Toa RX-7 Update

  • Thread starter Thread starter Somnium7
  • Start date Start date
PSU Completed

I hate this power supply! I never want to see the inside of it again ;)
It is working now ...and better than it ever did before I might add.

Check out the new regulator core PCB

reg-core-pcb.jpg


See the album for the entire story...
http://s108.photobucket.com/albums/n13/somnium7/gear/PSU/?albumview=grid

I still need to perform a few tests and take some measurements. Everything seems alright though. I can't wait to get back onto the audio stuff again!
 
Looks great :cool:

Question: how do you get desired output voltage with this design?

/respects
 
Dr ZEE said:
Looks great :cool:

Question: how do you get desired output voltage with this design?

/respects
Click to expand...

It's the voltage rating of the zener diode plus roughly 2.5V for the LED (can vary depending on LED specs). If you need to trim it finer then a normal rectifier diode can be used and they give a voltage drop of 0.6 each.

e.g. to obtain a 15V output you could use a 12V zener and a high brightness green LED with a 3 volt drop or a 12V zener and 5 regular diodes.
 
Somnium7 said:
It's the voltage rating of the zener diode plus roughly 2.5V for the LED (can vary depending on LED specs). If you need to trim it finer then a normal rectifier diode can be used and they give a voltage drop of 0.6 each.

e.g. to obtain a 15V output you could use a 12V zener and a high brightness green LED with a 3 volt drop or a 12V zener and 5 regular diodes.
Click to expand...
uh, cool. a bit tricky, but doable :D
where did you find this zen/led idea? or did you invent it? if you did - how did you get this idea? - just curious :)
 
Somnium7 said:
I hate this power supply! I never want to see the inside of it again ;)
It is working now ...and better than it ever did before I might add.

Check out the new regulator core PCB

reg-core-pcb.jpg


See the album for the entire story...
http://s108.photobucket.com/albums/n13/somnium7/gear/PSU/?albumview=grid

I still need to perform a few tests and take some measurements. Everything seems alright though. I can't wait to get back onto the audio stuff again!
Click to expand...

Nice work! I'm a little surprised though that the original PS seemed so puny for 32 current hungry channels. I imagine the LM317s will get pretty hot if running the board full out.

:)
 
Beck said:
Nice work! I'm a little surprised though that the original PS seemed so puny for 32 current hungry channels. I imagine the LM317s will get pretty hot if running the board full out.

:)
Click to expand...

Thanks Beck! This circuit is only the core of the PSU, it simply does the regulation. The output from it drives a pass transistor stage consisting of four power transistors and they provide up to 4 amps of juice to the console.
 
Somnium7 said:
Thanks Beck! This circuit is only the core of the PSU, it simply does the regulation. The output from it drives a pass transistor stage consisting of four power transistors and they provide up to 4 amps of juice to the console.
Click to expand...

Ah, that should do it. :)

I don't think I've ever used a TOA... not that I remember. From the looks of the channel card it's a pretty awsome console.
 
Beck said:
Ah, that should do it. :)

I don't think I've ever used a TOA... not that I remember. From the looks of the channel card it looks pretty awsome.
Click to expand...

It's getting there, one capacitor at a time. ;)
 
Decided to scrap that hand-wired board for something better. I just placed an order for this:

ln-reg_01.gif


I designed it to include all the circuitry in the original Toa regulator board. After all I want tis thing to last after doing all of this work! ;)

Also, about the schematic I posted earlier for my lo-noise regulator...

The proper way to calculate the output voltage is as such:
Vz + 1.25 + 0.6
Where Vz is the zener voltage rating, 1.25 is the internal reference of the regulator IC and 0.6 for one normal diode in series with the zener diode. In the case of an LED the 0.6 changes to 1.94 if it's green and 2.23 if it is red. Of course different LEDs from different manufacturers will have some varying drops.

Using the proper voltage of zener and a combination of diodes, LEDs or diodes and LEDs you can program the output for almost any voltage up to the maximum of the regulator IC.
 
Mike, thanks for the details on output voltage. I may try it someday...uhhh, if ever :(

Good luck with getting you board made WELL, where ever you ordered it from.
I've "struggled" with those "part # 276-170" twice ;) , not to say that they are useless, but kinda' hard to work with. The holes are kinda' too large and things "dont stick" well ...heh heh :D
 
Dr ZEE said:
Mike, thanks for the details on output voltage. I may try it someday...uhhh, if ever :(

Good luck with getting you board made WELL, where ever you ordered it from.
I've "struggled" with those "part # 276-170" twice ;) , not to say that they are useless, but kinda' hard to work with. The holes are kinda' too large and things "dont stick" well ...heh heh :D
Click to expand...

The PCBs from ExpressPCB are outstanding quality. I have been using them since 1999 and have yet to find a reason to complain. Their software is like using M$ paint - dead simple.

The ratshack proto-boards are nice for one reason only, they have the same layout as a breadboard. Strip-board is alot better for more complicated project as long as you have a steady hand with an x-acto knife.

The biggest problem I find with proto-boards is when you have to do rework for some reason. Reheating the connections makes the pads peel up and all sorts of nightmares. :mad:
That's one of the reasons I chose to get a PCB made - I needed to rework my circuit....
 
Somnium7 said:
The ratshack proto-boards are nice for one reason only, they have the same layout as a breadboard.
....
Click to expand...
yeah, that's a cool thing about them
Somnium7 said:
The biggest problem I find with proto-boards is when you have to do rework for some reason. Reheating the connections makes the pads peel up and all sorts of nightmares. :mad:
....
Click to expand...
Arrrrrrrrrr, you tell me. I wonder if this is the issue with the quality specifically of R-Shack boards.
The first time I was using that board was a real nightmare, as I was "designing" on the fly ..heh heh :D :o. The second time around I was planing everything ahead, used computer to draw layout, then printed it out and followed the 'blueprint'.
Those boards are sort of "one shot"-type, hit or miss :eek:
I even created printable templates for two types of r-shack boards to be used to draw/sketch the layout.
d-load and save them if you may need them some day, here are the links:

Modular Breadboard PCB Designer Tamplate (for RadioShack part # 276-170)

55x40 points PCB Designer Tamplate (for RadioShack part # 276-147)
 
The new PCBs shipped out today. I'll have them in hand on Monday. Can't wait!

In the mean-time it's back to the channels. I made a massive parts order awhile back including tons of metal film resistors and high quality caps. I just finished using these parts on one of the group modules where I have now replaced 87% of the original components on the PCB. I scrapped out anything and everything in the audio path that I deemed suspect in one way or another.

I also devised my strategy for swapping out opamps. The summing amps in the group modules and the mic preamp buffers in the channels are getting replaced with the $6/each LME49860. These are the crucial areas where I don't want ANY noise or distortion.
The EQ circuits in the channels and the group module Echo/Aux returns are getting the TLE2141 devices. These chips have a high distortion rating so I want them in there for "color". These EQs have a VERY retro 70s sound to them already so a little more distortion won't hurt. Certainly a big improvement over the original opamps :rolleyes:
The rest of the opamps will be swapped for the OP275 simply because I like how they sound. They have a sort of smiley-face EQ-curve sound. Works well with the music I make.

Still debating about ordering the John Hardy 990s. I originally planned to make my own DOAs. I might yet do this. Still a few 990s would be really sweet on the mic pres.

Finally, I did something cheesy :D:D
I will replace the channel-on LEDs as I go through the console with interesting new colors, like blue, aqua and purple. Yeah I know, really ghetto ;)
 
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