Model: 2325

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 2325 receiver.

I will be repairing a model 2325 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 2325.

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 info@irebuildmarantz.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?

A service manual PDF scan for the 2325 (complete with schematics and parts list) is available for download in our online store. All proceeds go to keeping this site up.

There is a DVD video of this restoration with all details and commentary available here

Dried up capacitor

(a note about bad caps)

A note about bad solder

S

T

O

P

Your Tools:
Cutters
Solder
Soldering Iron
Cleaner
Multimeter (DVM)

Solder Remover
Solder Wick
This is ok, too
But this is NOT ok
Here are the parts you will need: Although the 2325 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. Caps are rated today at about 15,000 hours to stay within tolerance, usually 15% or so. This might equate to 20 years or less, depending on many variables. However, that is today's standard and capacitors today are substantially better than the original parts in your Marantz. Of course, any part that is obviously damaged, leaking, discolored, burned, etc. should be replaced. And any hum or obvious malfunctions of the receiver are generally indicative of these worn out parts.
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: info@irebuildmarantz.com 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 caps and moving through the receiver board to board and finally ending with the power amps. Because the AM and FM circuits will require realignment which is way out of the scope of this website, you should consider attempting any changes there. And you should refer to qualified personell with the required tools to perform the alignments on these circuits if you decide to do restoration work on them (tuner alignments takes proper test gear and years of experience and knowledge to do).

This site's purpose is really to restore the circuits throughout the amplifier by restoring the capacitors and solder (at least) 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-bank while working the switch through its range many times.
Cleaning pots and switches
Now remove the front face of the receiver by removing the 4 screws at the corners, pulling off all the large knobs, the 4 dolby knobs, the balance slider knob, and by unscrewing the brass nut on the bass control shaft. Also remove the counter-sunk screw on the top edge (under where the cover goes). Remove all the nuts and washers to the tone board pots and disconnect the header connector to the board. There are small clips on either end of the connector that will need to be removed in order to remove the connector. They usually just pop off. Remove the 2 supports that hold the board and now pull the whole tone board out and place it on the bench. Now it is easy to clean the pots and switch-bank on this board as well as replacing the capacitors on this board. There are several electrolytics and tantalums that shlould be replaced.

Before reinstalling this board, remove the RF shield that lies directly under it by removing the 4 screws that align with it on the front of the chassis. Once this shield is removed, you will have access to the switches underneath. Using you contact cleaner with the tube attached, spray into the rectangle in the center of the switch and move the switch in and out many times to distribute the cleaner and clean the contacts. Do each switch one at a time. When all are done, reinstall the RF shield and reinstall the tone board.

Removing the tone board

Now let's 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. This is as easy and unscrewing the hold down screws, unscrewing the contact screws, and then sliding the old caps out of the holder rings. Slide the new caps into the holder rings, tighten the ring once you set the proper height and orientation, and then reinstall into the chassis. Connect the caps with the screws and that's it!
Replacing power supply caps.
These are the "Robin's Eggs" replacements for the 15,000 uF caps. Computer Grade, nice!!

These 18,000 uF caps are almost exactly the same size and fit nicely into the reciever. It takes almost no time to swap them out.

Once they are done, you can expect the low bass to return in a big way!

Now, we will remove the main amplifier boards to allow access to the other areas of the amp, and then we will restore the parts and solder in those last:

Disconnect the white molex connector and the RCA signal line from both amplifier modules and unscrew the 4 screws that hold each module to the main chassis. These amps can now be removed and placed aside on the bench.

Now, with the main amps out of the way we can get better access to the rest of the boards on the top of the receiver chassis. First we will start with the power supply/speaker protection board. This board tends to get the hottest and usually houses the worst caps in the unit. Also, the speaker protection relay has corroded or worn contacts, so it should also be replaced (Omron OEM Relay: LY2-0-DC24)
Unscrew the 4 hold down screws, flip the board and replace all the caps on this board keeping stock values. I use 105c rated caps here since they tend to last longer. 30 years has wreaked havoc on the solder as well, so be sure and touch up or replace the solder on this board.
Now we will simply go from board to board replacing electrolytic capacitors. I like to do the FM MPX board next since it is right there and the amp is out of the way. This board is a little difficult to get to the solder side, but just gently tug on each wire enough to allow you to flip the board. There are many electrolytics here that need to go! I use ceramic caps for the PLL filter (the .22's and the .47uf at 50V). They will last much longer and not cause problems later. I also use 1uF/50 and .22uF/50 ceramics for the tantalums on this board.
Tantalum caps in the 2325 are usually blue like this one. These are easily replaced with a ceramic 1uF/50V cap. Nice!
At this point I flip the receiver over and finish the boards on the underside. Starting with the PH01 board and move out finishing with the phono preamp board and the FM IF board. NOTE: The PH01 board on some revisions has the silk backwards on the filter cap (220uF) which will burn up the 100ohm power input resistor if the cap is inserted following this orientation. Be sure to have the negative pin towards the outside of the board for proper orientation. If you smoke the 100 ohm , you have it backwards! ;-) Be sure to fix the bad solder here as it is common.

The next board (lableled YD-288?) will require quite a few 10/25 caps. Resolder and make all nice again!!!

