Crawls Backward (When Alarmed)

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Disassembling the Dynaco PAS Beast, Pt. 1

We move forward with the rebuild of the Dynaco PAS.

Now it's a matter of removing all of the wiring that goes to the two PC boards and unbolting them from the chassis.  Originally I thought I'd unsolder them, but since most of the wiring is going to be redone, I just decided to snip them off.

Snip.

Snip snip.

A lot faster than unsoldering.

With the wiring removed, I just unbolt the boards from the chassis.  The bolts are 1/4" - I just use a nut driver.

A side note on the PC boards.  You may have read the earlier post where I referred to them as "PC-5" and "PC-6."  There was actually a method to Dynaco's numbering scheme.  They numbered all of their PC boards in succession, starting with their first product, which was a mono preamp (PAM-1).  I'm most familiar with the PAS and the FM-3.  We know the numbers of the PAS, and the FM-3 has 3 PC boards: PC-7, PC-8 and PC-12.

The genius of this numbering is that instead of numbering the boards, say, 1 and 2 for the PAS is that you automatically know that a PC-5 is the line board for a PAS and a PC-12 is the multiplex board for an FM-3.  Clever and thoughtful, and especially good since so many of this stuff was built up from kits.  Dynaco really put a lot of thinking into their products. 

Speaking of the PC-5, here's the backside of mine removed from the preamp.  After seeing the lifting traces, and the heat damage, I am doubly glad I have new boards.  The closeup here is the circle of connections for one of the tube sockets.  You can see where someone (maybe me) used solder to bridge some lifted traces.  Not good for long term reliability.

I also need to remove all of the wiring from the input board on the back of the chassis.  I do need to reuse these phono connectors, so I'm desoldering the old connections.

This is a fairly good shot of how I desolder.  With the iron pretty hot (mine has a thermostat), set to about 750 degrees F, I take a piece of desoldering wick and put it between the connection and the iron.  After a few seconds, the joint heats up and the solder wicks into the wick (hence the name!).  You can see a whiff of smoke in this picture if you look carefully.

Some folks use solder suckers for this, but they just don't get it for me.  Too big, too bulky, and they don't get all the solder off an old joint.  I like to have 'em nice and clean so when I put a new connection on, it's all pretty-like.  After you wick the old solder off, you can usually just pull the old wire or component off the connection.

A lot of restorers of old radios just clip the old leads and then crimp or hook or pigtail the new leads to them.  I think this is sloppy workmanship.  Why not take an extra 60 seconds and do it right?  I can understand that *maybe* on a component that's buried somewhere you may be forced to do that, but in general, I think crimping is lazy.  The people who put this stuff together in the first place were skilled, and we should honor that committment to quality work too.

Hokay, now I get off de soapbox!

I need to take of the front panel of the preamp so I can unbolt the selector switch from the chassis.  It always feels a little strange using a wrench to do this, but that's what it takes.   I encourage you *not* to use pliers for this kind of job.  Not only will they round off the nut, but they can slip and gouge your nice front panel.

 
 
 
 

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