Hello!

I recently inherited a prebuilt ZKIT1 amplifier, which I’m in the process of refurbishing into a new case. I tested it for a bit and it sounded great! However, while working on the amp, I’ve found a few oddities which I wanted to run by folks here:

First, it seems like there 2 missing 0.1uf400V capacitors — marked in PURPLE. Namely, the ones closest to the 6P15P tubes. The 2 capacitors in place seem pretty beefy (marked F104K S 630MEB1), but I was disconcerted to see the two other spots bridging the 6th pins on these tubes empty. Is this okay? While looking for other build examples, it seems like some boards don’t have these solder spots at all.

The next oddity has to do with the 1K 5W resistor — marked RED. This is straightforward enough imo, but my amplifier came wired with a Hammond 158M 10H inductor in place of this component. I’m going to replace this with the originally spec’d component, mostly since I don’t have room for that DC reactor in my new case; but I’m still curious as to what the logic behind that component choose was… is that a popular mod for this kit?

Lastly, I was reading in some posts (and also the instructions) that one should have a jumper bridge between the circuit ground and ground plane when building in a wood case. However, I can’t figure out where that jumper should sit, since there is no label for it…

Any commentary on the above would be very much appreciated!

Thanks a bunch! That’s really helpful, I’ll look into that mod. I mostly found it strange to have unpopulated components when the instructions don’t really specify anything as being optional during assembly.

So, they’re basically not hurting anything, but things can be improved further — great to know.

Thanks also for the explanation of the inductor! My understanding of electronics at this level is pretty rudimentary, and I never thought component types were interchangeable like that.

In regards to the grounding question, my board is actually a revision 9 from 2011. So, the mystery remains there a bit, but I’ll definitely be grounding my cable shields, potentiometer casing, and the board itself to the IEC ground pin. Fingers crossed that’s enough…