Big Power Amplifier
Hi,
I need information regarding mods and schematics for a C-Audio SR606 this is an English company I don't know the factory name but C-Audio and/or Cambridge Electronics is printed on the amplifiers it is NOT the Cambridge Audio HiFi company.
The problem is in the primary of power supply the soft start circuit has a problem, Poff and Blue smoke has occured!
Kamskoma
Hi,
I need information regarding mods and schematics for a C-Audio SR606 this is an English company I don't know the factory name but C-Audio and/or Cambridge Electronics is printed on the amplifiers it is NOT the Cambridge Audio HiFi company.
The problem is in the primary of power supply the soft start circuit has a problem, Poff and Blue smoke has occured!
Kamskoma
C-Audio SR606
The problem is that the large 47 Ohm resistor in series with 230V primary has blown, I think this resistor should be 10 Ohm as I have seen in other BIG amplifiers , this is a BIG amplifier with a Big toroidal transformer.
A rely will short the resistor after a while maybe the time delay circuit is broken.
Need info maybe some English member can help.
Kamskoma
The problem is that the large 47 Ohm resistor in series with 230V primary has blown, I think this resistor should be 10 Ohm as I have seen in other BIG amplifiers , this is a BIG amplifier with a Big toroidal transformer.
A rely will short the resistor after a while maybe the time delay circuit is broken.
Need info maybe some English member can help.
Kamskoma
Hi Kamskoma,
Okay, the soft start resistor can be shorted out temporarily. You will need to troubleshoot further as the unit has drawn excessive current causing the soft start to burn open.
Connect the unit to a variac after shorting the resistor, never plug it directly in until the resistor has been replaced with the same value. If you don't have a variac, you must use a low wattage lamp in series.
If you test the rectifiers and output transistors I will bet you'll find a short somewhere. I have seen the odd filter cap short without venting. You must find these faults before attempting to repair thesoft start circuit.
If you replace the resistor now, short it out and follow my advice before applying full power. If you do otherwise you will extend the amount of damage there already is.
-Chris
Okay, the soft start resistor can be shorted out temporarily. You will need to troubleshoot further as the unit has drawn excessive current causing the soft start to burn open.
Connect the unit to a variac after shorting the resistor, never plug it directly in until the resistor has been replaced with the same value. If you don't have a variac, you must use a low wattage lamp in series.
If you test the rectifiers and output transistors I will bet you'll find a short somewhere. I have seen the odd filter cap short without venting. You must find these faults before attempting to repair thesoft start circuit.
If you replace the resistor now, short it out and follow my advice before applying full power. If you do otherwise you will extend the amount of damage there already is.
-Chris
The SR606s are very reliable amps, so much so that I have never had to open one up apart from when I had to swap out a broken speaker post.
However, if I remember correctly they use a rectifier bridge with push on spade terminals. Disconnect those, wrap a bit of tape around them to prevent them shorting to anything, then you can test the soft start circuit without risking anything.
However, if I remember correctly they use a rectifier bridge with push on spade terminals. Disconnect those, wrap a bit of tape around them to prevent them shorting to anything, then you can test the soft start circuit without risking anything.
Thanks a lot for your kindness.
Ok, I found the schematics(old) but it shows that the soft start resistor should be 10 Ohm/50W not 47 Ohm/50W as I found in my two SR606.
For many years ago I troubleshoot a SR606 and I will remember that C-Audio had some problem with the rely circuit.
A Schrack 48V DC relay is the relay that shorts the 47 Ohm resistor ( there is three relays in this amplifier).
My idea is; if the resistor has 230V for a too long period it will blow, and the timing circuit may have some problem or if the shorting relay dont short the resistor effectively.
I can run one of the amps and it works OK but the resistor in this working amp looks very funny the internal resistor body have moved a bit from its housing ( it preparing it self for a small explosion and blue smoke).
I think that Mr CA have done some modification to this circuit but what and where can I get this information.
One more problem Tyco/Schrack has no 48V DC relay in their product catalogue, the relay types is RM805615 (115V AC) and RM 805048 (48V DC).
I have two more SR606 in alles four with exactly the same problem?????
So..... if I could fix them it would be nice.
I'll try to scan the schematics and send them in next reply.
Thank you
Kamskoma
Kamskoma
Ok, I found the schematics(old) but it shows that the soft start resistor should be 10 Ohm/50W not 47 Ohm/50W as I found in my two SR606.
For many years ago I troubleshoot a SR606 and I will remember that C-Audio had some problem with the rely circuit.
A Schrack 48V DC relay is the relay that shorts the 47 Ohm resistor ( there is three relays in this amplifier).
My idea is; if the resistor has 230V for a too long period it will blow, and the timing circuit may have some problem or if the shorting relay dont short the resistor effectively.
I can run one of the amps and it works OK but the resistor in this working amp looks very funny the internal resistor body have moved a bit from its housing ( it preparing it self for a small explosion and blue smoke).
I think that Mr CA have done some modification to this circuit but what and where can I get this information.
One more problem Tyco/Schrack has no 48V DC relay in their product catalogue, the relay types is RM805615 (115V AC) and RM 805048 (48V DC).
I have two more SR606 in alles four with exactly the same problem?????
So..... if I could fix them it would be nice.
I'll try to scan the schematics and send them in next reply.
