The curious elements of Unobtanium and Expensivium

A module upon which the Unobtanium evaporated as the Magic Smoke was lost.

Unobtainium and Expensivium are very vital, curious, yet annoying elements. They are commonly used in parts for electronic devices, particularly those in the world of broadcast RF transmission.

Although no link between actual physical toxicity to humans or any other animals has been proven with Unobtanium or Expensivium, those involved in occupations where they have to procure and work with Unobtanium and/or Expensivium parts tend to suffer a greater number of headaches.

Misspent youth – the Yihua YH-305D

Boy, was I ever young and stupid. It was the summer of 2004 or so, and various Chinese electronics vendors were just starting to flood the US market with some really cool looking toys, and the quality hadn’t faded to zero on them yet either! Mostly….?

At the time I’d just gone through a big mess with most of my workshop having been left out in the rain for several days in my absence, so I didn’t have a power supply. I bought this Yihua YH-305D on eBay and thought it was pretty great for the price, even after it arrived with the instruction manual calling it a “DC POWRE SUPPY” and the plastic nuts on the front panel binding posts don’t actually… work. (I got around this using banana plug leads.)

Years later it finally occurred to me to be suspicious of the fact that the constant current regulation is sloppy as hell, and the cooling fan starts to run if you draw more than one amp off it continuously. At five amps steady draw, the Powre Suppy doesn’t get noticeably warm, but the fan continues to howl forever.

I opened it and realized just how misspent my youth truly was.

wp-1483573643309.jpgThis… beautiful… board greeted me right away. There are places where traces kinda got half etched over there on the side then subsequently, but incompletely, covered with solder to fix it. Ummmmmmmm yeeeeeaaaaah D-

wp-1483573603318.jpgThe underside of the regulator pass transistor assembly. That’s three *supposed* 2N3055 transistors, paralleled. Why would you need three 2N3055’s for five amps?? You can run 15 amps through ONE real 2N3055 if it’s heatsinked properly. Oh wait, I forgot the key word… real. Genuine. Official. Not Pure Unadulterated Chineseium. I couldn’t get a picture of the labels on these “2N3055” transistors that were SO GOOD that they had to put three in parallel to pass 5 amps, but I was able to get a peek at it and they were printed in a gray looking ink with a nonsense logo– it looked like the Marvell Semiconductors logo??!! Either way, this video details what I’m probably actually looking at and why they are… very… very… derated.

The heatsink they are bolted to also explains the fan behavior. It’s nothing more than a flat plate with very little mass and surface area.

wp-1483574274591.jpgThe fan sucks up air from right above it and exhausts it out the back when the thermal switch seen in the background snaps on. I’m not sure how hot it has to get to trigger that, but it sure gets there in no time.

wp-1483573638001.jpgThe main filter capacitor looks underwhelming and I have my doubts it’s actually a Rubycon as its clothing would suggest.

 

This is paired to, uhhh, the death capacitor, as I lovingly call it. If you are using a power supply like this as a limited current source and you lose connection to the load momentarily, and the voltage limit is significantly higher than the voltage the load pulls it down to, any capacitor on the output will be charged up to that level. Once connection is reestablished to the load, it is presented with very high available current at this higher voltage. I detonated some high efficiency white LEDs under test with a power supply like this years ago while trying to develop a boost converter based driver for solar lighting applications and was royally pissed. So, without further ado, the death cap…

wp-1483573631845.jpgand…. the… rubber cement disaster of the century. The entire front of the supply is just…… bespooged with this cement…. Another red cement is found splattered all over the place as well. At left in the above picture is the digital meter board which I am not even going to touch let alone try to calibrate the screwed up zero point on, FORGET THIS

 

wp-1483573620558.jpgThe board is supported only by one small bracket from the rear; if I drop this power supply it will experience the sweet release of death it so sorely longs for.

 

Yeah. I was young and stupid and I bought this.

 

There’s a great thread on EEVBlog’s forum about these, including the wonderful thing that happens when you switch one on and it goes wham, overshoot, boing, boing, boing, and either stops bouncing or… not…

 

Measure up: a beautiful vintage meter.

