Friday, April 28, 2017
Hornby Skewes Zonk Machine
The Zonk Machine was one of the many British fuzz boxes that came out in the mid-60s. Like the Tone Bender Mk II it was designed to compete with, it also was featured 3 germanium transistors but offered more of a boost and slight oscillation (in a good way). This is a positive ground effect so unless you use a charge pump or can make it work with NPN germanium transistors you can't daisy chain it with other negative ground pedals. If you are going the NPN route, be sure to rotate the polarized caps an the diode 180ยบ. Here's the schematic for reference.
I etched fuzz centrals zonk machine and changed 3 components to make a mark 1 tone
ReplyDeletebender
verified today! I used pot b500k like a bias instead 470k from base Q2. Q2 should have 100 - 150 hfe. I tried silicon Q2 with 160,220,800 hfe, they all working bad. So i used all germanium mp38a. Similar to demo!
ReplyDeleteThanks Zzoyd! You're on a roll!
Deletetoday i found old this is PCB, & built Bender MK1. All PNP soviet:Q1-mp42b hfe=60, Q2-mp39 Hfe- 130, Q2-Mp20b Hfe-115. Scheme: https://www.madbeanpedals.com/forum/index.php?topic=8910.0
ReplyDeletereverse diode 4001!
ReplyDeleteI built this a while ago. The layout is verified, but there are two values that need to be corrected. Instead of 470n there should be a 47n. And the 3,3k going from Lug 2 of the Fuzz pot needs to be 33k. For reference: https://vero-p2p.blogspot.com/2022/12/zonk-machine-component-values-table.html
ReplyDeleteAnd for everyone building a Zonk or MK1 for the first time. Play around with the 470k resistor. Any value between 180k and 470k could be right for your Q2 transistor.