getting into the head of a amplifier designer @ wavetek and argue about berylium - Page 1
Forum section: electronics / projects

author: sarepairman2
author_rank: Frequent Contributor
timestamp: October 04, 2015, 06:34:56 pm
content: I got a broken wavetek FG, it has some fried transistors. I think its doing some kind of push pull thing, anyway I measured some transistors and their bad.Some of the resistors surrounded the transistors are fairly odd, like 61 ohm 1% base resistor.Transistor is a 2n5589.Am I being paranoid when I imagine then selecting resistors with regard to the tolerances of the transistor?The passives are fine, but I am worried that their catered to the transistor, and then I would need to retune the thing.The only tunable element I found is a adjustable capacitor btw.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: October 04, 2015, 09:28:04 pm
content: I would be surprised if that were the case.Particularly in "cost no object" test equipment, it's often done that all the resistors are 1%, whether they need to be or not. Especially the case with SMT chip resistors being as cheap as they are these days; even 0.2% are available for almost the same price, in relevant quantities.Tim

author: IconicPCB
author_rank: Super Contributor
timestamp: October 04, 2015, 10:05:36 pm
content: There may be select on test components especially since this is specified as a class C transistor in the upper half of VHF band.

author: sarepairman2
author_rank: Frequent Contributor
timestamp: October 04, 2015, 10:59:00 pm
content: this is an all through hole unit using through hole 5 band resistors

author: IconicPCB
author_rank: Super Contributor
timestamp: October 05, 2015, 03:18:31 am
content: Be extremely careful when handling the transistor. The ceramic( barium oxide ) in which it is packaged is bad juju if gets chipped.The dust/particles can get into the lungs and that spells the end of You.

author: ez24
author_rank: Super Contributor
timestamp: October 05, 2015, 03:26:13 am
content: Quote from: T3sl4co1l on October 04, 2015, 09:28:04 pmThe Wavetek is vintage (pre SMD). I remember driving by their building which means I am vintageFYI what FG are we talking about?

author: helius
author_rank: Super Contributor
timestamp: October 05, 2015, 03:57:42 am
content: Quote from: IconicPCB on October 05, 2015, 03:18:31 amBarium oxide is poisonous, but no great danger for inhalation. You must be thinking of beryllium.

author: sarepairman2
author_rank: Frequent Contributor
timestamp: October 05, 2015, 04:27:28 am
content: the transistors are all in metal cans as far as i can telloh, i must have wrote the # down wrong, i gotta look in it again and see

author: IconicPCB
author_rank: Super Contributor
timestamp: October 05, 2015, 07:33:05 am
content: Helios yes...If I may quote geoge Bush.. I mis spoke..or was it the brain mis fired?

author: helius
author_rank: Super Contributor
timestamp: October 05, 2015, 06:57:55 pm
content: Quote from: IconicPCB on October 05, 2015, 07:33:05 amI think he said "what a waste it is to lose one's mind, or not to have a mind at all"I learned something, though: beryllium oxide is as thermally conductive as diamond (more than gold!) And its natural gems are diamondlike and exceedingly rare.

author: AF6LJ
author_rank: Unknown
timestamp: October 05, 2015, 07:00:43 pm
content: Quote from: ez24 on October 05, 2015, 03:26:13 amYou also ?I use to work down the road from Wavetech.

author: AF6LJ
author_rank: Unknown
timestamp: October 05, 2015, 07:04:09 pm
content: Quote from: helius on October 05, 2015, 03:57:42 amYou have to work at it to make the stuff into dust, there is a 150W VHF amplifier in the garage that uses a welded beryllium thermal link to provide an electrically insulated heat transfer link for the single vacuum tube in that amplifier. The stuff is fairly robust unless you start taking grinders to it.

author: LaserSteve
author_rank: Super Contributor
timestamp: October 06, 2015, 02:22:08 am
content: Beryllium Oxide Dust really has to be less then say 5-10 microns to kill you.The following is my ill informed opinion, consult your workplace occupational health specialist if you really have to handle it daily:(If you have to handle it daily, find another job!!)For large chunks or solids of BeO:Wear latex gloves or nitrile gloves, dust mask, Flood it with water if broken. Then place in a wet plastic bag and seal. . I've had to handle it for years, a few times a year in large pieces in laser tubes, or in To3 pads in certain laser power supplies. Its hard as a rock in big pieces and when bonded into semiconductor packages. However, it is brittle in tension, compression, and shear in thin pieces such as TO3 and TO220 pads.Graphite, Boron Nitride, CVD Diamond (soon) Silicon Nitride, or Aluminium Oxide high conductivity pads are taking over except for a few military and aviation applicationsBeO transistor pads usually are coated in sticky heat sink grease, and crack into a few big pieces with no or almost no fine dust when stressed and broken.The workers at the BeO factory however, had chronic exposure to the dust from Hot Isostatic Pressing, and that was a long, slow, death in great pain. It liquefies lung tissue in chronic exposure. Basically catalyses its way down thru the lungs, making dead tracks of tissue as it goes. You can either breath it in, or in certain cases get it in the pores of your skin. There are two forms of the disease, One way makes granular tracks in the tissue, the other causes a permanent pneumonia that is really nasty.When the previous poster says NOT to grind on it, he means it. That is how you get Berylliosis, Breath very fine BeO dust or powdered metal, or inhale welding fumes.Steve