Antique Electronics and Vintage Solid State

I collect and restore antique vacuum tube electronics (i.e. "boatanchors") and vintage solid-state gear.


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Analysis of DC zero circuit in the HP 3466A DMM

Can someone explain how the DC zero on the HP 3466A works? The manual with the full schematic is on the Keysight web-site:

The first thing to note is that the topology of the input amplifier is non-inverting on the 20 mV and 200 mV ranges, and is switched to inverting on the higher ranges. …

Regency AR-136 Flight Monitoradio

A friend salvaged this from the Boxborough town dump. 

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It’s an aviation band receiver (108 to 136 Megacycles, amplitude modulation), one of several models of Monitoradio sold by Regency. They were forerunners of the scanner. …

Erectronics potentiometer

I came across this item in a box of random parts that someone gave to me.

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It’s a potentiometer that was once part of an Erectronics breadboard system.

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The Erectronics system was an interesting solderless breadboard. …

Sylvania Polymeter 134 and 134Z Manuals

Thanks to Kent Stephenson for scanning his copies of the manuals

Sylvania Electric Polymeter 134 Instr. Book 0 Cover.jpg

 for the Sylvania Polymeter Model 134 

Sylvania Electric 134Z Polymeter Operating Manual 1.jpg

and Polymeter Model 134Z

I’ve added them to my Liberated Manuals and Books archive.

Sylvania Polymeter 134 Ad Dec 1946

He also provided a

Tektronix 454A loose BNC

The mounting nut on the Channel 1 BNC connector of my Tektronix 454A was loose.

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It’s painful to get access as the channel 1 and 2 input circuitry is shielded. The screws are not Phillips; they are instead Pozidriv. …

Krohn-Hite UHR-220 Power Supply

I’ve acquired a Krohn-Hite UHR-220 high voltage power supply. Thanks Ross!

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I really like the styling on these old Krohn-Hites.

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The Jones socket offers the same voltages as the binding posts on the front panel. …

Tektronix 2213 focus repair

I was checking out my Tek 2213 scope before selling it, and noticed that the focus was fuzzy. 

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A little Duck-duck-go-ing informed me that this is a fairly common problem in this series of Tek scopes.

Probe accessories for the GR 1806-A VTVM

Over on the Antique Radio Forum, Philip Colston was asking about accessories for the RF probe of the General Radio 1806-A VTVM.

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It turns out that the tips are identical to the accessory tips for the Tektronix P6000-series scope probes:

Ballantine Model 300-E Sensitive Electronic Voltmeter Instruction Manual

I scanned the instruction manual for the Ballantine 300-E and added it to my Liberated Manuals archive. Click the image below to download the PDF.

Ballantine 300-E

Uniden BC-50XL Scanner service manual

My old Bearcat BC-50XL scanner is showing its age. The squelch has stopped working. It’s probably bad capacitors, so I guess it’s time to build that capacitor ESR tester I’ve been designing off and on for the past decade. 

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