Shaun Merrigan's Information Pages


Tag: Vintage Electronics


Tektronix 7854 Waveform Keyboard Rebuild

Posted by Shaun Merrigan in Electronics, Oscilloscopes, Tech. Comments Off on Tektronix 7854 Waveform Keyboard Rebuild

15th August

Tektronix 7854 Waveform Keyboard Rebuild

From the Tek Wiki:

The Tektronix 7854 Waveform Processing Oscilloscope, introduced in 1980, is a 400 MHz combined analog / digital mainframe in the 7000 series that takes two vertical and two horizontal 7000-series plug-ins. In addition to a conventional analog (real time) scope, it contains an equivalent-time sampling 10-bit digitizer and a programmable waveform processor with GPIB interface. The waveform processor can be programmed using a detachable calculator-style keyboard, using postfix operators (“reverse Polish notation” like HP calculators) that operate on entire waveforms, not just individual numbers.

Tek 7854 Mainframe #2 after cleaning

 

It is to the repair of the detachable keyboard that this post is devoted.  I purchased a keyboard for a reasonable price only to find that some keys were intermittent, and some did not work at all.

Opening up the keyboard showed that it was filled with debris:

The … Read More »


Tektronix Scope-Mobile Cart Repair Part 3

Posted by Shaun Merrigan in Electronics, Oscilloscopes. Comments Off on Tektronix Scope-Mobile Cart Repair Part 3

7th May

Tektronix Scope-Mobile Cart Repair Part 3

 

Part 1

Part 2 

This is the conclusion to my repair of a Tektronix 202-2 Scope-Mobile Cart.  Recall that the problem was three fractured trunnion mount bosses which rendered the cart useless (and unsafe) under load.  My proposed solution was to place the bosses into compression by putting a 6mm countersunk bolt through the trunnion mount concentric with the existing hole in the boss.  By using appropriate sized washers between the top of the boss and the frame member I ensure that the boss is placed into compression and the frame member is securely clamped.  This avoids the tensile loading which fractured the bosses initially.

 

The holes in the trunnion mount were countersunk to fit the flat head socket bolts:

 

 

 

 

The cart was reassembled with the repaired trunnion mounts:

Felt lining was added to the plug in storage compartment:

 

Finally, the cart … Read More »


Tektronix 556 Fan Motor Repair Part 2

Posted by Shaun Merrigan in Electronics, Oscilloscopes, Tektronix 556. Comments Off on Tektronix 556 Fan Motor Repair Part 2

22nd January

Tektronix 556 Fan Motor Repair Part 2

In this continuation of Tektronix 556 Fan Motor Repair Part 1, I have removed the motor and mount assembly and disassembled it.  Now I need to figure out the problem and rebuild the motor.

Tektronix 556 Fan Motor Overview, mounted in place

Tektronix 556 Fan Motor removed from mounts.  The Tektronix part number is 147-0029-00.

 

Tektronix 556 Fan Motor removed from mounts.

Tektronix 556 Fan Motor removed from mounts.

The next few images show the disassembled parts of the motor:

Rotor, end bells and bushing assembly

End bell inside, retainer, spring washer felt and bushing.

End bell and bushing assembly

Rotor and spacers

At this point I found several issues by visual inspection:

The original rear bushing had been replaced, probably due to excessive internal wear.
The replacement itself had excessive internal wear and it did not fit in the retainer properly due to its shape.
The replacement … Read More »


Tektronix 556 Fan Motor Repair Part 1

Posted by Shaun Merrigan in Electronics, Oscilloscopes, Tektronix 556, Vacuum Tubes. Comments Off on Tektronix 556 Fan Motor Repair Part 1

19th January

Tektronix 556 Fan Motor Repair Part 1

I was recently fortunate enough to acquire a Tektronix 556 Dual Beam Oscilloscope with many accessories and in good condition.  Unfortunately, the cooling fan on the scope was very loud and more concerning, it emitted an alarming metal on metal contact sound.  After verifying basic operation of the oscilloscope, I decided to repair the cooling fan.  This process is documented in the images and commentary that follow.

Part 1: Removing the Noisy Fan Motor

556 Cooling Module with filter and mesh screen removed.  The fan is connected to the chassis wiring at the ceramic terminal which is circled:

Fan to chassis wiring connection terminal.

 

Inside of cooling module and bottom side of motor (fan blade removed):

Back side of motor (fan blade removed).  This is a 4 pole 1725 rpm (loaded) motor.  It moves a very large volume of air.

An … Read More »


New Vacuum Tube Box Scans

Posted by Shaun Merrigan in Electronics, Vacuum Tubes. Comments Off on New Vacuum Tube Box Scans

6th January

New Vacuum  Tube Box Scans

I have uploaded several new vacuum tube box scans including Philco, Canadian General Electric, Wards, and Hitachi (Hit-Ray):

 

 

Thanks,

 

Shaun M.