Hello,
I have some TDA ICs, 2030A, 2003, 2006. The Pentawatt package pins do not fit on a typical perforated board. Is there some specific socket to use it with a perforated board? Otherwise I have to make bigger holes. Any suggestion? Maybe some of you have more experience.
Another question. I heard that Jfets with low pinch off voltage are better to use them as buffers, boosters? I guess it affects to the clipping, taking into account that a guitar signal has 200 mV peak to peak, let's say.
Thanks.
Cheers
You'll find that most chipamp packages do not line up to any pre-drill hole patterns, unless it's a DIP, and there's no such thing as a pentawatt socket as far as I can find. I wish I had thought of that when I was younger, I bet it'd make a few bucks.
My best suggestion would be to solder solid lead wires to the legs of your chipamp, so they go from your heatsink to your breadboard; you don't want to flex the legs of the chipamps themselves too much. They tend to weaken and break at the chip body. Ask me how I know... >:(
What *Edvard* said :tu:
You just need to get inventive,
Scrounge some electronic landfill for small header sockets with lead wires attached and use those to interconnect to Breadboard. some will be close to the spacing,,you just need to use 2 rows,, 3 and 2.
cut the rest off.
Or (just been said) just solder lengths of wire directly to pins.
And be darn sure you mount the chip to a heat sink before you fire it up. :trouble
Re Fets,, it's a no brainer,, any BJT will work as buffer.
Many hundreds of guitar pedals use a simple BJT buffer and I've not heard of any seriously limiting issues about their use.
Yes a Fet will do the same thing and I doubt you would hear any difference,, especially when used for guitar interface.
Phil.
I use Vector Flea Clips.
Link: https://www.ebay.com/itm/Vector-Push-In-Flea-Clip-Terminal-Printed-Circuit-Board-/362593814146
Notice how they extend from the hole in only one direction. You use two rows of holes on the board, each with 3 holes. For the center pin (3), orient the extended portion of the clip towards you, away from the heatsink. To the right and left of that pin, orient the extended portion of the clip way from the center pin to the right (pin 5) and left (pin 1). On the row between that first row and the heatsink, you use the holes behind those two outside pins except you orient the extended portion of the clip towards the center so you can solder to pins 2 and 4 of the chip. Did that make any sense ? Read it again.
From the top it looks like this:
HEATSINK
2x4
135
x= hole not used
JFETs with low pinchoff are easier to bias like tubes. If the pinchoff is too high, the bias will drift around when you overdrive the JFET unless you great lengths to control the bias.
Thanks a lot... :tu: About the heatsinks, do you think any piece/sheet of metal will do the job, or it is worth to use a proper one. Aluminum or denser... ?
Again Electronic junk comes cheap and I'm sure it won't take long to find a heat sink in any old computer, amplifier, dead battery charger or like gear that is thrown out.
Or just go to the hardware store and purchase a 2mmx50x50mm length of angle alloy (that's 2x2 inch for those in the land that still lives in imperial :-X)
Thickness, 2mm or thicker if you can find it. Cut at least 3 inches to give the heat somewhere to go. again more is better. And don't forget to isolate the chip with a non conductive washer.
Phil.
Quote from: Oooscar on May 29, 2020, 06:59:43 AM
Thanks a lot... :tu: About the heatsinks, do you think any piece/sheet of metal will do the job, or it is worth to use a proper one. Aluminum or denser... ?
Aluminum is the typical go-to for heatsinks. Also, I hit edit by accident on your post, it's been a long day. But I didn't actually edit the post.
I see, thanks a lot... I have read about mica washers. The idea is to use a washer that transfers well the heat but not the electricity. Usually, go together both properties. The reason to do that is to avoid kind of antennae effects? I have not thought in those issues. Sorry... Too many questions...
About the heatsink, I have a piece of solid metal from a car radio, this piece is one the sides of the whole radio. Pretty impressive heatsink.
The mica insulator (there are also silicone ones) is there to prevent the rear surface of the transistor, which is usually the collector, from making electrical contact with the metal heat sink, which is usually grounded. In the case of the five leg power amp ICs, the rear of the IC is usually one of the power rails, I forget whether V+ or V-. In any of those cases, touching the metal back of teh part to groundeD heat sink will short out the power supply.
The tab is connected to V-.
If you can avoid, or have no intention of, grounding the heat sink by attaching it to a metal chassis (most common)or other scheme, you can get away with mounting the chip directly to it with some thermal grease. CAVEAT: Make absolutely sure that there isn't or won't be the opportunity for some wayward part to short the heatsink to ground or the V+ rail.
Or just use an isolation pad. For breadboarding, I wouldn't risk going without one. For final assembly in a box, use some common sense (and a barrier between the heatsink and the rest of the circuit) and you can get away with it.
By the way, I've heard all the cool kids are using 1mil Kapton Tape for isolating their semiconductors nowadays. Good thermal conductivity (not as good as Mica, better than Sil-Pads), pretty tough, and one 36 yard/~33 meter roll oughta last you a while...
P.S. All you ever wanted to know about attaching something to a heat sink:
https://www.eg.bucknell.edu/~dkelley/eceg351/FairchildHeatsinkMountingGuide.pdf
http://www.junradio.com/Discretes/TI/9701.pdf