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Message started by goso64 on 07/01/22 at 01:57:01

Title: ZKIT-1 Short Circuit
Post by goso64 on 07/01/22 at 01:57:01

Hello,

This is the first time I turn on my Z-KIT and there is a short (see pic below, my safety bulb is lit).

I started poking around with my meter and found that all 5 of the secondary voltage wires on my power transformer are grounded (2 brown, 2 red 1 red/blk wires in pic below).

My question is: does this mean my transformer is bad? If not, I'm quite surprised that all 5 points in the pic below are somehow grounded due to something wrong on the board/solder etc. [smiley=peanuts05.gif]Your comments are very appreciated.

goso64

Title: Re: ZKIT-1 Short Circuit
Post by BWC54 on 07/01/22 at 13:43:03

NOTE CORRECTION ON VOLTAGES

Probably not the transformer. Red/Black goes directly to chassis ground. Both brown go to chassis ground through 100 ohm resistors. So brown to chassis ground should measure 100 ohms. Red to chassis ground should measure the resistance of the transformer winding. I would disconnect all the transformer secondary wires from the board and then see if any of the wires are grounded to chassis ground. Then you will know whether the windings are shorted to the Transformer housing. Then check the transformer voltages with it disconnected from the board. Red to red/blk should measure about 300 volts AC. Brown to brown should measure about 6.3 volts AC.

If the transformer check OK then post a pic of the entire bottom of the amp and a close up of the entire board and we might be able to see something wrong.

Title: Re: ZKIT-1 Short Circuit
Post by goso64 on 07/06/22 at 00:08:16

Thank you BWC54 for your response.

Here's an update - I just re-measured resistance for the power transformer leads to ground:

1. red/blk wire is 0 ohms
2. both brown wires are 50 ohms
3. both red wires are approx. 40 ohms

I'm attaching the pics you requested. I didn't bother measuring the transformer (yet) since I think it's working based on the current measurements.

Many thanks again for any advice that folks can offer.

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Title: Re: ZKIT-1 Short Circuit
Post by JBzen on 07/06/22 at 01:23:38

Looks like the power supply 33uf caps are in reversed direction. Also 1000uf cap is reversed. Will need replaced with new in the correct orientation. All are electrolytic caps and correct polarity is a must.

Title: Re: ZKIT-1 Short Circuit
Post by goso64 on 07/09/22 at 03:40:16

Thank you JBzen! I replaced the caps and reinstalled with the proper polarity. And now my safety light is dark - fantastic.

Next, I turned on the amp for about 5 min and then checked the DC Voltages as per the "PRE-FLIGHT CHECK" instructions. Here's the results:

A) 346 VDC +/- 10 VDC
ACTUAL: 306 VDC

B) 309 VDC +/- 10 VDC
ACTUAL: 266 VDC

C) 10.25 VDC +/- 2 VDC
ACTUAL: 10.49 VDC

D) 2.60 VDC +/- 0.5 VDC
ACTUAL: 2.76 & 2.7 VDC

While the voltages for C and D are spot on, I think the target voltages for A (340VDC) and B (309VDC) are too high. My Encore power transformer is rated at 300VDC so I'm thinking my actual voltages for points A and B are in line with each other and are also correct.

Can anyone confirm this? If this is confirmed, then the only thing left is to connect an input source and speakers and take it for a test drive.

Thank you all for your helping me get past these hurdles. Much appreciated.

Title: Re: ZKIT-1 Short Circuit
Post by BWC54 on 07/10/22 at 12:17:31

With 119.2 VAC in, mine measured 325, 284, 10.19, 2.63 and 2.54. I would hook it up.

Title: Re: ZKIT-1 Short Circuit
Post by goso64 on 07/17/22 at 19:36:05

Thank you JBzen and BWC54 for your help. I'm happy (giddy) to report that my amp works!!! Woohoo!. I tested it using an old iPod and a pair of backup speakers.

Now to connect it to my main gear and start playing tunes!!

Again, many thanks for the help - couldn't have done it without you guys.

Cheers.