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  #11  
Old 9th February 2017, 08:25 AM
Richard Richard is offline
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Default Re: WAD K5881 Circuit Diagram Needed

Quote:
Originally Posted by yuming916 View Post
I am also thinking that this kit might be the pse one.
Hello and welcome,
The PSE had gold/brass coloured TX caps (difficult to tell from your pic) and the OPTXs were taller stacks than the PP.

Last edited by Richard; 9th February 2017 at 08:58 AM.
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  #12  
Old 10th February 2017, 08:03 AM
yuming916 yuming916 is offline
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Default Re: WAD K5881 Circuit Diagram Needed

Hi Richard,
Many thanks for your reply.
You can see the gold/brass coloured TX caps
http://www.world-designs.co.uk/forum...38&postcount=1
and they look taller than MKII.
I have received the kit already. The high voltage of the secondary of the power TX is measured to be 350V AC.
The DC electric resistance of the primary of the OPTXs are measured to be 136Ω-146Ω. So the ratio is neither 44% nor 50%. So I am confused.

Last edited by yuming916; 10th February 2017 at 08:16 AM.
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  #13  
Old 10th February 2017, 09:32 AM
John Caswell John Caswell is offline
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Default Re: WAD K5881 Circuit Diagram Needed

An even simpler way to tell of it is an SE type is to see if the two anodes (plates) of the 5881s are connected together and then go to the output transformer.
Once you have eliminated which type it is PP or SE, then we can sort out which PP variant it may be.
Either way I can supply the schematics

John
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  #14  
Old 10th February 2017, 12:01 PM
Richard Richard is offline
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Default Re: WAD K5881 Circuit Diagram Needed

Quote:
Originally Posted by yuming916 View Post
Hi Richard,
Many thanks for your reply.
You can see the gold/brass coloured TX caps
http://www.world-designs.co.uk/forum...38&postcount=1
and they look taller than MKII.
I have received the kit already. The high voltage of the secondary of the power TX is measured to be 350V AC.
The DC electric resistance of the primary of the OPTXs are measured to be 136Ω-146Ω. So the ratio is neither 44% nor 50%. So I am confused.
Yes they look like PSE. Clean them with a damp (water) microfibre cloth, no solvents or abrasives.

Check as John says or check the connections between 5881 valves and the OPTX looking for 100R grid resistors between valve pin 4 to OPTX tap. These are on the PSE and not present on the PP. Voltages must be checked under load (valves fitted) and 350V HT looks about right.

If you PM me or John your email address I'll send what I have (personal use only).
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  #15  
Old 10th February 2017, 01:32 PM
yuming916 yuming916 is offline
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Default Re: WAD K5881 Circuit Diagram Needed

Hi all, Thanks for all your help.
Unfortunately, besides the two big capacitors, only the three transformers and the one inductor are left over inside the box. All the other components were gone. The wires were cut so that I could not trace the connections. Fortunately
the voltage of the power TX are correct. The AC voltage between the secondary big wires are: white-3.036V-green-3.038V-white.
So I input 3.036V AC into the secondary side of the OPTX, and measure the output in the primary side of the OPTX. For one I got the AC voltage: Black-49.5V-Red and Blue-21.87V-Red, so the ratio is 0.442. For another I got the the AC voltage: Black-49.5V-Red and Blue-21.76V-Red, the ratio is 0.440. So I got the right U.L. ratio. Can we conclude now that this kit is for WAD K5881 PSE?
I would appreciate it very much if I could have all the building information available.
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  #16  
Old 10th February 2017, 05:17 PM
Richard Richard is offline
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Default Re: WAD K5881 Circuit Diagram Needed

Yes that looks right.
The build article doesn't give wire colours but you seem to have found that red would be HT, blue the grid taps pin4, and black the anodes pin3. Maybe there are some colours left on the sockets if you still have them?
I've emailed the article, good luck and let us know how it goes
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  #17  
Old 11th February 2017, 02:01 AM
yuming916 yuming916 is offline
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Default Re: WAD K5881 Circuit Diagram Needed

Marvelous! Even an idiot can build it now.
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  #18  
Old 11th February 2017, 11:15 AM
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Wieslaw Lipowski Wieslaw Lipowski is offline
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Default Re: WAD K5881 Circuit Diagram Needed

Mind the high voltages inside!
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  #19  
Old 12th February 2017, 12:40 PM
yuming916 yuming916 is offline
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Default Re: WAD K5881 Circuit Diagram Needed

Quote:
Originally Posted by Wieslaw Lipowski View Post
Mind the high voltages inside!
Sure, Ill take care of it.
BTW, there is a footnote saying that C1 be soldered to the input phono socket.
Then how about an input aux socket? Is it the same connection?
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  #20  
Old 12th February 2017, 02:27 PM
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Wieslaw Lipowski Wieslaw Lipowski is offline
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Default Re: WAD K5881 Circuit Diagram Needed

I don't think it's a PHONO socket. There's no RIAA phono equalization circuit in the front end, and the sensitivity is too low.

It must be just a line input.
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