All I have on hand is deoxit, will that work alright?
Yet another Marantz 2325 restoration thread
- Thread starter goldswimmerb
- Start date
All I have on hand is deoxit, will that work alright?
Steven Tate
CEO Flat Forehead Soc.
The tone board is not the board that gives everyone nightmares. That would be the PU01 Blending Board buried somewhere behind the dial and above the tone board. I partially disassembled the chassis to get it out. But I think AK member Runningdog had an easier method of getting it out. It’s small and only has a few caps, but I think it is in the signal path all the time, so it’s a potential noisemaker.
I may leave out PU01 just because it doesn't look like there's really much on it that can cause trouble. Are you sure it's in the signal path at all times? That seems like a flaw on Marantz end if so...
kaplang
Works for me !
Steven Tate
CEO Flat Forehead Soc.
I'm not an expert on it, so I'm not sure. Maybe someone who knows will chime in. I'm pretty sure the Dolby board is in the path at all times, as I think a lot of the control boards are. I guess its hard to bypass a board that potentially affects the signal in any way.
catrafter
Marantz Specialist
Many of the switches on the PU01 board are in the signal path as are the pre-out buffer amps (consisting of the circuitry involving HU5,6,7 and 8). I use film caps for CU16 and CU17.
I don't think the Dolby processor is in use when the Dolby switch is off, but I've been wrong before.
Tom
I don't think the Dolby processor is in use when the Dolby switch is off, but I've been wrong before.
Tom
The PU01 board isn't that hard to do while undergoing a full restoration.
You have to loosen up the front chassis which makes doing the meter vellum and the P300 board a piece of cake at the same time along with making all the push button switches easily accessible to clean/deox.
Bob
You have to loosen up the front chassis which makes doing the meter vellum and the P300 board a piece of cake at the same time along with making all the push button switches easily accessible to clean/deox.
Bob
Hey, so I'm working on adjusting the bias on one of my channels, when the amp is cold (right after start up) the bias is 20mv or so, then as the amplifier warms up it drops down gradually. (I was messing with it last night, let the amp run for a good 40 minutes then set it in at 15mv) So I should probably just let it warm up then adjust it right? Even with the pots all the way to the right, when the amplifier is cold I cannot dial in 15mv as that would require further turning.
catrafter
Marantz Specialist
In a perfect world, the bias would 'track' the amp module temperature exactly.
This is generally not the case, sometimes the 'bias' rises with temperature, sometimes it falls.
I would let the amp idle (volume at zero) for 20 or 30 minutes and then set it to spec.
Tom
This is generally not the case, sometimes the 'bias' rises with temperature, sometimes it falls.
I would let the amp idle (volume at zero) for 20 or 30 minutes and then set it to spec.
Tom
So I've recapped the amp boards and replaced the diodes and transistors done in Stevens rebuild.
A few questions now, would it be a bad idea to swap out the film caps on the amplifer with WIMA films?
I also went ahead and did the buffer amp board capacitors (being lazy and waiting to do the transistors).
But the big issue while improved, is still there, immediately after the protection relay switches the amp emits a sort of low rumble/hiss from the speakers, which quickly goes away, any ideas what could be the culprit? I would guess it has to be something on the amp board since it's not affected by volume but I don't know if any of those transistors on there are known to go noisy.
A few questions now, would it be a bad idea to swap out the film caps on the amplifer with WIMA films?
I also went ahead and did the buffer amp board capacitors (being lazy and waiting to do the transistors).
But the big issue while improved, is still there, immediately after the protection relay switches the amp emits a sort of low rumble/hiss from the speakers, which quickly goes away, any ideas what could be the culprit? I would guess it has to be something on the amp board since it's not affected by volume but I don't know if any of those transistors on there are known to go noisy.
catrafter
Marantz Specialist
How long is the delay from when you turn it on (cold) until the relay closes?
It is possible that the amps haven't settled down before the relay closes.
R816 and C813 control the delay, the diff pair transistors (H701 and H702) usually control the amp settle time.
Tom
It is possible that the amps haven't settled down before the relay closes.
R816 and C813 control the delay, the diff pair transistors (H701 and H702) usually control the amp settle time.
Tom
Not completely certain but it's probably 5-10 seconds, from the way measurements look (DC offset, bias) it looks like the relay is opening before the amplifiers have settled down. Any ideas what would cause that? I've already replaced the differential pair with a matched set, as well as H703. Whld had send me matched pairs with the faceplate I bought off of him
Just checked, relay is switching approximately 5 seconds after startup. Then the low rumble runs for a good 10s before calming down
catrafter
Marantz Specialist
5 sec is about right.
To be sure it's in the amps and not in the pre amp, plug 'something' into the main-in jacks to isolate the amp sections, if the noise is still present I wonder if it could be in the constant current source for the diff pairs (H703 and it's associated circuitry) or in the dual zener regulators (H716,H717 and their associated circuitry). It is odd that you hear it in both speakers which would mean both amps have the same issue.
If it is in the pre amp section, I would look at the P800 power supply board, perhaps something in the +35VDC power source (backwards cap?).
Tom
To be sure it's in the amps and not in the pre amp, plug 'something' into the main-in jacks to isolate the amp sections, if the noise is still present I wonder if it could be in the constant current source for the diff pairs (H703 and it's associated circuitry) or in the dual zener regulators (H716,H717 and their associated circuitry). It is odd that you hear it in both speakers which would mean both amps have the same issue.
If it is in the pre amp section, I would look at the P800 power supply board, perhaps something in the +35VDC power source (backwards cap?).
Tom
Thanks, will take a look when I get the chance.
Also, would I be worth it to swap the silver film capacitors in the phono amplifier out for some newer WIMA films, or even some NOS PIO capacitors? I'm just trying to go all out on this recap.
Okay so an update, it appears to just be in the right channel, and in the preamp stage. Any ideas of where to check? I did have some issues with the RCA cable internally where it wasn't making proper contact, but I don't think that could be it. This definitely sounds like a transistor...
It also seems to go away only if there's a source plugged in, with no source the noise keeps happening.
And
If I poke PH01 it seems to get worse, I replaced the transistors as per Stevens guide, so maybe one of the original ones has gone noisy?
Alright, last update on this I think, I reattached the metal bracket that secures the tone board to the chassis and it seems to have gone away...
Update again, never mind, that just helped it... Any ideas?
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