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Zkit up in smoke (Read 652 times)
Mannytheseacow
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Zkit up in smoke
10/27/21 at 02:48:51
 
Hi, I just built a Zkit and when I finished it and went through the power checkpoints I had my multimeter incorrectly set and at the first point ďAĒ something shorted and I saw a puff of smoke come from the area of the board adjacent to the volume pot, by the 1k 6.5 w resistor and the 20 uf 250v caps.
I immediately saw my mistake with the meter settings and reset. I then went through the preflight check and everything tested exactly as supposed to. I connected speakers and input and only have one channel. The resistors looked ok so I replaced the 20uf250v caps since I had extras. Still only have the right channel making sound. Any ideas? Iíve checked all the solder joints and input/output joints.
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EdwardT
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Posts: 164
Re: Zkit up in smoke
Reply #1 - 10/27/21 at 13:23:06
 
I havenít built that kit but the many times Iíve had smoke from a circuit board itís been resistors or diodes. Resistors can fool you by looking fine and still being blown.
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Amp on order, Gr-Research X-SLS, Marantz HD CD-1
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Coyote
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Posts: 85
Re: Zkit up in smoke
Reply #2 - 10/28/21 at 15:24:53
 

If you let the magic smoke out of the box it is really hard to put it back in.

But seriously, good luck with trouble shooting it.

Cheers,

a.

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funch
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Re: Zkit up in smoke
Reply #3 - 10/28/21 at 17:31:47
 
Check the two 10K resistors at the center of the board. Power goes through each, then through the 47K resistors to one half of the input tube.
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Mannytheseacow
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Re: Zkit up in smoke
Reply #4 - 10/28/21 at 19:02:31
 
Thanks for the help everyone. I checked all the resistors and all were within range... except for the 100k potentiometer. One channel of the pot was fried. Whether it happened when I initially ran the test or maybe I overheated it when I did the install. When I bypass the pot both channels are working (at full volume). I have another pot on order.
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Brian
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Re: Zkit up in smoke
Reply #5 - 10/29/21 at 03:24:50
 
I am glad you found the trouble.
Having something wrong can be so frustrating until the cause is found.

I hope all goes well from here.  
Brian
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Mannytheseacow
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Re: Zkit up in smoke
Reply #6 - 11/25/21 at 16:42:16
 
Iíve been living with this amp now for a few weeks and loving it. It has an addictive sound I canít get enough of.
Iím still having as issue, though, where the left side keeps dropping out. I listen at about 60-70% volume and when the left side drops Iím able to bring it back by turning the volume up and then bringing it back to the original setting. Anyone have an idea where the fault is? Iíve gone through the components and everything is testing properly. Is this problem characteristic of anything that anyone else has experienced?
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Archie
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Re: Zkit up in smoke
Reply #7 - 11/25/21 at 17:04:15
 
Sure sounds like something in the pot if I understand your problem correctly.
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Lin
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Re: Zkit up in smoke
Reply #8 - 11/25/21 at 17:08:14
 
Sounds like it could be a bad connection somewhere, have you checked all the solder joints on that side?
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Mannytheseacow
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Re: Zkit up in smoke
Reply #9 - 11/25/21 at 18:18:23
 
I just replaced the pot and it seems smooth when I test it. I rechecked all the solder joints to be sure that wasnít the issue either.
I was able to trace it back to the 47k resistor, when I put a volt meter to ground on the tube pin 6 side of the resistor that channel comes back. Could it be the resistor is damaged but intermittently working? Sorry, Iím definitely an electronics newbie.
A couple of other things Iíve noticed- maybe itís just me but the left side power tube doesnít appear to glow as brightly as the right, and when I shut it down the left side distorts as it fades out.
I should also note that when I say I lose the left channel, it isnít totally gone, but sounds still comes out very faintly.
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Lin
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Re: Zkit up in smoke
Reply #10 - 11/25/21 at 18:44:49
 
Have you swapped the tubes?
I have tubes that work fine, but seem brighter than others because of construction.

Resistors are cheap and easy to replace, worth trying.
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EdwardT
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Re: Zkit up in smoke
Reply #11 - 11/25/21 at 19:47:10
 
Can you see if it's black where the lead exits the resistor body? That could be your puff of smoke.
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Amp on order, Gr-Research X-SLS, Marantz HD CD-1
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Mannytheseacow
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Re: Zkit up in smoke
Reply #12 - 11/25/21 at 21:41:24
 
Iíve changed tubes. The resistor doesnít appear abnormal but I ordered some more and will try replacing it.
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Lin
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Posts: 539
Re: Zkit up in smoke
Reply #13 - 11/25/21 at 22:53:23
 
To follow up on my earlier question since I'm not sure I understand the answer.

You mentioned the right tube being brighter than the left, is it always that way?
If you swap left and right tubes, does the right tube still seem brighter or does it follow the tube?
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Mannytheseacow
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Re: Zkit up in smoke
Reply #14 - 11/26/21 at 05:48:50
 
Thanks, Lin. Sorry I didnít answer your question more clearly. I tried swapping left/right and replacing with new tubes and in all instances the tube inserted into the left channel socket appears dim compared to the right.
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Lin
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Re: Zkit up in smoke
Reply #15 - 11/26/21 at 15:14:48
 
Can you follow the signal path and check voltages at each part to see if you find a drop on the left side?
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CAJames
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Re: Zkit up in smoke
Reply #16 - 11/26/21 at 18:14:40
 
It is possible the tube socket itself has gone bad. Doesn't happen often, but it does happen.
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