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Smash!




 
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ka1tdq
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« on: July 27, 2017, 10:18:30 PM »

I ordered a new 3-500Z tube from RF Parts.  Normally, you'd expect, that the tube would be boxed within a box.  I pulled the form-fitting packing material from the box and the tube came out with it.  It then fell out as I lifted it over the my kitchen countertop and it shattered into a million pieces.

I literally stood there for over a minute in sheer disbelief.   Angry Sad Shocked Huh Cry

I'm gathering parts to build an amp for 20 meters.  

Jon
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AG5CK
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« Reply #1 on: July 28, 2017, 09:59:36 PM »

That makes for a bad feeling in the pit of your stomach. UPS was kind enough to break mine for me. RF parts took care of it but that initial feeling of "they'll never believe I didn't break this"  was a bummer.
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WD5JKO
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WD5JKO


« Reply #2 on: July 29, 2017, 07:53:01 AM »



Jon,

   That tube must be for your 20m only DX-60...

Reading your post, I felt the same emotion that you must have felt. I bet it made a remarkable pop, and there are glass shards still yet undiscovered just positioning a sharp point for a big toe.

I seem to recall you had three of those tubes in the not to distant past.  Roll Eyes

You know, a quad or sextuplet of 7984's might do the trick.... Too bad the suppressor grid is tied internally to the cathode, which eliminates grounded grid operation.

I once drove to Houston to strip a BC-610 for parts. The prize was the 250th tube. Once I got back home, I carefully removed the tube from the trunk of my car. Well, I bobbled it, caught it, and bobbled it again....Boom! What a noise that tube made!  Cry

Jim
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ka1tdq
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« Reply #3 on: July 29, 2017, 09:19:43 AM »

Hey Jim,

Yes, it did make the big "pop!" noise on impact.  I think that's for added effect, you know, to make you feel even worse.  Smiley

You're right about the glass shards.  I swept, but then my wife and I were scouring the floor on hands and knees picking up pieces.  There was still lots, and I'm sure they'll keep turning up.

At least this wasn't a 250th, and 3-500's are still in production.  They just carry a hefty price tag.  I did have three a while ago for my big amp, but I sold those.  I guess I should've hung onto them.  But, plans change so it's best to just go with the flow.  

This is for my 20 meters only DX-60.  I'm attempting to build everything compact this time since I don't need it for such a heavy duty cycle (CW mostly).  

I did look at Russian Gi9b tubes.  They're like $25 for two, and they have a combined plate dissipation rating of 600 watts.  The sockets aren't cheap though.

Jon
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KF7WWW
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« Reply #4 on: July 29, 2017, 11:06:19 AM »

Jon
I have a couple 500z's, 4-1000's, gi7bs, a gs31b. Let me know if I can help.
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ka1tdq
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« Reply #5 on: July 29, 2017, 01:10:18 PM »

Thanks!

I'm going to stew over the amp idea for a bit and think about what I want to use for tubes.  In the meantime, I'm progressing with the CW-in-the-car project.

I bought a 20 meter MFJ Cub transceiver.  I've worked a guy on the air who was using one, and I could hear him drift.  MFJ supplies polystyrene capacitors for the VFO portion, and I'm going to use NP0 capacitors instead.  Also, I'm going to use a Motorola MRF237 transistor in the final to hopefully get 4 watts output rather than 2.

I'm toying with the idea of having a digital frequency readout for it too by tapping the unused pin 5 of U2.  MFJ now puts a hole on the back chassis for a spare BNC connector.  This would work perfect for that.

I also found a $13 shipped iambic keyer on eBay.  I've bought cheap-ie keyer kits in the past, and they were crap.  This is from an American supplier and it works excellent!  It uses on on-board watch battery and has a piezo buzzer if you want it.  Also has 2 memories.

http://www.ebay.com/itm/KIT-BUILD-IAMBIC-MEMORY-KEYER-HAM-MORSE-CODE-TELEGRAPH-/162402662634?hash=item25cff3f8ea:g:xcgAAOSw32lYqxcH#rwid

Jon


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wa1knx
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« Reply #6 on: July 31, 2017, 04:13:54 AM »

Jon,
        I've done stuff like that, lost some old vintage tubes.   Let me know what your plans are, I shift ideas
around to.  I've been collecting 3-500zs, thinking of 4 of them at 1500v.  The specs make for a super clean
linear 330-375w each!  or trying to plate modulate them, modulated by a pair. dunno.  but if yours is for CW on
20m you wouldn't need the super linearity.
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am forever!
ka1tdq
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« Reply #7 on: July 31, 2017, 05:39:45 AM »

Hey Dean,

I'm just looking for a little extra oomph on CW when I'm hankering for a little more than 50 watts.  I'm aiming for 600 watts.  1500 watts for CW is just overkill.  It even takes extra time tapping out your power to the other guy.  And then, if you do run full-tilt, you look like one of those guys driving driving an F350 with a super lift kit.  A Prius on steroids is good enough for me.

