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dual-4CX250B

====== Technical Profile: Pride “Amatuer” Dual-Tube Amplifier =========== 1. Unit Identification =====Manufacturer: Pride Electronics (California).Model: Likely a DX-3000 or a high-power variant of the KW-ONE.Production Era: Late 1970s.Defining Characteristics:“AMATUER AMPLIFIER” typo on the brushed metal faceplate.Red rocker switches for Power/Meter functions, riveted directly into the faceplate.Rectangular chassis wider than the standard DX-300/KW-1 “cube” design.Evidence of a missing adhesive-backed nameplate on the lower front panel.===== 2. Internal Architecture =====Vacuum Tubes: Two (2) 4CX250B (or similar 8930) ceramic power tetrodes mounted in parallel.Cooling: Centrifugal squirrel-cage blower designed for a pressurized plenum.Power Supply: * Massive high-voltage plate transformer (showing surface oxidation).Separate filament/control transformer.RF Deck: * Large ceramic multi-tap tank coil for band switching (80M through 10M).Dual variable capacitors for PLATE and ANT LOAD tuning.Parasitic suppressors (resistor/inductor combos) connected to the tube anodes.===== 3. Current Fault Analysis =====The unit reportedly operates but is limited to 100 Watts output. Potential “Cold Test” targets include:^ Component ^ Symptom ^ Suspected Issue ^| Parasitic Suppressors | Darkened/Cooked appearance | Resistor failed open; choking RF output path. || Input Swamp Bank | Resistor cluster near input | Drifting high or incorrect bypass “hack” limiting grid drive. || Mode/Tune Logic | Stuck in “Tune” or “AM-1” | Internal relay or rocker switch failing to engage high-voltage/high-bias state. || Tube Health | Visual debris in cooling fins | Tubes may have “gone soft” due to overheating from dust or airflow loss. || Transformers | Surface rust on laminations | Potential insulation breakdown or moisture damage from storage. |===== 4. Testing Objectives (Cold State) =====Objective 1: Use LCR meter to verify parasitic suppressor resistors (target ~$47-100 \Omega$).Objective 2: Check input attenuator resistors for value drift.Objective 3: Inject low-level RF via signal generator to trace signal loss through the band switch and grid drive circuit.Objective 4: Manually inspect blower rotation and clear debris from tube cooling fins.