Here is a big news item from 1972. Field Effect Transistors will be replacing tubes!



Cover photo courtesy of: http://semiconductormuseum.com/Museum_Index.htm

It happened, but not in the way that was predicted.

Rich

They destroyed a 12AT7 just to take a picture!

What a bunch of idiots!

Here is some good information on the Fetron

http://www.slack.com/misc/Fetron.pdf

Dave

When that article was written the valve (sorry tube) would have cost about $1.5 in the U.K.

Not quite a drop-in replacement. If some piece of gear had the heaters in series, this could cause a problem. At least a little rewiring needed. The 1st page of the PDF article states power savings due to no filament, not even as a resistive dummy path. But that would mean heat, which transistors don't like.

Even in 1972, this doesn't sound like a bright idea. Everybody pretty much new by then, that tubes were on their way out. The exception being some very niche areas. The article does mention their use in telecom installations. I would have hoped Teledyne had a big order, to justify developing and making them. And they were just trying to make a little extra gravy by selling them elsewhere.

Has anybody run across these, in an actual piece of gear ? I've come across SS rectifier replacements, but never an amplifying tube substitute. If you get one make something new with them, and also use a nuvistor, or two. Transistors that look like tubes, with tubes that look like transistors.

I received some from a person who worked for the company. Never saw Fetrons used in equipment.

Mesa Boogie guitar amps have used fetrons, amongst others. Also see: http://www.philipstorr.id.au/radio/eleven/fetron.htm

If I remember rightly, Western Electric wanted them to replace 6AK5s.

Never saw one in equipment.

We talked about it at Siliconix in the late 80s, but never saw any real need for it. Too many circuit variations to make a general replacement for any particular tube.

Rich

I have a complete unused Teledyne HP400D/H/L-5 fetron conversion kit for partial conversion of the HP 400D VTVM to a SSVTVM. It consists of five fetrons to replace the five 6CB6 tubes in the HP 400D, H, L, and ME-30A/U, B/U, and C/U. It is dated 1974, starts out "Conversion is simple" and includes 12 pages of recalibration instructions and service data. Apparently, the instructions discouraged the buyer of this kit from proceeding with the simple conversion.

Norman

used them to replace 403-b tubes in v-3 repeaters.never had a problem with
them.set the gain on the amps & never had to readjust.maybe 40 of the amps
were in use with the fetrons for 10 or so years.only reason they wern't used
longer was the system was replaced with t-carrier when fiber replaced the
copper pair cable .
steve

I was close, but not exact. 403-B was the AT&T / W.E. version of the 6AK5.

Rich

Western Electric called their fetrons "hybrid integrated networks" or HINs. They made at least five different types, but each type was designed for a specific location in a specific piece of equipment. I think at lease three of the 5 are 403A variants.

Jim Cross

you're right about the name HIN's they has a KS- spec number also.
used them in the LD-T2 transmitters where there were 403-b tubes.
they worked ok in that application too.rf didn't seem to cause any problems.
steve

Did WE actually make these, or buy them from Teledyne or some other JFET maker?

Rich

I do not know the answer absolutely, but sine they did make their own transistors, I am inclined to think they made these too.

Jim Cross

Teledyne made at least 14 versions of 407A and 17 versions of 408A. Looks like they couldn't use one Fetron to replace a tube in any circuit. They started assigning Fetron numbers with TR1000. The highest number I show is TR1095 and between those numbers only cover about a dozen tubes. They even made a Fetron, TR1010, for 2D21 thyratron.

Norm:

The HP400D/H/L-5 kit includes a TR1098 to replace one a 6CB6 tube in one application.

Norman

There were kits offered for the Collins S Line as well as some Drake gear. As with any SS back then what you gained in sensitivity you lost in overload handling. When used in other stages they did OK and reduced heat.

Carl

I stumbled upon this topic when Googling. Actually, I have a Heathkit IM-28 bench VTVM that I'm using Fetrons in. The 6AL5 is a TR-1002 (Heathkit # 150-57), and the 12AU7 is a TR-1119 (Heathkit # 150-58). I've had them installed for years and the meter calibrates and functions perfectly, just like it had the original tubes installed. I have also added a power supply to replace the 1.5V "D" cell ohms battery. Everything works great.

However, I've never seen another "set" of Fetrons on EBay or elsewhere.
Mike Harmon, WB0LDJ

Solid state "tubes" at least commercial products, targetted a few specific tubes. So if you could replace the tubes in telephone equipment, the "tubes" would last longer, and you'd reduce heat inthe equipment, so other components might have longer life.

But it was a brief period, keep tube gear running a bit longer. Once the tube gear was replaced, no more Fetrons and the like needed.

There was also a letter, in Ham Radio or QST, from someone who noted they weren't perfect. Something like the "6AK5s" were good as limiters in FM receivers, but didn't do agc well. I may be remembering the details wrong.

Hams did tube replacement in various ways. General plug in replacements, not sure how well those worked. Sculpting to the stage, but trying to keep the existing circuitry intact. Changing existing values as needed. Or start almost from scratch, using the equipment as a foundation and basically each stage new. An example of tye last was in Ham Radio for Feb 1969, Hank Cross converts a BC-348 and makes it better