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Calling all Marantz Phono (P700) Board Experts

gregmcm

gregmcm

Active Member
Have a 2270 that developed some slight noise in the right channel when either Photo 1/2 selected with or without a turntable connected. All other inputs perfectly quiet. Research suggested the 2SC458's known to be problematic so I pulled these and replaced them with KSC1845's. Also replaced the C713 cap.

Fired the unit up and no noise in the right channel. Do a test with a turntable and all good. I then reinstall the 2270, connect a Marantz 6300 turntable and everything is fine until the arm reaches the end of the record and the automatic shut off kicks in at which point I get a sudden loud sharp noise out of the right speaker that lasted a second or two.
Needless to say I was surprised and turned off the turntable. Checked the right channel Phono 1/2 again to find that the noise in the right channel had returned.

At this point I tried the turntable again, turned the volume to low and allowed the auto shut off to engage and once again got the sudden sharp noise out of the right speaker for a second or two. I would add that the lower volume setting lowered the noise level.

Anyone have some suggestions on what is happening and how to address the issue.

Note:
- prior to replacing the 2SC458's there were no issues when the auto shut off engaged. This leads me to suspect the KSC1845's or some other component affected by these transistors.
- the KSC1845's are installed correctly as per their pin out.
 
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Hi gregmcm, I have recently just finished up restoration of my 2230 which also has the P700 phono board.

Besides the transistors and cap C713, have you replaced anything else? The small red "bead" like diodes with a green dot at H707, H708 & H709 are also known "problem children"
They are 1S1212 (H707 & H708) and VD1212 (H709)

They can be replaced with the following:-

H707 1S1212 512-1N4148
H708 1S1212 512-1N4148
H709 VD1212 512-1N4148 (x2 in series)

This would be the next thing I'd repace if your previous work checks out fine. Just my two cents... :)
Hope this is of some help!
 
Sounds like a grounding issue if it buzzes during automatic shut-off, since these are two separate systems, but you may have two issues.

Flip your turntable inputs, to confirm that the turntable isn't inducing noise into your amp.
Did you pull pins out when you worked on it, and if so, Are you sure your pins are all soldered in good.
2SC1845 are ECB and 2SC458 Are BCE.
Make sure the c413 cap is oriented correctly, as the ground on the axial is toward the center of the board and if switching to a radial, the + marked hole on the board is really the negative of the cap.
There are tantilums @ c701/c702 you can use a 1uf film, polypropylene Panasonic, or? instead.

C703/704 use 22uf 6.3 use something like a 555-RFS10V220ME3#5 or a bi-polar.
Someone correct me if i am wrong, but the 2275 upgrades these caps to 35v 47uf nichicon bipolars. I am not sure if that can be done on the 2270 units.

As aforementioned, h707/708, use 1n4148
714/715 are your output caps. A polypropylene film would good here.

Did you try flipping your plug or running the turntable off another circuit?

I would guess that you cleaned the aux main connectors and sprayed your switches good.

Last but not least, Check your r410/411 trim voltages. Somewhere in my info i had found a way to do this without a scope.
i'll see if i can find that info
 
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All good suggestions. Going to check my work, change out the diodes and caps and see what results. Stay tuned. :)
 
Here is that info on adjusting the board and other good stuff. Even though i believe the 2325 p400 board is close or the same as the 2270 p700 board, This info should be verified First.

Thanks to Tom (Catrafter) for this info:
Tom said,
"If you are talking about setting the clipping level as indicated in section 20.5 of the service manual, it is just a whole lot easier to set the collector of H405 to about 17VDC with R408 and the collector of H406 to about 17VDC with R409.
More information about phono preamp updates can be found here. Note that the Phono preamp reference designator is P400 in a 2325."

