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Rebuilds & Repairs: A section that covers ongoing work and projects.

Entries by Chris (10)

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 

Monday
Jan282013

A nice Marantz Model 1040 gets it's turn on the work bench

This Marantz Model 1040 has been sitting on the shelf for a while, waiting for its turn on the work bench. I really like the look of the 1040, the black panel with the silver faceplate reminds me of the earlier models Marantz made.

This 1040 is in very good condition and with just a little work it will be ready form another 20 years of great sounding music. My initial testing of the 1040 showed no problems with the amplifier, the sound quality was great and the controls are crisp and clean.

I used my usual cleaning method which includes a soft bristle brush and a vacuum cleaner to clear away most of the dirt. Then I followed up with a damp cloth on the more stubborn spots.

I like to start with the power supply board, which only has 4 capacitors to replace. There's a lot of space inside the 1040 and it would be a good model for a beginner to practice on.

As usual, the capacitors on the power supply board were glued to the circuit board with some type of adhesive. When the original capacitors are removed, there's a ring of adhesive left on the board.

Most of the adhesive can be pulled off the board or if your really careful, you can use a flat screw driver to scrape it off. You have to be careful to not scratch up the circuit board.

I used some acetone on a rag, which dissolves the adhesive with some light scrubbing. If you scrub to hard or for to long, you can scrub away the printing off the board.

The power supply board has some unusual components mounted on it. Inside the red box are the 4 rectifier diodes. These are model U05B diodes which are available from specialty suppliers for around $6.00 each. A good replacement would be a 1N5401.

The red arrow points to a small dual diode assembly which is a DS131B. This is simply 2 diodes in a single package. It can be replaced with 2 STTH1R02 diodes wired in series cathode to cathode.

With the power supply board completed, the tone board is next.

See all of the Model 1040 pictures here.


Monday
Sep242012

Refurbishing of a newly cleaned Marantz 1030  #7066

You may have watch the video of this Maranzt 1030 being cleaned before I started the reimbursement. I have posted a detailed rebuild for a 1030 once already, so i won't bore everyone with another.

The high points of this rebuild were how well it initially cleaned up.  Just a little brushing and vacuuming made the wiping down with a damp cloth so much easier.

Replacing all of the capacitors was easy and straight forward.  I used Nichicon capacitors throughout the 1030, including the primary filter caps and the coupling caps.  I did not increase the values of these caps because I don't think it's necessary. 3

Since these three caps were snap-in models, I added solder lugs to their leads, which makes the installation easier and more secure.

Another surprise along the way was the unexpected broken diode H714.  This is a varistor diode and one lead snapped off while i was recapping the amplifier board.  Luckly I was able to buy a replacement from one of my regular suppliers.

After the electronics were complete I adjusted the bias settings as outlined in the service manual.  Then I adjusted the clipping levels. All of these adjustments are for right and left channels individually.

I gave this 1030 a quick listen and it sounded great! So it was on to final cleaning.

A little (and I mean a little) DeoxIt D5 in the control pots cleared away any static and restored their smooth feel. I cleaned all of the pushbutton switches and the selector switch.  

All of the RCA jacks on the back of the 1030 were cleaned with some D5 and pipe cleaners, the headphone jack and mic jacked were cleaned with Q-tips.

I went over the chassis one final time to make sure it shined, I washed the top and bottom covers and the faceplate and knobs.  Lastly the faceplate was polished with a little carnauba wax and shined up.

Everything was reassembled and I moved on to final testing.  Each input was tested including tape in and out and they all worked correctly.

This Marantz 1030 is ready for a new home. 

See all of the 1030 pictures here.

Monday
Jun112012

A Marantz Model 30 Integrated Amplifier Commission

Sunday was the day to start a new project. I have a commissioned project for a Marantz Model 30 Integrated Amplifier. The first and most important part of any project is the initial planning. Sunday was not about soldering or tinkering about with the model 30, it was all about planning. I spent time compiling a list of parts that will be needed and put together a list of this to be done.

The model 30 is often thought to be a combination of a Model 32 Amplifier and a Model 33 Pre Amplifier. This is not exactly correct, while the amplifiers in the 30 and 32 are the same, the preamp is considerably different. In a model 33 there are 2 identical preamp boards, one for each channel. In the model 30 there is a single board for both channels and the overall design is simpler.

There are 2 different amplifier board designs for the model 30 and this unit has the later design. You can tell this by carefully comparing the actual board to the drawings in the service manual. This board has TO220 transistors mounted on their own heat sinks, standing off the board. There are only a few capacitors on the amp board, 2 of them are tantalum’s, all of them will be changed.

Another unique feature of the model 30 is the way the bias transistor and diode are mounted on the back of the circuit board. These components must be mounted so they actually touch the output transistor heat sink. This physical connection allows for good thermal tracking in the bias circuit.

The preamp board is loaded with tantalum capacitors which should all be replaced. Because of the limited amount of space on the board I ordered Nichicon MW and SW series capacitors. All of the poorly installed radial caps will be replaced with the correct axial components.

Since this model 30 is in very good working condition this should be a straight forward rebuild. A little cleaning and polish will really make it shine.

If Mouser is true to form, my parts order should be here on Thursday. . . More to follow.

See all of the Model 30 Pictures.

Wednesday
Apr252012

An early 1060 integrated amplifier

While the 1200B is nearing completion and I spend more time waiting for parts than anything else, It's time to look ahead to the next project.  I have several nice 1060 Integrated Amplifiers which which will benefit from some rebuilding.  The one I choose is in nice shape and should be an easy project.

I spent a few minuets looking it over today and I noticed that it is somewhat different that other 1060's I have worked on before.  Usually there are two varistors (H713 & H714) on the P700 Amp boards that are glued to the heat sinks of H705 & H706.  This particular 1060 has diodes mounted on the circuit board.  I think this is an early design that was changed.

My early 1060 amp board.  The diode is inside the red box.

A later 1060 amp board. Varistor is glued to the transistor heat sink.

I haven't found any reference to this design in the service manual or schematic.