BC184L transistor component

Andy Betts wrote on Fri, 29 July 2016 03:50

it's probably quicker to copy an existing component and alter it, and

rename it than it is to create my own.

Only as long as you keep dumpster-diving for library components instead of

(gasp!) actually learning something.  A little work up front will save a

lot of work and frustration in the future.  Once you do that, you'll also

see how silly you've been.

--

Web access to CadSoft support forums at www.eaglecentral.ca.  Where the CadSoft EAGLE community meets.

Andy Betts wrote on Fri, 29 July 2016 03:50

it's probably quicker to copy an existing component and alter it, and

rename it than it is to create my own.

Only as long as you keep dumpster-diving for library components instead of

(gasp!) actually learning something.  A little work up front will save a

lot of work and frustration in the future.  Once you do that, you'll also

see how silly you've been.

--

Web access to CadSoft support forums at www.eaglecentral.ca.  Where the CadSoft EAGLE community meets.

Do I detect an essence of sarcasm?? ;-)

I'm qualified in using AutoCAD, have been using it for years... And I have to say that designing in Eagle is "clunky" to say the least and not at all intuitive. I will design my own devices if I have to.. but if there's something already there that just needs a tweak I'll do that. why try and reinvent the wheel when somebody has already done it. As a CAD program eagle is not a good program, and designing simple things takes thought... I'm used to using absolute coordinates.. Eagle doesn't appear to use that.

Overdrive? That's when the signal slams into BOTH rails, is it? Does that mean that the track title "Interstellar Overdrive" was a guitarist's joke?

The values on your schematic look reasonably sensible to me. It's a high impedance input, so the small capacitor there is alright (in a hi-fi preamp, with a 10k input, you'd expect to see something more like 10uF or 22uF to get the response down to 20Hz). The low frequency roll-off at the input is from a filter formed by the cap and the input impedance - as the impedance goes up , the cap can come down in value for the same cut-off frequency. The 220p from the collector to the base of Q2 rolls off the high response (above 20kHz, so beyond hearing). It might be necessary for stability - to stop the preamp oscillating - or might be there to try and stop it receiving mediumwave radio stations. It looks like a very small value but it gets magnified by the transistor's gain. Couldn't say whether the tone control capacitors look right.

The Mullard caps have the value as a 3-band (digit, digit, multiplier) colour code running down from the top. Here are photographs of 10nF, 100nF, and 220nF. You'll see the 220nF (red[2],red[2],yellow[4 zeroes]) has the two red bands running together and forming one fat band.

I seem to remember that the other bands are voltage and tolerance. Can't remember how they go, though.

The 220pf capacitor is the brown disc between the potentiometer in the centre and one of the transistors. It's called a disc ceramic. Might just have 220 written on it, or something like that. They come with different dielectrics [the ceramic insulator that goes between the plates]. They have different properties, temperature stability etc, but I wouldn't have thought any of that matters to you for this.

For the electrolytics, make sure that the working voltage is high enough. Designers vary in how much of an overhead they give themselves. It's probably good to have at least 1.5x, and 2x if you can. The one across the supply will need to be 25V or 35V. The others could be less, depending on what they are doing in the circuit.

How are the potentiometers labelled? There are two main track types linear and logarithmic. [The log track is tapered.] Log types are often used as volume controls because of the way the response then is similar to how we hear different sound intensities. I should think the bass and treble controls are linear. The 'volume' might be either [because it's a guitar effect and not an amplifier as such]. Sorry to be a bit vague, here - I'm not an audio designer. Here are pictures of old log and lin pots to give you an idea.

Sorry if you know all that and I'm lecturing you.

Andy Betts wrote on Sat, 30 July 2016 08:31

why try and reinvent the wheel when somebody has already done it.

In the case of ECAD library parts, that's already been answered.

Quote:

designing simple things takes thought

OMG!  You mean in engineering I have to use my brain!!?  I just wanted to

plug dis inta dat.  Now I have to add things and think and stuff?  Let me

outta here!!

Quote:

I'm used to using absolute coordinates.. Eagle doesn't appear to use

that.

This shows you haven't even tried to learn, let a alone experiment with

Eagle.  Just about everything in Eagle uses absolute coordinates.  One of

the first things I do when designing a footprint is to pick a origin and

determine the absolute coordinates of things to that origin.

Oh, right, that requires adding things and thinking, and a even more

advanced concept called subtraction.  Nevermind.

You're right. Eagle and any kind of engineering isn't for you.  Perhaps you

can go into politics, or practise really hard and get good as asking "Do

you want fries with that?".

--

Web access to CadSoft support forums at www.eaglecentral.ca.  Where the CadSoft EAGLE community meets.

Andy Betts wrote on Sat, 30 July 2016 08:31

why try and reinvent the wheel when somebody has already done it.

