Old Japanese Tube Amp Ground Wiring Woes

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Old Japanese Tube Amp Ground Wiring Woes

Postby Udonitron on Sun May 29, 2016 2:01 am

Howdy all!
Been ages but hopefully someone can make some sense of this mess as I swear I am getting it right but keep blowing fuses!
I totally recapped this amp a few years back and it was working fine with the 2 prong original set up but I decided to rewire with a 3 prong and ground it properly.
It had the respective 100v and 117v wires from the mains going to their respective fuse lugs but of course the 100v was the only one currently wired into the ground switch death cap set up.
In the image below you will see what is what and I wired up the 117v to the respective switch lug and each time I turn it on I blow the 2A fuse within 2 or so seconds after getting a hum from the tranny.

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I have included the schematic for this amp along with a shots of my recapping etc incase anyone can see anything wrong however each cap and wire was replaced one by one and wired exactly as it was originally.
Do you think I should pull one of the tranny wires off and see if it blows a fuse then to rule out a cap issue etc?
Much appreciated for any input!

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https://postimg.org/image/il61jwav3/

https://postimg.org/image/ar5fyi327/

https://postimg.org/image/fflftos8v/

https://postimg.org/image/zbhf989a7/

Original Wiring

https://postimg.org/image/4ju1yc7b3/
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Re: Old Japanese Tube Amp Ground Wiring Woes

Postby Udonitron on Sun May 29, 2016 8:46 pm

Did I post this in the wrong area? :cry:
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Re: Old Japanese Tube Amp Ground Wiring Woes

Postby Baron Von Machinenmann on Mon May 30, 2016 12:12 pm

We need a picture back a bit more to show ALL of the primary wiring, I can't tell exactly what you have going on with the top picture as it is in too close. If it worked fine before it is probably something very simple. :wink:
ImageImageImage

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Re: Old Japanese Tube Amp Ground Wiring Woes

Postby Udonitron on Mon May 30, 2016 4:59 pm

Cheers for the reply!
Does this one help?

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Re: Old Japanese Tube Amp Ground Wiring Woes

Postby pdf64 on Wed Jun 01, 2016 8:24 am

Ha, not really.
Need a full view of the left section of the chassis guts, to see what's going on with the mains / power transformer wiring.
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Re: Old Japanese Tube Amp Ground Wiring Woes

Postby Udonitron on Wed Jun 01, 2016 3:32 pm

Ah OK!
How about these?

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Also, I am curious as to using polypro axial caps to replace the polar specific PIO caps.
Since the PIOs are polar specific could that be an issue as you see how the current from the red and brown flows out of the mains to those two caps but one 0.005uF is off the neg and one off the positive and they both connect to the red off the mains which is feeding power?
I have done other maps with these yellow polypro's without an issue however.
See below of the tagged image.

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Re: Old Japanese Tube Amp Ground Wiring Woes

Postby Baron Von Machinenmann on Wed Jun 01, 2016 11:51 pm

Can't tell where the black/hot and the white/neutral are going, can't see what is going on with that DPDT switch, should be a hot going to it (Green?) to be switched to connect one of the power transformers primaries, the other PT primary going directly to the neutral.

The Neon lamp usually has one side grounded and a dropping resistor coming off of the switched hot side (PT feed). The back of the lamp socket from the angle shown looks like a possible solder bridge?
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Re: Old Japanese Tube Amp Ground Wiring Woes

Postby Udonitron on Thu Jun 02, 2016 1:22 am

It is up and running!
I tossed in new 100uF 450v caps where those blue new ones were as I tested em and one was totally dead and the other was way off on the microfarads.
That was the issue! :say_what:
Also tossed the 0.005uF caps back in as 2 of em I had tested fine and within spec at 0.007uF.
I omitted the light and playing some Free Fire & Water on it as we speak :D
Thanks again, mate!
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Re: Old Japanese Tube Amp Ground Wiring Woes

Postby Baron Von Machinenmann on Sun Jun 05, 2016 5:21 pm

Glad you got it sorted out. For anyone following this thread, those pictures show true point to point wiring, sometimes referred to by techs as "rats nest" wiring. :thumbsup:
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Re: Old Japanese Tube Amp Ground Wiring Woes

Postby Udonitron on Sun Jun 05, 2016 7:00 pm

Haha it is indeed! :cheers:
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