points: 27 		Post Options Post Options   Thanks (0) Thanks(0)   Quote totalAudio Quote  Post ReplyReply Direct Link To This Post Posted: 20 April 2020 at 12:49pm
Originally posted by service dept Steve service dept Steve wrote:

Originally posted by totalAudio totalAudio wrote:



I have checked over the amp in question and it has the 24k 1/2w resistor so this must be part if not all the trouble
 


Well, Only if they are open circuit otherwise it is just maintenance.

If both channels are misbehaving at the same time then I would be looking at the soft start circuit as previously mentioned. Can you hear the relays click after a short start up period? Does the 50 ohm resistor get hot during use?

yeh it clicks after a little while after startup so I will change the r14 & r50 and if I still have issues then ill have to move on with the fault finding cheers bud
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Points: 1110 		Post Options Post Options   Thanks (0) Thanks(0)   Quote simonp1100 Quote  Post ReplyReply Direct Link To This Post Posted: 20 April 2020 at 1:03pm
Hi, The circuit diagram says change the following on EACH driver PCB board from 24K 1/2 Watt to 27K 1 Watt 5%.

R24, R34 & R50. Hope this helps.

Again if both channels are doing this then it must be down to whats feeding both channels which is the power supply or soft start circuitry, and so i would also double check these parts of the amplifier.

Can you measure the DC voltages on the power supply capacitors and let me know what they are.

Clap


Edited by simonp1100 - 20 April 2020 at 1:09pm
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midas View Drop Down
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Points: 2117 		Post Options Post Options   Thanks (0) Thanks(0)   Quote midas Quote  Post ReplyReply Direct Link To This Post Posted: 24 June 2020 at 8:09pm
Well, it does look like this crazy time is quietening down. Hopefully I will soon be able to collect the 808, dump it round my mates on a pair of X1's.

I may put the 707 on the community tops as well...

Edited by midas - 24 June 2020 at 8:10pm
In bass no one can hear you scream!
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midas View Drop Down
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Points: 2117 		Post Options Post Options   Thanks (0) Thanks(0)   Quote midas Quote  Post ReplyReply Direct Link To This Post Posted: 30 June 2020 at 3:49pm
And........she is home...

I wonder how many people would consider the CAudio sr707 as a lightweight amplifier. Me either, but let me say that compared to the 808 it is. 

Something else that's surprising it wasnt old age that took the old girl out either. It was some NUMPTY with an electric drill. Correct, really yes.  It looks like someone has drilled one of the pannels and the tip of the drill has taken out a few of the outer strands, which in turn has taken out the secondary winding. 




Edited by midas - 30 June 2020 at 3:49pm
In bass no one can hear you scream!
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Sergio B View Drop Down
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Points: 13 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Sergio B Quote  Post ReplyReply Direct Link To This Post Posted: 29 May 2022 at 1:31pm 
Hello everybody

I'm new. Interesting this post because I also have a C-Audio SR808 with problems with a Driver board so much that I have to completely redesign the PCB, 
the driver board is badly damaged, copper traces burnt, so I had to completely redesign the PCB.

Following yours messages but sorry I didn't understand anything. In the first part we talk about the replacement of the R14 and R50 resistors, 
then it is said to update R24, R34 and R50, I think the latter is correct or am I wrong. 

Thank you 
Excellent discussion 
congratulations.


Edited by Sergio B - 29 May 2022 at 2:07pm
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Sergio B View Drop Down
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Edited by Sergio B - 29 May 2022 at 1:56pm
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Sergio B View Drop Down
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Edited by Sergio B - 29 May 2022 at 2:03pm
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simonp1100 View Drop Down
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Points: 1110 		Post Options Post Options   Thanks (0) Thanks(0)   Quote simonp1100 Quote  Post ReplyReply Direct Link To This Post Posted: 29 May 2022 at 2:05pm
I did the same thing as you for the C-Audio SR Series. I used Proteus CAD & done two versions,  the original PCB & an updated version with all the mod's (protection circuity, better legends where the wires go & bigger pads sizes around the zener diodes & wirewound resistors etc). WinkWinkWinkWink

You need to update the resistors R24, R34 & R50 to 27K 1 Watt resistors (pretty sure these were originally 22K)
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Sergio B View Drop Down
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Points: 13 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Sergio B Quote  Post ReplyReply Direct Link To This Post Posted: 29 May 2022 at 2:14pm
great! WinkWinkWink

I also did the same thing, I used Eagle as my design software, I would say that one is as good as the other.

I saw you mentioned the protection circuit, what did you specifically do if I may know
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