Re: MJE340/350
The PCB is layed out for the MJE types. Reason is simple: I could not find the originals here in Denmark and the MJE devises are used in some of the amps I have read about (Self + Slone)
Please refer to the partslist found here:http://www.delta-audio.com/Leach-Clone-6.htm
\Jens
still4given said:
The PCB is layed out for the MJE types. Reason is simple: I could not find the originals here in Denmark and the MJE devises are used in some of the amps I have read about (Self + Slone)
Please refer to the partslist found here:http://www.delta-audio.com/Leach-Clone-6.htm
\Jens
Re: Re: MJE340/350
Hi Jens,
Yes, I plan on using the MJE's in your PCB. I was asking because I have other amps that call for the 2N3440/2N5416 and they are more expensive and I would have to order them. If the MJE's will work in their place I can use them. I have several of the MJE340/350 units.
Thanks, Terry
JensRasmussen said:
Hi Jens,
Yes, I plan on using the MJE's in your PCB. I was asking because I have other amps that call for the 2N3440/2N5416 and they are more expensive and I would have to order them. If the MJE's will work in their place I can use them. I have several of the MJE340/350 units.
Thanks, Terry
Terry,
It's hard to say if they will work in a given amp.....
If reworking the pinout to match a give PCB, there is always the option of making your own layout ;-)
\Jens
It's hard to say if they will work in a given amp.....
If reworking the pinout to match a give PCB, there is always the option of making your own layout ;-)
\Jens
Hi Jens,
I was really wondering more if they would interchange electronically. I have a couple of production amps that I am trying to repair. I guess I was hoping that I could use an MJE340/350 in place of a 2N3440/2N5416 by just bending the pins. If they don't have the same specs then I won't try it. I'm not knowledgeable enough to tell.
Thanks, Terry
I was really wondering more if they would interchange electronically. I have a couple of production amps that I am trying to repair. I guess I was hoping that I could use an MJE340/350 in place of a 2N3440/2N5416 by just bending the pins. If they don't have the same specs then I won't try it. I'm not knowledgeable enough to tell.
Thanks, Terry
if i were you, i would go ahead and do it, electrically, there is not much of a difference between them, afaik, dr. leach used 2n3440/2n5416 in his designs because they were the one's available that fit the bill at the time he designed the amps.
to-39 trannies are hard to come by these days, even japanese ones...
jen's pcb design actually gives us more choices on which transistors to use:
this is how i separated the thermal compensation boards from the main amp board:
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
Jens
I have nearly compleated my amp , I have a few questions
1, what is the most suitable quesent current , I have varied from 10ma per device to 50ma per device and there is no differance in the sound , the transformer voltage is 50-0-50 volt and 4ohm loudspeaker , and 11 pairs of Toshiba 2SA1943/2SC5200 output devices , these high gain output devices are working fine at very low quesent currents also!!
2, I am using 20A fuses in the +/- rails so that there is no premature fuse blowing in using the amp up to 2 ohms , is this ok ?
I have posted a few pictures of my project of the leach amp in the thread " Favorite High Power Output Transistor"
I have nearly compleated my amp , I have a few questions
1, what is the most suitable quesent current , I have varied from 10ma per device to 50ma per device and there is no differance in the sound , the transformer voltage is 50-0-50 volt and 4ohm loudspeaker , and 11 pairs of Toshiba 2SA1943/2SC5200 output devices , these high gain output devices are working fine at very low quesent currents also!!
2, I am using 20A fuses in the +/- rails so that there is no premature fuse blowing in using the amp up to 2 ohms , is this ok ?
I have posted a few pictures of my project of the leach amp in the thread " Favorite High Power Output Transistor"
To be determined
So I'm ready to start putting together an order for the parts I don't have for this amp. When will we have the values for the resistors labeled "To be determined"? What is the reason for this designation? Are their values determined on an amp by amp basis?
Thanks, Terry
So I'm ready to start putting together an order for the parts I don't have for this amp. When will we have the values for the resistors labeled "To be determined"? What is the reason for this designation? Are their values determined on an amp by amp basis?
Thanks, Terry
Terry,
I have not had a chance to find the resistor values yet. They will depend on the rail voltages you use, SOA of your transistors, and the emitter resistor value on the output transistors.
I think maybe it's time for the for a combined effort, to create a way of calculating the resistor values needed based on the number of transistors, type of transistor (SOA), Re and rail voltage.
Right now I'm sitting here completely surrounded by no PCBs for this project (No worries gengis 😉 ) So I have not had a chance to build one of these things yet to see that everything is in order.
\Jens
I have not had a chance to find the resistor values yet. They will depend on the rail voltages you use, SOA of your transistors, and the emitter resistor value on the output transistors.
I think maybe it's time for the for a combined effort, to create a way of calculating the resistor values needed based on the number of transistors, type of transistor (SOA), Re and rail voltage.
Right now I'm sitting here completely surrounded by no PCBs for this project (No worries gengis 😉 ) So I have not had a chance to build one of these things yet to see that everything is in order.
