Can Anyone Identify This Component in Meridian 103/5 Power Amps Please?

Thomo · 19th April 2010, 06:49 PM

I have a Meridian 103 power amp that doesn't work, and was wondering if anyone could identify this component that is superglued (or similar) to the heatsink.

I'll post a pic of the schematic shortly once I've drawn on where this part is connected.

Lee.

Thomo · 19th April 2010, 06:56 PM

Here's the schematic for the 103 with arrows drawn to show where it's connected.

Cheers, Lee.

http://www.diyhi-fi.co.uk/pdf/Servic...cuits_edit.pdf

AndrewT · 19th April 2010, 07:06 PM

can you identify the 2off 10V Zeners on the PCB, or is that them glued to the heatsink?

PhaseLockLoopy · 19th April 2010, 07:12 PM

Is that not just a thermal cut out? -- the wires are both the same colour and go back via two rails that come up through the centre of the PCB on fairly hefty track

cliffforrest · 19th April 2010, 07:16 PM

Quote:

Originally Posted by PhaseLockLoopy

Is that not just a thermal cut out? -- the wires are both the same colour and go back via two rails that come up through the centre of the PCB on fairly hefty track

But if that were the case it would short out the rails, which is a bit drastic ....

It would work though!

Steve Dunlap · 19th April 2010, 07:32 PM

I may be missing one transistor in the picture, but the schematic seems to have 19 and I see only 18 on the board.

Andrew Eckhardt · 08:09 PM

It has to be a normally open thermal switch. (or a big NTC thermistor, you'd have to look much closer into the circuit to see what that would do, but measuring the part is easy) When the sink rises to the trip point it clamps off the supply to voltage stage through the isolating resistors.

tvi · 20th April 2010, 12:23 AM

Can you post a pic of the copper side of the board,
might help?

Rgds
James

Andrew Eckhardt · 12:32 AM

I tried to edit that post 15 times. It's the input stage left after the resistors, the stage that handles voltage gain is before it, and those aren't just isolation resistors, they're dropping resistors for the zeners. An NTC on there would have to seriously drop the supply to the input section before the bias regulator dropped out, so it probably wouldn't be any more effective than a thermal switch. An ohm meter will give you the answer.

Thomo · 20th April 2010, 09:34 AM

Hi guys, thanks for your answers. I too thought it was a thermistor or some sort of thermal cutout. I've measured it with an ohm-meter, and it's open circuit. I'll try heating it slightly with a hot-air blower and see if that changes anything.

Cheers, Lee.

19th April 2010, 06:49 PM	#1
Thomo diyAudio Member Join Date: Nov 2006	Can Anyone Identify This Component in Meridian 103/5 Power Amps Please? I have a Meridian 103 power amp that doesn't work, and was wondering if anyone could identify this component that is superglued (or similar) to the heatsink. I'll post a pic of the schematic shortly once I've drawn on where this part is connected. Lee.

19th April 2010, 07:06 PM	#3
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	can you identify the 2off 10V Zeners on the PCB, or is that them glued to the heatsink? __________________ regards Andrew T.

19th April 2010, 07:12 PM	#4
PhaseLockLoopy diyAudio Member Join Date: May 2008 Location: On a mushroom	Is that not just a thermal cut out? -- the wires are both the same colour and go back via two rails that come up through the centre of the PCB on fairly hefty track __________________ Hum likes to have a nice "Noise to Signal" ratio To "Hum" is to be noticed Quality hum is when it pours out of Electrostatic speakers

19th April 2010, 07:39 PM	#7
Andrew Eckhardt diyAudio Member Join Date: Nov 2005 Location: PA	It has to be a normally open thermal switch. (or a big NTC thermistor, you'd have to look much closer into the circuit to see what that would do, but measuring the part is easy) When the sink rises to the trip point it clamps off the supply to voltage stage through the isolating resistors. Last edited by Andrew Eckhardt; 19th April 2010 at 08:09 PM.

20th April 2010, 12:23 AM	#8
tvi diyAudio Member Join Date: Apr 2001 Location: Moonee Ponds, Vic, Australia	Can you post a pic of the copper side of the board, might help? Rgds James __________________ The border between the Real and the unreal is not fixed, but just marks the last place where rival gangs of shamans fought each other to a standstill. Robert Anton Wilson


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19th April 2010, 06:56 PM	#2
Thomo diyAudio Member Join Date: Nov 2006	Here's the schematic for the 103 with arrows drawn to show where it's connected. Cheers, Lee. http://www.diyhi-fi.co.uk/pdf/Servic...cuits_edit.pdf

19th April 2010, 07:32 PM	#6
Steve Dunlap diyAudio Member Join Date: Sep 2008 Location: Here	I may be missing one transistor in the picture, but the schematic seems to have 19 and I see only 18 on the board.

20th April 2010, 12:30 AM	#9
Andrew Eckhardt diyAudio Member Join Date: Nov 2005 Location: PA	I tried to edit that post 15 times. It's the input stage left after the resistors, the stage that handles voltage gain is before it, and those aren't just isolation resistors, they're dropping resistors for the zeners. An NTC on there would have to seriously drop the supply to the input section before the bias regulator dropped out, so it probably wouldn't be any more effective than a thermal switch. An ohm meter will give you the answer. Last edited by Andrew Eckhardt; 20th April 2010 at 12:32 AM.

20th April 2010, 09:34 AM	#10
Thomo diyAudio Member Join Date: Nov 2006	Hi guys, thanks for your answers. I too thought it was a thermistor or some sort of thermal cutout. I've measured it with an ohm-meter, and it's open circuit. I'll try heating it slightly with a hot-air blower and see if that changes anything. Cheers, Lee.

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