Welcome to the restoration tutorials from the "classic" irebuildmarantz.com website. These how-to guides encouraged and enabled countless newbies to rebuild their own Marantz stereos, myself included. The models 2225, 2230, 2235B, 2245, 2252, 2265B, 2270, 2285B, and 2325 are covered.
These guides were created by Robert D. Bowish, the founder of irebuildmarantz.com. Robert once told me that IRM was originally an experiment with building a website, and that it grew into a restoration and kits business fueled by the content on the site. The how-to guides quickly became popular and they hit the top of search engines frequently.
Robert played a significant part in building interest in restorations with these guides being a big part of that. Robert is no longer associated with IRM but the best parts of his work with Marantz continue on today here at the new IRM.and the considerable traffic these pages have seen over the years shows the amount of interest in vintage stereo equipment restoration.
Some of the methods shown would not be considered best practices today, but the guides are still solid after all these years. Part of doing a restoration should include Google queries to audiokarma.org for specifics on how best to work on different issues you encounter with your model Marantz.
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 2252 receiver.
|I will be repairing a 2252 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 2252.
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 , some things you will need before we get started:
A service manual PDF scan for the 2252 (complete with schematics and parts list) is available for download free at <a href="http://hifiengine.com/">HiFiEngine.com
|Dried up capacitor|
|This is ok, too|
|But this is NOT ok|
|Here is where I get my parts: www.mouser.com I buy hi-temp rated aluminum electrolytics at the stock uF value but at one voltage level up from stock. I replace the tantalums at 1uF with 1uF/50V ceramics or metalized foil caps for better failure safety and better sound. I replace the bi-polar electrolytics at .22 and .47 with multilayer ceramics and the larger 4.7uF with 50V bi-polar electrolytics. These caps represent the best value and won't break your pocketbook, and also won't require any modifications to the original design and board layouts. Get a pair of 10,000uF/63V electrolytics for the main filter caps.|
|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 major changes there. 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. However i will include the recap instructions for those areas...
|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|
|I like to give the switches and pots time to soak while I do the rest of the restoration.
I usually give them another shot of cleaner just before I close up the receiver when I am all done with the work.
|Now I am going to replace the main power supply capacitors. I am going to start with the 2 large filter caps since they are a good place to start and they are the most easily accessible.|
|Replacing power supply caps.|
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 bond so it is recommended that all old solder be removed 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.
|This board commonly has bad caps due most likely from the heat this board produces. Changing the caps here will clean up the supply 35VDC that is required for many of the circuits throughout the receiver.|
|Use your solder sucker to pull the solder out from each leg of the capacitor you are replacing. Once clear of solder, genely wiggle the old part out. I often use solder wick to mop up the excess old solder.
Now install the new part and push it against the circuit board. Apply a slight bend to each of the legs to hold it in place while you solder.
|Moving on to the tone control board:
This board may require some mechanical disassembly to get access to the component side. You will need to remove all the control knobs (they just pull off) and the front face (a great time to clean them BTW) to remove this board. Then you will need to remove all the hardware holding the pots and the board. (sorry, no pictures) Use caution not to damage the wires or parts as you remove this board. We will be changing all the electrolytic caps on this board.
Be sure to reassemble in reverse order of removal.
|Now the tuner board. Go from one cap to the next, replacing with a new cap, resoldering and clilpping leads. Be sure to get the new part oriented correctly. Look for the + symbol next to the circle on the board to get the polarity correct. When done just move on to the next board.
|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 lift out the amp, heatsink and all. Remove the screws that hold the board to the heatsink. I then separate the board from the heatsink to allow access to the solder side of the board. You shouldn't have to remove any wires to do what is needed here.
Because this board tends to get hot, be sure to really go over the solder to eliminate intermittence in these circuits. (VERY IMPORTANT!)Reinstall in the reverse order and check to make sure there are no broken or pinched wires.
|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.
If all is well, we will now proceed to the bias asjustment phase of our project.
Connect a DVM between J726 and J723 on the power amp board.
Adjust R731, for 8mVDC.
Connect the DVM between J723 and J709. Adjust R711 for 0mV DC
Connect the DVM between J727 and J722. Adjust R732 for 8mV DC
Connect the DVM between J722 and J709. Adjust R712 for 0mV DC
Repeat after 30 minutes (after the amp has time to warm up to normal operating temperature)
Connect a DVM between J805 and J814.
Adjust R808, 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 replacing the original incandescent lamps with new white LED's. Often the diffuser paper behind the tuner scale needs to be replaced due to yellowing. Chaning these lamps with LED's and putting in a new diffuser really bring back the deep blue original look. If you are interested in more information on this easy to do mod, send me an email and I would be happy to provide you with more info.|
|Once you feel that the unit is ready to put back into use, replace the covers and reconnect to your speakers and inputs. Listen for any strange sounds, pops or things out of the ordinary. If she is running well, give her a good test and see how she does. You might want to recheck the adjustments in a few days for any drifting. Other than that, you are likely ready for another 30 years of great sound and enjoyment from your Marantz receiver.
Some people feel very strongly about the sound of foil capacitors. You might want to consider changing some of the remaining caps to foil caps to continue with the spirit of this website. There are many other considerations (like precision resistors and such) that are beyond this sites scope but hold equal importance in the continuing persuit of the longevity of these amplifiers. If I can be of any assitance in following this road, just email me and I will aid you in any way I can.
Good luck and thanks for keeping these HIFI legends alive!