Curiosity

[John]

Hi fellas, I picked this little "broadband amplifier" up for a couple bucks on ebay, solely because I think that kind of cage is cool, and figured I could just use the chassis someday to build a tiny little amp. Anyway, when I peaked inside I see there's no resistors like I'm accustomed to (because after all, I have this wealth of knowledge and experience  ) but just bare wire coils. I am *ass*uming these function as resistors though? Anyway, attaching some pics; any info is as always appreciated.
Oh yeah, what are the square things in the second picture?

Thanks!

[sluckey]

Oh yeah, what are the square things in the second picture?

Selenium rectifier diodes.

It's got resistors too. It's a broadband RF amp.

[eleventeen]

A Sluckey said, it's an rf (radio frequency) amplifier...also evidenced by the PL-259 connectors. It's basically an antenna booster. It's a nice cage/chassis, though it looks like the cage height might limit the height of any tubes you'd care to convert to. 6BQ5/EL84's would work, it would seem. It's likely there isn't a single part in there you'd be able to reuse other than an AC switch/fuse/linecord. Maybe a few tube sockets, terminal strips. If you can reuse the power transformer, that would be a plus, but I will bet you'll need to use a voltage doubler power supply. Which is fine. Looks to me like you'd be best off stripping it down to bare metal if you want to make a small amp out of it.

[John]

Thanks for the thoughts, and yep that's basically what I figured on doing. I *think* I can find a small PT that would fit the opening, and was figuring on doing a real simple 2-tube SE. I just like the way the cage looks.

[Danskman]

Nice "Arefesus Fiftius Apparatus" dinosaur P2p !
A perfect chassis for a new homebrew amp...
BR,
Danskman

[HotBluePlates]

Anyway, when I peaked inside I see there's no resistors like I'm accustomed to ... but just bare wire coils. I am *ass*uming these function as resistors though?

They do, but maybe not like you think.

They're probably peaking coils, given this is a video amp. Imagine using a coil instead of a resistor as a plate load for a tube. It looks like a dead short to d.c., which makes setting the operating condition easy. But because an inductor has a rising impedance with rising frequency, they look like a high impedance way up at RF. So they perform the function of a plate load resistance.

Don't think you can reuse them, outside of another RF amp. They are generally a quite small inductance, because once the frequency is as high as that amp operated with, it doesn't take much to present a significant impedance to a.c.

[John]

Thanks for that info too!

Almost forgot to post this little tidbit about the selenium rectifiers. Just tickled my funnybone.

Selenium rectifiers had a shorter lifespan than desired. During catastrophic failure they produced significant quantities of malodorous and highly toxic fumes that let the repair technician know what the problem was. By far the most common failure mode was a progressive increase in forward resistance, increasing forward voltage drop and reducing the rectifier's efficiency. During the 1960s they began to be superseded by silicon rectifiers which exhibited lower forward voltage drop, lower cost, and higher reliability.[4] They are still manufactured for exact replacement purposes but are not designed into new equipment except for some automotive battery chargers.[5]

[HotBluePlates]

I haven't smelled one fail, but I think it was Sluckey who noted they smell like sulfur.

It seems the magic smoke doesn't smell too good.