Skip to main content

Bell & Howell Oscilloscope Model 34 DeVry Tech

The Bell & Howell Oscilloscope Model 34 was purchased at an auction and then give to me. It was made by Heathkit for DeVry Tech (DeVry University). Below is a photo of the front after I finished electronically going through it.

There was nothing interesting that came up while working on it. Below you can see some before and after of the underside.

Below is the top side. The 2 filter cans were 4 sections of 20mfd for a total of eight 20mfd capacitors. 

Below is the solution I came up with to replace them. It consists of eight 22 mfd on a PCB that is zipped tied to the bottom of the chassis.  

Overall this is a simple oscilloscope and was a simple electronic restore. 

Here is the schematic.


  1. Hi Cody, I was given the exact scope from a relative and since I have only basic electronic repair experience, I was wondering if you could possibly point me in the correct direction towards doing some basic diagnosis on the unit? Removed cover and did a visual inspection. Unit is VERY, very clean inside and out. No bulging or burned components or caps. All components look like brand new (I know you can't tell from cosmetics, just saying). All tubes heat-up and glow including the back of the scope tube, however no trace is visible at any intensity. Guess I should start with the caps. Is there anything you would recommend first. Thanks in advance for any suggestions.

    1. Mine surprisingly worked when I initially powered it up before I began any work. Not a lot of advice I can give to you. If you are familiar with electronics and high voltages you may want to check for B+ coming off the 6X4. My other thoughts would be to check for any voltages missing on the plates.

      Good Luck,
      Cody P.

  2. hey cody! i've got the same model and i'm trying to understand the pinout of the filter cans. I've got a bunch of 450v 22mfd caps for replacement. These shouldn't be in series right? There's only 4 pins on the filter cans so I assume each one holds a capacitance between its corresponding lead and ground, with the cans bolted connection serving as the ground?


Post a Comment

Popular posts from this blog

Seeburg Digital Control Center

The Seeburg Digital Control Center came into use around the 1970's. This was model DDC1. Seeburg continued the use to the digital control center line until around 1977. The last model used was a DCC42-56. The DCC is used to supply 27 volts DC, -27 volts  DC and -13 volts DC to the jukebox. The DCC has test points on the side to measure these voltages.  Below you can see a DCC3. Once you flip over the DCC you will see two circuit boards. The top board is the data buffer board. Generally you will not have any issue with it. The second board (on bottom) is the power supply board. This where you may have issues. The power supply board is where the DC voltages are created and regulated. Below is the power supply board removed. The first thing I always do when working on a DCC is start by replacing all electrolytic capacitors. Below is the schematic.  In my case as you can see below I had other issues. As you can see transistor Q3120 has been repla

Seeburg SHP3 Repair July 2017

I have just finished repairing this Seeburg SHP3 for a friend. My friend collects and refurbished jukeboxes and he occasionally brings me the amplifiers. Initial Photos : The above photos show the amplifier as I received it. It was obvious someone had done some work before. The driver transistors as well as the output transistors were not originals. Also, Q5114 had been changed. It is the big silver transistor you see on the driver board. The initial power up  using a dim bulb tester showed that the right channel was not working and too much current was being drawn. Why I use a dim bulb Tester:  Notice the red enamel wire running along the top edge of the driver board. A trace should be there, but someone ran the amplifier with shorted transistors and burnt the 32+ volt trace off the board. Repairs: Replaced Q115 and Q116 (Driver Transistors Right Channel) -Shorted Replaced Q5117 and Q5118 (Output Transistors Right Channel)- Shorted Replaced Q5114 (Signal