Let’s play Wheel… Of… DUMPSHIT!!!

I just received two new 4CX250B / 7203 tubes for one of our transmitters, an old Continental Electronics with the tube intermediate power amplifier (IPA).

I’m already wondering just how they’re going to fail. Not IF they’re going to fail, more like, how, and how much collateral damage will occur.

The sad story: These tubes used to be produced by Eimac and were perfectly fine. At some point, Eimac got sucked into some giant ugly conglomerate that consolidated their tube manufacturing and made some awful changes, then hacked and slashed at their product line. That effectively led to a quality fade then discontinuation of the tubes.

I’ve been pretty much informed that the way to get GOOD 4CX250B tubes is to either go back to 1981 and stockpile them, or find someone who has them sitting around from back then and hope that they’re not gassy or badly manufactured tubes from Eimac’s Salt Lake City facility.

So now, what do you get when you try to buy a 4CX250B?

….this. this is the dumpshit you get. alibaba.com’s finest, I’m sure.

FEELING LUCKY?

These are “National Electronics” marketed by Richardson Electronics. Richardson’s website only mentions the Eimac tubes that they were a dealer for, and when these were ordered, there was a week’s delay in getting them shipped. National Electronics used to be a perfectly legitimate tube dealer or manufacturer – I think they went with contract manufacturing back in the day, as you’d see a really wide variety of their tubes out there, everywhere from receiving valves to power tubes and even indicators like Nixie tubes. Now, my best guess is it’s just a shell being kicked around via brand name necrophilia.

I don’t know if these even work at all, and won’t until I can get to a mile-high transmitter site whose means of access are currently buried in snow and ice.

So, for now, let me compare them to a new old stock Eimac tube. This is a 3CX800A7, a different tube entirely, but using the same sort of package and plate structure.

Eimac tube on left.

Immediately the bright silver plate finish becomes apparent, along with a far different cooling structure. The fins are brazed or soldered to the plate. This is important as the outside of the plate cooler is usually used as the electrical connection via a clamp around the tube. You do not want a bad connection in there.

And now, the Richardson/Alibaba Special – they just… lovingly shoved it down in there with a press and called it a day.

No signs of soldering or brazing are visible.

All in all, it looks like it was just smashed together using the same tooling one would use to make cheap and nasty refrigerator coils.

Now, about that gray mystery metal….

I looked at the socket pins and saw no marks on them at all, just a uniform gray coating of… whatever.

On the Eimac? There are marks in the silver plating from where the tube was put in a socket for factory testing.

Did they even——??? Is there any factory testing??

How’d this Oddish get in my transmitter?

what the fuck is any of this, i need a nice adult beverage

So yeah— I’m NOT convinced these are even going to work, but I guess that’s what I can get now. Thanks, Crapitalism!

Well that’s why the start ladder is all pooched

There’s a Paras in it.

In all seriousness though I’m starting to fear I’m temporarily buried in craziness. My boss is trying to track down some 4CX250’s for a Continental IPA and the answer as to where to find these is “go charge up the Delorean and go back to 1985 to pick up some Eimacs”. This business gets weird sometimes.

Annoyance

Sometimes you just wonder “what was ANY OF THAT?”… yeah.

I dunno, I got pretty frustrated trying to get some old equipment up and running again, and then discovered that my wonderful old Tektronix 2232 oscilloscope started also suffering Capacititis or something. First I came in this morning and was like, what on earth even happened to the bench— oh wait, an amazing struggle with a QEI 675…

Then the scope went blank with a weird whining sound that suggests ye olde crapacitors have failed… I had previously had an issue with the screen getting garbled on this, and percussive maintenance brought it back, but not this time. I went to open it up and look around inside and the blue painted aluminum shell got jammed. I even had a coworker tug on one end while I tugged on the other, it was kind of amusing but pointless. I finally got it loose with silicone spray and slowly wiggling it off. What a mess.

Intel Inside

The usual fancy custom silicon that’ll effectively e-waste the whole scope if any of it gets damaged. Luckily, on this scope, they did NOT use a whole horrible death forest of tantalum capacitors.

Guess it’s all just telling me to slow down for a day and get some smaller things done…

Deep thoughts

Why do we call it plate voltage and not bowl voltage? The plate (anode) of the tube is that radiator-equipped bowl over the top. It’s not a flat plate by any stretch of the imagination.

Plus, saying “bowl on” is more satisfying than “plate on”.

BRAWNDO! It’s got electrolytes!!

Unknown energy drink spilled in very unobtainable telephone hybrid control surface.

The small is like that of old Jolly Ranchers and BRIMSTONE.

Welcome to Monday Night Rehabilitation. Chances of this thing’s survival are probably about 60%. Chances of the survival of whoever spilled their drink down this and said nothing about it until it hardened into foul lacquer—-???

Clearing out the “shitposts” folder

I apparently had a folder of images prepared for technical grade shitposting that were going unused so it’s time for a SHITPOSTING FESTIVAL OF LIGHTS

This shitposting festival made possible by the PTek corporation.

Your transmitter with the patented Crown of Thorns, guaranteed to send you running to the friendly local general store for first aid supplies and to clean up in their washroom after slicing your freaking knuckle open

In theory maybe this just means the top cover was put on backwards but I don’t want to open the top cover. Why? I don’t want to know what’s inside this unit because this is what was inside the older FM-500 series and it makes me a sad panda. (Spooling up turbocharger for powerful shitposting of… shit!)

The power supply system is three switching PSUs with their outputs wired in series and grounds floating. OOOOKAY, NO, DON’T DO THIS

Here’s the PTek FM500 series pallet overall. Not visible, or even particularly accessible, above the top of this photo, is the control logic board buried between the heatsink and the housing. Input (and output) are the tiny white cables to the right. Input’s at the top. It first goes through a buffer/driver stage, a Wilkinson 2-port power divider, through the finals, through some very unusual stripline transformers, then to a Wilkinson 2-port combiner ending with the start of the output lowpass filter, a fourth-order pi network apparatus. Seems legit, but look at those RF FET modules.

Post continues to be image-heavy so I’m going to place a break here to avoid excessive page length

Continue reading »

1 2 3 9