\Jens
OK Jens,
I am planning on using a NOS Hafler Transformer that has three sets of secondaries. 15VDC, 65VDC and 75VDC after rectification. I was thinking of running the front end off of the 75VDC and the outputs off of the 65V rails. If that's a bad idea i could just run the whole thing off of the 65V rails. What would you recommend as the best outputs to use? I have all of the MJL's that you have listed in the BOM.
Please let me know when you have the formula worked out for determining the values for all of the resistors.
Blessings, Terry
I am planning on using a NOS Hafler Transformer that has three sets of secondaries. 15VDC, 65VDC and 75VDC after rectification. I was thinking of running the front end off of the 75VDC and the outputs off of the 65V rails. If that's a bad idea i could just run the whole thing off of the 65V rails. What would you recommend as the best outputs to use? I have all of the MJL's that you have listed in the BOM.
Please let me know when you have the formula worked out for determining the values for all of the resistors.
Blessings, Terry
Sorry, Jens,
Got swamped with work.
It will go out tomorrow morning, I am trying to cut it nicely. Also Mr. JonDoe in Romania.
pooge:
yes, that makes sense.
now that i am working on something entirely unrelated to audio at the moment, i think what i was remembering before was about using a bipolar transistor as a low noise zener.
sorry,
mlloyd1
you can even mount it like this (TO126 package instead of TO220):
http://www.diyaudio.com/forums/attachment.php?s=&postid=687023&stamp=1121967453
yes, that makes sense.
now that i am working on something entirely unrelated to audio at the moment, i think what i was remembering before was about using a bipolar transistor as a low noise zener.
sorry,
mlloyd1
you can even mount it like this (TO126 package instead of TO220):
http://www.diyaudio.com/forums/attachment.php?s=&postid=687023&stamp=1121967453
pooge said:
Hi Still4given,
you could try using 65Vdc for the driver, predriver & outputs (VCC+VSS).
The 75Vdc could be regulated down to 67Vdc for the amplifier board (VC+VS). The regulated supply can be fused at about 100mA (F3+F4) or use foldback limiting in the regulator. A nice touch here would be automatic shutdown of the other rail if one rail fails. Could someone design a piggy back board to achieve this?
Some others may want to suggest a better voltage difference from my 2volt. Any ideas?
Remember to omit R1 & R23 if you use two supplies.
Design idea:- how do you crowbar ( force the second fuse to blow) the other main PSU rail if the fuse blows on a bad rail supply?
you could try using 65Vdc for the driver, predriver & outputs (VCC+VSS).
The 75Vdc could be regulated down to 67Vdc for the amplifier board (VC+VS). The regulated supply can be fused at about 100mA (F3+F4) or use foldback limiting in the regulator. A nice touch here would be automatic shutdown of the other rail if one rail fails. Could someone design a piggy back board to achieve this?
Some others may want to suggest a better voltage difference from my 2volt. Any ideas?
Remember to omit R1 & R23 if you use two supplies.
Design idea:- how do you crowbar ( force the second fuse to blow) the other main PSU rail if the fuse blows on a bad rail supply?
the "usual" way i've seen this done is put an SCR across the rails. you trigger the SCR to short the rails and consequently blow the rail fuse "on demand"
AndrewT said:
Yes, how do you trigger the other SCR when the first rail fails? and this needs to work both ways depending on which fuse blows first.
I'm thinking of putting some front end regulation consisting of LT1033 & LT1085 using LM317/337 as tracking preregulators on the previous. Terry's transformer's at 75 VDC feeding the front end regs and the outputs at 65 V would be a nice combination.
As for the thermal diodes I normally go right through the heatsink and use epoxy to seal them in there.
As for the thermal diodes I normally go right through the heatsink and use epoxy to seal them in there.
AndrewT said:
The main benefit, i think, is that the powersupplies are separated.
Under load voltage of the output PS will drop more than the one for the front end.
For those that have complete separated supplies the smaller powersupply will have a higher regulation factor.
Even with both PS's having the same nominal voltage the front end one will be higher.
A Mosfet amplifier i constructed had a 30vac 30va toroid for the front end and a 30vac 300va toroid for the output.
The poor regulation of the smaller transformer made its Vdc value good enough to get more than 28 volts rms out of the output in 8.
Adding 3 times a diodedrop for the Vbe drops would make it enough under any circumstances,i would say.
But does it hurt to add some more if someone has 10 volts to spare minus the needed voltage difference for proper regulation ?
mlloyd1 said:
I wouldn't mount the sensor on the transistor like that. I would use TO-220 packages for their low heat resistance, and mount them on the heat sink. Mounting on the transistor has been discounted before:
http://www.diyaudio.com/forums/showthread.php?postid=545653#post545653
Another reason I wouldn't mount a sensor there is because it monitors only one transistor. If it is not the sensor that is overheating, you might have a problem. Further, by covering the transistor, you are changing the heat radiating characteristic of that transistor compared to other transistors that are not covered.
- Status
- Not open for further replies.