RF Power Transistors

Well, I'm no wizard and not even an expert. I can't answer your question on whether you can just glue the cap back on. Only guy from a semiconductor manufacturing facility can say for certain.

However, I typed ENI-20A into the Google search engine and got 39 hits. One of them: http://www.icelect.com/catalog/E/E-146sum.htm gives the exact part number as you typed it.

May be it is temp of transistor which is making it to fall. So if you want to glue it glue with some high temp glue that can cure at room temp.

I am not clear why gold plated?

Is it something like golden or is it gold plated?

You mean the lid? If that's the case, just glue it back on. If the part's still good you'll be OK, if not, no big loss.

I've cracked the lids off of IC's by subjecting them to thermal stress -way in excess of what should have happened here, so either it's just bad glue, or the thing has gotten incredibly hot, and may be dead or dying.

As its a high power rf transistor I would be extremely careful what you do...

I don't want to alarm you but for these power transistors the manufacturers sometimes use beryllium oxide as an insulater with excellent thermal transfer characteristics...

Beryllium oxide is toxic in tiny amounts. Most rf power transistors come with a large warning about NOT opening the case because of this...

Having said that though, if the cap is intact and not broken use epoxy resin to glue it back on... DO NOT try to force it or file it etc...

If its for industrial use and subject to health and safety issues, then put the whole instrument in a sealed bag and mark it as dangerous until you can confirm its okay...

John.

I do not believe this...

You are supposed to be engineers and yet nobody, except myself, has warned the OP about the extreme dangers he risks with an opened rf power device!!!

Beryllium Oxide is LETHAL and you should NOT open any rf power device as its commonly used instead of ceramic because of its high thermal conductivity!!

Here is an extract on its uses and dangers... Please take note !

Beryllium oxide is used in many high-performance semiconductor parts for applications such as radio equipment because it has good thermal conductivity while also being a good electrical insulator. It is also used as a structural ceramic for high-performance vacuum tubes, magnetrons, and gas lasers.

[edit] Safety

WARNING: BeO is carcinogenic if the powder is ingested or inhaled and may cause chronic beryllium disease.

John.

Hi John. et-al

Thanks for your concern. I am very familiar with BeO toxicity. I would never open or mess with anything containing it. The lid is made of common ceramics, just fell off for no apparent reason. My question was , as I am not a semiconductor manufacturing guy, if this can be glued back. As yo know some of them are glued under vacuum, to avoid possible oxidation. Looks as if this one is not, and can simply be re-glued. Question now is which adhesive to use as it must be immune to RF absorption for obvious reasons. Or maybe I could just leave it as-is, no lid? Any info out there?

The idea of replacing all of these, ( I also believe that more will show same symptoms), appeals to me. However at $100.00 each it will make it over $3000.00 total. can't do it...

Wangito.

I didn't mean to sound hysterical Wangito, or to make out you were incompetant...

But there are some youngsters who come on here asking the oddest questions and for nobody to warn you would have been a bit irresponsible I feel.

I still reckon a nice dollop (not too much) of two part epoxy resin would do the job nicely...

Its what I've used in the past!!

John.

Hi John, I still remember my lab professor saying : "I am still waiting to see what is too much safety" as if it was yesterday. (But it wasn't...)

Could you remember what was the name of that adhesive?

Wangito

Yes of course.... in the UK its called 'Araldite' but its commonly used around the world so you must have some available to you somewhere...

Its a two part adhesive, a hardner and the resin, mixed it gives superb strength and rigidity - But most importantly it fills any gaps between mating faces, so its ideal for this application.

John.

Thanks

I sure know Arladite, We have similar things here. I thought it must be this or any high quality 2 components Epoxy adhesive. (I hate the smell, it reminds me of laboratory mice odor for some reason...) Am going to this now.

Wangito.

Johan,

The problen is not BeO in solid form. If cut or ground, the dust migrates to the lung lining. As with Silicosis or Asbestosis, Choose your flowers now!

Dave

BeO Toxicity.

LD-50 for rats (kills 50% of them) The 30-day intraperitoneal LD₅₀ of beryllium as beryllium chloride was 0.56 mgm./kgm. for rats and 6.3 mgm./kgm. for guinea pigs.

A 220 pound rat needs 56 milligrams to kill it.....which is not much, so heed the warnings

It looks as if it is unanimous decision that this is only a lid and can be glued back on. I will do just that and see what happens.

BTW- the bars and the frame are gold plated. being I guess, a high frequency RF amplifier. Any one with replacement source info?

Thanks to all those who came back, and to those who will.

Wangito.

They plate them with gold and sometimes make them with gold for superior surface and bulk conductivity, as well as corrision resistance.

As for the cap/ The glue you must use must cure and must be RF inert or it will absorb a little of that 1000W and fall off or char.

Delta RF Technologies, Inc. Makes commercial high-power (300w to 1000w) solid state RF modules that are stand alone units for incorporation in broadcast transmitters. You can go to your kilowatt power level without combining, or go higher by doing the combine thing. They purchased Silicon Valley Amps some years ago and can be accessed at svpa.com. The units I am familiar with are in the 88-108MHz range but I believe they can supply your needs. Another source would be a solid state transmitter company called "Bext". They'll come up on a search also. Also, High power RF transistors are a little tough to check in my experience--about all you can do is put them in and turn them on. Good luck.

Lon

If you want reliability, I personally would not repair it, I would replace all the transistors as they are all probably going to go the same way, one after another....they are probably all from the same day,date code and probably are all bad!

As someone mentioned, the substrate doping chemicals are often very poisonous.....be carefull.

Hi, I've done lots of repairs on the ENI amplifiers. Never run into the cap of the transistor falling off though! If it is still working, then try gluing it back with epoxy. You haven't got much to lose. I'd suspect that you might have troubles with vapour from epoxy contamination transistor surfaces, but they might have good enough passivation to cope. It's worth a try. I'd be inclined to replace though if possible for best reliability. It is a big job doing all transistors and the final setup can be lengthy, so just replace the broken one. Look on the net for equivalents to the ENI branded transistors, they are usually common types and can be purchased cheaper than the ENI branded types. ENI might have done some parameter selection with their branding so be aware that there may be some small differences, although I have no evidence that is the case. I'd have no problem replacing just the broken one, so long as you check all the others. They do seem to degrade with aging. Their output power can drop off a little and they start to run hotter than when new - leakage issues I would guess. My experience with older ENI amps, is that you often have to replace the lot to get it up to spec. However, if the whole amplifier performance is still good, replacing the single one is likely to be quite successful. Cheers, Colin

Hi Colin

Thanks for detailed answer. Replacing all transistors is out of question for budget reasons and is a huge task. It really doesn't seem to be necessary. I already glued it to place with instant glue hoping that this one will be the less contaminating one, and it has good high temperature characteristics. What I don't know is, was the transistor originally glued under vacuum? and the loss of it will have any consequences on the transistor performance? oxidation ? I didn't find an equivalent to the original transistor it is marked ENI-20A, which appears to be a proprietary P/N. I am not so much worried about the super linearity as we do some simple plasma work, and when not in this, some HF radio games. The one million dollar question, as an ENI expert. Anything I can do about the tremendous noise these Tarzan blowers are making?

Wangito