Help with a busted MSV11-L?
ard at p850ug1.demon.co.uk
Sun Dec 7 13:44:41 CST 2014
> And should I always install the replacements in sockets, or is it OK to just
> go ahead and solder them straight in? (The socket obviously doesn't cost
> much, and I'm less likely to damage the chip installing it like that, and of
> course if I get it in and it's U/S, it's easy to swap out from a socket, but
> I'm wondering if the use of a socket has any downside, electrically.)
Sockets have basically 5 problems :
1) Extra stray capacitance between the IC pins. This is the normal reason for not using a socket in high-
2) Extra inductance of the connection to each pin. This can affect certain ICs which need external decoupling
(e..g for a clock multiplier PLL) as close to the pin as possible
3) Extra thermal resistance. This is a reason for not putting some power devices in sockets
4) Extra height above the board. In your case Q-bus is tightly spaced anyway, so check there is enough
space for the socket you are using.
5) Reduced reliability. My experience is that formed-pin (cheap) sockets are a pain. Turned pin (machined
pin, whatever) are fine. I have never had a bad contact on the latter. Yes, if you are doing military or medical
work it will matter but for classic computer systems I don't think that a turned pin socket will degrade
reliability at all.
Personally, if there are no problems due to the above I solder common TTL parts and the like in directly.
I socket anything expensive, anything hard to find, or anything complicated. And of course a programmed
device (ROM, PAL, etc) gets socketed if at all possible.
In yuo case I'd socket the Q-bus buffer chip, but not the TTL latches.
More information about the cctalk