My Philips PM3055 oscilloscope

I recently got my hands on an old Philips PM3055 (AKA Fluke PM3055) oscilloscope. This page is dedicated to knowledge about this instrument. I have created it in the hope that it may be useful to others.

News (July 2002): I now have both the manual and the service manual for the PM3055. Thanks to an anonymous visitor from Australia, who mailed me the two! I am very grateful!

• Specifications
• The buttons
• Scans from the service manual

Specifications

Source: University of Toronto.

Input

Frequency Range: DC to 60 MHz DC coupled
Rise time: 5.8 ns
Max input: 500V
Measuring accuracy: ±3%
Voltage scales: 2 mV/div - 10 V/div
Input Impedance: 1 MOhm / 20 pF

Main Time Base

Speeds: 50 ns/div - 0.5 s/div
Accuracy: ±4%

Delay Time Base

Speeds: 50 ns/div - 1 ms/div
Accuracy: ±4%

The Buttons

This explains the buttons one by one: Still incomplete!

AUTOSET

Starts the auto-set feature of the instrument in which it automatically detects the correct settings for the given input signal(s). This works rather well, actually, the instrument sets both the input sensitivity (and even does it independently for each input channel), trigger, and the time base. It has a tendency to pick AC input for most input signals, but that's about the only draw-back I have experienced. This button is a great way to start making the more advanced setups because it ensures that you have something on the screen quickly.

GND (channel A)

Grounds channel A input internaly.

AC/DC (channel A)

Switches between AC and DC coupling of channel A input. In AC position the DC component of the measuring signal is rejected. In DC position the full bandwith is available.

AC coupling is used when a small AC signal has to be measured that is superimposed on a large DC voltage. For example, noise measurements on power supply voltages.

VAR (channel A)

Adjusts the input sensitivity. Turn all clock-wise to reach the calibrated position (marked with "CAL").

A/B

Selects the channel you want to see: A, B or A and B simultaniously. If the ADD function is in use, it is possible to switch off the channels A and B.

ALT/CHOP

Selects alternated or chopped display.

This selection isused if two signals are displayed.

In alternate mode, the CRT beam alternately traces one signal sweep and then the other. At low repetion rates this can be seen, so ALT is mainly used for high speed time-base settings (from around 0.1 ms/div and above).

In CHOP mode, the beam chops from one signal to the other at a fast switching frequency and is therefore suitable for low speed signals. At high frequencies interference can occur between the switching signal and the measured signal, so take care when using the chop mode with high frequency signals.

ADD/INVERT

Selects add, normal, inverted or add-inverted display.

• Add: Channel B is added to channel A (A + B).
• Invert: Channel B is inverted.
• Add-inverted: Channel B is subtracted from channel A (A - B).

The differential mode (A-B) is useful for rejecting common-mode signals. By measuring in differential mode, the common mode signal on one channel cancels out the common mode signal on the other channel, leaving the actual signal visible on the display. For example to eliminate hum from a signal.

Scans from the service manual

Files are in format 'multi page TIFF'. They are viewable with 'Imaging' in Windows. Choose 'save as' if you cannot view them directly in the browser or can only view the first page. Some files are in 'PDF'. They are viewable with Acrobat Reader.

Service manual

• Front page, table of contents, specifications (TIFF, 2501 kb)
• Circuit introduction and block diagram (TIFF, 834 kb)
• Further pages from circuit introduction (TIFF, 577 kb)
• Attenuator unit, description (TIFF, 319 kb)
• Attenuator unit, diagrams (TIFF, 1195 kb)
• Attenuator unit, more diagrams (TIFF, 55 kb)
• Pre-amp unit, description (TIFF, 623 kb)
• ... to be continued!

Older scans

• Section 14.5: Trouble Shooting (TIFF) including wiring diagram between the PCBs.
• Schematics of the power supply TIFF
• Front unit description PDF
• Front unit schematics PDF