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Technical Profile: Pride "Amatuer" Dual-Tube Amplifier

1. Unit Identification

Manufacturer: Pride Electronics (California). Hy-Gain and Sonar Communications also used similar hardware
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.

Vacuum Tubes: Two (2) 4CX250B (or similar) 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.

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-bias state.
Tube Health	Visual debris in cooling fins	Tubes may have “gone soft” due to overheating.
Transformers	Surface rust on laminations	Potential insulation breakdown from moisture.

Objective 1: Use LCR meter to verify parasitic suppressor resistors (target ~47-100 Ohm).
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.
Objective 5: inspect and test passives under chassis.
Objective 6: Perform out-of-circuit testing of each tube, filament characteristics, micro-mhos where possible

later on

hot testing at lowered voltages with dummy load, measurement of all key power supply points and cathode, grid, suppressor and plate on the tubes as well as output and tuning.
hot testing ramped up

out of scope (for now):

The presence of a dedicated FM position on an HF amplifier of this era is highly unusual and provides specific insights into its design and origin.

Efficiency and Bias: The FM setting likely switches the 4CX250B tubes from Class AB (linear for SSB) into Class C.
Duty Cycle: Class C operation is non-linear but much more efficient, allowing the tubes to handle the 100% duty cycle (constant carrier) of FM without overheating.
Voltage Regulation: In FM mode, the screen grid voltage and plate bias are adjusted to maximize saturation rather than linearity.

Export Market Focus: While FM was rare for US hams on HF in the 1970s, it was popular in the European and South American “Export” markets for 10-meter and 11-meter operations.
Pride Fingerprint: This specific mode sequence (AM-1, AM-2, SSB, CW, FM) is a definitive characteristic of late-production Pride Electronics units.
Competitive Differentiation: Brands like Sonar and Hy-Gain (Afterburner) typically lacked a dedicated FM tap on their HF linear units.

Switch Failure: If the Mode switch has carbon tracking or mechanical wear, the unit may be “latched” into a low-bias or TUNE state internally.
Logic Conflict: If the bias relay does not engage the “High” voltage/current state when moving from FM to SSB, the output will hit a hard ceiling regardless of drive levels.

Task: Verify continuity across the Mode switch wafers for each setting.
Focus: Inspect the bias resistors connected to the FM/AM-1 positions for signs of thermal drift.