Classe DR-15 schematics / Info?

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So as it turns out one channel is dead. Looks like all the small devices survived and it the problem is localized to the larger TO-3 devices.

Now i need to determine what these devices are as classe polishes the tops of the cans off so you cannot read them.

I see that they have used 150003/4 devices in other amps. but i want an exact match.

I have sent an email to the company.


Zc
 
it looks like Classe has parts available. here is the list of the output section parts

MJ15024 Transistor +ve (you will need 4 of these)

MJ15025 Transistor –ve (you will need 4 of these)



2N3773 Transistor +ve (you will need 1 of these)

2N6609 Transistor –ve (you will need 1 of these)



2N6426 Sensor (you will need 1 of these)

K4-04 Silpad (you will need 10 of these)
 
I managed to get all the output devices removed last night. what a major P.I.T.A. I do not like how this was assembled. very heavy pads on the PCB and one of the devices had the signal traces on the top side where you could not get to them or see them. the bottom side, the side you could get to was just the pad for the plated through hole. so it wa tricky getting enough heat in there to melt the solder all the way through and not damage the traces.

I damaged one through hole. there wasnt much i could do. the top pad came loose the second i hit it with the soldering iron so it was already loose from the pcb. and in the process i then could not get enough heat to get the transitor to fully let go. it ended up pulling the pad off up from the other side.

I found this neat plated through hole repair kit. seems everyone sell them but DANG there expensive!

http://www.engineeringlab.com/pthrepair.html

$200.00 for the kit!!! the parts alone would cost $300 so thats not a bad deal. i am going to buy just the parts i need instead and that should run me about $80.00, i can then just get what ever eyelets i need in the future instead of having a bunch i never use.



Only one + and one - output device was found shorted and none of the emitter resistors failed. Not bad! I am of course replacing everything anyway. but. this amp ran with the 800va or so power supply dead shorted through these 2 output transistors long enough to burn up the 10 ohm 25 watt soft start resistor and they didnt even kill the emitter resistors! not bad! Dumb previous owner!

FOLKS, TURN OFF YOUR AMP! before attempting to reverse polarity or swap speaker cables!


Zc
 
I got the dead channel of the DR-15 running today. but havent fully set the BIAS and offset adjustments yet. I am waiting on some replacement handles fot the back of the amp to arrive before i can button it back up 100% and do all the final adjustments.

I need to change the way i am monitoring the BIAS level. I forgot and left the bias pot at its last setting and when i fired up the amp the bias was a little too high. With the leads of my Fluke 189 connected across one of the emitter resistors i was getting some oscillation happening when i would drop the bias down to a certain point. the leads of my meter seem to eb the cause of this.

the service manual say adjust the bias for 22mv across the .27 ohm emitter resistor and no more then 6mv of deviation from device to device. with the bias pot left from its last posistion i was reading 35mv and when i would drop the level down and get close to anything in the 20's the amp would start to oscillate at a very low level around 3mhz!

Moving my meter leads around made that go away. At that point i realize i was just too tired to be working on it and shut the shop down for the night. will get back at it when i am in a better frame of mind.

Zc
 
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