Rebuilt the P-800 power supply all voltages are good, replaced all of the lights turn on the radio stereo light is on audio sounds good after a few minutes both channels sound garbled and volume drops radio signal is good so I turn off the power turn it back on the same thing happens again hooked up my cell phone through the auxiliary it does the same thing any help is appreciated
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Marantz 2325
- Thread starter Kevingray
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petehall347
the brandy coffee man
poor connection in the power supply
petehall347
the brandy coffee man
corroded fuse maybe or bad power switch
audiocrzy
Super Member
This is an example of what I’ve said many times before. Something I learned from AK
Let me repeat it.
Only address the initial problem before doing any rebuilds. In this case it was the power supply. The OP went to all the trouble to rebuild it and it didn’t resolve the problem. Now he still has to figure out what’s wrong. He may have isolated the power supply being the problem but maybe not.
That’s my 2 cents and I’m sticking to it.
Let me repeat it.
Only address the initial problem before doing any rebuilds. In this case it was the power supply. The OP went to all the trouble to rebuild it and it didn’t resolve the problem. Now he still has to figure out what’s wrong. He may have isolated the power supply being the problem but maybe not.
That’s my 2 cents and I’m sticking to it.
petehall347
the brandy coffee man
a good start would be closely look for bad connections .then monitor supply voltages whilst its working and whilsts its breaking down .
Both channels... hmmm. Do have schematic and scope and vom? Fading away into distortion and radio section remains working... thinking of power distribution and fading away into distortion, like failing voltage... I'd start checking the schematic for anything common to both channels in the power supply, on circuit board divider and filter... or use the scope and see if it will isolate to a board then look for something common to both channels. First thing I'd do is look at the schematic. Does the protection relay stay in or does it release... have signal at the tape out? A few quick checks with signal flow in mind can often eliminate whole sections as having the problem. Nice Marantz by the way.
audiocrzy
Super Member
I’m an ameteur too but what I said should apply to all repairs. A professional technician I use to deal with believed in it too.
That is the correct approach for the basic reason you don't want the possibility of creating a new problem which can make diagnosing more difficult. Other than that... and that's a big that... one can proceed any way they like if they intend to blanket rebuild an area anyway. Myself, I'd fix the problem first.
You do need the schematic, at least should have it available.... a bit of analysis with particulars of the problem in mind can take you to the most likely source of the problem for quick checks, the relay closing eliminates a lot. That should be fairly easy to find, the fading away into distortion problem.
I usually like to fix the problem, test to make sure (usually leaving a few screws out) then go for the rebuild. We all make dumb mistakes sometimes...
runningdog
Super Member
-Why the power supply?
You started with the power supply. Given your description of the issue, where both channels are breaking up after a few minutes of use, the power supply is a reasonable suspect. This is because it is the source of power for all of the circuit boards except for the main amplifiers. So an issue with it affects both channels. There are not many parts in common between the main amplifiers. They are powered by leads from the transformer, going through a rectifier, and then to each amp. So the transformer and the rectifier are the only parts in common between the main amplifiers.
-How to be sure
The main amplifiers, rectifier, transformer, the protection circuit, the relay, and the main/remote speaker switches can be tested and ruled out, just to be sure. There are two ways to use the Main In/Pre Out jacks to do this:
1. With the 2325 powered off, connect a music player to the Main In jacks. The music player can be a phone. It has to be something with a volume control, because the signal will be going straight to the main amplifiers, bypassing the volume control on the 2325. With the volume on the music player turned all the way down, turn on the 2325. After the relay clicks closed, slowly turn up the volume on the music player to a normal listening level. Then wait to see if the issue occurs.
2. Or you can use the Pre Out jacks to confirm the issue is before the main amplifiers. Connect the Pre Out jacks to the inputs on another receiver or amplifier. This way the other receiver is the main amplifier, and the 2325 is just a pre amp. Connect your source to the 2325, and speakers to the other receiver. Start with the volume control on the other receiver at about 12 o'clock, and slowly turn up the volume control on the 2325. Wait to see if the issue occurs.
The second test is more definitive, but either will serve.
-Back at the power supply
The power supply provides 35V, 19V, and 14V. This redrawn schematic for the power supply board shows everywhere the power is distributed (highlighted):
1. J805 (35V) supplies:
PH01 buffer amplifier
P400 phono amplifier
P300 MPX amplifier
PU01 FM muting
PE01 pre/tone amplifier
PT01 tape monitor
2. J806 (19V) supplies:
P600 Dolby amplifier
PL01 Dolby meter
3. J807 (14V) supplies:
The Mode switch, for power to the stereo lamp
The Selector switch, for power to selected AM and FM boards
Whew. That just saved hours studying the schematic. It also helps with where to focus on the power supply. Issues with 14V or 19V outputs are unlikely to affect the sound as described. That leaves the 35V output which obviously touches a lot.
