Skip to main content

Seeburg MRA1-L6

Seeburg MRA1-L6
A friend of mine sent this Seeburg MRA1-L6 to me to be gone through. At first glance I thought it should be a typical recap job, but it was quickly discovered this things has some big issues . I will discuss those a later. 

This amplifier came out of a Seeburg M100A.  This jukebox plays 100 sections. There is a total of 50 discs and this player will play either side. My friend is currently working on mechanics of jukebox while I am working on the amplifier.The photos below show the amplifier as I received it.

The issues with this amplifier besides the old capacitors from about 1948 is the output transformer and possibly the power transformer. The output transformer is near the center of the first photo at the top. I believe it has been chewed on by possibly mice. The inner wrapping is showing and the wires are loose. The power transformer checks out fine with an ohm meter, but the wires to the primary and the center tap of the high voltage has been cut. This made me wonder why they were cut.

The solutions to the problems would have been more expensive than finding a complete amplifier. So that is what we did, we found a complete amplifier. I am hoping it arrives early next week. I will then post about it and the work to be done on it. 
  
The amplifier as I received it.
The underside.
Up close of the old caps.
Up close of the power plug and the splicing of the output transformer. If you look close in the bottom center you can see the cut wires.
Labels:

Comments

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 ...
Post a Comment
Read more

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.
3 comments
Read more

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...
Post a Comment
Read more