Digital Test
Philips PW4032

Manufacturer: Philips
Model: PW4032
Year: 1959 ?
Schematic: RE
Max. Rate: ~ 62 KHz (visual observation)
Display: E1T counter tubes
Digits: 5
Logic: tube, E1T counter tubes

This counter is notable for it's use of the E1T counter tubes. Functionally this unit is just an event counter, it does not include an internal timebase.

The E1T tubes are functionally similar to dekatrons in that they are a combination decade counter and decade display device, however their operating principles are entirely different. The E1T is a cathode-ray device with a flourescent screen with 10 marked positions for the display. A complex arrangement of electrodes form electrons emitted from the cathode into a beam which will hold state in one of ten positions spanning about 60 degrees of arc.

Appropriately formed and timed pulses applied to a deflection electrode 'bump' the beam from one position to the next. On the 10th pulse the beam hits another electrode, producing a pulse which is amplified and shaped by an additional tube. The output from this tube is applied to yet another electrode to reset the beam to the '0' position, and acts as the carry pulse to the next digit stage.

Roland Decker explains the E1T in much greater depth, along with an investigation into the development history of the tube, at his site (link below).

Other sites mentioning the E1T tube:



- Unit Log -

Serial Number: MB622
Year of Manufacture: "March 25/65" written on transformer, but not likely the manufacturing date. Construction looks more like 1950s. A manual for related equipment supplied by Martin Forsberg indicates the PW4032 was produced at least as early as 1959.
Date of Receipt: 2005 Apr 28
State upon Receipt: Non-functional. Fair physical condition. Dusty. Some rust on chrome handles.

Date: 2005 May 02
Procedure: No B+. Three filter resistors open (2 of 390, 3.3K). Second 390 ohm resistor had been bypassed by a 220 ohm resistor. With resistors replaced B+ present, display lights up but counting is erratic.

Date: 2005 May 02
Symptoms: First and last digits count but reset at 9, other digits cycle from 4 to 6 or 6 to 8 or so.
Analysis: Cathode of digit 1,2,3 E1Ts ~ 30V, reset grid (pin 2) ~ 20-30V, compared to 12V and 13V for digit 0. Presumed to be from leakage of reset driver plate capacitor, thus raising reset grid voltage and hence cathode current. Digit 0 okay because of diode clamp.
Solution: Four 0.0082 capacitors replaced with 0.0078.

Date: 2005 May 04
Procedure: Oddball power connector replaced with IEC standard.

Date: 2005 May 06
Procedure: Front panel and switches dismantled for cleaning.

Date: 2005 May 09
Procedure: B+ filter resistors replaced with 500, 300 and 3500 ohm units. Filter capacitor ground wire rerouted.

Date: 2005 May 13
Procedure: Cathode current on first divider flip-flop seems rather high (~17mA, slightly over tube specs) but no faults are apparent.

Date: 2005 May 13
Symptoms: V7 plate measures 150V while plates of V9,11,13,15 all measure around 100V.
Solution: 0.01F capacitor at grid of V7 replaced. V7 plate voltage now matches others.

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Early Digital Test Equipment