This is Toms post(#6) from the "Here" thread above:
My 2230 factory service manual doesn't have any service bulletins with it, if someone has them, I'd really like a copy.
From my experience with other Marantz models that have commonality with the 2230 and from what I have learned from other knowledgeable techs both here on AK and in the field, I perform the following updates.
Replace the 2SC458 transistors (H705 and H706) on the Phono preamp board with 2SC2240BL or KSC1845 types. The originals fail noisy with age.
If H709 looks like an epoxy bead, replace it with 2 1N4448 diodes in series.
If H707 and 708 look the same as H709 replace them with ONE 1N4448 each.
I like to replace C713 with a 220uF/50V Panasonic EEU-FC1H221 part to improve local filtering, watch the polarity on this, some boards are marked wrong.
If the input and output coupling caps (C701, C702) are electrolytic types, replace them with 1uF/250V film types, Panasonic ECQ-E2105KF.
If they and the output coupling caps are .47uF, you might gain a few Hz on the bottom end if you change them to 1uF/250V types like the later models have.
The 2230 Phono preamp has a reference designator of P700. Most other models designate it as P400, but the same updates apply.

In the models that use this (or similar) tone/preamps and based on my client's wishes, I perform these upgrades.
I replace C401, C402 with Panasonic ECQ-V1H224JL and if there are caps installed in place of R418 and R419, use Panasonic ECQ-E2474KF, these are smaller and just look better.
For the electrolytics that I can source small enough film caps to fit the board, I use these:
C416, C417 Panasonic ECQ-V1H474JL
C404, C405, C414, C415 Panasonic ECQ-V1H105JL
C407, C408, C410, C411 WIMA MKS2-3.3/50/10

The main filter capacitor and output coupling capacitors can be increased to about twice the original capacity and bypassed with a small film cap such as a 2.2uF/250V Panasonic ECQ-E2225KF. This will cause longer run-down on power off and a bit more speaker pop on turn on, however.
 
Looks like success. Replaced the following - C701/702 and C714/715 mylar caps, C703/704 caps, H707/708 diodes with 1N4148 and H709 with two 1N4148's in series. Tested and both channels dead quiet. Plugged in the turntable and tested if I was getting and noise when the auto shut off engaged and nothing unusual. Testing the original components and the C703/704 were way out of spec. Been running for a couple of hours and working perfectly.
 
gregmcm said:
Looks like success. Replaced the following - C701/702 and C714/715 mylar caps, C703/704 caps, H707/708 diodes with 1N4148 and H709 with two 1N4148's in series. Tested and both channels dead quiet. Plugged in the turntable and tested if I was getting and noise when the auto shut off engaged and nothing unusual. Testing the original components and the C703/704 were way out of spec. Been running for a couple of hours and working perfectly.
Click to expand...


There ya go :thumbsup: Glad you got it back to spec. Enjoy :music:
 
I took a different route. I rebuilt my P400 (Marantz 2325) using surface mount transistors which more closely matched the spec's of the original transistors. I used BC849C with a Surfboards 33003 adapter from Digikey. I have only tested for basic operation during the rebuild because I'm in a small apartment with only small set of test speakers (not my Klipsch Chorus II's). But once we are in our house I'll be able to do a definitive test. The spec's of the KSC1815 suggested above is a much better solution and easier to implement than mine. Wish I had found these before I settled on the BC849C's. Next Time. I'll report back on testing after the new year.
 

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gregmcm said:
Looks like success. Replaced the following - C701/702 and C714/715 mylar caps, C703/704 caps, H707/708 diodes with 1N4148 and H709 with two 1N4148's in series. Tested and both channels dead quiet. Plugged in the turntable and tested if I was getting and noise when the auto shut off engaged and nothing unusual. Testing the original components and the C703/704 were way out of spec. Been running for a couple of hours and working perfectly.
Click to expand...

What are these 1N4148 diodes rated at? Would 100v suffice?
 
dukeofurl said:
Old thread, I know, just to report:
I had the hum issue after rebuilding the P700 board.
I attached the bottom cover and now the hum is gone! - Something to consider before running down the rabbit hole.
Click to expand...

I'm glad I found this thread/post before going down that rabbit hole... Thanks!

Most of my experience is on Pioneer units of this age. Not familiar with common issues on Marantz.
(And I absolutely HATE trying to follow signals from board to board on a Marantz schematic. Pioneer schematics are a lot easier to follow.)
After recapping this 2325 everything worked fine except for a slight hum on phono.
I would have wasted a lot of time looking for the source of the problem if I hadn't found this post.
It's now nice and quiet with the bottom cover in place.
 
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