The phono preamp board will require an axial cap (to allow the bottom cover to fit, I think). It is a 100/35V, but I use a 100/50V 105c here. If you are into listening to phono albums, you may want to invest in the foil caps for replacing the tantalums here. It takes a bit of effort to get them to fit. Replace the 4.7uF electrolytics here as well. Touch up that crappy solder!!

That leaves the FM IF board which is hiding under the chrome RF shield in the center bottom of the receiver. Remove the RF shield, the hex standoffs, and flip this board. Clean, replace caps, resolder and replace. We are now done with the restoration of the bottom boards. YEA!!

Now turn the receiver over and we will finish up with the boards on the top of the receiver.

I Start with the AM board and then move to the Dolby board.

AM board

Remove the cover being careful since I have found that these screws tend to be really stuck. I have had to drill out a screw here before so be warned!! Flip this board, clean, replace caps, solder and reinstall.

That leaves only the Dolby board and we are pretty much done with the caps that need replacing. The rest will be adjustments and that's about it. Remove the 4 screws that hold the dolby module, remove the 2 screws at the top and remove the main cover. Now you can access the 4 screws that hold the board to the cover back. Pull the wire loom out from the nylon holder on the chassis to allow for some slack to manipulate the board.

Dolby board
There's about a dozen 10uF/16V's on this board that I replace with 10/25's and resolder the entire board. This is a descreet Dolby circuit that is pretty much unheard of these days anymore, and it comes back quite nicely once the restoration is done. Change out the caps and resolder, reassembly in reverse order.
This is when I move back over to the power amps. Unscrew the 4 hold down screws and the smaller screw on the heat sink and genly bend the wires opening up the amp board and heatsink like a book. Replace the 2 electrolytic caps and the tantalum cap. I use same values at one voltage level up. The tantalum I replace with a 33uF/25V 105c electrolytic cap.

SERVICE MOD:

There is a fairly serious service mod that needs to be done on these amps before we put them back together. You will need two 1N4148 diodes for each amp board. Replace H718 and H719 on each board with these 1N4148 diodes being EXTRA CAREFUL to get the polarity correct. Follow the silk screen on the board for orientation.

Remove the other channel amp and perform the exact same procedure on it replacing the caps and diodes. It's essential that you get the solder back up to snuff here since these boards get really hot and over 30 years... well, you know the story! You will likely see some bad solder around the larger power resistors at least. I personally resolder EVERY connection on these amps.

Note: not this model

Reassemble each amp and reinstall them back into the main chassis. Reconnect the white molex connectors and RCA signal lines. Screw down each amp with the 4 screws. _________________________________________________________________________________________

So at this point we should be in pretty good shape for the first power tests. We've replaced nearly every electrolytic capacitor in the receiver and soldered pretty darn most of it. We've cleaned the switches and pots, we've replace the speaker protection relay and we've performed the service bulletin mods. I think we are ready to power test and get to doing the adjustments.

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 bias asjustment phase of our project.

If you feel everything is ok but the protection relay still doesn't engage, we can go around the relay and make the first adjustments (this will likely fix the problem). Connect the DVM (set to DC volts) to the amplifier's output by shoving the red DVM probe into the white molex connector that is connected to the power amp that you will be adjusting (black probe in any black speaker terminal). The pin you want to look at is the one that has either the blue or yellow wire coming out of it, so shove the red probe in the wire end of that connector until you get a connection. You should be reading low voltage, hopefully less than 3 volts. If you are reading high voltage, over 5 volts or even 60 volts, you have a problem with that amp. Stop here and troubleshoot the amplifier.

Adjust R713 on the power amp board you are connected to for 0VDC reading on the DVM (or as close as you can get). Switch probes over to the other amp and do the same adjustment. You will probably hear the familiar protection relay "click" at some point in the adjustment as you get things into spec. This is what you want. If all went well, you can make the remaining adjustments following the procedure starting with the green words below. If you still have problems, or can't make the adjustments within the range of the potentiometer, you will have to stop here and troubleshoot...

Main Adjustments:

First : Voltage Regulator Adjustment:

Connect your DVM to pins J804 and J805 on the speaker protection circuit board (it has the large relay on it). Adjust resistor R809 for 35VDC reading on the DVM.

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)

On the amplifier board for that channel, Adjust R713, for 0 VDC.

Move the DVM leads to the Right channel Main speaker terminals and adjust R713 on the amplifier for that channel for 0 VDC

On the Left Channel, Connect a DVM between J702 and J708 on the power amp board.

Rotate R740 fully CCW and then Adjust R740 CW, for 15mVDC.

Repeat for other channel (J 702 and J708.) Reverify the output voltages and readjust R713 if necessary


Repeat after 30 minutes (after the amp has time to balance)

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 replace the lamps with white LED's and I replace the dial diffuser paper. This really brings back that original blue look and is quite striking. Email me if you are interested in this mod and I would be happy to provide you with the information on how you can do yours, too. And, since I have the test gear, I perform full AM and FM alignments since the tuners now have new parts and will need adjustment. Contact me regarding this service if you are interested. info@irebuildmarantz.com

Once you feel that the unit is all adjusted and ready to be put back into normal 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 ceramic 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!

~Rob

info@irebuildmarantz.com