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Old 27th June 2012, 03:31 PM   #131
xslavic is offline xslavic  Moldova
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Default :)

the maxium power they can output so if a device needs more than rated power it will burn out the zener
divide W/V=mA
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Old 27th June 2012, 03:34 PM   #132
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Hi Xslavic,

Aha, I understand. So using 3W in stead of 400mA zeners is not a problem at all. Thanks!
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Old 3rd July 2012, 03:39 PM   #133
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Little kick :-) Is there really nobody who can explain to me which parameters in the datasheets are most important when comparing the 2SJ313 and 2SK1023 to the original VP/VN0210N5?
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Old 3rd July 2012, 11:05 PM   #134
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Sorry for the unnecessary kick, I was not able to edit the post above to add the next text :-)

I was able to change a few things the last few days to the build. There just were some aspects which I was not realy statisfied with. I've bought a few nice fuse sockets, so why not using them. I added a fuse in series with the primairies of the little transformer which powers the speaker protection. Chances of failure are not very likely, but better safe than sorried. I think I will add in the next few days also fuses in series with the secondairies of the 'big' transformers.

Click the image to open in full size.

I also changed the connections to the TO-3 devices. At the time I mounted them to the heatsinks almost a year ago, I soldred thick copper wires directly to the leads of them. But I realised later that the copper wires could, when you apply little force, easily detach from the leads of the TO-3 devices. The warm / cold enviroment inside the amplifier does no good to the strength of the solder connections, so it will even get worse. In worst case scenario the copper wires could detach from the leads and make short circuit to the heatsink. Sure this would give nice fireworks, but hey 31 december is actually far away, and to be fair I prefer a working home made amplifier above home made fireworks haha. The copper wires were isolated by PVC. Altough PVC has a melting point at about 180 degrees Celsius, it's glass temperature (Tg, which is temperature at which the isolation becomes a bit brittle/liquid) is 80 degrees. Since the heatsinks get hot, no doubt about that, I had to think of a better candidate. So I replaced the cable with thick öilflex cable. This cable can withstand 180 degrees easily. I tried to lit it on fire (Kaplaars is sometimes a little pyromaniac haha), but that was very hard. Conclusion great cable for the task! I attached little thimbles to the cables. This way I made a much more reliable and stronger connection. Offcourse, the best solution would be using 'real' TO-3 sockets, but they would not fit perfectly to the heatsinks, so I hope this compromise will do.

Picture:
Click the image to open in full size.

Last edited by Kaplaars; 3rd July 2012 at 11:17 PM.
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Old 7th July 2012, 07:30 AM   #135
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Wow it is realy quiet here. But not in Wageningen, Holland were a KSA-100 is born because, yes friends........ IT FINALLY WORKS!!!!!!!

I was realy nervous when powering it up. I've hooked the dummyload together with a Zobel network to the outputs. This was it, was al the effort I've made going to pay off, or did I make a nice piece of expensive firework. With a fire extinguisher in my left hand and with my right hand across the dial of the variac, I slowly powered it on. Hmm, no fireworks... that seems good. And It kept good!!!

Click the image to open in full size.

But there is a but friends, I got no bias to one halve of the MJE15004's. I discovered a little mistake on Jims boards, there is missing a little track from the emitter of the middle MJE15032 to the MJE15033 compaired to the original. So I had no bias on connection DRIVE P1. But that was fixed easily with a little wire:

Click the image to open in full size.

Click the image to open in full size.

After fixing this, there was also current from DRIVE P1. Everything seemed to go OK so I pressed the proverbial gas pedal a bit more ;-). Freakin unbelievable how much power it has. I've measured 40 VAC max output across 8 Ohm load!!! I was able dial the DC offset to 0 mV very easy. Bias spread is about 10 mV across the different TO-3 devices. Not bad, I since I have not matched the devices :-).

Click the image to open in full size.


After some testing (it was 2:00 p.m. already) it was time for some music! It's is unbelievable how it sounds, I try to be as objective as possible, but it is so dynamic, so much power. No hiss, no hum, nothing!!! I've set bias to 450 mV right now. Fans are running full speed right now (fan control is not finished yet). For Dutch standards today is pretty tropical, it is about 26 degrees outside and here in house it is almost 33 degrees. But despite of that, the tunnel cooler gets mildly warm.

