Johnny D's 700 Adventure

[laatsch55]

I believe a regulated power supply of the + and - variety is called for, an adjustable one at that. OK, back to work I've stirred up enough s%$# already. Good idea on the matching though. It should give the outputs some more reliability.

 

[Gepetto]

Hi John and Lee
Here is the schematic for what I described earlier in this thread.

 

[laatsch55]

Thank You Sir.

 

[soundude]

thanks Joe...

 

[soundude]

Joe I was trying to figure out the rating of the transformer, lee said its around 2.5k, so I did the math for the voltage. converted from dc to ac voltage and came up with 70.92 from center the one leg so total winding is 140v, and with the VA rating got about 18 amps for the output.
Is this correct? I could just stick my probes in for the voltage but have to disconnect and put on the cheaters with the surgical light so I dont miss the bridge connections....Zaappp!!

 

[laatsch55]

What do you want to measure John. I still have access to the inside of Kevin's.

 

[Gepetto]

Roughly 1.3KVA for the PL700 John.

 

[soundude]

Lee / Joe, trying to figure the trannies current rating, know the voltage on the ac is roughly 200vac across the entire winding. I'm figuring current roughly rated 6.5 amps...??
I(A) = 1000 × S(kVA) / V(V)

Your thoughts...

 

[laatsch55]

The service manual; calls it a 2.5 killowatt transformer. So that would give you 20 amps total on the secondary with that amperage shared by the two sides of the centertap. 10 amps on the plus side, 10 amps on the minus side.

But the AC voltage on the secondaries is 162 VCT. so for a 2500 watt transformer with a voltage of 162 we have--
Watts =amps X volts or Amps = watts/ volts- or amps = 2500/162 amps =15.43 7.73 amps per side.

 

[soundude]

cool, thx Lee...was on the rite track just didn't have my numbers rite.
DC voltage I got was 210v and almost 108vdc on each rail so 108/1.41 = 76.5957vac...
2.5k/153.191 = 16.319amps...rite?

 

[laatsch55]

To convert to DC you need to go peak to peak not RMS, I THINK. There's something funky happens when you go DC. There are some losses but you are close on the amps. Remember , commercial audio equipment isa designed for 60-70% loads on the power supplies due to the non-continous nature of music. Usually the hardest load will be simultaneous tyesting of both channels to maximum output.

 

[kevin]

Yea..... What he said !!! lol

 

[soundude]

Lee / Joe I'm lovin this 700 now..I'm going to venture and build a 400 from scratch.
So my first order is going to be the power supply. I found a company close to me called antek that makes toriodal transformers..they have a dual 75 volt 1.5kw which would give me 10 amps per winding. What you think?
http://www.antekinc.com/details.php?p=153

 

[ksrigg]

Hey Soundude....If you start turning this into reality, start a thread and document everything. I'd love to do the same thing. I already have the TO-3 sockets and all the resistors for a 400.....if you find a workable transformer that would be cool....then chassis....then.....wow this could be major cool...there may be some ideas which could be borrowed from this Recording Studio Designs 800b Phase Linear 400 clone that I have.....( it has a fan, you select the AC power foom 220, 240, 110, 120....) There may be some cool ideas in the circuitry too, I'm just not smart enough to know..

 

[soundude]

Ksrigg, definitly, it going to be a reality for sure, I have the heatsinks already from a old altec lansing 200w amp...
I want to do this but I just need info on the transformer, have a bunch of sources...antek seems to be the choice..noticed the 400 is only 10amp on the PS so this tranny will be great, parallel the windings for 20amps..[attachment=1:2hs3znn2]Picture1 001.jpg[/attachment:2hs3znn2][attachment=0:2hs3znn2]Picture1 002.jpg[/attachment:2hs3znn2]

 

[ksrigg]

I hadn't given much thought to heatsinks....yet.....are you going with everything inside a chassis? I might emulate the Recording Studio Designs model. The transistors are mounted on heatsinks, but the majority of the heat is handled by a big fan...I think a donor PL 400 from the early days of 4 finned sinks might fit nicely in the chassis I have in mind.

Do you have any concepts in mind? Big VU Meters? Any switches, or like a PL 400? Capable of mono/stereo, or strictly stereo? Targeting 200....250 watts per channel into 8 ohms? Gotta use the White Oak driver board !! And while he has them...some BIG MONSTER CAPS from APEX JR. 35,000 mfd 120 VDC....but they are 3" in diameter and about 5 1/2" tall....BIG MONSTERS...

 

[soundude]

I have a few ideas, thinking of mounting the heatsinks to the sides of the chassis, that will keep it from the powersupply and be readily avalible to the atmosphere for easy cooling. also have couple of sites for meters, but was thinking of a peak meter, 10 leds per channel. dont know what kinda chassis to go with aluminum or steel or wood...
The key is getting the right size trannie with enough reserve..joes input and board are goin to be key as soon as powersupply is complete. If I double the size of the chassis I can do a stereo amp if not then 2 monos, but like i said the transformer is the issue rite now. I can get 2 smaller trannies for mono or the 1.5k for stereo. If that size is suffiecent. Need joes and lee's input in this area. Have no paperwork in this area for size or voltages.
http://www.antekinc.com/gview.php?d[]=0

 

[ksrigg]

The idea of creating an amp from a concept is great, but as Mark told me, much easier said than done. I have a small tube amp that was designed and built by a guy who sells them on eBay, and I know there are some tube amp designs that are proven and can be built without much, if any designing, but a solid state amp might be a different animal altogether, and especially for someone who isn't an EE. And when you start adding meters and lights or LED's other stuff, it looks like it gets very complicated very fast. bout the only thing I MIGHT be able to do would be scavenge all the parts from a Phase Linear, and put it in a different chassis d hope it worked...I know Lee will pull off his big 1.5 KW amps running 220V....and I'm sure you can pull this one off. I only wish I had some electrical background so I understood a little of this stuff, but I don't so I can wish all I want to, but I just don't have the background or knowledge to pull something like this off.

 

[soundude]

its never to late to start, its really not hard if you can read schematic and know the parts symbols and direction of them.
use this anology, if you can play a piano you have 75% of the knowledge to to play any instrument, other 25% is the keying or fingering of the notes.
I've been doing this very young around 9 years old, 46 now. Tube amps I basic dream circuits in my sleep, problem with home brews from ebay is the builders don't use high quality. Best to buy a tube device from a old guy who dabled in it than a kid tinkering.
Tubes are the easiest to learn because there is basically caps and resistors thats it, of course transformers and tubes.
I design many amps and preamps that have been proven and still workin for 20 something years.
I posted one somewhere around the fourm.
Tubes are more robust than transistors, you can short a tube circuit and the tube still lives, don't try it with transistors though...huge chain effect...POOF!

 

[soundude]

lets see if this works, posting a link within the forum.
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