Hi,
I'm going to build a Leach Amp using TO-3 output devices. The way I'm planning to build the output stage, TO-220 driver transistors will be the link to a PCB with the rest of the circuit. It would be nice if I could have the capacitors that decouple the power supply rails (C21 through C24) on the PCB next to the driver devices. As you can see on the picture below, collector on the output and driver transistors are wired together via their mounting screws. If I connect VCC to the collector pin of the driver (next to the capacitors), this would mean that all current to the output transistors must flow through the TO-220 cases. Would this be ok? Another option is to connect VCC to the wire between the mounting screws that hold the transistors. This would mean that VCC and capacitors have the TO-220 case between them. Does anyone have comments on this issue please?
-truls
This is how I'm planning to mount things:
I'm going to build a Leach Amp using TO-3 output devices. The way I'm planning to build the output stage, TO-220 driver transistors will be the link to a PCB with the rest of the circuit. It would be nice if I could have the capacitors that decouple the power supply rails (C21 through C24) on the PCB next to the driver devices. As you can see on the picture below, collector on the output and driver transistors are wired together via their mounting screws. If I connect VCC to the collector pin of the driver (next to the capacitors), this would mean that all current to the output transistors must flow through the TO-220 cases. Would this be ok? Another option is to connect VCC to the wire between the mounting screws that hold the transistors. This would mean that VCC and capacitors have the TO-220 case between them. Does anyone have comments on this issue please?
-truls
This is how I'm planning to mount things:
Attachments
I cannot agree with your project. In my opinion the problem is that PCB is not sufficiently fastened by the solder joint of the TO220 leads. Vibrations and other mechanical stress will soon destroy the assembly, with electrical unforeseeable damages.
You have to fasten firmly the PCB , the TO220, and the heatsink together (the PCB on one side of the heatsink, and the TO220 on the other side, with bolts).
Regards, Pierre Lacombe.
You have to fasten firmly the PCB , the TO220, and the heatsink together (the PCB on one side of the heatsink, and the TO220 on the other side, with bolts).
Regards, Pierre Lacombe.
I concur with Pierre's mechanical concerns.
Electrically I think either of you schemes is probably ok. Usually with TO220 the collector pin is bonded directly to the heatsink plate. Slightly better to join Vcc at the connection between transistors if you are thinking of pulling really big currents (>10A).
Another consideration is whether you want the drivers to be thermally coupled to the power transistors. This means the drivers characteristics will vary more than if they are on a private heatsink. Depends on the design. In general I would want the drivers to be thermally separated.
Electrically I think either of you schemes is probably ok. Usually with TO220 the collector pin is bonded directly to the heatsink plate. Slightly better to join Vcc at the connection between transistors if you are thinking of pulling really big currents (>10A).
Another consideration is whether you want the drivers to be thermally coupled to the power transistors. This means the drivers characteristics will vary more than if they are on a private heatsink. Depends on the design. In general I would want the drivers to be thermally separated.
When I said the TO-220 driver transistors will be the link to the PCB, I meant electrically (like instead of using a wire). Traderbam's answer tells me this would probably be ok. What I'm more concerned about now is how the thermal connection will affect the characteristics of the drivers. Maybe I should reconsider the design just a bit. Has anyone ever built a Leach Amp using the same heat sink for both driver and output stage?
-truls
-truls
Heatsink
Hi
I have my layout made so it's possible to mount the driver on the main heatsink, although it's not needed, they barely get warm, so i mounted only a small dink on each of the drivers.
I have the amp made into two sections....se this thread for idears
http://diyaudio.com/forums/showthread.php?s=&threadid=4091
\Jens
Hi
I have my layout made so it's possible to mount the driver on the main heatsink, although it's not needed, they barely get warm, so i mounted only a small dink on each of the drivers.
I have the amp made into two sections....se this thread for idears
http://diyaudio.com/forums/showthread.php?s=&threadid=4091
\Jens
Jens, I've already seen the thread and I must say your four channel Leach really looks nice. How is it coming along, I understand that you've had various problems with hum and such? Do you have any pics of its outside?
I guess I'll end up using small TO-220 heatsinks rather than go into the trouble of mounting the drivers togther with the TO-3s.
-truls
I guess I'll end up using small TO-220 heatsinks rather than go into the trouble of mounting the drivers togther with the TO-3s.
-truls
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