Jon


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KF7WWW
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« Reply #8 on: August 01, 2017, 12:12:02 AM »

Jon

Blf188xr..
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ka1tdq
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« Reply #9 on: August 01, 2017, 12:46:19 AM »

Very nice!  Pricey though at $200.  I'm scared of expensive semiconductors.  They fry too easily.  Class E stuff is nice because they're just a couple dollars each.  If I blow them up, oh well... $20 total.  

I like tube amps because they're forgiving to abuse (aside from drops on the floor).  

By the way, I finished my 20 meter MFJ Cub.  Output is almost 3 watts but the drift problem is still there even with NP0 capacitors. The VFO is super touchy too.  One smidgen and you've moved in frequency 3kc.  It gives me greater appreciation for my DDS VFO/DX-60 combo.

Jon
  


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WB2EMS
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« Reply #10 on: August 01, 2017, 02:04:53 PM »

Ah yes, the sounds of a vacuum implosion. I had a 250 th I took to the Rochester hamfest one time to sell. It didn't sell, so I was putting it back in the box and bobbled it and dropped it. Toast!

More recently I had scored a nice vacuum variable for experimenting with mag loops at a hamfest. Got it home and grafted it onto my loop. Worked nice, so I tried to snug it down mechanically with a hose clamp. Wrong move!!!   Shocked  Glass shards everywhere! And such a sinking feeling. The new cap is one of the ceramic VVC units.

Been doing some long distance driving lately to Detroit and back and was getting into some CW on the long straight superslab. 40 meters up around 7100 has some stations that are reasonably easy to copy in my head and keep up with on the paddle. 200 watts from the TS480 into the Tarheel works good, but I usually dial it down to 25-50 watts.

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73 de Kevin, WB2EMS
KF7WWW
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« Reply #11 on: August 01, 2017, 04:24:19 PM »

Jon

Then you need a 4-1000. Plenty of headroom for whatever you need. I probably have 90% of the parts if your interested.
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K1JJ
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« Reply #12 on: August 01, 2017, 04:34:57 PM »

I feel your pain... Grin

Probably the worst smash I've had was with a near-new 4-1000A standing inside a new glass chimney on a shelf. They were reasonably stable until I accidently banged into the shelf. I saw the 4X1 and chimney wobble out of reach towards the back of the shelf. There was a pause and then... !!SMASH!!  It took some time to finally find all the broken glass in the room with the broom and vacuum cleaner. What a mess.

I was yallowfied  cuz I use 4X1's in several rigs and was getting short. (six 4X1's total)

The heartbreaker was I had to call Nebraska Ripoff to replace the chimney at top $$ dollar.

The second event was with a 750TL on display on another shelf. A friend tripped and rocked the shelf and that precious 750TL hit the floor. You wuda thunk I had learned my lesson.  These days my rule is no more tubes sitting on shelves without being in a padded box.

T
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WD8BIL
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« Reply #13 on: August 01, 2017, 05:57:27 PM »

K1JJ said (with correction)
Quote
.... being in a padded box.

That's where my wife keeps me!
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KA2DZT
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« Reply #14 on: August 01, 2017, 08:40:54 PM »

I have lots of shelves, all steel, all bolted together.  If you bump into them you're going to get hurt.  The shelves aren't going to move even a fraction.
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ka1tdq
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« Reply #15 on: August 01, 2017, 09:44:16 PM »

Actually, I have most of the parts to keep continuing with the single 3-500 plan.  It needs to fit in the rack behind my chair with the DX-60.  And really, 5 or 6 hundred watts on 20 meter CW is really good for me.  I also want to power the whole thing from a 120 volt outlet.  When I had my big amp, I paralleled the 240 volt line going to the oven (not safe or code). 

I ended up repurposing that electrical feeder for 120 volts from another circuit than the one in the shack.  That line now powers the audio amp for my 75 meter class E transmitter.  It's nice to be able to run a full powered class E transmitter from 120 volts.  I get the carrier supply from the shack's 120 volt circuit.

Displaying tubes on shelves is cool, but can be very costly.  It might be wiser to display a solid state device on a piece of styrofoam (like in the attached photo).

Jon


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ka1tdq
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« Reply #16 on: August 01, 2017, 10:03:17 PM »

Actually, my bad.  It takes a few more to equal a 4-1000.

Jon


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KF7WWW
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« Reply #17 on: August 01, 2017, 11:09:59 PM »

A few more and not nearly as forgiving as a tube.
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steve_qix
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« Reply #18 on: August 03, 2017, 12:28:40 PM »

Hmm.. to equal a 4-1000 operating at full power would take about 48 FQA11N90s.

If you build it right it will never fail due to external conditions or misadjustment - just dumb stuff like rectifiers or plain old bad or wearing out components (relays, things like that) should be all you'll ever encounter.

48 FETs isn't bad to build actually.  2 24 FET decks (less tank components of course), into a simple combiner and then the output tank.  You be styling with that !
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