Re: Just rebuilt two Friden 132s

From: Rick Bensene
Email: rbensene@gmail.com


Hi, Cliff, An amazing accomplishment! Yes, the earlier Friden printed circuit boards used a very unique method for doing the etching. There is an article by Nicholas Bodley (you can find a it in the "Articles" section of my web site) that talks about this, and I've verified it through contact with a number of other folks who were involved with the development of the 130/132 that also tell of this. The machine used high-current DC to do etching, and it had a tendency to "short out" on the feedthroughs, vaporizing part of the metal inside the plated through hole. This lead to a great many problems with unreliable feedthroughs. It wasn't uncommong for a Friden tech to have to go to the site of a newly-installed machine, and hand-resolder every single feedthrough to get a machine to work after it went through the rigors of shipping and arrived non-operational. The plating machine involved two drums that had inverse "master" images of the circuit board traces and pads on them, and passing metal-clad circuit board between the rollers, and using high-currents and some chemival to vaproize off parts of the metal cladding where traces and pads were not to exist. However, since feedthroughs were apparently plated through before the board went through this machine (still all metal clad, and drilled, with feedthrough plating already done), the feedthroughs could create a short-circuit between the two drums, and destroy parts of the plate-thru. The process was faster than normal manufacturing processes, which was very nice, but, clearly frought with problems. Flow soldering was also a bit of a problem, because the machine would live a little ridge around the edge of a plated through hole, which could cause poor solder joints for leads of components that went through the hole. The worst part about it is that on visual inspection, everything looked fine. But, get out an ohm meter and start checking between pads and component leads, and you'd find opens or intermittants. I admire your patience and engineering prowess to go through and get the machines running again. Did you reverse-engineer schematics, or have you found a source for the schematics for these machines? It seems like it'd be quite a chore trying repair these machines without some kind of reference material. I'm also amazed that you were able to find CRT's for them. I'd be interested in hearing if you learn of any sources for the original CRT's, as I would like to have a spare. Congratulations on the successful restoration of these great old machines. They are certainly worty of restoration, and truly wonders of their time...and still are today. Best regards, Rick Bensene The Old Caculator Web Museum http://oldcalculatormuseum.com Beavercreek, Oregon