Thank you
Kamskoma
Kamskoma
Hi Kamskoma,
I think you may be on to something there. Defective design will do it! If the relay does not operate the resistor will overheat and fail. The largest one I've seen in Canada was a 20W unit. Most are around 10W.
If you scan it, would you please send a full resolution copy to: bhomester at gmail dot com ? Thanks!
Sounds like you can fix them all. There is more than one make of relay out there.
-Chris
I think you may be on to something there. Defective design will do it! If the relay does not operate the resistor will overheat and fail. The largest one I've seen in Canada was a 20W unit. Most are around 10W.
If you scan it, would you please send a full resolution copy to: bhomester at gmail dot com ? Thanks!
Sounds like you can fix them all. There is more than one make of relay out there.
-Chris
sr606
kamskoma: It would be great if you send me schematics of C-audio SR606 too, because I have one to repair - one channel PCB is totaly destroyed - there are holes in PCB, but second channel looks good. My email is hanzs23@centrum.cz
But I think there is a strange thing - used power mosfet transistors 2SK135/SJ50 have Uds only 160V, but rails have +/-95V....? so Uds should be min. 200V..?
kamskoma: It would be great if you send me schematics of C-audio SR606 too, because I have one to repair - one channel PCB is totaly destroyed - there are holes in PCB, but second channel looks good. My email is hanzs23@centrum.cz
But I think there is a strange thing - used power mosfet transistors 2SK135/SJ50 have Uds only 160V, but rails have +/-95V....? so Uds should be min. 200V..?
Hi Kamskoma,
Thanks for the schematic set!
I can't believe they allow the thermals to open the surge relay!!
I would rewire the surge relay to tun off the DC supply rail through a timer circuit. Double the coil voltage for the speaker relay and short across where the surge relay coil was.
Check the thermal switches for poor contacts. Check the two 100uF caps to make sure they are not going open.
-Chris
Thanks for the schematic set!
I can't believe they allow the thermals to open the surge relay!!
I would rewire the surge relay to tun off the DC supply rail through a timer circuit. Double the coil voltage for the speaker relay and short across where the surge relay coil was.
Check the thermal switches for poor contacts. Check the two 100uF caps to make sure they are not going open.
-Chris
Hi,
Yes! I have checked the timer circuit and it seems Ok, but I have also established a fact, the two solid wires from the resistor rely poles are connected to the relay PCB, where the resistor is mounted, has a very bad soldering, they put the two wires into the pcb without bending the wires toward the PCB copper tracks.
The two solid wires barely go trough the PCB and can hardly get any solder, it is exactly the same in the three other SR606.
That's the entire story, I replace the two solid wires with new longer wires and also using both rely poles for the shorting process.
The CAudio amplifiers sounds very nice and after this repair they will probably last forever the Hitachi FET power devices seems to be very robust.
Regards
Kamskoma
Yes! I have checked the timer circuit and it seems Ok, but I have also established a fact, the two solid wires from the resistor rely poles are connected to the relay PCB, where the resistor is mounted, has a very bad soldering, they put the two wires into the pcb without bending the wires toward the PCB copper tracks.
The two solid wires barely go trough the PCB and can hardly get any solder, it is exactly the same in the three other SR606.
That's the entire story, I replace the two solid wires with new longer wires and also using both rely poles for the shorting process.
The CAudio amplifiers sounds very nice and after this repair they will probably last forever the Hitachi FET power devices seems to be very robust.
Regards
Kamskoma
Well, bitter with no s. Bitters is what you put in cocktails. 
To get briefly back to the topic, I'm glad you got the amp sorted. I've always had a soft spot for C-Audio amps, and it's nice you've got one of the classics back up and running, Though in listening tests, I always rated the 404 to be the better amp.
To get briefly back to the topic, I'm glad you got the amp sorted. I've always had a soft spot for C-Audio amps, and it's nice you've got one of the classics back up and running, Though in listening tests, I always rated the 404 to be the better amp.
Hi,
The slow start resistor is 47 Ohm and it may break for many reasons.
The most common problem is the relay circuit, the relay poles are contaminated and the connections from relay to PCB is bad, and if so the slowstart resistor will blow, BANG and POOF a lot of blue smoke will occur.
Second if the amplifier has a short somewhere most common is the bridge rectifiers.
Please do a careful examination before you attach a new resistor.
You can have the schematics by email if I you want but I need your email.
Regards
Kamskoma
The slow start resistor is 47 Ohm and it may break for many reasons.
The most common problem is the relay circuit, the relay poles are contaminated and the connections from relay to PCB is bad, and if so the slowstart resistor will blow, BANG and POOF a lot of blue smoke will occur.
Second if the amplifier has a short somewhere most common is the bridge rectifiers.
Please do a careful examination before you attach a new resistor.
You can have the schematics by email if I you want but I need your email.
Regards
Kamskoma
From the description of the soft start circuit it seems to be the same as that fitted to the big musical fidelity amps (A370, SA470 etc). The main problem I used to have with these was that the internal insulation of the 50W 8r2 resistor would fail, the metal body of the 50W resistor would become live.....as it is bolted to the earthed chassis of the amp the result is easy to imagine!
If the resistor is bolted to the case I would check this out first.
If the resistor is bolted to the case I would check this out first.
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