Conquest 1200 amp

mickb · 19th June 2009, 08:49 PM

Hi everyone, I'm looking for information regarding a Citronic Conquest 1200 amplifier, does anyone know where i could buy a replacement power device board for one of these amps?.

mickb · 21st June 2009, 09:18 PM

Hi everyone i'm repairing one of these amps and have a couple of questions which i hope some kind soul will help me with.

On this amp there is a bead thermistor placed in a hole in the heatsink, it doesn't actually touch the heatsink but is in a blob of grease like substance, it maybe a silly question but i'm not that up on electronics but i'm trying to learn.

My questions are.
1) What is this grease called?
2) The thermistor is coloured gold tip red band green band, does this indicate a value?
3) It is placed across + & - GATES of power output Mosfets what does it do?.
Thanks in advance to anyone who can help me.

jaycee · 22nd June 2009, 12:10 AM

The white paste is thermal conductivity paste.

The bands most likely indicate the value, yes.

What it does is provide biasing and thermal feedback for the output stage. Most of the time, this is done with an active device, usually a transistor, or sometimes just diodes.

Apparently, Citronic will email you a schematic if you ask them to.

mickb · 22nd June 2009, 05:34 PM

Thank you for your reply, the grease is not white conductivity paste, it looks more like vasaline, do you think it is just a different type?.

The thermistor measures cold approx 1K5 ohm out of circuit do you think that sounds about right?.

I have already got the Schematic for this amp the marking for the thermistor is VA1098 but i can't find any information about this.

megajocke · 22nd June 2009, 07:31 PM

What is wrong with the amplifier?

mickb · 22nd June 2009, 08:56 PM

Hi the power device board is burnt out and four out of the six power mosfets are destroyed.
I bought this amp in this condition.

megajocke · 22nd June 2009, 09:34 PM

Is the printed circuit board itself so badly burnt that it can't be repaired?

The thermistor is in parallell with the bias set pot and decreases bias voltage when temperature of heatsink rises. The themistor is probably OK if you measure 1k5 cold resistance.

mickb · 22nd June 2009, 09:58 PM

Hi the board is beyond repair, i've etched a new one, the thermistor has a broken leg it was just long enough to test, the suppliers i have checked so far only seem to have thermistors with ranges ie 300r 1k etc, would i be looking for one with lower range than 1k5 to slightly higher than 1k5 ie 900r 2k?.

19th June 2009, 08:49 PM	#1
mickb diyAudio Member Join Date: Oct 2007	Conquest 1200 amp Hi everyone, I'm looking for information regarding a Citronic Conquest 1200 amplifier, does anyone know where i could buy a replacement power device board for one of these amps?.

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21st June 2009, 09:18 PM	#2
mickb diyAudio Member Join Date: Oct 2007	Hi everyone i'm repairing one of these amps and have a couple of questions which i hope some kind soul will help me with. On this amp there is a bead thermistor placed in a hole in the heatsink, it doesn't actually touch the heatsink but is in a blob of grease like substance, it maybe a silly question but i'm not that up on electronics but i'm trying to learn. My questions are. 1) What is this grease called? 2) The thermistor is coloured gold tip red band green band, does this indicate a value? 3) It is placed across + & - GATES of power output Mosfets what does it do?. Thanks in advance to anyone who can help me.

22nd June 2009, 12:10 AM	#3
jaycee diyAudio Member Join Date: Apr 2004 Location: Norwich, UK	The white paste is thermal conductivity paste. The bands most likely indicate the value, yes. What it does is provide biasing and thermal feedback for the output stage. Most of the time, this is done with an active device, usually a transistor, or sometimes just diodes. Apparently, Citronic will email you a schematic if you ask them to.

22nd June 2009, 05:34 PM	#4
mickb diyAudio Member Join Date: Oct 2007	Thank you for your reply, the grease is not white conductivity paste, it looks more like vasaline, do you think it is just a different type?. The thermistor measures cold approx 1K5 ohm out of circuit do you think that sounds about right?. I have already got the Schematic for this amp the marking for the thermistor is VA1098 but i can't find any information about this.

22nd June 2009, 07:31 PM	#5
megajocke diyAudio Member Join Date: Jan 2003 Location: Solna	What is wrong with the amplifier?

22nd June 2009, 08:56 PM	#6
mickb diyAudio Member Join Date: Oct 2007	Hi the power device board is burnt out and four out of the six power mosfets are destroyed. I bought this amp in this condition.

22nd June 2009, 09:34 PM	#7
megajocke diyAudio Member Join Date: Jan 2003 Location: Solna	Is the printed circuit board itself so badly burnt that it can't be repaired? The thermistor is in parallell with the bias set pot and decreases bias voltage when temperature of heatsink rises. The themistor is probably OK if you measure 1k5 cold resistance.

22nd June 2009, 09:58 PM	#8
mickb diyAudio Member Join Date: Oct 2007	Hi the board is beyond repair, i've etched a new one, the thermistor has a broken leg it was just long enough to test, the suppliers i have checked so far only seem to have thermistors with ranges ie 300r 1k etc, would i be looking for one with lower range than 1k5 to slightly higher than 1k5 ie 900r 2k?.

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