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member - Wednesday, July 11, 2012 at 11:25:03
Marconi TF 975 Absorption Wavemeter.
A simple test instrument, no batteries required.
Frequency range 100 kHz to 100 MHz.
Not to be confused with a GDO.
Very well made.
All 'workie workie'.
Lawrence 7/07/2012
admin - Thursday, June 21, 2012 at 10:03:17
Please refer to comments in photo. "General View".
admin - Thursday, June 21, 2012 at 10:00:40
Marconi TF 868B - a universal L-C-R bridge.
Dates from late 1950s → early 1960s.

Brief spec., measurement capability:
L: 1 µH → 100 H in 7 decades @ 1 and 10 kHz.
C: 1 pF to 100 µF in 7 decades @ 1 and 10 kHz.
R: 0.1 Ω to 100 MΩ in 8 decades @ d.c.
Q: 0.1 to 10 @ 1 kHz; to 100 @ 10 kHz
tanδ: 0.001 to 0.1 @ 1 kHz; 0.01 to 1 @ 10 kHz
As Q = 1/tanδ, scales combined to give extended Q coverage up to 1,000
and tanδ up to 10.

Marconi also manufactured a d.c. choke adaptor as an accessory, so that inductors in the range 100 mH to 100 H can be measured @ 1 kHz whilst a direct current up to 200 mA is passed through that inductor from an external source.

General comments.
As this item's appearance suggests, it is a solidly-built item of T & M gear. The range switch on the top LHS is mechanically linked to a rotating disk that sits beneath the circular perspex cover. As the range is changed, so different values appear in the windows of that disk. There is also a linkage to the L-C-R rotary switch mechanism, so that the values that do appear in those windows display units that are appropriate for the electrical parameter selected on that L-C-R switch.
Valves: uses 12AT7, 12AX7, 12AX7 and 6X4.

Maintenance is a decidedly non-trivial affair, mainly on account of the mechanics - as outlined above. However, mine has proved reliable over the years, the main work having been to replace various resistors that have 'gone high'. It has been known for the Q / tanδ toggle switch to go non-low resistance on its contacts, giving misleading results and for the wiper of the main balance pot to go noisy; intermittent contact. Many parts in this unit are Marconi specials, so corrective maint. could be difficult in some respects.

Photos. and write-up by Skywave, June 21, 2012.
member - Monday, April 9, 2012 at 07:49:47
Eddystone S390B Power Supply, picture showing a general internal view, note the large 7.5k body tip dot resistor, this resistor is connected in to circuit directly across the HT supply when the Eddystone 400X receiver is used.
The connection is made via the 400X power lead plug, the reason for this is to keep the HT at 175 volts as the the 400X has a reduced power output stage current consumtion. Hope all of this is of some use to someone, the PSU has not been fired up for a long while.

Lawrence 9/04/2012.
member - Monday, April 9, 2012 at 07:40:18
Eddystone S390B Power Supply, picture shows side view, showing the case in general.

Lawrence 9/04/2012.
member - Monday, April 9, 2012 at 07:38:01
Eddystone S390B Power Supply, picture shows the rear view, showing the power out socket and the earth bonding terminal, note the two tapped screw holes above and below the socket (Top left & bottom right) these take the retaining screws for the receiver power lead plug.

Lawrence 9/04/2012.
member - Monday, April 9, 2012 at 07:31:30
Eddystone S390B power supply, picture shows the front view showing the On/Off Switch, ID Plate & Power On Indicator (Green Bezel)
The S390B Power Supply was designed to supply the Eddystone 358 Receiver including the 358X & the 400X.

Lawrence 9/04/2012.
member - Saturday, March 17, 2012 at 12:31:03
BC 221-Q Frequency Meter, well known and lots of info on the web so I will keep it brief.
This particular one was made around 1944/5 by the Alan D Cardwell manufacturing Co. Brooklyn, New York, also made by other manufactures notably Zenith.
A hetrodyning frequency meter it was suprisingly accurate in it's day and is still. Covers 125 Kcs to 20 Mcs.
This particular one is in mint conditon inside (no modifications) and externaly in very good condition too. It is missing it's original headphone set, however the all important frequency/ dial log book is all complete and is shown at the bottom of the unit, it has it's matching serial number to the unit. All workie workie.

Lawrence 16/03/2012.
member - Thursday, March 15, 2012 at 08:12:30
All workie workie.

Lawrence 15/03.2012.
member - Thursday, March 15, 2012 at 08:11:20
Hickok designed I-177B Tube Tester made by Supreme Inc. Greenwood, Missisipi.
Came of the Ark Royal, see details in other picture.

Lawrence 15/03/2012.