This page will get you started on rebuilding/restoring your Marantz receiver!
The intention of this site is to show how to replace the old electrolytic capacitors in Marantz receivers that have likely dried up over the years to restore proper functionality. This site will also show the proper steps to perform bias and DC idle current adjustments on the Marantz 2270 receiver.
|I will be repairing a 2270 model in the following photos but you should be able to do virtually any Marantz receiver by generally following this guide, however the bias settings we will be performing and the parts we will be replacing are tailored to the 2270.
Just to let you know, I am an electronic technician and engineer and have been working in the broadcast equipment manufacturing sector for over 20 years, so you can rest assured that I know what I am doing. I have restored and/or repaired hundreds of electronics devices over the years. I've worked on and personally aligned audio equipment for places like Skywalker Sound in Marin County, CA, Paul Allen's offices in Seattle, WA, Bill Gate's residence in Redmond, WA, just to name a few. You are in good hands here :-)
I will be assuming that you know how to solder and desolder on printed circuit boards, have basic understanding of electronics and electronic components and the tools shown below, and have a decent amount of common sense. I hope I haven't assumed too much. If you have questions or get stuck somewhere, just email me here email@example.com Use the word "marantz " somewhere in your subject line so the spam blocker doesn't eat your message, and I will do my best to help you.
PLEASE PLEASE PLEASE, if you are headed out the door right now to buy your first soldering iron and solder with the idea that you are going to learn how to solder and repair your Marantz from this website, STOP RIGHT THERE!! Do not attemp any of the repairs on any page in this website if you have not previously had extensive soldering experience. Now, you do not have to be a full fledged engineer to work on your receiver, you do have to know how to produce very solid solder connections, however, and that only comes with plenty of soldering experience. You can very easily destroy your receiver or at least make it worse than it was by simply not knowing how to solder properly, not knowing how to use soldering tools effectively, not using the correct type of solder, the correct type of iron, the correct temperature, etc. If you still think you can do this project as a first time electronics experience, email me first and let's talk about it, BUT BY NO MEANS REMOVE ANY COVER OF THE RECEIVER, OK?
Ok , something you will need before we get started:
A service manual PDF scan for most models (complete with schematics and parts list) are available for download for free at HiFiEngine.com. High quality paid scans are available for a modest cost from vintage-electronics.net.
|Dried up capacitor|
|This is ok, too|
|But this is NOT ok|
|Here are the parts you will need: Although the 2270 has many capacitors, usually only the electrolytics go bad after a few years. The most important ones are the ones that provide filtering for the power supply and the power amplifiers. So, rather than a list being shown here, I am suggesting only a handful of capacitors to be replaced. I replace with same value capacitance, 105c rated, at one level higher voltage than original (10V-->25V, 25V-->35, etc.). Parts are easily obtained here: www.mouser.com
Also get a pair of the main filter capacitors: 10,000 @80VDC and you may want to get a speaker protection relay also: OEM part is Omron MY2-0-DC24
|Ok, before we get started a few words: First and foremost, DO NOT ATTEMPT TO REPAIR YOUR RECEIVER WHILE IT IS PLUGGED INTO THE WALL. You would be surprised at how easy it is to forget to unplug the unit and how many people get zapped these days. Next, don't fool yourself. If you don't have the tools or know-how to unsolder and resolder new parts into a printed circuit board, you are best to leave these repairs to someone who does. You could easily make scrap out of your Marantz by not knowing what you are doing. Make sure your solder is NOT acid core. Take that roll and put it with your plumbing stuff and go get some good rosin core solder (or mildly active, organic flux solder is best). Not sure? ask me: firstname.lastname@example.org use the subject "Marantz questions". Personally, I use a quality eutectic solder (63/37) with rosin flux (yes, it IS important!). Eutectic solder has the narrowest plastic range which yields the best connections with hand repair work. You however might like to use silver solder in your work. Nice call you HIFI tweak! ;-)|
|Once you have your tools ready, prep your receiver by first unplugging it from the wall (Have I made my point yet?). Prepare a work area by laying down some cardboard on your kitchen table, or use your shop work area that is well lighted. Remove both top and bottom covers from the receiver and set aside. I use an old film canister to hold the screws so they don't get lost. You may want to blow the unit out with compressed air at this point (or use a vacuum cleaner) to remove accumulated dust.
I will be starting with the power supply and moving through the receiver and finally ending with the power amp. Because the AM and FM circuits will require realignment which is way out of the scope of this website, I will not be attempting any changes there (I also don't use the phono preamp, so I will not be working on that circuit either). You should decide if your receiver is functioning well enough in these areas before working in these circuits. And you should refer to qualified personell with the required tools to perform the alignments (you don't have them, ok?).
