Glass Pin Diodes

As the years have passed on from the 1970s, thru hole components are becoming more difficult to obtain. Few parts manufacturers are still making thru hole components because they've switched their manufacturing processes over to surface mounted PC board parts. Thru hole PC board parts have little metal legs extending from their body and have to be soldered to metal holes in the PC board. Surface mounted parts have no metal legs, only tiny metalized pads instead. They are soldered to metal pads on the surface of the board. When surface mounted technology first appeared, there were some serious problems. One problem was temperature. As electronic devices are powered up and running for long periods of time they generate heat and cool down rapidly when turned off. Surface mounted PC boards would bend slightly, or flex somewhat causing tremendous strain on the metal pads. Solder joints fractured or broke completely causing the instrument to fail. Thru hole PC boards on the other hand are almost bullet proof, they are much more resistant to temperature changes and such. They are extremely susceptible to Dendrite crystals and contamination, but I will cover that another time.

Most of our new generation test and measurement instruments are all surface mount PC board technology, but there are some with mixed technology boards, that is thru hole and surface mount parts on the same design. The stuff I primarily work on is all thru hole. These days, we just can't get quality components anymore. The only places we can buy vintage components from are what we call "Sunset Houses". A Sunset House is a part factory that will take on dead technology and continue to manufacture it for a dwindling customer base at a premium price. They are much like a print shop in so far as the more quantity you purchase from them the larger discount you get. If you require a limited run they delibrately price the parts so high that it's not worth anyone's money or time to place an order. This is the recurring situation we find ourselves in dealing with this vintage product line of RF Signal Generator.

Every couple of weeks another manufacturer of thru hole components throws in the towel and that leaves us holding the legendary empty bag. Our engineers and senior technicians have to scurry around in the component world for a suitable replacement part and trigger an MST (Manufacturing Special Test) to evaluate the new part. It's a mess. For the past year one of the parts that has been a thorn in my side are the glass pin diodes for our Voltage Controlled Oscillators (VCO) that go into each box. Without the VCO, the test instrument is entirely worthless. And without good glass pin diodes, the VCO is junk. It's a vicious circle of component hatred. We did have a backup plan although it's a rather shoddy one. It's called a Lifetime Buy. I'll get into that some other time as well as the Dendrite scare of the 1980s.

Diodes are a fairly basic electronic component. They are like a water valve that only lets water pass through the valve if it's at a certain level, and it only allows the flow in one direction. We need 17 or 18 matched value glass pin diodes in the VCO and if they don't meet our specs, we have serious problems. Serious. Nearly a year ago our primary diode manufacturer bailed out on us and we were left with taking whatever we could get. The Sunset House we are contracting with has sent us thousands upon thousands of diodes claiming they meet our specs, but the reality is the things are complete ass. I've never seen such shitty measurements. Almost entire production lots from these guys are totally out of the value range we expect. Since there is no other supplier, we have to go with what we have. We're totally fucked.

Compounding my problem with building and testing good VCOs is my sometime nemesis, The Squirrel. We know the diodes are funky, we know we have no choice but to use them, and we know each and every diode has to be tested for it's value and sorted out. There are thousands of them here on the line to sort through, and Squirrel will only test enough diodes to build a few VCOs at a time. If anyone else comes along to build VCOs, there are no diodes in the sorted bins ready to use. I know she's doing it on purpose because she is 1) lazy and 2) trying to fuck with other employees. I would like to strangle her on a daily basis for this.

I have no control over The Squirrel. In fact if I even try to ask her to start testing more that a couple dozen diodes at a time she will more than likely run to management with tears in her eyes and tell them I harassed her. She does this to get out of work responsibilites constantly. I could lose my job so it's not worth the risk. This week I decided to bite the mother fuckin' bullet and test every last one of these god damned shitty diodes. Thousands of 'em. Let me honestly tell you, it made me want to die. Imagine yourself sitting in front of an eight foot tall test rack loaded with cutting edge equipment and you place one diode at a time into a fixture, take a value reading, and place the part in the appropriate bin. Repeat this hundreds of times. Then you come back the next day and do it again. And again. While you're doing this you discover that these diodes are so fucked up, so far out of specification for the application we need, that you know most of them will not work properly. But it's all you've got.

I have a few thousand more to go. I am in diode hell. Maybe this is going to take another week of eight hour shifts to get through but by God I am going to do this. I am going to do it just to spite The Squirrel even though I know I'm playing into her game. What she doesn't know is, I won't forget and I will have my revenge...