https://audiokarma.org/forums/index.php?threads/starting-marantz-2325-rebuild.736819/
This thread is also helpful.
This thread is also helpful.
Starting my first 2325 Restoration and Looking for Guidance
- Thread starter richiem46
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- 2325 first marantz restoration
cemerson
Active Member
Do you have the part number and dimensions for your big blue Nichicon Capacitors?
I bought the 22,000 main caps from:
peace.love.music
on the big auction site. I don't have a part number. I believe they are 50MM in diameter. I have used other screw terminal caps in 2275's but the screw posts were not high enough to work in the 2325. Some folks flip the caoacitor bracket upside down so the ridge that normally faces downward faces upwards so as not to get in the way. That may work with the caps I used in the 2275 which were mouser number 661-E36D750N183TC79M.
The ones I used bolted right in in just a few minutes, a pleasure compared to the 2275 installs as I said earlier. Pricier but a real time and frustration saver!
peace.love.music
on the big auction site. I don't have a part number. I believe they are 50MM in diameter. I have used other screw terminal caps in 2275's but the screw posts were not high enough to work in the 2325. Some folks flip the caoacitor bracket upside down so the ridge that normally faces downward faces upwards so as not to get in the way. That may work with the caps I used in the 2275 which were mouser number 661-E36D750N183TC79M.
The ones I used bolted right in in just a few minutes, a pleasure compared to the 2275 installs as I said earlier. Pricier but a real time and frustration saver!
I received the transistors I needed to restore the PH01 Buffer board so I started working on it Thanksgiving Eve and finished it up last night after a Turkey-induced nap. The Ph01 board has wire-wrap terminals on both ends of it so to allow easier access I unsoldered the pins at one end and removed the ground lead on the other which was short and restricted access. Of course I took several photos before starting to facilitate properly connecting everything once I was done replacing all the components. The board is very dense with 10 transistors, 8 caps and one diode to be replaced. Several of the transistors (HH01-04 and HH05-08) have connections to an adjacent transistor or cap. As I removed each transistor and replaced it I soldered the center (collector) lead to hold it in place until all were in place along with the caps. After HH01 to HH08 and the adjacent 4.7 uf. electrolytic caps CH05-CH08 were in place I soldered the remaining connections after double checking all polarities. I was also able to adjust the transistors left to right before soldering to make sure they were straight.
I used WIMA .22 uf caps for CH01-CH04 as I had them on hand.
Here is a before picture of the PH01 board before:
And here is a picture of it after I re-installed it:
I tested the 2325 afterwards and I could hear a difference in the sound. It seemed more open to me with clearer highs. I will have to listen for a while to see how I feel about the sound after the refurbishment.
I used WIMA .22 uf caps for CH01-CH04 as I had them on hand.
Here is a before picture of the PH01 board before:
And here is a picture of it after I re-installed it:
I tested the 2325 afterwards and I could hear a difference in the sound. It seemed more open to me with clearer highs. I will have to listen for a while to see how I feel about the sound after the refurbishment.
Tonight I removed the tone board again to replace caps CE01 and CE02, 680 PF ceramics that other akr's suggested should be replaced. While I had the board out I removed the steel plate that is below it to better access the linear balance control that is below it for cleaning. The plate is held in place by four screws through the front panel. I de-oxed it as there was some static when I manipulated the balance control to the extreme left. The sequence of pictures below shows what I am referring to. The balance control worked well afterwards.
Plate below the pre-amp board.
Here is the linear balance control mounted on the front panel.
Here is the linear balance control after removing the two screws that secured it to the front panel. Much easier to clean now.
Plate below the pre-amp board.
Here is the linear balance control mounted on the front panel.
Here is the linear balance control after removing the two screws that secured it to the front panel. Much easier to clean now.
I decided to be optimistic and re-install the front panel and knobs tonight with the hope that I will no longer need to access the tone board going forward. I also felt better with it installed to prevent me inadvertently damaging the dial pointer which was relatively exposed during the restoration.