So a meter is a meter is a meter, right?

Bzzzzzzzzzz.

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This monster is nearly eight and a half inches wide.

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Neat scale.

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Spade tipped needle.

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The passive scale illumination: a ground glass band on top allows ambient light to light the dial.

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Connection post. This isn’t exactly a blazing sensitive meter– putting a digital multimeter set to ohms across it yields no visible deflection. (Some meters peg!) Setting the DMM to diode check, which usually applies 5mA or so, gave me about a 61. Please admire that rough carpentry. I love finding things like this!

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Better view of that nicely made wooden base. Unlike the edges of the connection post holes, the outside is immaculate.

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Dwarfing a Gossen Lunasix.

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Hand written serial number.

What was this made for? Judging by the lack of any visible brand name, wood tabletop base, and unusual scale with no units, I’m suspecting it was a classroom/lab piece. You’d calibrate with a known voltage reference and do the math yourself. You know, old school nonsense. 😉

The low sensitivity is curious too. I’ll have to test later and see just what scales out to a 100.

I did open the meter briefly because there was some loose material rattling around that I didn’t want damaging the movement. An old wire wound spool resistor is mounted inside in parallel with the movement, likely for damping. It looked similar to the spools in my Weston but covered in cloth tape instead of wax.

Crap Power Strips

This has significantly bothered me for a while.

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This is one of the most common power strips available now, as it’s the least expensive available out of China. Note what happens if you miss just a little plugging in a two prong plug. If you touched the prong here and any grounded object, hi diddly shockarino, neighbor!

But guess who doesn’t seem to have a problem with this.

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Genuine meaningless hologram.

This strip is available under a number of brand names including General Electric, Westinghouse, Belkin, Sunbeam, whoever the retailer licensed a brand name from that week. You should not buy it.

Percussive Maintenance

I was testing something with my trusty old Tektronix 2232 100 MHz digital storage scope and this happened:

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My guess as to what I’m seeing: a pretty significant bit of the input to the DAC (digital to analog converter) that sets the beam’s horizontal position is stuck, causing the display to break up and overwrite itself in unreadable stripes.

This display is of the vector type. There is no linear, raster scanning like in television or computer monitors; it’s more like an electron beam Etch-A-Sketch. Two DACs driven by the microprocessor set the beam’s horizontal and vertical deflection and it excites the phosphor wherever it lands. A control grid in the cathode ray tube allows it to be blanked to be moved without lighting the phosphor it crosses.

When this skipped around the beam wasn’t blanking; you could see it smear right back.

I tried power cycling. It’d be okay a minute or so after a minute off then do that again.

I tried clearing all settings and memory.

I tried looking through the service manual.

Then, finally….

I smacked it.

Gong!

The problem immediately cleared and does not come back.

Why didn’t I try this first? Am I losing my mind here?!

The fault was likely a loose connection at a backplane connector, socketed IC, or ribbon cable down inside, or maybe even a cracked solder joint.

If it recurs I’ll investigate, but for now I’ll rest easy knowing I don’t have to replace this wonderful scope I’ve used for years with some soulless modern piece of Chinese plastic poo that can’t actually do X/Y plot mode right.

Weston Super Sensitive Analyzer

For a while I’ve wanted one of those Simpson multimeters like we have at work, with the big needle analog meter…

Today I found something a little neater. Someone set one of those Harbor Crack multimeters down on top of it and I laughed and groaned at them all at once.

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Needs work in the battery area
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Great! Where's my nearest radio parts distributor or jobber?

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The gunk on the faceplate cleans off easily. Now I just need to make up new test leads and it’ll be good to go.

The meter has a hilarious ballistic to it. It’s not entirely undamped, but it basically overshoots the reading once then drifts back down onto it. I’m guessing that’s the result of the armature coil being a bit heavier than usual from all the turns to make it… super sensitive.

On a side note I’m looking at the schematic and there’s no diode to rectify AC to DC for the meter… This means the meter must actually have a field winding for AC measurement and thus, by design, it’s true RMS! Not bad at all for a meter made in 1948.