This site's purpose is really to restore the primary audio path through the amplifier to provide better security against a future component failure due to failed electrolytic capacitors, and as a result move toward a receiver that is closer to the original design specs.
|Ok, let's get started. Take your component cleaner (make sure it is the correct cleaner for potentiometers and switches. Be aware the wrong stuff can ruin your pots! I have used Radio Shack 64-4315 safely, for instance) and soak each switch while working the switch in and out multiple times. Do each switch one at at time. When you are satisfied you have worked it enough, move to the rotary switches and soak and work them over their entire range multiple times. Then move on to each potentiomenter (bass, treble, volume) doing the same. You will likely have to use the adapter tube to get the fluid into the potentiometer. You want the cleaner to get into the canister of the pot itself to clean the inside. Don't forget the balance control. You can access it through the front of the receiver's face.|
|Cleaning pots and switches|
|Don't worry if you can't get to every pot or switch just yet. We will have better access to the controls once we get to that board in the procedure.
I just like to get these pots soaking for awhile so I tend to like doing them first. There is 30 years of gunk in them and it is going to take some effort and time to loosen it all up and make them reilable again.
|Be sure to get the cleaner on both sides of the switch banks.
There are surface switch contacts on both sides of the switch board material.
|Now I am going to replace the main power supply filter capacitors since they are a good place to start and they are the most easily accessible. This replacement often restores the real low bass and warmth that these receivers are known for.|
|Replacing power supply caps.|
|I cut the old cap leads at the cap to make it easy to install the new caps. This also keeps the wiring correct and eliminates easy mistakes.
Note the polarity here. Both caps' negative terminal are pointed towards the rear of the receiver.
|Now unscrew the cap hold downs and remove the old caps.
Since the caps are physically smaller than the original caps I install the new caps in these hold-downs using silicone gasket maker to secure. Thanks! Bakersfield, CA USA is in the lead for donations currently!them.
|Notice the difference in manufacturing over the last 30 years? These caps are both the same value.
Beware, you might want to install larger caps to take advantage of the additional room. This will put undue stress on the upstream power supply and could cause serious problems. Better to stay with the original design values.
|Now, working on the power supply PC board:
Heat the solder at the connection to the circuit board on the solder side and using your solder sucker, remove the solder from each leg of the component to be replaced. You may want to remove any excess solder afterward using solder wick. Old solder leaches copper from the PC board which deteriorates the intermetallic so it is recommended that as much of the old solder be removed as possible when replacing parts.
Measure the new part if possible before installing it. Remove the old part and replace it with the new one, pushing it gently down against the PC board. Note the polarity of the device. Electrolytics explode like firecrackers if you install them backwards! You don't want a surprise later when you power the unit, so get this one right the first time.
Now resolder the leads, adding solder slowly and letting the solder flow. Then remove the heat and let it cool making sure not to disturb the joint until it is solid. When you are satisfied with the connection, use your cutters to remove the excess leads (don't cut into the solder!). You may want to clean your work with Alcohol and a cotton swab (or I use an old toothbrush), that is fine. The flux in your solder may or may not need to be removed. Check with the manufacturer of the solder to be sure. This is important as some fluxes are very active and can harm the metals if not removed. I personally use Kester 245 rosin core eutectic silver solder. Eutectic solder has the narrowest plastic range which is best for hand rework as it tends to have fewer cold solder joints. The rosin flux is mildy active and doesn't need to be removed and actually will protect the solder.
|Moving on to the tone control board:
Remove the knobs and front face of the receiver. Remove the hardware from the control pots and gently push the board out allowing you to flip it over to get access to the component side. Use caution not to damage the wires or parts as you remove this board. Spray contact cleaner into these pots if you couldn't get access to them in previous steps. With this board flipped and moved out of the way, you will have access to the switches. Give them a shot of your contact cleaner / lube and then replace the control pot board. Then we can do the preamp board just behind it next. Remove the 4 screws that hold the preamp board to the chasis and work through the board replacing all the electrolytic capacitors. I replace the 3.3uF's with foils and the 1uF's with ceramics or foils. The fewer wet dielectric parts the better (and foils sound better than electrolytics).
