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SUPPORT FORUMS FOR ZKITS >> ZKIT 1 Support forum >> Will these voltages cause harm?
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Message started by knowsound on 09/23/24 at 20:48:47

Title: Will these voltages cause harm?
Post by knowsound on 09/23/24 at 20:48:47

Hi everyone, first time poster. I got a Zkit partially assembled by the previous owner and just got it finished up with Edcore power transformer and musical supplies OT's. Initially had issues with bad tubes but since a new full set those issues are history. I am getting high voltages for the C and D measurements though.

A 344
B 304
C 12.4
D 4.36
DD 4.19

A and B seem fine, but my concern is about C and D. C is just a touch above the tolerance but both D's are quite a bit above the tolerance. Will these cause harm, either short term or long term? The amp sounds great with no hum.

Title: Re: Will these voltages cause harm?
Post by Gilf on 09/23/24 at 22:49:05

Welcome! It seems like something is not right after the power supply section. Can you post some photos?

Double check the correct values for the 47k 1/2w resistors coming off the B+.

Title: Re: Will these voltages cause harm?
Post by knowsound on 09/23/24 at 23:43:32

Hi Gif, thanks for the welcome and reply, I'll try and get some pics up after meeting the obligatory post count...

Title: Re: Will these voltages cause harm?
Post by knowsound on 09/23/24 at 23:44:47

3rd post

Title: Re: Will these voltages cause harm?
Post by knowsound on 09/23/24 at 23:47:55

And 4th

Title: Re: Will these voltages cause harm?
Post by knowsound on 09/24/24 at 00:42:30

Title: Re: Will these voltages cause harm?
Post by Gilf on 09/24/24 at 01:20:44

Looking at the build sheets the spec at C is 10.25v +/- 2v so you are within spec there. You are high at D by ~1v. If it isn’t humming, sounds good and isn’t blowing a fuse I’d roll with it.

What’s going on with the missing 2.7k resistors grounding the input tube? That could be your problem there.

I fretted over my first zkit and the last two I built I don’t even think I’ve checked the voltage. I recall adding the anniversary mods affected the voltage but that was a long time ago and I don’t remember how far out it was.

Title: Re: Will these voltages cause harm?
Post by knowsound on 09/24/24 at 03:45:06

This info is appreciated. I checked the 47k resistors and they are both measuring around 46.5 give or take. Good eye on the missing 2.7k resistors coming off input tube. Like I’d said, someone else did the early heavy lifting on this build, I just finished it up and am an utter novice to boot. The one pair of resistors that are in there at the moment coming off the input tube are both measuring 1.5k ohms according to my meter. I happen to have a single pair of 2.7k ohm resistors on hand can I put them in there with the other existing 1.5k ohm resistors or will I be even further out of spec ? I apologize for slow response, I was booted off the forum after multiple times trying to upload pics.

Title: Re: Will these voltages cause harm?
Post by JBzen on 09/24/24 at 11:25:05

Hi guys,
I'm with Gilf - if it seems to be working fine then roll with it. My voltages were on the limits with the Zkit and it has been running fine over the years.

Those missing resistors are just part of a voicing tool that Steve designed into the kit. Eliminating the 2.7k as in your build provides a more laid back sound. Adding the 2.7k along side the 1.5k will sharpen the sound. Both installed was/is the preference in my build.

Title: Re: Will these voltages cause harm?
Post by knowsound on 09/24/24 at 22:17:56

Thanks JBzen, you helped clarify that along with Gilf. I put the 2.7k resistors in place and it seems to have brought the voltages within spec, my readings are now :

A 340
B 304
C 12.29
D 3.1
DD 3.2

I also tried the 4 ohm tap from the output transformer and it seems to have improved the sound a touch (a little less "distortion"), as if I thought it could get any better!? I'm astounded by this thing, and among the very grateful for it being offered in kit form for reasonable $. This has been the biggest jump in quality of sound in my experience thus far, a distant second was the revelation of a nice set of Klipsch Forte ii.

Title: Re: Will these voltages cause harm?
Post by Gilf on 09/25/24 at 00:21:36

That’s great, I’m glad you got the voltages in the intended range. These little amps just sound amazing, don’t they? And all the tweaking you do from here will just get better and better.

Interesting about the voicing resistor- JB. I didn’t know that, or if I did know that at some point I slept since then and lost it!