After a short (30+ years) break...
As title says, the last PCB that I made was 30+ years ago and it was done using letraset (and marker). Now, thanks to you guys, Bora and Viktor for being patient with me, providing schematics and PCB layouts, as well as Sylvain (Algar_emi ) for support to make my own PCB from the scratch, here is what I done tonight. These small buggers on the lower left side are made first (I guess that you can tell) so I am not that proud of them, but rest is not that bad.
Am I happy, well, you should see the wrinkled smile on this old farts face B-))
And now real fun begins…
As title says, the last PCB that I made was 30+ years ago and it was done using letraset (and marker). Now, thanks to you guys, Bora and Viktor for being patient with me, providing schematics and PCB layouts, as well as Sylvain (Algar_emi ) for support to make my own PCB from the scratch, here is what I done tonight. These small buggers on the lower left side are made first (I guess that you can tell) so I am not that proud of them, but rest is not that bad.
Am I happy, well, you should see the wrinkled smile on this old farts face B-))
And now real fun begins…
Attachments
1. This is the latest version
2. No, but others did
3. 100W 8ohm
4. Should be used +/-50V DC power supply
First of all make pcb, solder all the elements and then we'll adjust easily to.
hi viktor.
sorry for late construction.
can u tell me how to adjust those two presets.
another thing is can i use 2k preset instead 1k.? because not available 1k in here.
thanks.
Attachments
Bora circuits are always a great option
Bora is a very good designer...he is a teacher from a College.... this is his profession...so... his products are always excelent.
I have built several amplifiers from him (3), and i found them awesome.
I am proud to have Bora as a good friend.
regards,
Carlos
Bora is a very good designer...he is a teacher from a College.... this is his profession...so... his products are always excelent.
I have built several amplifiers from him (3), and i found them awesome.
I am proud to have Bora as a good friend.
regards,
Carlos
........ I have layout one of many great design of Dr.Bora J , T REFERENCE AMPLIFIER
Alex.
You have no protection for short circuit and DC...use Triac Crowbar for DC, good speaker expensive
--Provide two big ceramic power resistors of 10-22 ohms/10-20W each (I am using 20ohms/17W). Connect them to both supply rails - one resistor on each rail - in the same position where you normally place the fuses, so that all current reaching the amplifier board has to pass through those two resistors. Those resistors play a significant role in protecting your unit from possible catastrophic failure in a first power up. If anything goes wrong for any reason, the unit under test will probably have a tendency to a draw very high current. All currents must go through protective resistors and it will produce a big voltage drop (the higher the current - the higher the voltage drop) that way protecting your unit from burning out (and your "pocket" and nerves too!)
--Now place a short accross the amplifier's input terminals and leave the output open - for the first power up, no load of any kind should be connected to the output, just DC voltmeter between output terminal and ground and on the range of 20-50V.
--Use another instrument as DC voltmeter on a 100mV range and connect it across one of 0,22ohms Source resistors. By measuring voltage drop over those resistors you can calculate quiescent current of outputs.
--Apply power but BE PREPAIRED to switch it off momentary if anything goes wrong! Observe readings of both instruments. Voltmeter on output terminals should read as close to 0V as possible. That voltage you should adjust with 1k preset. For fine adjustment turn your meter on more sensitive range as you approach low mV readings. It doesn’t have to be exactly 0V… everything in the range +/-20..50mV should be OK!
-- Millivoltmeter across source resistor should read about 13 to 18mV and that corresponds to about 60 to 80mA of BIAS per pair.
--Leave amp on for a 5-10 minutes and monitor readings on instruments. Output symmetry probably won’t change at all, but BIAS probably will as amp is heating up. From time to time readjust BIAS preset (10k) to return previous reading (13..18mV). After about 10-15 minutes amp should reach some kind of stabile temperature and you should readjust symmetry and BIAS one more time if necessary!
--If everything looks OK and stabile, turn power off, connect speaker on the output, remove short on input and apply some signal but DON’T REMOVE protective resistors yet!
--Turn power on again and slowly turn volume pot to apply signal. Don’t play it loud for now… just a few watts (5-10W max). Run it like that for a few minutes and if everything seems OK turn volume to not more than 1/3 from zero position. Don’t play on that power for longer than few moments because protective resistors will overheat and blow!
--Turn everything off, remove protective resistors and apply power directly, turn back volume to zero again and then power up!
Amp should be OK for use now.
Various problems are possible during this procedure. If you notice that you have high BIAS and you can not correct it to lower value with preset, it might be that amp is oscillating. That could also be with symmetry jumping up and down for a few volts and doesn’t respond to adjustment. In such cases you will have to provide oscilloscope for further investigations and problem solving.
hi dr bora.
thanks for the reply.
can i use 2k preset instead 1k for dc offset. because 1k preset is hard to find. or other type of preset can i use?
is it possible to adjust bias preset without power transistors ?
what is the maximum dc voltage for legend basic and stage master?
thanks.
thanks for the reply.
can i use 2k preset instead 1k for dc offset. because 1k preset is hard to find. or other type of preset can i use?
is it possible to adjust bias preset without power transistors ?
what is the maximum dc voltage for legend basic and stage master?
thanks.
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Sorry Nazirdigi but I really don’t have time to lead you or anyone else through fault finding procedures. That design has been done so many times by so many people and it is sure to work perfectly if assembled properly and with good components. Check you’re soldering and part placement for mistakes… many omissions and overlooked details are possible.
You can use 2k preset for SIMETRY and maximal supply voltages are written on schematics. They can vary +/-5..10% without problems but not more!
You can use 2k preset for SIMETRY and maximal supply voltages are written on schematics. They can vary +/-5..10% without problems but not more!
hi dr bora,
i found the problem.
my 220nf capacitor is bad (short).
now i adjust the bias to 13mv but little heat on heatsink and dc offset to 10mv, now amp is working.
Hi Dr. Bora and everybody! I'm new in forum.
I've read this topic, from page 1 to here. I'm interested in building the Sigma & Techno amps. They look seem similar topology, only difference is between BJT and MOSFET in OPS. My computer does not CAD program to draw the PCB. Someone please send to me the PCBs of both (top & bottom)?!
I've read this topic, from page 1 to here. I'm interested in building the Sigma & Techno amps. They look seem similar topology, only difference is between BJT and MOSFET in OPS. My computer does not CAD program to draw the PCB. Someone please send to me the PCBs of both (top & bottom)?!
