Product Overview
RCA 2N3731 PNP Germanium Power Transistor - 320V, 10A, TO-3 Package, NOS
Condition
Unused NOS. Photos show the specific unit you will receive - polished TO-3 metal can stamped with the 2N3731 part number and RCA logo, consistent with unissued old stock. Evaluation: Visual inspection only. Function testing not performed. Sourced from an electronics distributor consolidating inventory.
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Product Overview
RCA 2N3731 - PNP germanium power transistor in a TO-3 metal case. Originally designed by RCA for TV horizontal deflection circuits, this is a high-voltage, high-current germanium device rated at 320V collector-emitter and 10A collector current. It also sees use in audio amplification, power supply circuits, and switching applications. Germanium construction gives it characteristics distinct from silicon - useful in circuits where that distinction matters.
Key Features
- Polarity: PNP
- Material: Germanium
- Maximum Collector-Base Voltage (Vcb): 320V
- Maximum Collector-Emitter Voltage (Vce): 320V
- Maximum Emitter-Base Voltage (Veb): 2V
- Maximum Collector Current (Ic): 10A
- Maximum Collector Power Dissipation (Pc): 5W at 55°C
- Minimum Forward Current Transfer Ratio (hFE): 15
- Transition Frequency (fT): 1 MHz
- Maximum Junction Temperature (Tj): 90°C
- Package: TO-3 metal case with two leads and mounting flange
Applications
- Desoldering a failed horizontal output transistor from a 1960s-era tube-hybrid television and dropping in the 2N3731 as a like-for-like germanium replacement - without the oscillation risks that come with swapping in a silicon part
- Restoring the horizontal deflection stage in a vintage TV where the circuit geometry was tuned around germanium behavior - substituting silicon can degrade scan linearity, and this part avoids that entirely
- Building or repairing a Royer inverter or similar germanium-era switching circuit where the transistor's specific saturation and switching characteristics are part of the design
- Output stage work in vintage audio amplifiers where germanium transistors were specified - for builders chasing the bias behavior and sonic character of the original design
- Custom power output stages and low-frequency transmitter circuits where experimenters want the high voltage and current handling of the 2N3731 in a proven TO-3 form factor
- Hobbyist and maker projects exploring germanium circuit topology - vintage-style audio preamps, retro strobe circuits, or any application where the PNP germanium character is the point
Frequently Asked Questions
Is this an NPN or PNP transistor, and does polarity matter for my circuit?
PNP. This matters significantly. A PNP transistor requires the base to be negative relative to the emitter to switch on. It is not a drop-in replacement for an NPN part without circuit modification. Confirm polarity in your schematic before ordering.
Can I substitute a silicon transistor for this in my vintage TV?
Not without potential problems. Circuits designed around germanium transistors - particularly TV horizontal deflection stages and Royer inverters - can exhibit high-frequency oscillations or degraded scan linearity when a silicon part is substituted directly. The 2N3731's germanium characteristics are part of what these circuits were tuned for. For authentic repair, germanium is the right choice.
Does this require a heatsink?
Yes. As a power transistor, the 2N3731 requires a heatsink for proper thermal management. The TO-3 case mounts directly to a heatsink via the flange. Maximum junction temperature is 90°C - germanium devices are more temperature-sensitive than silicon, so thermal management matters here.
What is included with this unit?
The transistor only. No documentation or accessories included.
Is this a genuine RCA part?
Yes. The TO-3 can is stamped with the 2N3731 part number and the RCA logo, visible in the photos. Sourced from an electronics distributor that was consolidating inventory.
Germanium power transistors from this era do not come back into production - when the old stock is gone, the search begins in earnest. This one is still here, still unused, still waiting for the circuit that needs it.
