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Everything seems fine except....no sound (Read 1078 times)
Evo
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Posts: 53
Everything seems fine except....no sound
03/31/10 at 10:23:52
 
I have just finished off my zkit1. As per the instructions I have checked all resistance values and solder joints prior to powering up.

First I powered it up without anything attached and check the voltages at the four locations specified in the instructions. Tube lit up and voltages were good.

I then attached the speakers. You could hear a quiet speaker noise, but no hum. Good.

Then attached a cd player - nothing. Turned the volume up and down and the background noise increased and decreased accordingly, but no music. Checked the source elsewhere - no problems with the source.

What might the problem be? What things should I check? How do I check that?

Any help welcome,

Matt
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dank
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pair of dual 18
Imperials

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Re: Everything seems fine except....no sound
Reply #1 - 03/31/10 at 13:07:22
 
Matt

I'll assume you have a VOM and no oscilloscope, right?

There are a couple of revisions of Zkit1 printed circuit boards out there.  Mine, which is probably older than yours, had the input to the power tubes wired to pin 8 (an unused pin) and left the control grid input pin 2 open.  The fix was to install a short jumper wire on each output tube from pin 2 to pin 8.  Check that the 1k resistors go to pin 2 of the power tubes - check with your Zkit1 unplugged and your VOM on ohms...one side of the 1k to pin 2 should read around zero ohms, the other side of the 1k to pin 2 should be around 1000 ohms (1k).  If you read infinite - try measuring to pin 8.  If you get good readings to pin 8 you will need to install the jumpers.  This problem would account for no sound.

Try this and let me know what happens.

Dan
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Evo
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Posts: 53
Re: Everything seems fine except....no sound
Reply #2 - 04/01/10 at 23:06:22
 
Thanks Dan.

I checked the board layout and the new board has the 1k resistors connected to pin 2 of the tubes.

I found out the problem - I hadn't wired the RCA connectors on the board correctly to my remote RCA sockets. Music is now playing, the problem now is that one channel is quieter than the other.

I have swapped the speaker connectors around and the RCA connectors from the CD player to just exclude speaker/source issues first. I have also swapped the tubes over. It is definitely the amp.

My next plan was to work back from the speaker outputs using my multimeter. Sound like a good idea? Any ideas what the most likely cause would be?
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