Change of subject: Beautiful work of art

[w1vtp]

Let's change the subject for grins.  I think this is the greatest form of art:

http://www.k7jrl.com/projects/bc1t/

I'm still sitting here soaking in the beauty

Al

[W7TFO]

Man, what a memory jogger that was...how many of them did I have to get back on the air after a 'tar bath' blowout!

I really like the custom VFO and the Russian caps in the tank...you can't get a better cap for the $ today.

73DG

[W1AEX]

Wow...

I love the 833 deck all lit up. That whole project looks like a labor of love.

Rob W1AEX

[ke7trp]

Very nice.  What a beast.  Cant wait to hear it.

C

[k4kyv]

In mine, I made a few wiring changes and converted the 12BY7 xtal oscillator to a buffer stage driven by the external VFO (a T-368 master oscillator unit) that sits on the operating desk, and runs any one of my 3 transmitters.

I got about 30% more grid drive by replacing the original grid/driver plate coil using the bakelite form, with a piece of air-core inductor.  The thing stays perfectly neutralised all the way across the band.

I swapped out the mod reactor with a potted unit, because the stock reactor had too much talk-back.

I reconfigured the relay system to  run off DC, because the big contactors buzzed like a chainsaw and I never could quiet them down.

Some day, I plan to have a flat louvred grill made up to fit under the door to replace that stupid-looking thing that protrudes out at the bottom and causes the transmitter to take up an unnecessarily large foot print on the floor. I also plan to carefully cut that silly little triangular-shaped viewing window into a full rectangle, which will allow me to see all four 833As from the operating position. I think the guy who designed the cabinet must have been high on LSD at the time.  It looks more like a soda machine than a radio transmitter.

[Opcom]

That must have been a labor of love! nice and clean now. sort of new and improved!

[W4AAB]

I hope that mine will look half that good when I get it going on 160.

[flintstone mop]

Really nice work. The before and after shots.
He made some nice improvements.
I could NEVER get a DMM to read anything above 600vdc, before popping itself.
I went out and got an RCA Senior VoltOhmyst.
Surprised that his Rat Shack was dealing with it.

Thanks Al

[K5UJ]

I'm surprised to see PCB in there.  When did Gates get away from point to point wiring by hand for everything?  I think that's the first time I've seen a photo of 872s working.

[The Slab Bacon]

I went out and got an RCA Senior VoltOhmyst.

I always got a kick out of that name.

Hmmmm.............. sounds like one of the "specialists" I have been to.

"I started to get a little worried when the VoltOhmist pulled out his scope......." 

  

[k4kyv]

I'm surprised to see PCB in there.  When did Gates get away from point to point wiring by hand for everything?

I think the BC1-T was the first transmitter. Those printed circuit driver boards were always a weak link in the chain. The carbon composition resistors were too small for the job and tended to drift in value or crap out altogether, and even if the resistors themselves didn't fail, they typically burnt holes in the board composition material under where the resistors were placed.  At the radio station where I worked back in the mid-60s, I replaced a couple of those paralleled sets of 2w carbon comps with single 10w wirewounds, and had no further trouble.

I always thought vacuum tubes on circuit boards was a bad idea. The two are about as compatible as open flame and gasoline. Nearly any piece of consumer electronic junk, such as TVs, hi-fi amps, AM/FM tuners, etc, and some of the old ham gear like the Tempo One and early Yaesu FTDX rigs would eventually develop intermittent crackles, pops or downright failure. The heating/cooling cycle of the tubes tended to generate an expansion/contraction cycle on the board which eventually created microscopic cracks in the circuit board traces and solder connections.  These were all but impossible to find and correct, and even if you were successful, it would be only a matter of time before the problem re-appeared elsewhere.

I really like... the Russian caps in the tank...you can't get a better cap for the $ today.

They look like they are probably ceramic.  How well do they compare to the large transmitting micas, like the stock originals used in the Gates transmitter, particularly regarding stability of capacitance value, as well as running hot with circulating current?

[KL7OF]

Great pictures....What a gob of tar to clean up...


My BC1-G has circuit boards in the oscillator, low voltage diode rectifier board, RF driver(2x807), and audio driver(4x807)...The audio driver board has been patched up a couple times...The traces weren't big enough and burnt up after a while..

[W7TFO]

Every old RF mica I've replaced with one of those grey Russki jobs has been very stable, no signs of heating.  They are indeed ceramic with what looks like silver under a powder coat finish.

The ceramic substrate is so hard it rings like glass when tapped.  Ratther than rating them in Amps @ KHz, they are marked in KVAr.  Not too hard to figure the handling ability.

Numerous sellers on eBay have them for a reasonable price, sometimes in assortments.  The only down side is the metric threaded bosses require stocking those size bolts before going into battle as they never seem to come with them.

73DG

[KD0HUX]

 HARD CORE AM PORN KEEP THE FILAMENTS LIT

[K5UJ]

The only down side is the metric threaded bosses require stocking those size bolts before going into battle as they never seem to come with them.

You have to bet the brass hardware for them from McMaster  Carr.

[W7TFO]

Ace Hardware has them in stock in brass. 

Some of the ones I bought had non-magnetic stainless in them. 

I suspect the guys stripping the military TX's these come out of never hang on to the screws.

73DG

[K5UJ]

Ace Hardware has them in stock in brass. 

Ace is great for brass hardware as long as it isn't metric, at least that's the case for the Aces around here.

[KL7OF]

The ceramic substrate is so hard it rings like glass when tapped.  Ratther than rating them in Amps @ KHz, they are marked in KVAr.  Not too hard to figure the handling ability.


73DG

What does KVAr mean?

[W3RSW]

Whatt?

[W7TFO]

Kilovolt Amperes reactive.

In other words, Watts in an AC circuit at something other than 100% power factor.

73DG

[Opcom]

I went out and got an RCA Senior VoltOhmyst.

I always got a kick out of that name.

Hmmmm.............. sounds like one of the "specialists" I have been to.

"I started to get a little worried when the VoltOhmist pulled out his scope......." 

  

Just worry about what kind of probe is being used. 8-o

[Opcom]

I always thought vacuum tubes on circuit boards was a bad idea.

When repairing TV sets and finding burned boards and resistors, knowing TV sets are probably the most notorious and cheaply made tube-type things in the world, I'd always use at least the next wattage up resistor and form its leads to space it up off the board. I'd tell the customer what had happened and what I had done to prevent a recurrence. they always appreciated things like that.

What about using a modern glass epoxy board with 12AX7 or 6J6 type tubes?
Would it be acceptable if the board had 807's or 6V6's or something, and  fan was used to cool the the board especially blown at the tube sockets?

We got a 'real' CAD package at work, Eagle CAD, and I have been asked to practice on it when not making a board, so I thought a little audio compressor/limiter project with 6BC8's would be nice.

I found out that the base cost of the boards is a bit much, but for a few bucks more you can have a thicker board, thicker copper, other materials, all kinds of things.