Kenwood PS-33

A 15-amp regulated DC supply for Kenwood's HF rigs. It now sells for less than the shipping on some of them.

Overview

The PS-33 is a regulated DC power supply from Kenwood. It sits under a transceiver and delivers a stable 13.8 VDC rail to gear that would otherwise run off a battery or a cheap wall wart. The Italian dealer listing at the core of the archival record describes it plainly: "Alimentatore di linea Kenwood PS 33 12 volt - 15 ampere ben tenuto e perfettamente funzionante" - a well-kept, perfectly functioning 12-volt, 15-amp line supply. For a power supply, that's enough of a pitch.

These units still turn up working in 2026. Universal Radio catalogued it under "Discontinued Power Supplies" with a fuller set of numbers than the Italian listing carried: 13.8 VDC at 20.5 amps on a 25% duty cycle, or 15 amps continuous at 50% duty cycle, fed from 120 VAC 60 Hz. The dual duty-cycle rating shows it was designed for amateur radio rather than bench work. Duty cycle is HF operator vocabulary, where you're key-down for a few seconds and then listening for a minute.

The two sources disagree on nominal voltage. The Italian dealer calls it a "12 volt" supply; Universal Radio's catalogue copy says 13.8 VDC. Both are defensible - 12-volt lead-acid batteries sit around 13.8 V under charge, and most "12-volt" ham gear is happiest right there. If you're buying one to run something picky, trust the 13.8 VDC figure from the catalogue listing and check the unit's own meter before you plug anything expensive into it.

Key Features

Dual Duty-Cycle Current Rating

The current rating is stated two ways for a reason. Universal Radio's catalogue lists 20.5 amps at a 25% duty cycle or 15 amps at 50%. That's an honest thermal disclosure, not padding. The pass transistors and heatsink can handle a 20-amp surge for short bursts, but if you lean on it continuously, 15 amps is the real ceiling. A 100-watt HF transceiver pulls 20-plus amps on transmit and idles at a fraction of that on receive, so the 25% figure is the one that counts there. For sustained work, like a linear amplifier's relay supply or a packet station left keyed, plan on 15.

Regulation and Ripple

Universal Radio's listing gives two specs that separate a real regulated supply from a transformer in a box: ripple voltage of less than 20 mV rms at 13.8 VDC and 15A, and regulation of ±0.7 V at 10% input variation at 15 amps. Twenty millivolts of ripple is quiet enough that it won't show up as hum in an HF receiver's audio. The ±0.7 V window means the output doesn't sag noticeably when the mains dips or the load current swings. Both figures are stated at the 15-amp continuous rating. Plenty of supplies spec ripple at half load and let it fall apart when you need the current.

Serviceable, Documented Design

Two things suggest the PS-33 was built to be maintained rather than replaced. First, a capacitor replacement kit sold on the Italian eBay market is titled for the PS-53, PS-50, and PS-33. The electrolytics are a known wear item, and someone is still cutting kits for them. Second, a service documentation archive lists "Kenwood PS-33, PS-53 - instruction manual, schematics" under Manual Model 2624, so the schematic is available for a rebuild.

Input and Market Variant

The Universal Radio catalogue copy specifies 120 VAC 60 Hz input, which points to the North American market version. Keep that in mind if you're buying from overseas. A European or Japanese unit will have a different mains transformer tap, and nothing in the available documentation confirms the PS-33 was multi-voltage. A new-old-stock unit from Japan was noted for sale on a collector's blog back in 2015, so these were sold into multiple markets with different mains requirements.

Collectibility & Value

The PS-33 is useful, which keeps prices from collapsing, but it's a power supply, which keeps them from climbing. The Italian dealer listing carries a "Prezzo di listino" of €150.00 EUR, undated. A Brazilian seller was asking R$450.00 plus shipping for one, also undated. A Dutch listing on Marktplaats priced a used unit at €100.00, and a separate Marktplaats entry offered a new one with no price shown. An eBay Ireland listing (item 226039910189) described it as a DC power supply for Kenwood and universal applications, again with no price captured.

Working used units trade in the €100 range, NOS examples command a premium when they surface, and the market is thin enough that a single listing can define the price for months. The 2015 sale of a Japanese NOS unit, marked sold on a collector's blog, suggests a small appetite for sealed examples.

The case for collecting the PS-33 is about what it powers. Anyone running a vintage Kenwood HF transceiver needs a stable 13.8-volt rail, and a period-correct Kenwood supply fits. The capacitor kit availability and the published schematics mean a non-working unit is a viable project rather than a parts donor, which keeps the floor under prices. If you find one cheap and it hums, recap it; if it's silent and holds voltage, use it.