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Clipperton V




 
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Author Topic: Clipperton V  (Read 332 times)
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KD1SH
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« on: September 15, 2021, 09:50:25 AM »

Picked up a Dentron Clipperton V at Moxboro. Never owned any Dentron gear before, but I can't say I'm terribly impressed by the build quality, or the schematic. Check out this snippet of the schematic. How can this work? Unless I'm missing something, there's no return path to ground for the filament current. C31 is 200pf; filament ac comes up through RFC3 but can't get back to ground through RFC2 with C31 in the way. I'm thinking C31 was intended to be a bypass but got drawn as a series element instead.


* Clipperton V PA.png (22.74 KB, 331x458 - viewed 86 times.)
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KA2PTE
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« Reply #1 on: September 16, 2021, 10:28:13 PM »

Does it match whats physicly in place in the chassis?
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KD1SH
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« Reply #2 on: September 17, 2021, 08:01:26 AM »

No. Confirmed by ohmmeter check rather than visually because getting access to the underside of the RF deck requires significant disassembly. The schematic is generally quirky: parts not shown, shown but not included in the parts list, etc.
My consulting the schematic came about as a result of not being able to adjust the idle bias to the value called for in the manual: manual says 50ma, but can only get about 15ma on the meter. Got B+; got screen V; got filament V; got bias V, changed out tube; but only 15ma with bias set to -38 V.
Testing reveals that the metering circuit is fibbing, and tube exhaust air warms up with idle bias, so it's definitely pulling idle current.
Eimac 4CX250B specs say 100ma idle for AB1 - Dentron says 50ma - and I'm not sure if the bias adjustment could even get to 100ma as it is; I haven't worked through the curves to figure it out. My plan, anyway, is to replace the 4CX250B with a 4CX400A to get better plate-diss headroom for AM use (the amp is converted from 2 meters to 6 meters).

Does it match whats physicly in place in the chassis?
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