AVO Valve Characteristic Meter Mark IV

AVO Valve Tester Mk 4

My Main Valve(tube) tester , It been a good old friend for a number of years

It was missing its Vset ~ knob when I had it and 

years later I have never needed to adjust the V set ~

This can test all types of normal valves , Diodes , Triodes , Pentodes, Tetrodes, indirect or directly heated.

Tests:

Inter electrode leakage/shorts

Mutual conductance

Plot Ia/Vg at a range of parameters

this machine is an excellent compliment to any workshop

Lafayette HA55A, Air band Receiver

                                                                     Lafayette HA55A

A 1960’s Air band receiver

This was one of my few encounters with a Nuvistor 6CW4 in the front end

The set now works however I have noted a few issues with regards to its original specification

Tuning range 108 –136 Mhz

See below

Sensitivity 4uV

Even with a Nuvistor the 4uV is quite poor

Image ratio 40dB

Actually the set suffers from poor image rejection and one can receive a range of Band 2 Broadcast stations which can swamp the receiver

The set does use a strange selection of valves even for the 1960’s,

Apart from the above negatives the radio receives Birmingham very well

HA55A Circuit Schematic 

HA55A Alignment 

Hope this helps

 

KW Radio On Air Event

Do you own a KW radio ?

KW 76 ,KW Atlanta, KW 204, KW Valiant, KW Viceroy, KW201, KW Vespa, KW2000, KW2000A KW2000B

Get It on the Air

KW Weekend 5^th- 6^th January 2014

 

This is one of my collection a KW2000's acquired in the late 1990's in a very sad state .

All the Hunts have been changed, the PSU electrolytic's have also gone and a few resistors changed

then a full realignment 

I never fully addressed the aesthetics, as the tuning escutcheon plate is from a 2000a

and I never quite got around to changing the 1/4” Microphone jack socket back to a DIN

The mechanical Filter did not require any work at all

A superb radio of British manufacture from the early 1960's giving excellent audio

Spark Transmitter

This is one of my oldest Transmitters

a home built sparker dated 1911 

I believe was a Gammage's of London set 

and No , I have not fired it up