Be sure to reassemble in reverse order of removal when you are done. It's good to check out the board you just did to veryify you did everything ok (that there are no solder bridges or other mistakes that you might have to locate later when it's more difficult to narrow down).
|Now we can do the next few boards:
Remove the screws that hold each board. You shouldn't have to remove wires, just flip the board over carefully to allow access to the solder side of the board. I have found that every board has just enough slack in the wiring to allow you to flip each board over and do the work. Do each board one at a time and be extra careful to avoid solder bridges!
|And lastly, the power amp capacitors. Be extra careful to get polarity and voltage values correct here. A mistake will likely cause catastrophic damage to the amplifier. Un screw the hold downs and gently lean the amp back heatsink and all. Remove the screws that hold the board to the heatsink. Seperate the board from the heatsink and replace the caps on this board. The power amps get the hottest, so the solder tends to be the worst here. You know what to do!.|
|This area often has bad solder. Be sure to keep an eye out for ringlets like this one while you are working on each circuit board. These intermittent solder connections wreak havoc on the Marantz's finely balanced circuits.|
|Note: not this model|
URGENT SERVICE BULLETIN MOD:
I recommend performing the service bulletin mods for this model. Basically you will need to replace H760 on each of the power amps with a 2SC496-O (NTE295 which is 526-NTE295 at www.mouser.com) if they are the original 2SC984B transistor (don't need to do the mod if yours doesn't have the cylindrical transistor). This involves removing the existing transistor and reinstalling the replacement transistor. The replacement transistor will need a slight mod to fit properly.
|Bend the collector over like the image here. Use a small piece of shrink or wire insulation to isolate the pin.|
|Install the new part with the back towards the outside of the board as shown here. Solder and then gently bend the legs so that the transistor is vertical (parallel to the board).|
|Reinstall the hardware and affix the transistor to the original hold down using a small drop of glue or heatsink compound. Perform this procedure on the other amplifier module and you're done with this mod!|
|Make a quick but thourough inspection of your work and rework any areas that you were not happy with. Once you are sure that all is perfect, reassemble all mechanical components as necessary but hold off on reinstalling the covers to the receiver.
At this point I like to clean up my area and put away my soldering tools. It gives me time to go over the repairs in my head. You never know, you might have missed something and remember it now. A hasty power test can be a bad thing. I understand the excitement but go ahead and take the 10 minutes it takes to clean up to make sure in your own mind that all is done and done right.
|Beware: The following tests will require the receiver to be powered up and could result in electric shock if you put your skin where it doesn't belong. Don't put your hands (or other body parts) anywhere inside the unit that doesn't require it!! Move slowly and deliberatly to the task at hand. Be aware of the over 100VDC potential that exists inside the device and where those potentials exists!
If you don't know what you are doing, YOU COULD BE KILLED! Although most of the circuits are running on 35VDC or less, you could still get a good shock and that is no fun. Just take your time and follow my instructions carefully (remember the old Operation game?) and all will go just fine!!
OK? Let's go:
Power test the unit: Without connecting anything to the receiver, power on the unit. Be very aware of strange odors, smoke, noises, dimming of the lights. If anything out of the ordinary happens, quickly kill the power and inspect. Did you put a cap in backwards somewhere? DId you squish a wire between 2 parts? These things happen.
Upon power you should hear the speaker protection relay engage the speaker circuit, the familiar "click". Did you hear it? Yes, continue on at the next Purple words. NO?, stop at "No click? STOP!!!!" below.
No Click? STOP!!!!!!! What to do? You powered it up and it is just sitting there staring at you. Well, this means that the speaker protection circuit has determined that there is sufficient DC at the output to damage your speakers and has, thus, opened the output to protect them. If this problem was not there before, it means one of 2 things. Either the bias is off enough to engage the protection circuit, or there are more serious problems like a backwards cap, solder bridge, somethinge else. Power down and reinspect your work. Email me if you need to and I will help if I can.
If all is well, we will now proceed to the amplifier and power supply adjustments.
|Connect DVM to the Left channel output terminals (speaker outputs) black on black or ground. It is of course important to turn on the speaker outputs, so engage the Main speaker switch at the front panel, and connect the DVM to the Main speaker terminals. If you heard no click of the speaker protection relay when initally powering the unit, you will be reading an open circuit which is not what you want to do. (see "no click "above)
Adjust R762, for 0 VDC.
Move the DVM leads to the other channel Main speaker terminals and adjust R762 on that channel for 0 VDC
Connect a DVM between J756 (J753 on older models) and J754 on the power amp board.
Adjust R763 fully counter clock-wise and then turn clockwise adjusting for 5mVDC.
Repeat for the other channel.
Connect a DVM between J802 and J803 on the speaker protection-voltage regulator board.
Adjust R809, for 35VDC.
That's it.. We're done!!
|At this point you may want to replace burned out lamps, and do any other repairs and additional cleaning before replacing the covers. I recommend LED lamp replacement for their long life and low power/low heat.|