Just thought you should know…

I have a thing for hand drawn traces.

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This is on a Shure M267 mixer. I’ve seen at least three different variations on this same mixer. The one I’ve got at home contains only one transformer, at the output. This one contains five.

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Who wired this nutty thing? Me?

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“Vactrol” style lighted photocell in optical limiter circuit. The audio envelope is detected, amplified, passed through a slow filter and applied as a bias voltage to adjust the light brightness. The photocell half of the device is used as a variable attenuator to back the volume down as needed to prevent clipping.

These devices are also commonly used in DJ mixers.

Transmitting from the Troll Bowl

You know you’re doomed to be an RF person forever when you look at this…

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… And just keep thinking “damn that’s cute”.

That’s a Troll auto tracking antenna system for broadcast microwave from a helicopter.

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Swapped this corroded yackage out. So far, so good.

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Hey News Desk, can you hear me now? Good.

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Whose AM DA is this again? North of US 41, just west of 137 Ave...

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I could never do this stuff regularly and am really hoping this project’s done. For a good long time. The Jet A fumes make me feel sick after a while of working around the bird or after being in the air a while. It’s not motion sickness; I literally just don’t get that… it’s the fumes. Yeeech. The weird part is when turbulence rocks the craft, it makes me feel better for a bit??

Can’t explain that one. Dammit I’m a broadcast engineer, not a doctor.

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Good day, sir.

The whirlybird

We’ve had an ongoing issue at work with the helicopter’s MRC microwave transmitter powering down on us. The silly thing is really obtuse; the user interfaces won’t tell us after the fact why it happened. Don’t you love faults like that? It’s almost as great as on ham and other 2 way radio equipment where a high VSWR condition causes the transmitter to fold back its power output but not indicate to the user that this is happening. Come on man…

Anyway here’s the box.

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The remote controller at bottom. The top unit is the N Systems antenna pod controller which allows aiming of the antenna or selection of which receive site to automatically aim at. The NSI antenna’s servos make a comically mad sound as the unit initializes on power up and they seek home position at full tilt.

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The bird at roost.

The fault cannot be replicated on the ground; this has been tried several times with no success. Therefore the only way to figure this out…..

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That’s Hollywood Beach down there.

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I believe this is where parts of “Santa and the Ice Cream Bunny” were filmed, notably the fire truck driving through the dirt road and Tom Sawyer and Huckleberry Finn rafting down a waterway accompanied by “Old Man River” on kazoos.

I Am Not Making This Up. This film is fascinating as hell.

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The A/V box. At right, radios and audio controls. At left, video switches, CCUs for a couple of small Toshiba cameras mounted in the helicopter interior.

Never photographed because I simply forgot: the FLIR pod ‘laptop’ controller. It’s a big chunky panel you actually just rest on your lap while using it, with a damn near fire hose sized cable coming out.

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At about Atlantic Shores Boulevard.

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Suspicious: this isn’t the RF cable for the MRC radio but was installed at the same time and is identical. To be replaced MoNday.

Part of the testing included putting a phone in there recording video of the transmitter front panel. What it revealed was just the unit going into standby and back. No informative messages. Meeehh!! I don’t know if these MRCs keep an internal log file like Nucomm radios do.

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It Fell Out Of The Box Like That!

Really.

Seriously.

A refurb DirecTV Slimline receiver we had in service a while just up and died with no warning. It was opened up and showed no signs of trauma but I saw something everyone else missed….

Hmm. Let’s flip it and see what that is at the edge. It’s probably nothing at aaaaaaaaaaaaaa

Aaaaaaaaa
AAAAAAAAAAAWHATTHEAAAAAAAA

What.

A while back I found these units tended to burn the access card. This appears to be the fix – first, note how far heat would have to travel down those fingers to toast the card. Second, the card is actually heatsinked by a plate above the socket.

Front panel with mystery antenna. Also note the dual die IR LED next to the black lens IR receiver. This is probably used for the unit’s very user – friendly universal remote system.

The rectangles are touch button sensors.

RF filter and very big silkscreen note on where to find power.

The external converter.

Excuse me, I’m going to go wash my hands.

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