A few more beginner questions...

Started by deadlyshart, December 17, 2016, 01:16:23 PM

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deadlyshart

Quote from: robthequiet on December 19, 2016, 02:49:29 PM
They usually have a sticky base, you peel off the plastic and they last a good while.

Ahh, excellent... I think I'll buy some then. I guess I could also use stickies/velcro myself, too.

EBK

#21
Quote from: deadlyshart on December 19, 2016, 02:54:49 PM
Hey guys, one other more general question. I'm going to try and build a really nice version of my next pedal (a Small Clone... clone). I've already printed and etched a PCB for it, but I want to do this one as right as possible (hence all the questions).

How much do you guys layout the parts before you assemble it and stuff? So far most of my projects have pretty much involved me assembling the circuit board, and then drilling the chassis to fit it after the fact. It's worked alright, but always been a bit of a shitshow when I've tried to get things to fit. Do you guys used CAD software? Or at least draw it out, saying "here's where the PCB is gonna be, here's how it's gonna attach, etc?

I don't use CAD software, but for my latest pedal (still in progress), I found it useful to lay things out in Inkscape (free vector graphics software)
https://inkscape.org/en/
using the Pedal Builder's Vector Art Pack from OTRFX:
http://www.ontheroadeffects.com/vectorpack/
My sketch (multi-layered -- this particular view shows all the visible stuff in the complete pedal, although my graphics have been adjusted a bit since I saved this image):

It takes a while to get the hang of it, but I was able to produce a good drill template (as a separate layer), which helped assure me that everything would fit well:


Basically, in my drawing I have separate layers for components (inside), components (outside), drill template, knobs, labels, graphics, enclosure outline, enclosure top, with everything aligned to a set of guides.
This was the first time I did this kind of component layout mock-up for one of my pedals, but I'll probably do it again in the future.
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Technical difficulties.  Please stand by.

PRR

> transistors are really sensitive to heat

Modern Silicon transistors will "work perfectly well" when as HOT as molten solder.

(I noted this when a power regulator transistor seemed mighty hot, and saw that the leads were moving around in their solder-- the transistor body must have been far past solder-melt temperature. And been that way for some hours.)

"Work" is not the same as "works to spec". Self-leakage in a hot part will be very high. A regulator driver may be able to absorb that. Simpler amplifier bias schemes might not. However my experience is that "good quick" soldering does NO harm to Silicon parts; and the datasheet guidance agrees.

Germanium is more sensitive. We usually favored long leads, or flat spring clip heatsinks (have not seen those in years). However milions of low-price Germs were soldered into transistor radios on 10mm leads.

Sockets for chips vs transistors: a transistor does not have as many legs to hold it in, and the pin-size is not what the socket designer aimed at. I recall LOTS of socket-creep in 14-pin ICs, and a socketed transistor would be worse.

OTOH, in experimental electronics, part-swapping is far faster with sockets. Socket everything, change everything. But don't expect it to survive the spring potholes on Bayside Road.
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