Have to say, the 2325 really cleaned up nicely!
Now I will tackle the P700 power amplifiers and then some final alignment.
Have to say, the 2325 really cleaned up nicely!
Now I will tackle the P700 power amplifiers and then some final alignment.
The P700 power amp board for the left channel was my next project. The left channel had some static on power-up which sounded like the sound generated by someone rubbing on a microphone. It was present for about a minute or so after a cold power-up and then faded. I confirmed (to my relief) that it was a P700 issue by swapping the power amps temporarily and the problem followed the p700.
I used the "complete" kit from peace.love which replaces all of the transistors on the board except the output transistors as well as a lot of the caps and the diodes including the two zener diodes.
First, I removed and tested the four output transistors to confirm they were ok. I cleaned them and the heat sink and re-installed them with new heat compound . I was surprised at how loose the mounting screws were on the power transistors. When I re-installed them I tightened them firmly but not excessively. The thermal compound on two of them had definitely seen better days and replacing it was a good idea definitely after 50 years.
Here is a picture of the heat sink afterwards.
I used the "complete" kit from peace.love which replaces all of the transistors on the board except the output transistors as well as a lot of the caps and the diodes including the two zener diodes.
First, I removed and tested the four output transistors to confirm they were ok. I cleaned them and the heat sink and re-installed them with new heat compound . I was surprised at how loose the mounting screws were on the power transistors. When I re-installed them I tightened them firmly but not excessively. The thermal compound on two of them had definitely seen better days and replacing it was a good idea definitely after 50 years.
Here is a picture of the heat sink afterwards.
Here is a picture of the P700 circuit board after I did the restoration.
C701 was replaced with a 1.0uf Panasonic cap from the kit. C703 was replaced with a 33uf audio grade electrolytic from the kit. C706 and C707 were replaced with 10uf 50V caps from the kit. I also replaced C702, C710 and C713 with 100pf Wima caps as they were called out in other threads. I replaced the 0.1 Film caps C708, C709, C714 and C721 as folks on Audiokarma advise that the grey films can be problem-prone.
Diodes H718, H719, H720 and H721 were replaced with 1N4148 glass diodes from the kit. The two Zener diodes H716 and H717 were replaced with two 20V 2W Zener diodes from the kit.
1.2K 2W Resistors R719 and R720 were replace with 1 .2K 3W resistors from the kit.
Transistors H701, H702, H703, H711 and H712 were all replaced with KSA992 transistors from the kit. H701/H702 are the differential pair which I matched and coupled together with a dab of heat sink compound between then, using heat shrink tubing to keep them in place.
H704 was replaced with a KSA1013 from the kit. H705,H710 and H713 were replaced with KSC2383's from the kit. The circuit traces for several of the transistors are very close together so a lot of care and a fine-tipped soldering pencil are a must.
H708 was replaced with a MJE15032G and H709 was replaced with a MJE15033G. These are mounted on heat sinks but no mica insulator is used as the heat sink, other than being connected to the collector, is electrically isolated.
H715 which is under the bracket connecting the aluminum heat sink to the circuit board was replaced with a MJE243G from the kit.
H706 is replaced with a KSA1318 and H707 is replaced with a KSC3503, both from the kit. Both of these new transistors are ECB while the transistors they replace are EBC. The good news is that the new transistors are not metal-backed so you do not need the mica insulators. The bad news is that they are thicker than the ones they are replacing so the mounting hardware screw is too short to secure the dual heat sink to the circuit board. I went to the hardware store and bought a screw that was 1/4 in longer than the factory screw. The thread pitch was different so I bought nuts and lock washers to go with the new screws and mounted the two new transistors on the heat sink with the new screws and the first nut after bending the leads to match the old ones. I bent the center lead a little bit closer to the transistor body to facilitate tucking it over to the "C" hole on the board around the third lead which, in turn, is crossed over to the "B" hole. This must be done for both new transistors and yes, it is a PIA for sure but I found by pre-mounting the two new transistors and bending the center lead a little closer to the transistor it was manageable. Use a piece of clear insulating tubing on the center lead trimmed to fit to prevent the crossed leads from shorting out. The tubing is supplied with the kit. Don't forget to get the heat sink orientated the right way as it goes in either way so the proper replacement transistor is installed in the proper position. You do not want to have to undo things and then do it all again.........What could be easier!!!!
