Hey A.
I have been working on finishing up the Super A and a peeceebee. I still need to buy some decent size heatsinks for the MKIII. The boards are so long it is hard to find long enough heatsinks. I may have to go with Conrad but the shipping if very expensive. I've had my Super A and peeceebee playing sind by side now for two days. Both sound very very good.
I see you having fun mister Terry that is great
Regards
Juan
enclosure
In which country is this shop?
I'm afraid about customs costs.
Best regards.
Thimios.
Thanks for reply.
In which country is this shop?
I'm afraid about customs costs.
Best regards.
Thimios.
OK so I finally got some large heatsinks and set things up yesterday. I had a couple issues. First off, my power supply is sitting right at +/-73vDc on the rails. I have 0R47 emitter resistors on the outputs. I began gradually raising the bias. I started with about 32mV across a pair of resistors. (16mV across one). I let it run for a while and kept feeling for the sinks to warm up. After about 20 minutes I gradually increased it until I had 50mv across a pair. Everything seemed fine and the offset was about 16mV on both channels so I hooked up some speakers and started playing music through it. It sounded good so I let it play, all the while watching the voltages across the emitters and feeling for heat. After about 15 minutes I noticed the mV start to rise on one channel. All of a sudden it shot up to about 250mV across the emitters so I shut it down. I hooked everything back up through the lightbulb tester and variac and tried bringing everything up slowly. As soon as that one channel would start to warm up the bias would shoot up again. I pulled the BD139 and replaced it with a 15032. Now the channel will hold bias but I haven't tried going above 16mV. Could it be that the BD139 has trouble with the rail voltages or is it likely that I just had a faulty one?
Thanks, Terry
Thanks, Terry
Your adjustment makes the amplifier dissipate almost 50 watts per channel
Without audio.... just in iddle...this drives the amplifier to drain a very high current in dinamic operation.
The heatsink is too much hot, and because of that the drivers are also too much hot and this increases the temperature.
Reduce your current or remove the drivers from the main heatsink and connect individual heatsinks to them to avoid them to pick up the heat from the main heatsink.
Another way is to re adjust your bias when the amplifier is very hot..this way when iddle and cool it gonna show a lower current.
I have used 1 milivolt maximum measured over the emitter resistor....to avoid excess of heat.
Carlos
Without audio.... just in iddle...this drives the amplifier to drain a very high current in dinamic operation.
The heatsink is too much hot, and because of that the drivers are also too much hot and this increases the temperature.
Reduce your current or remove the drivers from the main heatsink and connect individual heatsinks to them to avoid them to pick up the heat from the main heatsink.
Another way is to re adjust your bias when the amplifier is very hot..this way when iddle and cool it gonna show a lower current.
I have used 1 milivolt maximum measured over the emitter resistor....to avoid excess of heat.
Carlos
This video show the increase of current when the heatsink overheat
Also you can see clearly that when you overheat the drivers the current increases a lot...so...i you gonna use it class A, or with this range of milivolts your are adjusting, them it is better to remove the drivers from the heatsink and use separate heatsinks to them.
Meter show voltage drop....and voltage drop increases when current increases...you see that heat increases current..also you see the drivers are very sensitive to current.
You can see the video if you want.... also you can remove audio as the image explains by itself.
Part one, amp heat sensitivity - YouTube
Part two, amp heat sensitivity - YouTube
regards,
Carlos
Also you can see clearly that when you overheat the drivers the current increases a lot...so...i you gonna use it class A, or with this range of milivolts your are adjusting, them it is better to remove the drivers from the heatsink and use separate heatsinks to them.
Meter show voltage drop....and voltage drop increases when current increases...you see that heat increases current..also you see the drivers are very sensitive to current.
You can see the video if you want.... also you can remove audio as the image explains by itself.
Part one, amp heat sensitivity - YouTube
Part two, amp heat sensitivity - YouTube
regards,
Carlos
Sorry, I thought I read somewhere that you suggested 16mV across the .47R emitter resistors. I have it set at 12mV per emitter and that gives 156mA at the fuses. IF this is too high I will reduce it. I'm just looking to get it to the proper bias. Certainly not looking to run at Class A. Just want it to sound its best.
Thanks, Terry
Thanks, Terry
It is all right.... listen it this way... test it this way
And you gonna see the heat and then you can reduce a little your current, or install some fan, or you can put your driver transistors outside the main heatsink.
I am uploading a video, in special for you..no rarsh or hard or "F" words, explaining and showing in details what is going on inside your amplifier.
One more hour...or two hours (video is big, detailed and has real overheating) it gonna be here for you to see..also for all my friends to understand what is going on,
Video gonna be edited , rendered and uploaded...this gonna take some time.
regards,
Carlos
And you gonna see the heat and then you can reduce a little your current, or install some fan, or you can put your driver transistors outside the main heatsink.
I am uploading a video, in special for you..no rarsh or hard or "F" words, explaining and showing in details what is going on inside your amplifier.
One more hour...or two hours (video is big, detailed and has real overheating) it gonna be here for you to see..also for all my friends to understand what is going on,
Video gonna be edited , rendered and uploaded...this gonna take some time.
regards,
Carlos
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