Really Expensive Stuff

 Some of these items cost a tremendous amount of money when they were new but today they are hardly worth their weight in scrap metal.

If they stop working you'd have to pay to have them carried away!

 Hewlett Packard HP8551B Spectrum Analyser


 HP8551B with the 5th harmonic of a 500MHz signal displayed at 2.5GHz

The top unit is valve-less, using transistors

The bottom unit is a "plumber's delight" handling the 10MHz to 42GHz specification

I suspect the lower limit may be a lot less as the dials imply that it beats a 2GHz oscillator with a VFO, tuning down to 2GHz

My Marconi sig genny has a similar arrangement which lets you generate zero Hz (is that meaningful?) when the dial is set to "0"!

 Hewlett Packard 608E VHF Oscillator

 Below, my Type 608E VHF generator, which isn't much use in a domestic repair workshop as it do not include FM. I suppose they would be more useful for overhauling aircraft equipment as they still use VHF-AM.

This monster, weighing in at around 100lbs covers 10-480MHz.

These equipments were made in the days before clever methods of frequency stabilisation had been invented and relied on mechanical ruggedness (=weight) to ensure that the output frequency was stable. Another requirement of these things, with their very accurate output attenuators (the dial on the bottom right), was not to leak any RF which might upset measurements.

Even with professional test equipment, RF leakage can pose problems. I was once servicing a marine VHF transceiver and was checking the distress frequency calibration, when the local Coast Guard popped up and complained about my test signal on his receiver. This despite the use of screened leads and a dummy load.

Click to see the HP608E circuit diagrams

And click to see the full manual (13MB)



Above, you can see a row of 8 rectifier diodes, and below on the left a pair of disimilar 6080 double-triode valves which have a very low value of anode resistance so waste little when used for say regulating HT.


 Below, the metal cover conceals a turret tuner.

 And with the cover detached you can see a good example of precision mechanical engineering. Two sets of coils can be rotated by the front panel bandswitch knob. I didn't remove the top cover, but this conceals three triode RF valves. These being a 4042, 4043 and an EC8010. Clipped to the chassis behind the scale is a special tool for extracting the 4042 and 4043 valves. Another valve is V9, a 6U8 which from the presence of the adjacent 5Mc/s crystal is an oscillator.



 Not only a set of valves, but lots of transistors. I counted the following 13 valves. V2 and V21 12AU7; V9 6U8; V10, V11 12AT7; V12, V14 6AU7; V13, V16 6080; V15 5651 (=86V stabiliser); V18 V19 6AH6; V20 6AL5. Inside the RF box are V6 RF oscillator and V8 RF amplifier disk seal triodes types 4042 and 4043 plus V22 RF buffer EC8010. Stop looking at this point because numbers V1/V3/V4/V5/V7 and V17 are not allocated.



 Above... I didn't think it was advisable to mount valves upside-down, and what's that bulb-like object.. a barettor?

Below, lurking in a corner of the chassis I spotted this 2N1544 Germanium PNP 106 watt power transistor, and also what appears to be a mixer diode inside the RF box. In the centre is a picture of a 4042 triode (similar to the 4043)



 Cossor Model 1052 Oscillograph



 To me, it's just an oscilloscope, but the label tells me it's a portable oscillograph. I read that the latter can make a permanent record and if so it must be via a camera fitted at the front. This example was made in 1952 and of course uses valves, 14 of them. These are two 7Y4, eight 6AM6, two 12AT7 and one each of 6F33 and 6AL5. Notable are the full wave rectifiers; the 7Y3 was a pre-war American valve which was made by Cossor after 1945, and the 6F33 which is able to be cut off by some 10 volts negative applied to its suppressor grid. The CRT is a type 89D. Pictures below...





 The labelling of the front panel controls is not particularly forthcoming when it comes to details, although it's clearly a twin beam scope, given Y1 and Y2, but timebase-wise is anyone's guess. The implication is that if the Y bandwidth is no better than 2Mc/s, and if that refers to the 3dB point, then the timebase must range up to say a few microsecond per cm.

I've now found an instruction book so can reveal some details:-

Time Base Ranges:


 Velocity Anti-Clockwise

 Velocity Clockwise






















 External Scan



The Y amplifiers are identical and have a 3 position switch controlling gain and bandwidth.


 Max sens.


 B/width from

 B/width to

 Undistorted deflection






 Full screen




 15c/s -250Kc/s









Y inputs are 1Mohm and 50pF


Plessey Test Equipment

As the name says.. these 19 inch rack mount panels form part of a tester for integrated circuits. When was it made I wonder? Well, many parts are labelled "RS" so it doesn't date as far back as the "Radiospares" brand name, but careful scrutiny of some parts reveals dates of 1970 and 1972 so my guess it was made in 1972 or 1973. Around that time Plessey at their Poole factory had a number of in-house PP250 computers and it's likely that one of these was used with these panels to test I/Cs. In 1973 there were a fair number of integrated circuit types around but most common was the "74" series using the 14-pin dual-in-line package. The panels came from a fellow ex-Plessey engineer, Laurie Hannington who found them whilst tidying his garage.
 When this equipment was designed the term "GUI" hadn't been invented so communication between this equipment and its host computer was via switches and lamps. The panel below shows what I mean. A user needed to be familiar with a range of tasks so that he could key in appropriate data. From the labelling (bottom left) you can see that a facility for paper tape is also provided. This meant that a variety of keystrokes and button pushing could be replaced by reading a paper tape. Nowadays a display with mouse and a graphics user interface would make all of this childs' play. Although read-only memory chips were in use around the time this tester was designed it was easier to provide a matrix into which plugs could be inserted (top picture). A handbook would have been provided so that the user could program the matrix for a specific type of integrated circuit.

 It's interesting to look back on this era. The cold war was going strong and WW3 was a distinct possibility so no expense was spared to protect the country from attack. WW2 air defence arrangements were being updated through the use of vast computer systems. The computers were completely different to those with which we're familiar today because they worked in real time. Radar echoes were fed into computers, were processed and resulted in almost immediate responses at RAF West Drayton where some 1,000 racks of equipment handled the workload. Recently I visited the Radar Museum near Horning on the Norfolk Broads where one of the UK cold war air defence stations remains just as it was when in use during the cold war. Whatever might be said about the 1950s Linesman Project it did do its job despite its millions of germanium transistors and reliance on paper tape, key pressers and button pushers. Alas, I don't have a photograph of a Linesman equipment rack. It was around 7 feet tall, finished in stove enamel and had dozens of slide-in units with chrome handles. Each unit carried some 20 odd printed circuit boards and each board represented maybe one logic circuit. For example a board would carry a single digital toggle or "flip-flop" as they were known or maybe an "And", "Or", "Nand", "Nor" or "Exor" circuit. By the 1960s a tiny integrated circuit could carry maybe four flip-flops, which brings us back to the era of the IC tester pictured above.

Below is an advertisement for the Plessey XL9 computer dating from 1966. This machine was a commercial development of the Linesman XL series of computers (XL2, XL4 and XL6) and was used in a range of applications during the 1960s including wide area traffic control, message switching at GCHQ and an air defence system for Burma.


 Below is a picture of the IC tester I use in my repair business.
   This tester is pocket-sized and is decades newer than the one made by Plessey. In fact 4 decades plus some years newer and can test most 74 series TTL, CMOS and even chips with 24 legs. A tiny battery provides the power and it doesn't really need to be told what type of chip is being tested.


 And at the other end of the scale the cheapest piece of test equipment ever?

A WW1 bulb tester that came with some very early reflector bulbs


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