To add to the fun, while you have the dual heat sink out be sure and replace H714 that is under it with a MJE243G supplied with the kit.
The kit also contains replacement fly back diodes which I will install after testing the board in the 2325.
I de-oxed the two trimmer pots and then installed the board back in the 2325 after closely reviewing all the components I installed to be sure the polarities were correct.
C701 was replaced with a 1.0uf Panasonic cap from the kit. C703 was replaced with a 33uf audio grade electrolytic from the kit. C706 and C707 were replaced with 10uf 50V caps from the kit. I also replaced C702, C710 and C713 with 100pf Wima caps as they were called out in other threads. I replaced the 0.1 Film caps C708, C709, C714 and C721 as folks on Audiokarma advise that the grey films can be problem-prone.
Diodes H718, H719, H720 and H721 were replaced with 1N4148 glass diodes from the kit. The two Zener diodes H716 and H717 were replaced with two 20V 2W Zener diodes from the kit.
1.2K 2W Resistors R719 and R720 were replace with 1 .2K 3W resistors from the kit.
Transistors H701, H702, H703, H711 and H712 were all replaced with KSA992 transistors from the kit. H701/H702 are the differential pair which I matched and coupled together with a dab of heat sink compound between then, using heat shrink tubing to keep them in place.
H704 was replaced with a KSA1013 from the kit. H705,H710 and H713 were replaced with KSC2383's from the kit. The circuit traces for several of the transistors are very close together so a lot of care and a fine-tipped soldering pencil are a must.
H708 was replaced with a MJE15032G and H709 was replaced with a MJE15033G. These are mounted on heat sinks but no mica insulator is used as the heat sink, other than being connected to the collector, is electrically isolated.
H715 which is under the bracket connecting the aluminum heat sink to the circuit board was replaced with a MJE243G from the kit.
H706 is replaced with a KSA1318 and H707 is replaced with a KSC3503, both from the kit. Both of these new transistors are ECB while the transistors they replace are EBC. The good news is that the new transistors are not metal-backed so you do not need the mica insulators. The bad news is that they are thicker than the ones they are replacing so the mounting hardware screw is too short to secure the dual heat sink to the circuit board. I went to the hardware store and bought a screw that was 1/4 in longer than the factory screw. The thread pitch was different so I bought nuts and lock washers to go with the new screws and mounted the two new transistors on the heat sink with the new screws and the first nut after bending the leads to match the old ones. I bent the center lead a little bit closer to the transistor body to facilitate tucking it over to the "C" hole on the board around the third lead which, in turn, is crossed over to the "B" hole. This must be done for both new transistors and yes, it is a PIA for sure but I found by pre-mounting the two new transistors and bending the center lead a little closer to the transistor it was manageable. Use a piece of clear insulating tubing on the center lead trimmed to fit to prevent the crossed leads from shorting out. The tubing is supplied with the kit. Don't forget to get the heat sink orientated the right way as it goes in either way so the proper replacement transistor is installed in the proper position. You do not want to have to undo things and then do it all again.........What could be easier!!!!
To add to the fun, while you have the dual heat sink out be sure and replace H714 that is under it with a MJE243G supplied with the kit.
The kit also contains replacement fly back diodes which I will install after testing the board in the 2325.
I de-oxed the two trimmer pots and then installed the board back in the 2325 after closely reviewing all the components I installed to be sure the polarities were correct.
