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June 25, 2018, 03:46:43 AM *
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 11 
 on: Yesterday at 08:39:36 PM 
Started by PA0NVD - Last post by WBear2GCR
Got to ask, why would you want to live in a place like that?

 12 
 on: Yesterday at 08:06:05 PM 
Started by ka1tdq - Last post by ka1tdq
I bought an audio compressor and did a more accurate efficiency reading.  I'm getting 93.7% efficiency.  I don't have a digital wattmeter, but the Daiwa CN-801 is a pretty good meter.  I made my adjustments with the dial right on the 200 watt mark. 

I still had audio distortion and a little hum though.  Long story short, it was from the audio amp that I use to drive my Heising modulator.  Side A has distortion, but side B is crystal clear.  I'm guessing that something in the audio amp took a hit during one of my explosions.  Anyway, I'll just use side B and run everything very conservatively at 200 watts. 

Clean waveforms, crystal clear audio... 4 pages later and I'm calling this one good. 

As a parting note, this picture was taken at the wax museum in Vegas over the weekend.  It's a little cleaner than my other pictures, just like my audio!

Jon

 13 
 on: Yesterday at 04:09:17 PM 
Started by KD1SH - Last post by KD1SH
    Well, at this point I'm planning on making the output transformer mod.  I've looked at the Hammond site, and like you say, great selection there.  I'll be headed to a hamfest in a few weeks, where I'll scout around for some used stuff before I spend bigger bucks on new Hammond parts.
    I've also considered going solid state with the rectifier - replacing the 5U4 - save a little filament heat and get a tad more power out.  Makes me just a bit uncomfortable, though: the 5U4 is easy on tired old circuitry - the ultimate soft-start - bringing up the DC nice and slow.  I'd put some resistance in series with the diodes to soften the surge a bit.  Maybe some NTC resistance - start off with higher resistance when cold and gradually decrease as the filter charging current and bleeder resistor current heats it up.

 14 
 on: Yesterday at 12:48:53 PM 
Started by KD1SH - Last post by PA0NVD
I am quite similar, I like to keep it original when possible. When the saturation is a problem for the audio quality, you can also lower the power and the 6L6 current a little too. 20% less power will keep the choke out of saturation and will hardly be noticed.
You can do that by increasing the G2 resistors for the 6146 and for the 6L6. But, also that is a change, and you have less power.
Operating with a little less load, a deeper dip, also lowers the power and current of the 6146, but you are prone to over-modulation. The balanced transformer mod is to my opinion the technical most clean modification. I do not know how the mod choke looks like. Hammond has nice output transformers of all kinds.

 15 
 on: Yesterday at 11:27:51 AM 
Started by WU2D - Last post by Opcom
Some Ameco Pics.

How did you bring back the black lettering so well?

 16 
 on: Yesterday at 11:18:45 AM 
Started by WU2D - Last post by W3GMS
Have you ever felt so sorry for a radio, that you had to buy it because of its abuse? Well that happened at Nearfester when I saw this little Ameco TX-86 that was literally eaten through with rust on one side. It was ridiculous looking, but I bought it for a donation of 10 dollars.

After I pried the perforated box off the front panel, which was a tough enough job, I saw that there was surface rust on most of the the inside chassis. Also, ALL of the tubes were smoky. All gassy - not one good tube. Where the hell had this thing been stored? It takes a lot to penetrate the vacuum seal of tubes. My guess is that it took years of wet and fantastic temperature extremes to accomplish this. So the old Naval Jelly and wire brush came out in force. Some of the fasteners simply broke, they were so bad.

The refinishing was a lot of work. I used black crackle on the outside perforated box and copper spray paint to touch up the copper plated front panel that was missing copper in places.
Then after quite a bit of sleuthing work (worst schematic ever drawn by a supposedly professional company), some rewiring and undoing mods, some parts replacement like all electrolytics, and a fresh set of tubes - My lord it puts out clean CW on all bands. Even with my command set power supply which is a bit low in recommended voltages, it does 35 Watts out. It has an extra stage that provides plenty of drive for the 8552 (6883B) (8032A) 12V mobile version 6146B final.

I have not tried AM yet. It has a primitive screen modulator.   

The line up is a 12BY7 Oscillator multiplier, 6BQ5 Driver (way overkill probably so it works on 6M!), 8552 Final, 12AX7 speech, and 12AQ5 modulator. It also can be wired for 6V if you substitute a 6146 final and 6AQ5 modulator. They play games with the fils to retain the 6BQ5 in either configuration and I will let you figure that cleverness out.


Wonderful job Mike.  It just goes to show that with enough passion, pretty much anything can be brought back to working condition.  Its good to hear the performance is equally as good.  Now what about that waxed cap under the tuning control  Grin

Joe-GMS   

 17 
 on: Yesterday at 09:00:09 AM 
Started by n1eu - Last post by n1eu
Here's a lightly used Presonus AudioBox 22VSL USB Audio Interface, the optimal microphone-to-computer interface.  In addition to superior audio quality, this is the only interface that provides zero latency filtering, noise gate, compression, 3-band parametric EQ, and effects right in the driver software.  You can also store unlimited number of presets.  The built-in compressor and noise gate work great with amazing fidelity.  $100 shipped CONUS - for more info see https://www.presonus.com/products/audiobox-22VSL

 18 
 on: Yesterday at 08:16:20 AM 
Started by KD1SH - Last post by KD1SH
    Yeah, being able to work out my mods externally before doing any permanent stuff would be  great. The radio is in beautiful shape: the chassis shines like a mirror - I can literally see my reflection in it - and the Heising choke is riveted on.  I try to walk a line between being a "restoration purist" and an actual user.  It's nice to leave classic gear as original as possible, but I'm a user of the gear rather than a collector.

 19 
 on: Yesterday at 06:21:33 AM 
Started by n1eu - Last post by n1eu
Modulation monitor is sold.

Thanks & 73, Barry N1EU

 20 
 on: June 23, 2018, 10:40:21 PM 
Started by KD1SH - Last post by PA0NVD
balanced output transformers are quite plentiful, eg for 2 x EL34, 2 x KT77 or KT88, etc. I even used a 6 Volts filament transformer with a 110 / 220 Volt primary winding with success. I didn't really notice a high end roll-off as I expected. It worked nice up to at least 5 - 6 kHz.
The nice thing is you can try a transformer outside the transmitter connected with long wires, so you don't have to take the old one out

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