990 opamp - suggest a stuffing order?

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jeffrey_burr

Well-known member
Joined
Jul 5, 2005
Messages
89
Location
Oakland, CA
So I've got these 990 kits from Ptownkid (thank you BR!) and am about to embark on the construction o' deez badboys.  I think I'm straight with the thermal coupling and ferrite winding situations.  I'm curious if anyone has any dire warnings for me about stuffing order?

Also, referring to part numbers in Mnats' documentation, I presume that 43K will work okay for R10/11, with +/- 18V rails?

Thanks all.
 
havent done mine yet but i ve done some think'in.  lowest profile stuff first. start in the middle and work outward. use the narrowest solder tip i can fine and the narrowest solder.  but i could sure use any tips or warnings from members who have already tackled this project.
 
They are a bit of a bugger to do, you will need VERY small tip and solder
and an illuminated magnifying glass is highly recommended !
I blew one up by not properly "thermally coupling" the diode to the output chip.
I'm still not too sure what that entails but I did get two others working !

I just did all the small stuff first and it seemed to be OK

MM.
 
I do inductors first, can second then move outwards from there.

When I get near the mounting pins, I do them first cause they can be a
bugger to get to if you do them later.

When I do the flat transistors, I leave enough pin height to snugly
fit the diodes between the board and the plastic package of the transistor.

Make sure you get those output transistors the right way around.

 
I do legs first (in a socket) then I did the inductors, then inside to out.

Make sure you strip the inductor wires. I found butting them up to the edge of a table worked the best for me with a razor blade striping away from the inductor. The inductor is held in place against the tables edge.


 
i would check the pins (output, +,-, etc) first to make sure there are no internal shorts. I drove myself mad, only to find that 2 of my boards had shorts in the soldermask..
Also, make sure that you have the proper resistors for the power supply you are using. I had some 990's in an Averill rack with the resistors for 24v rails, Averill are 16..
Lastly there are 2 hand matched resistors, i think they are the load on the diff pair on the input. They are supposed to be matched and a specific value.
I don't have a "true" 990 to match them with, but i assume these parts could make a difference in distortion and performance.
Ian
 
thanks everyone.  I'll check carefully for shorts and get a narrow tip.  I'll probably use 43k for those resistors unless someone has something to say about it.
 

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