Thursday, September 24, 2009

Soldering resistors and ceramic capicitors

So today I got a package in the mail from Surplus Sales.... which contained all of the carbon composite resistors (EXCEPT for the (12) 3k ohm), the ceramic caps, the 47pF capacitor, and the 100 ohm video trim potentiometer. I soldered the A14F rectifiers, the MPS transistor (video signal), the .1uF, .01uF and .001uF ceramic disc capacitors, the 47pF dipped cap, and the 14.138 Mhz crystal.
In the image at the top, you can see that I shorted the (2) "6502" bridges, as well as the No DMA bridge. I used wire that was trimmed from the resistors to short the (2) "6502" bridges.
(The No DMA short only has one hole in the PCB, not sure why?)

Anyhow, here are a couple of things that I learned tonite:

1) The MR501 rectifier diodes have wire leads that are too big for the holes in the PCB so I used A14F rectifiers instead. (A friend of mine sent me these from Ca. as I could not find them anywhere -- apparently they are only 15 cents each at the electronics shops in the Bay Area)

2) If you are working with ceramic caps with really short leads, make sure that you tape them to the PCB before you solder them. Otherwise they might fall out when you turn the board over. And if they do fall out *while you are soldering*, as did for me, you will be swearing for the next 15 minutes trying to get the solder out of the holes so that you can start over. Luckily, it only happened once. I didn't have much luck removing the solder using copper braid. So I ended up using a piece of trimmed resistor wire and a pair of plyers to hold the wire (so I wouldn't burn myself). I reheated the solder in the hole while plunging the resistor wire into the hole until it came loose. After a few tries I was able to remove enough solder to get the capacitor back into place AND TAPED to the PCB before attempting to solder. (I will purchase a solder sucker soon...)

3) If you use too much solder on resistors, caps and diodes, the solder will seep through to the other side and "ball up", creating small BB like balls of solder on the top of the PCB. (Maybe my iron is a little hot?)

4.) I am finding that a setting of about 3.4 on my soldering iron is a good heat to work with.
I let the iron heat up for at least 5 minutes before using it.
(Model = Weller WLC100)

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