Hi all
I did what would be called the C300.3 into a vero board
but the vas and drivers are running very hot,
I changed R31, R32 and R24 to 100Ù
But the vas still too hot.
I'm using 2SC2333/2SB633 for vas and drivers.
outputs 2SA1094x6 at 49volts.
I did what would be called the C300.3 into a vero board
but the vas and drivers are running very hot,
I changed R31, R32 and R24 to 100Ù
But the vas still too hot.
I'm using 2SC2333/2SB633 for vas and drivers.
outputs 2SA1094x6 at 49volts.
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.
An externally hosted image should be here but it was not working when we last tested it.
what would be nice to know
is the voltage you have across R24 & R31
this way we can know like what current you have in stages
--------
What sets the voltage across R24 is the RED LED.
Most RED LEDs have 1.7 Volt at 7 mA
so the voltage across R24 normally should be ~1.0 V
But there are RED LEDs with higher Voltage than 1.7V.
And these can be used just a well. See below.
With original 56 Ohm for R24, we get a bit less than 20 mA in this stage
--------
Voltage across R31 (and R32) can be something like 0.9 Volt
With original 33 Ohm, this may give something like
35-40 mA in Q15 and Q16 at idle
AS the 2SA1094 have good gain, the base current into those 8 transistors is only a few mA, of that 35-40 mA value.
If you have normal Class AB bias: 50-100 mA into each Output transistor
Gives 20-40 mV across those Emitter resistors.
---------
I would recommend you use the orignal values for R31,R32.
And you should try to get ~18-20 mA through R24.
Depending on your used LED and so the voltage across R24,
you may have to adjust the value of R24 (56 Ohm),
until you get like 18-20 mA.
---------
It is nothing wrong those VAS driver transistors get a bit hot.
Q15, 2SC2333 is one 15 Watt TO220
Q16, 2SB633 is one 40 Watt TO220 (as what I got from datasheets)
With small separate heatsinks they can take a couple of Watt.
40 mA x 50 Volt = 2 Watt
20 mA x 50 Volt = 1 Watt
---------
The reason I should want to use original current levels in VAS driver
is that this is probably tested to work well.
At least I would not change, reduce the current, too much.
Lineup
is the voltage you have across R24 & R31
this way we can know like what current you have in stages
--------
What sets the voltage across R24 is the RED LED.
Most RED LEDs have 1.7 Volt at 7 mA
so the voltage across R24 normally should be ~1.0 V
But there are RED LEDs with higher Voltage than 1.7V.
And these can be used just a well. See below.
With original 56 Ohm for R24, we get a bit less than 20 mA in this stage
--------
Voltage across R31 (and R32) can be something like 0.9 Volt
With original 33 Ohm, this may give something like
35-40 mA in Q15 and Q16 at idle
AS the 2SA1094 have good gain, the base current into those 8 transistors is only a few mA, of that 35-40 mA value.
If you have normal Class AB bias: 50-100 mA into each Output transistor
Gives 20-40 mV across those Emitter resistors.
---------
I would recommend you use the orignal values for R31,R32.
And you should try to get ~18-20 mA through R24.
Depending on your used LED and so the voltage across R24,
you may have to adjust the value of R24 (56 Ohm),
until you get like 18-20 mA.
---------
It is nothing wrong those VAS driver transistors get a bit hot.
Q15, 2SC2333 is one 15 Watt TO220
Q16, 2SB633 is one 40 Watt TO220 (as what I got from datasheets)
With small separate heatsinks they can take a couple of Watt.
40 mA x 50 Volt = 2 Watt
20 mA x 50 Volt = 1 Watt
---------
The reason I should want to use original current levels in VAS driver
is that this is probably tested to work well.
At least I would not change, reduce the current, too much.
Lineup
Q11 should be placed onto Main Heatsink
close to those 8 Output transistors.
I do not see any BASE stoppers resistors.
Not even to the 8 output transistors.
And not to Q15, Q16.
for the 8 power devices, you may use 8x10 Ohm resistors into Base
and put as close as practically possible to the base pin of each T
close to those 8 Output transistors.
I do not see any BASE stoppers resistors.
Not even to the 8 output transistors.
And not to Q15, Q16.
for the 8 power devices, you may use 8x10 Ohm resistors into Base
and put as close as practically possible to the base pin of each T
I built C200 and 300 ...
1.Put the drivers on the main heatsink.
2.make sure red led is 1.6-1.7v (most are 1.9+ except deep red
low brightness-low current Al-GA-AS .I use red led CSS on ALL
my amps.)
3.large VAS heatsinks/change r16 to 10K-2w (helped me).
I eventually scrapped the c300 because I didn't like the sound
but it never blew up
and seems to be a
stable design...good luck..OS
1.Put the drivers on the main heatsink.
2.make sure red led is 1.6-1.7v (most are 1.9+ except deep red
low brightness-low current Al-GA-AS .I use red led CSS on ALL
my amps.)
3.large VAS heatsinks/change r16 to 10K-2w (helped me).
I eventually scrapped the c300 because I didn't like the sound
but it never blew up
and seems to be a stable design...good luck..OS
Ok for some reason R19 went into a flame after some seconds
I power it. I don't dare to keep using this now at least
on this vero board. I did two channels of this amp before
on a breadboard and never had problems only the heat.
My favorite amp is this one
n55n.com_86DKCckL0A.jpg
the Melody 400 but I need to know how to do it quasi
I will do a new topic about it later.
Thanks ppl for the quick help.
I power it. I don't dare to keep using this now at least
on this vero board. I did two channels of this amp before
on a breadboard and never had problems only the heat.
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.
My favorite amp is this one
n55n.com_86DKCckL0A.jpg
the Melody 400 but I need to know how to do it quasi
I will do a new topic about it later.
Thanks ppl for the quick help.
That amp is
very similar to the Leach amp, same triple darlington outputs
but with a different CSS.
I never had problems with amps blowing up
mainly because I make boards. All those wires up in the
air greatly increases the chances of noise and instability.
I draw these amps out on graph paper first:
An externally hosted image should be here but it was not working when we last tested it.
lay the graph paper on top of the board, center punch the pads
use the design as a drawing guide and get:
An externally hosted image should be here but it was not working when we last tested it.
etch it,
An externally hosted image should be here but it was not working when we last tested it.
very low tech, but cheap and the amps don't blow up.
BTW , amp above is similar (QUASI) to c300 but a better design.
To do the melody Quasi (pnp) reverse the layout of this:
http://www.ampslab.com/c200qc.htm
same as you did to your c300 but add 10 ohm basestoppers
to all output devices.
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