Starting my first 2325 Restoration and Looking for Guidance (2024)

I just acquired a decent 2325 on the big auction site with the wood case. I received it several days ago and my first reaction was I could not believe how heavy the thing was! Even after removing the heavy wood case it is still a beast to move around the bench.

The seller said the unit worked and it does initially but after about 10 minutes the right channel quits and the left is weak and has static. If I power it off and then back on it plays again but just briefly. I am attaching a few of the seller's photos. The case is decent with some dings but it is serviceable and the faceplate other that needing a good cleaning is good.

I opened the amp up and it looks like the Power supply board was removed, worked on and then re-installed. The relay looks like it was replaced but the wrong one was installed an my4-02-us-dc24 which is a 3 amp relay. It is hard to determine what else has been done to the power board but my first order of business is to completely rebuild it and the main power caps to ensure the power supply is stable.

Last evening I replaced the two main caps with two 22,000 MF. 100V Nichicon Caps. I have restored four Marantz 2275's and replacing the main caps in them is quite a project. In the 2325 the old caps used screw connections and I just unscrewed them, slid them out of their brackets and slid in the new caps being careful to maintain polarity. I re-attached all the leads where they were previously tightened everything up and was finished. What a pleasure compared to the same procedure in the 2275. I spent way more time cleaning the chassis while the caps were removed than in the actual install.

Tonight I will start re-building the power board.

I have read many of the previous restoration threads on the 2325 and appreciate the shared knowledge of all who have come before me. In one of LeeStereo's posts I read some great information on the P700 main power amp boards in the 2325. Looking at the two from my unit it looks like I have some early models of the boards. They do not have flyback diodes installed and several of the capacitors C708, C709, C714, C719, C720 and C721 are the old "Grey" caps that pretty much everyone agrees should always be replaced. I attached an annotated picture below.

It looks like the P700 boards are original but am not sure if the power transistors have been touched. The white heat sink compound looks odd to me. I would appreciate it if some of you who are more familiar with the 2325 would look at the pictures and give me their opinion as to whether the power transistors are original or maybe replacements that potentially could be fakes. They do not have "Marantz" stamped on them but I know that is not definitive in determining their authenticity.

Thanks for any and all suggestions and comments in advance.

richiem46 said:

I have read many of the previous restoration threads on the 2325 and appreciate the shared knowledge of all who have come before me. In one of LeeStereo's posts I read some great information on the P700 main power amp boards in the 2325. Looking at the two from my unit it looks like I have some early models of the boards. They do not have flyback diodes installed and several of the capacitors C708, C709, C714, C719, C720 and C721 are the old "Grey" caps that pretty much everyone agrees should always be replaced. I attached an annotated picture below.

It looks like the P700 boards are original but am not sure if the power transistors have been touched. The white heat sink compound looks odd to me. I would appreciate it if some of you who are more familiar with the 2325 would look at the pictures and give me their opinion as to whether the power transistors are original or maybe replacements that potentially could be fakes. They do not have "Marantz" stamped on them but I know that is not definitive in determining their authenticity.

Thanks for any and all suggestions and comments in advance.

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See Also

Marantz 2325 Receivers user reviews : 4.8 out of 5 - 25 reviews - audioreview.comMarantz 2325 | Classic ReceiversMarantz 2325 Stereophonic Receiver ManualMarantz 2325 Vintage "Stereophonic Receiver" - Full SkyFi Restoration

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Original as they come. It looks the boards were never worked on and the diff pair is missing some shrink tubing to keep them together. The compound looks dried out, not unusual. The 2325 is a pleasure to work on.

My favorite 2325 rebuild tip:

I find it much easier to work on the receiver with the main amps taken out.

Removing both amplifiers reduces the weight of the 2325 and gives you a pair of convenient handles to wrestle it around with. I do most of a 2325 rebuild with the amps out. I still test after each board is rebuilt by connecting the receiver Pre Out jacks to a 1060 integrated amplifier that is by my bench. And it's easy to pop the amps back in and out as needed.

runningdog said:

My favorite 2325 rebuild tip:

I find it much easier to work on the receiver with the main amps taken out.

Removing both amplifiers reduces the weight of the 2325 and gives you a pair of convenient handles to wrestle it around with. I do most of a 2325 rebuild with the amps out. I still test after each board is rebuilt by connecting the receiver Pre Out jacks to a 1060 integrated amplifier that is by my bench. And it's easy to pop the amps back in and out as needed.

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Good tip! I have both Power amps removed and it helps with moving it around for sure as well as access to the main power caps and the power board.

I was up until late last night working on the power board in the 2325. I replaced all the caps, diodes, transistors and the 150 ohm resistor. It all went relatively smoothly until I went to replace the relay. The power board had been previously worked on by someone and they had installed the wrong relay on the board. It was a my4-02-us-dc24 which is a 3 amp 4 pole relay which did not even closely fit the board. To make it "fit" some heavy-gage solid copper wire was used to fashion new connections to match the board perforations. The wire was bent over on the back of the board making de-soldering and removal quite a chore. It took me almost an hour to finally remove the old relay without doing too much damage to the foil on the board. I am amazed that in such a high-end receiver the repair technician did not obtain the proper relay that would fit the board. OK, end of my complaining, just glad the rest of the 2325 is (hopefully) is all original. On the good news front, cap C805 a 470UF 16V unit was completely blown, split seam on the bottom which could explain the 2325's issues I mentioned earlier.

