Upgrading Sub Amplifier

[Brain Fried]

OK i have a ASW -10-120 (aka as KLH) i keep killing the output transistors. I go through a set about once a month so i decided to look for better transistors and driver stage and i think i found what i am looking for i just want to make sure i am on the right track the stock output transistors are 2sa1516 and 1sc3907 and the drive stage is 2sd1563 and 2sb1086 i want to replace the outputs with 2sa1216 and 2sc2922 and the drive stage with 2sb649a and 2sd669a. So my main question is am i on the right track and do i need ot update anything else. Here is a picture of the schematic i will appreciate any help you guys can give.

[Brain Fried]

Datasheets

2SA1516
2SA1516 datasheet, Pinout ,application circuits Isc Silicon PNP Power Transistor

2SA1216
http://www.ampslab.com/Freewares/2sa1216.pdf

2SC3907
2SC3907 pdf, 2SC3907 description, 2SC3907 datasheets, 2SC3907 view ::: ALLDATASHEET :::

2SC2922
http://www.ampslab.com/Freewares/2sc2922.pdf


2sd1563
2SD1563 pdf, 2SD1563 description, 2SD1563 datasheets, 2SD1563 view ::: ALLDATASHEET :::

2sd669a
http://www.audiolabga.com/pdf/2SD669A.pdf


2sb1086
2SB1086 pdf, 2SB1086 description, 2SB1086 datasheets, 2SB1086 view ::: ALLDATASHEET :::


2sb649A
2SB649A pdf, 2SB649A description, 2SB649A datasheets, 2SB649A view ::: ALLDATASHEET :::

[djk]

What is the ±V ?

What is the voltage across R46, R47 ? Across R48, R49 ?

Consider MJL21193/94/95/96, should drop right in (no extra holes).

Consider MJE15032/33/34/35 drivers, they have reversed pin-out but should drop right in.

[infinia]

If something is blowing up there must be a reason. I'm not sure just beefing up the outputs and drivers will put an end to it.
What Q devices are failing and what are the failure mechanisms. Things like accidental disconnecting of gear still powered up or shorting stuff??
This schematic is very basic! You might think about using a couple of freewheeling diodes on the output as well as HF loading zobels. Any service bulletins from the factory?

[MOER]

You need emitter resistors on the output devices, use 0.22 ohm or 0.27 ohm 5W types. Also add base stopper resistors on each output device right next to the base connection.

Diode D3 is shown backwards and the circuit cannot work with the diode shown in your schematic.

Check thr voltage across the bias spreader it should be less than 1.5v as the the output devices are not in the thermal loop.

Where are the bias spreader devices bolted to? They must be in contact with the drivers and NOT the output devices.

Of course upgrading to the larger MT200 Sankens makes the output stage more reliable in terms of SOA but without the above mods, the big Sankens will go just as quickly.

Steve Mantz
Zed Audio
Zed Audio Corporation

[Brain Fried]

Originally Posted by infinia

If something is blowing up there must be a reason. I'm not sure just beefing up the outputs and drivers will put an end to it.
What Q devices are failing and what are the failure mechanisms. Things like accidental disconnecting of gear still powered up or shorting stuff??
This schematic is very basic! You might think about using a couple of freewheeling diodes on the output as well as HF loading zobels. Any service bulletins from the factory?

The factory sub failed so i upgraded it to RFD2210 (aka HX2 Fosgate)Dual 4 ohms set at 8ohms this sub is rated at 1000watts RMS and i retuned the cabinet to 35Hz now i have sub that can take the heat and sounds great but now the amplifier output transistors are failing ( dead short ) and there no updates from the factory this design was discontinued eight years ago and it took a month to get this schematic.

[Brain Fried]

Originally Posted by MOER

You need emitter resistors on the output devices, use 0.22 ohm or 0.27 ohm 5W types. Also add base stopper resistors on each output device right next to the base connection.

Diode D3 is shown backwards and the circuit cannot work with the diode shown in your schematic.

Check thr voltage across the bias spreader it should be less than 1.5v as the the output devices are not in the thermal loop.

Where are the bias spreader devices bolted to? They must be in contact with the drivers and NOT the output devices.

Of course upgrading to the larger MT200 Sankens makes the output stage more reliable in terms of SOA but without the above mods, the big Sankens will go just as quickly.

Steve Mantz
Zed Audio
Zed Audio Corporation

There is emitter resistors on the output devices a .22/5w now for D1 it wrong on the schematic but right on the board here a picture of the top of the board

[djk]

"You might think about using a couple of freewheeling diodes on the output "

If it had foldback current limiting I would agree with you, but it doesn't.

"HF loading zobels"

R52/C23 serve that function.

"Diode D3 is shown backwards and the circuit cannot work with the diode shown in your schematic."

If you reverse D3 it will have no bias, I know it will work with D3 removed, I'm not sure what the function of D3 is as shown.

[djk]

"D1 it wrong on the schematic but right on the board here a picture of the top of the board"

There is no D1 on the schematic (or do you mean D3?), there is a ZD1, but it is drawn correctly.

[infinia]

Originally Posted by djk

"You might think about using a couple of freewheeling diodes on the output "

If it had foldback current limiting I would agree with you, but it doesn't.

The diodes will be a whole lot faster than the latching relay, even if it works in normal operation. I'd do it anyway. It's cheap and easy. YMMV