In the case of ECAD library parts, that's already been answered.

Quote:

designing simple things takes thought

OMG!  You mean in engineering I have to use my brain!!?  I just wanted to

plug dis inta dat.  Now I have to add things and think and stuff?  Let me

outta here!!

Quote:

I'm used to using absolute coordinates.. Eagle doesn't appear to use

that.

This shows you haven't even tried to learn, let a alone experiment with

Eagle.  Just about everything in Eagle uses absolute coordinates.  One of

the first things I do when designing a footprint is to pick a origin and

determine the absolute coordinates of things to that origin.

Oh, right, that requires adding things and thinking, and a even more

advanced concept called subtraction.  Nevermind.

You're right. Eagle and any kind of engineering isn't for you.  Perhaps you

can go into politics, or practise really hard and get good as asking "Do

you want fries with that?".

--

Web access to CadSoft support forums at www.eaglecentral.ca.  Where the CadSoft EAGLE community meets.

Hi Andy,

The Cadsoft Guest (I can't see the username) means well, basically he's strongly pushing you to create your own parts, for three main reasons:

(1). You can then guarantee (to yourself) they are correct, since you will have created them. There can be mistakes/room to improve with other people's libraries, because they don't necessarily test them, or take as much care as you will for your own project(s).

(2). You will learn in the process, and that is super-important because in electronics it is impossible for CAD libraries to contain every component you may wish to use, and it is therefore inevitable that you at some stage (usually sooner rather than later) will need to create your own anyway

(3). It might seem surprising, but in EAGLE it actually is quicker to create from scratch than to copy and edit. Less risk of error too. This is because EAGLE is designed for fast creation of components, for reason (2) i.e. that it is inevitable that users need to create their own components, so this part of the workflow needs to be speedy

I've just been working on a circuit and every active component (ICs and transistors and diode) were custom parts. Only the R's and C's were standard (and even a couple of those were custom parts). By creating the part, you get to know the functions of each pin, and the physical details in immense detail, and that helps you when you start routing the signals onto the PCB layout, to know what kind of traces to use, where to locate components, etc.

If you want, I'd be happy to send you an EAGLE recording which contains some detail of parts creation (it isn't intended to replace the EAGLE manual, rather it is just some tips/guidelines that work for me. It is on a server and the presentation was not originally created for a wide audience i.e. isn't for sharing, but you're welcome to view it. If you want to view it, let me know and I'll send access details (i.e. to do so you'll have to approve my 'follow' request to you which I've just sent, and then you'll have to click on 'follow' on my username to allow me to approve, we both need to simultaneously 'follow' each other to be able to send messages).

Am 30.07.2016 um 14:31 schrieb Andy Betts:

Do I detect an essence of sarcasm??

 

I'm qualified in using AutoCAD, have been using it for years... And I have to say that designing in Eagle is "clunky" to say the least and not at all intuitive. I will design my own devices if I have to.. but if there's something already there that just needs a tweak I'll do that. why try and reinvent the wheel when somebody has already done it. As a CAD program eagle is not a good program, and designing simple things takes thought... I'm used to using absolute coordinates.. Eagle doesn't appear to use that.

 

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Do I detect someone comparing apples with pears?

Eagle is a layout program autocad is not, so your argumentation is for

the birds.

Imho this thread is by far too long just for modifying a lousy transistor.

And I see your qualification: This little work took you a week...

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Mit freundlichen Grüßen / With best regards

Joern Paschedag

Thanks for your help guys... This is new territory to me, and don't want to spend too much time designing parts in Eagle, although I suspect that isn't going to happen. I'm currently copying and tweaking existing devices, and doing that is helping me learn how they're created. As I said before I don't find Eagle very intuitive but I'll persevere :-)

Jon Clift: You've been very helpful, thank you. The pots I'll be using are volume reverse log @ 10k, and the bass and treble will both be linear @ 100k. I'm using reverse log on the volume as historically it's said to give a better sweep... I'll try it, and if it isn't good I'll change it out. The current power boost reissues are all reverse log on the volume. Yeah, I'm aware of the stripe colour codes on the tropical fish caps.... I have a chart with the codes on. Pretty simple really. All my electrolytics are 50v or there abouts... The power boost works at 18v so there's plenty of head room voltage wise. regarding the 220pf ceramic, I've just ordered some multilayer Kemet caps... I think 10 for £2 (about $1.6)

Shabaz: Thanks for the offer.... And I'd like to take you up on the offer :-)

Cadsoft guest: Thanks for your words of wisdom..... I'll take it all on board ;-)

Hi Andy,

I'm not sure what I did, but I seem to have accidentally 'dismissed' rather than 'accept' the invite.

Anyway, I just realized your e-mail is part of the username, so I've directly e-mailed you with the info. I hope it helps.