-Where to go next (after doing the Main In/Pre Out jack tests)
1. Looking at the simplified schematic, the voltages are marked in red at the transistors H802, H803, and H804. Checking the voltages at those locations before and after the channels distort may prove useful.
2. Freeze spray on the three transistors, one at a time, or the rectifiers at H808/H809, may reveal a heat related issue with them. The suggestion that there is a connection failing on the board is also valid, and might be located with the use of freeze spray on the foil side of the board.
3. Were there any semiconductors in the parts you replaced on the power supply? Or just capacitors?
Many thanks to Tim Cartier for the redrawn schematic, and for documenting what every single lead connects to on a 2325. Including paths through the switches.
-Randy
You started with the power supply. Given your description of the issue, where both channels are breaking up after a few minutes of use, the power supply is a reasonable suspect. This is because it is the source of power for all of the circuit boards except for the main amplifiers. So an issue with it affects both channels. There are not many parts in common between the main amplifiers. They are powered by leads from the transformer, going through a rectifier, and then to each amp. So the transformer and the rectifier are the only parts in common between the main amplifiers.
-How to be sure
The main amplifiers, rectifier, transformer, the protection circuit, the relay, and the main/remote speaker switches can be tested and ruled out, just to be sure. There are two ways to use the Main In/Pre Out jacks to do this:
1. With the 2325 powered off, connect a music player to the Main In jacks. The music player can be a phone. It has to be something with a volume control, because the signal will be going straight to the main amplifiers, bypassing the volume control on the 2325. With the volume on the music player turned all the way down, turn on the 2325. After the relay clicks closed, slowly turn up the volume on the music player to a normal listening level. Then wait to see if the issue occurs.
2. Or you can use the Pre Out jacks to confirm the issue is before the main amplifiers. Connect the Pre Out jacks to the inputs on another receiver or amplifier. This way the other receiver is the main amplifier, and the 2325 is just a pre amp. Connect your source to the 2325, and speakers to the other receiver. Start with the volume control on the other receiver at about 12 o'clock, and slowly turn up the volume control on the 2325. Wait to see if the issue occurs.
The second test is more definitive, but either will serve.
-Back at the power supply
The power supply provides 35V, 19V, and 14V. This redrawn schematic for the power supply board shows everywhere the power is distributed (highlighted):
1. J805 (35V) supplies:
PH01 buffer amplifier
P400 phono amplifier
P300 MPX amplifier
PU01 FM muting
PE01 pre/tone amplifier
PT01 tape monitor
2. J806 (19V) supplies:
P600 Dolby amplifier
PL01 Dolby meter
3. J807 (14V) supplies:
The Mode switch, for power to the stereo lamp
The Selector switch, for power to selected AM and FM boards
Whew. That just saved hours studying the schematic. It also helps with where to focus on the power supply. Issues with 14V or 19V outputs are unlikely to affect the sound as described. That leaves the 35V output which obviously touches a lot.
-Where to go next (after doing the Main In/Pre Out jack tests)
1. Looking at the simplified schematic, the voltages are marked in red at the transistors H802, H803, and H804. Checking the voltages at those locations before and after the channels distort may prove useful.
2. Freeze spray on the three transistors, one at a time, or the rectifiers at H808/H809, may reveal a heat related issue with them. The suggestion that there is a connection failing on the board is also valid, and might be located with the use of freeze spray on the foil side of the board.
3. Were there any semiconductors in the parts you replaced on the power supply? Or just capacitors?
Many thanks to Tim Cartier for the redrawn schematic, and for documenting what every single lead connects to on a 2325. Including paths through the switches.
-Randy
Thanks randy this is exactly what I was looking for very much appreciated
Hi Randy I tested the main input with a player and it seems to be okay then I hooked up the preamp output to another receiver and the issue was still there after a minute or two the audio was garbled so I tested the voltages on the power supply in red and they are okay I also have 35 volts and 20 volts and 13.57
The corollary to this is when beginning a rebuild, and two working channels are involved, do only one channel, and prove it good before disassembling the second channel. If you mess something up, you have a correct one to reference when troubleshooting.
That's what's good about having stereo, two channels, usually one good for quick comparison.
runningdog
Super Member
You have successfully ruled out the issue being related to the main amplifiers, the relay, and the main/remote speaker switches.
It's not certain that the issue is in the power supply but it's worth pursuing it further. Do you have a signal generator and an oscilloscope? If not, here is another test to do.
Because it seems to happen after the receiver warms up, freeze spray may be a way to narrow the issue down to a specific transistor or diode. Here is one option for freeze spray, from mouser.com:
MG Chemicals Super Cold 134
Mfg number: 403A-285G
-Randy
All of the diodes and transistors and Caps and relay are all new on the main power supply (p-800) board I rebuilt it