Bellum fuzz mkII germanium diodes

boji

Active member
I bent the legs of one of the germanium diodes too close to the glass casing and destroyed it.

Do the two germanium diodes need to be the exact same model? Or can they be mismatched?
 
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They can be mismatched if they're just for clipping.

Probably can be for octave-fuzz, too, so long as the Fv is the same.


I always socket clipping diodes 'cause I've broke my fair share of the little glass buggers.
 
I've already broken 3. I know they're really fragile, so I was really gentle. And it broke, but gently :)
Take needle-nose pliers and grab the lead at least 1/2 mm away from the edge of the glass (from the taper of the glass on the lead itself, not just from the main body of the glass). With the lead held firmly by the pliers (the needle-nose giving an extra buffer zone of 1.5–2mm) bend the lead. If you need to bend it a bit more after trial-fitting it, use the pliers again to hold it. Never try to bend the lead without the pliers holding the lead, acting as a buffer zone.

Doing it this way has reduced my breakage ratio greatly.



That is probably a silly question: but how do you know that they're used for clipping?
Not a silly question.

Look at the schematic, where are they placed? Are they in a position similar to a TS-808's, a Muff's, or a Rat's?

Another clue:
Clipping diodes usually come in anti-parallel pairs (symmetrical):
—>
<—
or vertically oriented on the schematic like a Rat's which go to ground.


A pair and a single together (asymmetrical):
—>—>
<—


Mutliples of 4 (or even 6)
—> —>
<— <—

asymmetric mutiple
—> —> —>
<— <—



If you have two diodes with a big difference in forward voltage, it may seem symmetrical but the difference in forward voltage makes it asymmetrical clipping:
—> Fv 0.2 Schottky
<— Fv 2.2 Green-LED
 
Something I do for .125w resistors and glass diodes is to hold the leg with a pair of narrow blade tweezers up against the body and bend using the other edge of the tweezer as a guide. The pair I have are perfect for the 5mm bends, and you are not putting any pressure on the body of the component.
 
You guys must be Supermen! I haven't broken a diode by forming the leads in ages. The needle-nose pliers method is the best way, but make sure that the pliers do not touch the diode body when you are forming the leads. You want at least 2mm from the body to the start of the bend. If the hole spacing on the board is closer than the formed leads, then space the diode up from the board so the leads can gently bend back on themselves. PedalPCB makes beautiful boards, but sometimes the footprint for the diodes is too small.
 
Fig has better-described exactly what I do, except with tweezers instead of the needle-nose pliers.

CDB has described exactly how far from the glass my needle-nose pliers take me — 2mm.
I'm not a Superman, not even a Super, man; and I've never managed an apartment building — I'm just clumsy.
 
*/ Begin Boring Story
Back when I first started in aerospace, I was working on an experimental satellite instrument that had to be build in a hurry to meet the launch deadline. I was working a double shift, testing my electronics unit when I bent several pins on a 78-pin D-connector. There were two ladies working in the manufacturing area that night and I sheepishly asked them to replace the bent pins in the connector I messed up. They gave me no end of razzing...
"Look at this! We got us a Superman here."
"Boy, you don't know your own strength."
I just had to sit there and take it. If that had been a full-fledged flight program, I would not have been allowed to mate or demate connectors because that required training and certification which I didn't have. Soldering, lead forming, all that stuff required special training and certification.

Compared to all that, the stuff we do is like a blacksmith shop in the Wild West. And somehow, it all works!
End Boring Story /*
 
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