Glad that it works, and VERY VERY happy that it sounds even better!!!!!!! But there is still a lot of work to be done, because now I know it works I can and thus still have to mount the lot in the cabinet :-)

Last edited by Kaplaars; 7th July 2012 at 07:58 AM. Reason: Pressed enter to fast
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Old 7th July 2012, 05:33 PM   #136
spurlte is offline spurlte  United States
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Quote:
Originally Posted by Kaplaars View Post
Wow it is realy quiet here. But not in Wageningen, Holland were a KSA-100 is born because, yes friends........ IT FINALLY WORKS!!!!!!!

I was realy nervous when powering it up. I've hooked the dummyload together with a Zobel network to the outputs. This was it, was al the effort I've made going to pay off, or did I make a nice piece of expensive firework. With a fire extinguisher in my left hand and with my right hand across the dial of the variac, I slowly powered it on. Hmm, no fireworks... that seems good. And It kept good!!!

Click the image to open in full size.

But there is a but friends, I got no bias to one halve of the MJE15004's. I discovered a little mistake on Jims boards, there is missing a little track from the emitter of the middle MJE15032 to the MJE15033 compaired to the original. So I had no bias on connection DRIVE P1. But that was fixed easily with a little wire:

Click the image to open in full size.

Click the image to open in full size.

After fixing this, there was also current from DRIVE P1. Everything seemed to go OK so I pressed the proverbial gas pedal a bit more ;-). Freakin unbelievable how much power it has. I've measured 40 VAC max output across 8 Ohm load!!! I was able dial the DC offset to 0 mV very easy. Bias spread is about 10 mV across the different TO-3 devices. Not bad, I since I have not matched the devices :-).

Click the image to open in full size.


After some testing (it was 2:00 p.m. already) it was time for some music! It's is unbelievable how it sounds, I try to be as objective as possible, but it is so dynamic, so much power. No hiss, no hum, nothing!!! I've set bias to 450 mV right now. Fans are running full speed right now (fan control is not finished yet). For Dutch standards today is pretty tropical, it is about 26 degrees outside and here in house it is almost 33 degrees. But despite of that, the tunnel cooler gets mildly warm.

Glad that it works, and VERY VERY happy that it sounds even better!!!!!!! But there is still a lot of work to be done, because now I know it works I can and thus still have to mount the lot in the cabinet :-)
I am also VERY VERY happy that you stayed on this thread. Where else would I have found the little missing emitter track. Thank you so much. Now I am wondering what speaker system you will setup for this successful power amplifier. No hiss and no hum. Will you still change the 75C temperture sensor to a higher sensor? Very nice dummy load--May I ask what was the current to it at full load? Are you expecting more than 100 watts?
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Old 7th July 2012, 09:29 PM   #137
Jozua is offline Jozua  South Africa
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Kaplaars

Congratulations !

Very nice work. You still not 100 % in the clear as within the confined space of the cabinet, things can get a bit hotter.

Regards and welcome to the club.

Jozua
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Old 7th July 2012, 09:56 PM   #138
a.wayne is offline a.wayne  United States
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Glad to hear the boards work , funny how The error was never noted before , did Jim not know ...?

Anyway thanks for the results and info Kaaplars , could you post scope pics ...

Regards
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Old 7th July 2012, 10:10 PM   #139
AVWERK is offline AVWERK  United States
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Feels good after all the hard work doesn't it? Glad to hear you kept the smoke contained.
What does a 10k squarewave look like? Nice and square corners, peaks, or any fuzz on top of the signal?

If you ever do a full load power test, you will be inputing a 1vrms sine with and without a 8 ohm load.
A full frequency sweep should show equal amplitude with no peaking
A severe test is at full load you remove a load and place a .1uf 400v film cap and remove the cap quickly if it oscillates. This must be a tight connection if you decide to do this. I used a banana plug with the cap across it.
This will cover most of worst speaker loads you might come across and bring any issues to the surface.

Regards
David
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Old 8th July 2012, 07:28 AM   #140
neychi is offline neychi  Croatia
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Michael,

As I already told you, I'm glad it works, conngratulations! Be gentle to your parents at this summer time.


@a.wayne: this error is not on all pcb's. On my boards this trace exist.
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