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I powered up the 2325 with a variac and at around 70V it came out of protection so I plugged it in to the main with test speakers attached and the left channel played well. I let it warm up for about 15 minutes and then set the idle current and DC offset without issue. The next day I powered it on and confirmed there was no scratchiness on power-up. After 15 minutes I checked the idle current and it was exactly 15mv.
Needless to say, I am quite pleased with how things worked out but I have to say this P700 board restoration was quite challenging.
Initially I thought that I would just do the basics on the right P700 board but now that I know what I am dealing with I will probably do the full upgrade on the right channel as well to maintain symmetry, hopefully I won't regret my decision. It is for the best as a lot of the heat sink compound on the board-mounted heat sink transistors was pretty much gone on the left P700 so the right channel should be tended to as well.
Needless to say, I am quite pleased with how things worked out but I have to say this P700 board restoration was quite challenging.
Initially I thought that I would just do the basics on the right P700 board but now that I know what I am dealing with I will probably do the full upgrade on the right channel as well to maintain symmetry, hopefully I won't regret my decision. It is for the best as a lot of the heat sink compound on the board-mounted heat sink transistors was pretty much gone on the left P700 so the right channel should be tended to as well.
I Restored the Right P700 board yesterday and installed it in the 2325. I used the same procedure as I did on the first board which is described in a previous post. I am pleased to say the second board is working well, idle current and DC offset dialed right in after a 15 minute warm-up and are stable. I had a bit of trouble with H706-H707 install. The circuit traces are very close together and one looked suspect after I soldered them in. I checked with an ohm meter and the BC leads showed a short. I confirmed that the crossed leads were not the issue and then cleaned the board connections with a solder puller. There was a fine strand of solder between the two leads which I was able to remove, re-soldered the connections and they then measured normally. I use a bright light and a magnifier to inspect close together connections and in this case my caution saved me some heartache for sure.
Next I install the fly back diodes and align the phono board before final testing.
Next I install the fly back diodes and align the phono board before final testing.
I installed the fly-back diodes on both P700 boards tonight. I also replaced caps C719/C720. They appear in the parts list and on the P700 board drawing in the service manual but not in the schematic that I could find. They are .033 grey film caps so for sake of completeness I replaced them on both P700 boards. I photo of one of the boards is shown below. I installed both P700 boards in the 2325 and played it for several hours and then touched up the bias and idle current adjustments and called it an evening.
I personally see no reason to replace the drivers and pre-drivers on these boards unless they were defective. And I do have NOS originals when that time comes.
I do not disagree with your sentiment regarding the pre-drivers. On this 2325 one of the P700 boards was the source of some noise in the left channel speaker. It looked like it had been worked on long ago though the components on it were OEM replacements. Given the history and the noise issue I erred on the side of caution and rebuilt the board completely. Given that I had the parts and like to maintain symmetry in the channels of a given unit, I re-built the second P700 board. I usually only do the "usual suspect" components on the P700 boards unless there are issues with a given board.
Today I performed the Phono Board alignment per the Maintenance Manual. Both channels are working well and I am attaching a scope trace of the Left and Right channels below. The trace is from just before the point where clipping started. I aligned both channels so they both begin to clip at the same point at 1KHZ per the manual. I will now re-install the 2325 in the wood cabinet which will give me my exercise for the day!
I finished installing the 2325 in the wood case. I applied a coat of furniture polish to the case and it looks pretty nice though there are some significant blemishes on the left rear corner. Overall I am extremely pleased with how it came out!
icko30
Super Member
You can get some artistic acrylic paint and a fine brush in some art shop and repair worn out edges and that little damage from the back. It should cost you a few bucks and result could be perfect regardless of the fact that the damage hole will still remain.
BTW Well done. She just looks like a big momma to my 2275. Top.
BTW Well done. She just looks like a big momma to my 2275. Top.