AK47 (REDD47 ) documents

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mitsos

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May 4, 2007
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I'll be posting some documents here to help people build the AK47 pcbs sold in the black market.  The schematic is pretty much the same as the REDD47.  I'll be editing this post to add more into later, but for those who may have gotten the PCBs already, see the attached schematic.  I'll post an image of the PCB with some notes soon. 

cheers! 
 

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Hey all, I'll be out of town for the next week or so. 

Here is the schematic for the PSU. 

The 48V is a doubler circuit.  Should work fine with around 20-0-20 VAC or so.  I have made it into a tripler with a couple of trace cuts some diodes and jumpers. 
 

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Hi
Thanks for your PCB !
I'm starting to build a a stereo version of the AK-47.
Waiting for some information  for PSU pcb (48v schematic).
Thanks a lot!
 
manulaf said:
....  :'(
Hi, the PSU schematic is posted above. I'm not sure if that's what you were looking for?  Like I said it can be made into a tripler or even higher with a couple of trace cuts and jumpers. For that you should use discrete diodes instead of bridges though.  Is that what you'd like more info on?  I think I may have one around that I can post pics of. 
 
madriaanse said:
Where can I find the PCB's?
Hi,

I designed them for a  project I did a few months back and had a few leftovers, which I sold in the BM last month.

FWIW, it's not a hard circuit to do P2P.  First time I just soldered everything directly to the tube sockets and a couple small pieces of tag strips, with no noise problems or anything.


EDIT: Attached image of silkscreen to help with building. 
 

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Winetree said:
Or just a BOM for the AK47 P.S.B. there's no labeling on the board.
Hi, yes, the values didn't print out on the silkscreen layer, but the component numbers are there and also in the schematic in the first post.  Most can be 1/4W resistors, except for R1 and R2, which should be 2W and 5W, respectively. 

For the film caps I had originally laid it out for Wimas but I've used Panasonic polypro as well and they work just fine.
 
Hi
I need some advise to find the right power transformer. I live in europe and I saw on this website severals ones.

https://www.don-audio.com/toroid-toroidal-audio-transformers-power-trafos

Is there somebody who can advise me ?


Thanks



 
going over schematic for BOM.
AK-47                      C6  Can't read
Power Supply      C4-C9  Value and voltage not listed.
                                      B1 & B2  ?
Resistors                  Metal film 1 %  or any Carbon Comp?
 
Winetree said:
going over schematic for BOM.
AK-47                      C6  Can't read
PSU decoupling cap, 10uF/450V will work. 8u2 on original schematic IIRC.
Power Supply      C4-C9  Value and voltage not listed.
                                      B1 & B2  ?
100uF usually. Voltage depends on what you start with and what you are multiplying to.  First couple I usually use 35V, then go up to 50 or 63, even 100V, depending what the voltage ends up at.  I have blown up a couple here, so be careful.  Might be best to install them in stages and test voltage before installing the next stage.  Also, you can modify this part, like I said above, in case you need a higher multiplication factor (for example, if you have 2x 6VAC windings). I think I might be able to post a pic of that in case it's useful.
Resistors                  Metal film 1 %  or any Carbon Comp?
I use metal film for most things, that's usually what I have around. The higher wattage I use what I can find.
 
Do you think this power transformer can do the job for your PSU?
https://www.don-audio.com/Toroidal-Transformer-Mila-sec-250vct-63vct-48V

Thanks !
 
Sure.  With a 48V winding you don't need a multiplier, so you'd build it like a normal rectified PSU:

(double check this)
Solder jumpers in place of C4, C5, and C9.
Diode bridge in B1

Leave B2, C6, and C7 empty.

That reminds me, Winetree asked about B1 and B2 and I forgot to answer:
Winetree said:
Power Supply     
                                      B1 & B2  ?
You probably figured it out by now, but they are those little 1-2A diode bridges. Honestly,  they are more expensive than individual diodes, so if you don't mind the PSU not looking "clean," I would just use diodes in their place.
 
manulaf said:
Now I have to find tubes. Any advise ? Expensive NOS or new production ?
Hard to say. I've only used old EF86, but most were used, so not NOS. Most worked fine, but I never knew until I tested them. 0  I wouldn't go out and buy the most expensive NOS tubes right off the bat, I'm sure EH or JJ or someone make them currently. While some "audiophiles" might frown upon new tubes, those will be your best bet at getting a working tube.  Of course, if you find someone selling a bunch of NOS tubes for cheap, it might be worth the gamble.

I've also used 6N1P instead of the E88CC. It's marketed as a replacement, but is not really the same tube. It does work though and you can get them cheap from ebay sellers in ex-soviet countries, so those are worth a try too. You can always find another use for them if you don't like them in the 47.
 
Ok thanks !

There is something that I don't understand about tube socket implantation. You say that I have to solder tube socket below the PCB with taller component. But were did you put the input transformer (cinemag 75101 in my case) ?
Thanks
 
Hi, just saw this.  The ones I built had the tubes on the bottom (actually on top...the PCB was upside down).. Every other component was on the silk screened side of the PCB. 
 
Hi !

I began my stereo Redd 47. But before plug it to Main AC, I have few questions:


1- I use a secondary center tap power transformer (HV secondary and heater)
Do I need to plug them to ground or keep them floating ?

2- What voltage I have to set B+ ?

3- I use cinemag 75101 as input trafo and cinemag cm-9661 as output trafo both have dual primaries. Can you tell me the better way to plug them.

I will post some pictures soon.
Thanks a lot
Manu
 

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