Thanks for all the suggestions. I'm using my SB-200 now, so I'm not rushing to get my Clipperton L going, just so I don't make a mistake. I removed the choke from the amp, and it looks like the arc was from one of the leads of the inductor arcing to the coil itself. That means that my choke is damaged and unusable, but still good so we can measure the different parameters and see why it arced. When connected to my friend's Rig Expert antenna analyzer you could see a point starting a the top end of the 17 mtr. band that showed something was happening. I then rigged up W8JI's test rig with a transmitter, a dummy load and the choke with a 12V miniature lamp connected in series with the choke. You tune this across the spectrum and the lamp will light if the coil is resonating. Mine did at 18 MHZ, peaking about 18.150. Then I arranged the leads from the choke so they left the coil at right angles to the body. It resonated @ 18.453. Now this amplifier was made before the WARC bands were given to us, so this may have always been there. I've ordered some wire with Polyimide insulation. We're going to rewind it and seeing that I can see where it's resonating, hopefully it'll be between 2 bands. If it still resonates in the same spot (who knows if it will or not) I'll try one of the coils from CTR engineering or RF Parts.
The Clipperton L does have room for the RF Parts choke, but it'll be a bit tight
IF u rewind it with the same number of turns, and same ga of wire, it will resonate on 18-mhz, and blow up...again. Watch out, you can buy magnet wire, in 4 x different thickness's of 'goop'. Depending on thickness, the number of turns per inch will vary, and change the resonance point. Polyimide insulation is typ 200 deg C rated...and also HV rated, BUT that depends on the gauge used. On the larger gauges, like 8-10-12-14-16 ga, it's good for 15 kv..and 30 kv between turns. Can't remember what the HV rating is on the typ 27/28 ga used on the typ plate chokes.
To do this right, re-wind the coil to original turns, then do the various tests. If it resonates within 5% of 18.168, then remove 1-2-3-4 turns from the top of the choke, 1 turn at a time (and re-test each time). This will shift the 18 mhz resonance up higher in freq. Ideally, you want to ..'park' the resonance point at 19.584 mhz. Then it's midway between 18.068 and 21.000 mhz...(and 7.7% away from both 17+15m).
On the old B+W 800 chokes, they resonated just beyond the top of 15M band. 50-50 chance it would blow up on 15m ssb. Back then, we all removed 4 x turns from the top of the choke, and shifted the resonance higher in freq, like 23-24 mhz. Back then, we didn't have a 12m band.
Parking resonance points is a trick in itself. Removing a few turns from the top is the easiest way to shift the resonance point higher. Conversely, if turns are increased, resonance will decrease. 16.209 mhz would be midway between 20m and 17m.... BUT the required extra turns won't fit on the oem choke...too short.
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Topic: Dentron Clipperton L-open plate choke (Read 248 times)