SYLVANIA 5U4G

*BOGEY*

FULL WAVE RECTIFIER

BOTTOM GETTER

BLACK RIBBED PLATES

ROUND MICA TOP

Extremely Rare - NIB
(Original Factory Box)

EXCLUSIVE HI FIDELTY/RADIO TUBE

⚡🔥 SYLVANIA 5U4G FULL-WAVE RECTIFIER • JANUARY 1947 • BLACK PLATE • MADE IN USA 🔥⚡

A superb early-production Sylvania 5U4G from January 1947, built during the golden age of American tube manufacturing. Featuring the highly desirable black plate construction, classic ST coke-bottle envelope, and exceptional build quality that made 1940s Sylvania rectifiers legendary among collectors and audiophiles alike.

✅ Genuine Sylvania USA Production
✅ Date Code: AC
✅ Heavy Black Plates
✅ Classic ST Glass Envelope
✅ Strong Original Green Lettering
✅ Original Vintage Sylvania Carton - Rough
✅ Clean, Bright Internal Structure
✅ Professionally Tested

🎵 Audiophile Reputation

The early black-plate Sylvanias are prized for their:

âš¡ Exceptional reliability and longevity
âš¡ Powerful, authoritative bass response
âš¡ Rich harmonic warmth and natural tonality
âš¡ Excellent dynamic impact and soundstage depth
âš¡ Smooth, non-fatiguing presentation

Widely sought after for vintage hi-fi amplifiers, mono blocks, restorations, and premium tube audio systems where quality rectification directly contributes to musical performance.

📊 Test Results Posted

🦅 A scarce and highly desirable 1947 black-plate Sylvania from one of the finest periods of American vacuum tube production. A beautiful example for the collector, audiophile, or serious tube enthusiast.

🔥 Tested • Verified • Carefully Packed 🔥


***Please read the entire listing thoroughly and ask any questions prior to purchase***

★★★ Amazing Historic Vintage Tubes â˜…★★

Production Year: Emporium, PA - January 1947

Coded: AC

Tall Black Base

Green Label

Single One (1) Tube

***The Tube Pictured is the Tube Offered***

Made In the U.S.A.


★★★ These Tubes are Very Rare in Brand New Condition â˜…★★

BEST TUBES ON THE MARKET...  NO LEAKS...  NO SHORTS...



★★★ HICKOK TESTED â˜…★★

Tested on Hickok 750 for Emission, Mutual Conductance

Where 50 (μ) is Good these tubes peg at 68 for Emission

Tube 1. Plate 1. - 68 (μ) - at Idle - NOS

             Plate 2. - 68 (μ) - at Idle - NOS

Perfectly Balanced - Rare and Exceptional

Full Tonal Range - Powerful Emission

***We are Top Rated for a Very Good Reason. Buy with Complete Confidence***


*Test Ratings are Specific to My Fully Calibrated Test Equipment! The tubes are put through a Life Test and each plate is warmed and measured for mutual conductance, emission, leaks, and shorts... Each tube is thoroughly inspected, they are described accurately and listed based on fair value!

My Return Policy: 30 Days - Seller pays return shipping! All tubes are Guaranteed to be as described... Tube rolling will not be tolerated! Any and all returns must be in identical condition as when they were received... Test Driving Vintage NOS Tubes is completely unacceptable and highly unethical... Buyer will be charged for mishandled and damaged returns! 

I mark every tube in order to avoid tube rolling! ***Variations in Line Output and Test Equipment excludes any claims regarding matching test results on any equipment other than mine... ***Test results from different Test Equipment IS NOT Guaranteed...


A Hickok 750 tube tester measures mutual conductance in micromhos (µmhos), not emission in milliamps (mA) or microamps (µA). Confusion likely arises because micromhos are based on a ratio of a change in plate current (measured in µA) to a change in grid voltage. 
Here is a breakdown of what the Hickok 750 measures and why it's not only an emission tester:
  • Mutual Conductance: The 750 is a dynamic mutual conductance tester. This is a more sophisticated test than a basic emission only test, which only checks the cathode's ability to emit electrons (super heated).
  • Micromho units: Mutual conductance is measured in micromhos, which translates to a specific change in the plate current per a change in the control grid voltage. The unit ma/V is the same as 1000 micromhos.
  • Superior test: A mutual conductance test is performed under simulated operating conditions and is considered more reliable for evaluating a tube's actual performance. This is why the Hickok 750 can identify weak tubes that might pass a simple emission only test.
  • Emission vs. Mutual Conductance: In contrast, a simple emission tester (like a Heathkit and many others) treats a tube like a simple diode, measuring only the cathode's emission strength. While useful for finding dead or very weak tubes, this method is not as thorough and test results are very unreliable.
A Hickok 750 tests for mutual conductance in micromhos (μmhos), which is sometimes abbreviated as μmos. The unit is a measure of a vacuum tube's transconductance (g{m}). Here's a breakdown: Micromhos (μmhos): This is the unit used to measure mutual conductance. A mho is an older term for the unit of electrical conductance, now called a siemens (S).Transconductance (g{m}): This is the technical term for mutual conductance. It is the ratio of the change in plate current (measured in microamps or milliamps) to a change in grid voltage (measured in volts).μmos: The term "umhos" or "umos" is sometimes used colloquially as an abbreviation for micromhos. Although the Hickok 750 measures the effect of microamps and volts to determine the final reading, the scale on the meter is calibrated to show the overall mutual conductance in micromhos.

International Buyers Welcome! I use eBay Global International exclusively, unless otherwise stated... I am unable to change declared value on customs forms, and International Buyers are responsible for all taxes, customs and additional fees!  Each tube is fully insured, boxed and shipped safely!

 â˜… Expedited Shipping â˜…

★ Shipping times may vary based on region â˜…

★ *Honesty, *Reliability and *Integrity are *Everything â˜…