Resources
Main | A nice Marantz Model 1040 gets it's turn on the work bench »
Monday
May062013

Refurbishing a Marantz Model 140 Power Amplifier

A while ago I picked up this Model 140 Amplifier along with its matching Model 3200 preamp. These are really a matched pair when it comes to looks and design.

Both the 140 and 3200 are in good working order and they will just need some basic rebuilding and general cleaning to make them really shine.

I decided to start with the Model 140 Amplifier, this compact model weights in at 28 pounds and is rated for 75 watts per channel. The model 140 was in production from 1975 through 1977 and if the date code on the transformer is correct this is an early production model from October 1975.

 

At first glance I thought this 140 was all original, but upon closer inspection I found the signs of a previous repair.

 

Most of the weight is from the huge transformer mounted right in the middle of the chassis. In front of the transformer is a dual-core capacitor, which is no longer available. Part of this rebuild project will be to design a cleaver replacement for the dual core unit.

 

The amplifier boards are attached to the heat sinks and the complete module simply unplugs from the wiring harness and lifts out of the chassis. This makes working on the 140 real easy.

There is a relay protection board mounted at the rear of the 140. This board shows signs of aging parts and it will be rebuilt.

One of the unique features for the 140 are the twin Vu meters. There are two meter control boards with adjustments for calibrating the meters.

The meters will be getting new velum and the original lamps will be replaced with fuse style LED lamps. The LED lamps not only brighten up the meters, they also deepen the blue and red markings on the meter faces.

As with most vintage units this model 140 need to be cleaned as well as refurbished. After looking carefully at how it is constructed I decided that it will be best to simply take it all apart.

I removed the amplifier modules, the meter lamp housings, the meter board and the meters. Then it was really just a matter of detaching everything else from the chassis. The wires on the dual-core capacitor were carefully desolder and the transformer was unbolted from the bottom plate.

The complete wiring harness was lifted of of the chassis and put aside to be cleaned and renewed.

The front and rear panels just unscrew from the bottom plate as do the 2 reinforcing struts on the bottom plate.


It's easy to see now how dirty everything is and all of the scratches and gouges make the chassis look shabby. A repaint will really improve the final look of this nice amplifier.

After washing all of the panels, I masked off the silk screen on the rear panel and gave everything a sanding with some 320 wet/dry sandpaper. Then the panels were sprayed with a self-etching primer.

After the panels were dry, I sanded them with some 400 wet/dry and gave them a coat of flat black.

 

The final coat for the outside of the panels is a semi-gloss black. The inside of the chassis will be painted in flat black.

My shopping list for this model 140 is growing, I need new velum for the meters and the LED replacement lamps, new feet for the chassis.

 

The lamp housing for the meters are in somewhat melted condition. The left housing is worse than the right, I haven't decided what to do with this problem yet. The housings are also very yellowed from the heat of the original lamps, I do know that both housing will be resprayed a gloss white inside to make them more reflective.

See all of the Model 140 Pictures Here 

Reader Comments (2)

What quality work!!! Wish I had those skills to restore the vintage stuff. I own a Marantz 140 so it was fascinating to see the insides so detailed. Fortunately, my 140 has never given me any issues (other than bulb replacement) so opening it up is a rarity. I just enjoy it!!!
Also have a 2325 and a 2226 (the latter acts as the pre-amp for the 140) but I read your comments about receivers...and can appreciate that.
Great post!!

October 26, 2013 | Unregistered CommenterRob Burns

Chris, I wanted to tell you about a little jewel I found at Lowes home improvement warehouse. They sell something called Blue Hawk semi-gloss black spraypaint. It's not too expensive and seems to match the original semigloss of most original equipment. I know you have completed this one......it might help in the future. If you can't find it in store its is available on their online store.

April 14, 2015 | Unregistered CommenterWhitelephant

PostPost a New Comment

Enter your information below to add a new comment.

My response is on my own website »
Author Email (optional):
Author URL (optional):
Post:
 
Some HTML allowed: <a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <code> <em> <i> <strike> <strong>