I will install the new relay today and perform some initial testing to see where things stand with the restored power supply components installed.

Here is a picture of the old relay I removed on the left and the proper replacement on the right.

I installed the new relay this morning and re-installed the P700 power amps in the 2325 and performed some testing. The good news is that the new board and relay work perfectly and I dialed in the DC voltage to 35V per the manual. The even better news is that the amp plays more consistently now. The right channel now cuts out but by moving the Tone Mode switch I can get both channels to play strong. I have seen this same symptom on two of the 2275's I have restored and once I restored and cleaned the Pe01 Tone amp board and it's associated switch and pots they played well. I am confident that since the tone board in the 2325 is the same once I restore it the amp should play well.

I will now remove the PE01 board and also do some cosmetic work on the dial panel, replace the lights, vellum etc. since to access the PE01 board you have to remove the front panel.

I am very pleased with things so far.

Last night I removed the front panel and PE01 tone board from the 2325. The PE01 board is different than the one in the 2275 as it contains the volume control in addition to the tone circuitry but is familiar territory for me. The caps that were blue in the 2275 board are red but otherwise familiar. I will replace them along with others that are recommended as well as all of the transistors. I will also replace the two BA312 IC's with custom replacements built from discrete components.

I replaced all of the dial and indicator lights, fortunately the lamp housing, while yellowed, is structurally ok. I attached a picture of it after the bulb replacement. Replacing the tiny indicator lights was a comparative breeze on the 2325 compared to the 2275. The board holding the lamps came out easily and there was enough slack in the wiring harness to make it relatively easy to manipulate it to de-solder and re-solder the new lamps. That was mot the case with the 2275......

But before I start on the board I plan on breaking out the Krud Kutter and cleaning the face panel and knobs and clean and re-vellum the dial. I would like to re-vellum the meters also but based on some of the things I read removing them can be quite an undertaking. I will have to research that a bit more before proceeding.

Here are some photos of how things stand currently.

Krud Kutter works great!

Here are the BA312 replacements assembled and ready to install.

I started work on the pre-amp board last evening and got about half-way through. Not sure what it means but the board has multi-color coded caps in place of the "Blue Blobs" that are normally on these boards. Today I will finish replacing the caps, replace the four transistors and replace the BA312's. There are many threads in the Marantz forum about sizzles, crackling and other forms of distortion that end up being caused by failure of components on this board. Replacing the possible offenders seems prudent given this history while I have it out and on the bench.

I completed the work on the pre-amp board this afternoon and re-installed it in the 2325 for a test. I am pleased to report that it is working well, the amp is sonically much improved though there was some crackling initially when I advanced the volume control to a moderately loud level. The crackling did not occur once the amp was on for about 10 minutes. I am not sure if it is the volume pot or something else so I will have to determine what is causing the crackling.

The new lights look good behind the new vellum and cleaned dial, I am pleased with how the amp is looking and sounding so far.

I am looking to work on the PH01 Buffer board next.
I plan on using the following transistors:
HH01-04 2SC1345 Using KSC1845FTA as sub KSC1815 is on Back order on Mouser
HH05-08 2SA720 Using KSA1013
HH09-10 2SC1318 Using KSC2383TYA
VD1222 Two 1N1418 diodes in series.

The caps are pretty straightforward.

The transistor substitutions match the Marantz substitution spreadsheet except for KSC1845 for HH01-04 which is kind of a second choice.

Have to place a mouser order so it will be a few days.

richiem46 said:

KSC1815 is on Back order on Mouser

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peace.love.music has those if you need them
He's safe to use. Well-known on here too.

richiem46 said:

Krud Kutter works great!

View attachment 2714927

Here are the BA312 replacements assembled and ready to install.

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Hi Richiem do you have create a part list that i can use ? im starting a 2325 rebuilt too. It would be very helpfull if you have it. Thx!

pat2330b said:

Hi Richiem do you have create a part list that i can use ? im starting a 2325 rebuilt too. It would be very helpfull if you have it. Thx!

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I ordered the rebuild kits from peace.love.music on the bay for the Phono, Pre-amp, Power amps(2) and the power supply board. He also has the 22,000 MF power supply caps which I used as well as the lighting kit to replace the dial and indicator lamps. You will have to inspect the power supply board to determine which relay you need to order as there are two possibilities. The power amp rebuild kits are complete except for the output transistors. You do not necessarily have to replace the heat-sinked transistors on the P700 board but I probably will. Based upon the threads I have read the transistors in the kit match the ones that give the best results when setting the 15MV bias. I did a couple of P700 boards on 2275's and depending on which transistors are used the bias setting can be affected.

The Ba312 replacement boards were a gift from an AK'r. I hesitate to provide contact info as I do not want to presume to do so. I have also used this replacement:

Which I got on the bay. Just search for BA312 in the bay and you will find it. They are $18 each plus shipping. I generally just replace the BA312's weather they are good or bad when I restore the Tone board for sake of completeness as the kit of parts replaces all of the other transistors on the board and the Ba312 can cause issues going forward. This unit installed easily and worked well.

Let me know if I can help you further, I will be glad to do so.

Rich