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SUPPORT FORUMS FOR ZKITS >> ZKIT 1 Support forum >> Trying to avoid a fire in my point-to-point.
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Message started by timh on 02/26/13 at 15:59:12

Title: Trying to avoid a fire in my point-to-point.
Post by timh on 02/26/13 at 15:59:12

I don't know what possessed me to do this but i thought it would be a good idea to tear down my zen kit and build a point to point amp with it.  My intentions are to buy enough components for a second kit and run them as two mono's.  But, I've got to complete the first one.  I put it together and the heaters light up without blowing a fuse.  Here is the problem:  I have 400 volts at the 5W resistor and when I hook up the red wires from the output transformer in between the 5W and the 6.8 K 2W resistors, the 5W resistor glows red hot.  I'm not sure that this won't eventually cause a fire. Does anyone have any suggestions?

Title: Re: Trying to avoid a fire in my point-to-point.
Post by timh on 02/28/13 at 17:01:53

I figure the resistor is overheating because of the increased voltage but the question is why?  I checked power coming off the transformers is right about 345VAC.  When I hook up the diodes the VDC is over 400.  When I disconnect the 6.8K resistor from the rest of the circuit the voltage is still 400 but the 5W resistor doesn't heat up.  I'm assuming the 5W resistor is heating up because of the increased resistance caused by the rest of the circuit.  I have tested all of the resistors and caps in the circuit and they are all working fine. Next I'm going to try new diodes.  I would appreciate help if possible.

Title: Re: Trying to avoid a fire in my point-to-point.
Post by jpv on 03/01/13 at 13:39:35

Post some photo's of your wiring. I do know the only thing that should glow red are the tubes.

Title: Re: Trying to avoid a fire in my point-to-point.
Post by timh on 03/02/13 at 20:39:30

Here it is.  This is a 1st trial using components off the PCB so the all of the leads are short.  I intend to order two sets of components when I am reading to make the final revision.  So, yes, I know this looks crappy and sketchy.  

Title: Re: Trying to avoid a fire in my point-to-point.
Post by timh on 03/05/13 at 23:11:20

I figured out the problem. I had the 330k resistors on the wrong side of the caps and my 0.1 uf cap was not connected. I must have looked at this wiring diagram 100 times before figuring this out.
Once I hooked it up correctly it worked.  Imagine that.  Will do the cce mod next and then start on the other side. I will update with photos if anyone else is interested in the dual point-to-point version of this kit.

Title: Re: Trying to avoid a fire in my point-to-point.
Post by jpv on 03/06/13 at 13:09:04

That is good to hear. I did look at the photo but it is hard to follow the path you had wired. Yes post photo's we like pics

Title: Re: Trying to avoid a fire in my point-to-point.
Post by Peter on 04/28/14 at 16:50:02

Very nice to see your humble approach to this, many wont admit that they had made an error!

Title: Re: Trying to avoid a fire in my point-to-point.
Post by Core32 on 11/07/14 at 21:28:33

Way after the fact so you may not care at this point, but if a resistor got hot enough to glow red, it is most certainly damaged internally.
At the very least it's operational life has been shortened and at worst it's resistance value is no longer accurate, possibly even open circuit.
If you still have the amp in use I would suggest replacing that one.

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