Marantz 2275 Recap & more

[Golanr]

A few weeks ago I completed a recap (and much more) of a Sansui G-9000DB, following an issue with the left Channel. http://audiokarma.org/forums/index.php?threads/g-9000db-distorted-sound-on-left-channel.810653/

I've decided that it's time for a recap of my 2275. I plan on documenting this here.

Started with taking it apart and updating P800 (Power Supply)
I replaced all Electrolytes with Nichicon caps, Rectifiers, R807 Resistor & Relay.
DC voltage easily adjusted to 35V



Any ideas about H801 and H804 transistors? should I replace them? I have enough MJE15030G for the job.

Tomorrow I plan to complete P400 (Phono stage) and at least one of the P700. (Power Amp) Will post photos when I'm done. I welcome all input and advice from the forum

 

[wlhd1610]

Yes , I would.
Don’t forget about those old nasty cracked rubber tuner isolation grommets!

Bob

 

[Jailtime]

Those 2SD331 on the power supply are junk, do replace them.

I like working on 2275s, all the modular boards are great, just pull and rework on the bench.

 

[Golanr]

Yes , I would.
Don’t forget about those old nasty cracked rubber tuner isolation grommets!

Bob

Thank you Bob and Jailtime both have been replaced. Time to go to bed...Will continue in the morning. BTW, can I turn the 2275 on without one P700? I want to test the changes I just did to the P800 but I already have one P700 out. Will it work one channel only?

 

[Golanr]

Right P700 is complete.
Replaced all the Electrolytes, H715, H716 15v Zeners, H701,702 dual transistors and made sure to put a shrink wrap around to keep them at the same temperature, and H703 Transistor.
I also replaced C701 With Wima Cap and changed the trimmers to 25 turns Bourns.



Any Recommendations as to H711,H712,H713 & H714? should I replace them too?

Also in the Sansui, I just left the new Bourns as they came from the factory (they are adjusted to the middle) and adjusted from there. Should I do the same with the Marantz? (for Bias and DC Offset)

 

[wlhd1610]

You can run the 2275(or any other Marantz with plug in amp boards) with the amp modules unplugged.

That makes it easy to check out the preamp,etc. for operation before you have gotten to rebuilding/repairing the amp modules.

It is also a quick way to isolate a problem with the relay not picking up or failing the dim bulb test when a receiver first comes in.

Bob

 

[Golanr]

You can run the 2275(or any other Marantz with plug in amp boards) with the amp modules unplugged.

That makes it easy to check out the preamp,etc. for operation before you have gotten to rebuilding/repairing the amp modules.

It is also a quick way to isolate a problem with the relay not picking up or failing the dim bulb test when a receiver first comes in.

Bob

Thanks Bob,
Made a rookie mistake and installed C703 with reverse polarity (You can see it in the P700 Photo). After 15 minutes, it was easy to hear the pop . Replaced with a new one and was able to properly adjust Bias and DC Offset. Hint to anyone replacing to Bourns 25 turns, you rotate clockwise to hit 0.00mv (I'm glad I tested the Bourns outside the board)



Also finished P400, with some nice WIMA and Nichicon Audio caps, as well as replaced H401-H406 with ON Semiconductor KSC1845. VD1212 diode was replaced with a pair of 1N4148 in serial as recommend by @EchoWars. I Need to find a local AK'er with a sound generator and OC to test clipping, but it sounded great with a turntable.



Waiting for a 5pF cap for the second P700 and then I can put it in and move on to the next boards.

 

[Steven Tate]

Just a question about the trimmer. If you were going to start with an extreme setting, wouldn’t you want maximum resistance and then adjust to spec? It seems like zero resistance might vastly overshoot the desired idle current. Of course, I don’t really know what this trimmer is doing in the circuit, so I might have it bass-ackwards.

 

[Golanr]

Just a question about the trimmer. If you were going to start with an extreme setting, wouldn’t you want maximum resistance and then adjust to spec? It seems like zero resistance might vastly overshoot the desired idle current. Of course, I don’t really know what this trimmer is doing in the circuit, so I might have it bass-ackwards.

You make a good point. I'm still learning here, but when I turned it all the way clockwise, the Bias showed 0.00mv as I turned the 2275 on. Turning it to the left, CCW, slowly increased the Bias until i reached 10mv.

 

[Steven Tate]

You make a good point. I'm still learning here, but when I turned it all the way clockwise, the Bias showed 0.00mv as I turned the 2275 on. Turning it to the left, CCW, slowly increased the Bias until i reached 10mv.

Well, that sounds like you did the right thing. I don’t understand exactly what that trimmer does in the curcuit, but it sounds like starting at full CCW with that trimmer (normal for the stock trimmer) could be the wrong move. Maybe one of the experts can explain this.

 

[highvoltage_]

Well, that sounds like you did the right thing. I don’t understand exactly what that trimmer does in the curcuit, but it sounds like starting at full CCW with that trimmer (normal for the stock trimmer) could be the wrong move. Maybe one of the experts can explain this.

R742 is the Bias Adjust, R741 is the Offset Adjust. The Burns 25 turn trimpot moves the wiper (Pin 2) from Pin 1 to Pin 3 when turned clockwise. I can't find a data sheet on the original trimpot but I suspect that it might have been the opposite.

 

[Golanr]

R742 is the Bias Adjust, R741 is the Offset Adjust. The Burns 25 turn trimpot moves the wiper (Pin 2) from Pin 1 to Pin 3 when turned clockwise. I can't find a data sheet on the original trimpot but I suspect that it might have been the opposite.

And according to the Bourns drawing, turning clockwise should give zero resistance. And yet, Bias measured 0.00mv when I turned the 2275 on and adjusted to 10mv as I rotated it CCW. Strange

 

[highvoltage_]

And according to the Bourns drawing, turning clockwise should give zero resistance. And yet, Bias measured 0.00mv when I turned the 2275 on and adjusted to 10mv as I rotated it CCW. Strange

Full clockwise should be zero resistance when measured across pins 2 and 3, but full resistance when measured across pins 1 and 2. The opposite is true when turning full counter-clockwise. This will yield zero resistance across pins 1 and 2, but full resistance across pins 2 and 3. Here's a picture of what I'm trying to describe:

 

[Golanr]

Full clockwise should be zero resistance when measured across pins 2 and 3, but full resistance when measured across pins 1 and 2. The opposite is true when turning full counter-clockwise. This will yield zero resistance across pins 1 and 2, but full resistance across pins 2 and 3. Here's a picture of what I'm trying to describe:

View attachment 1155193

Thank you! I’m guessing Marantz used pins 1, 2 for adjustment, which aligns with my observation. In that case, the original trimpots used the opposite mechanism as you suggested.

 

[highvoltage_]

Thank you! I’m guessing Marantz used pins 1, 2 for adjustment..

Actually all three are used, you can see R742 (BIAS ADJUST) to the left of H709 below. You can see +5 mV at the emitter of H713 and -5 mV at the emitter of H714. This is the 10 mV of bias adjustment one is trying to achieve. Anyway, it sounds like you've achieved your goal. Good luck with your effort.

 

[Golanr]

Back from vacation and managed to complete PE01, (Tone board) as well as thoroughly cleaning all pots and switches.
Upon completion, I reinstalled it (Reminder Left side P700 is still on the bench) and turned the 2275 on. FM radio came on for 5 seconds and then I turned the source button to check auxiliary. From that moment on, AM/FM are no longer working. Aux, Phono, Tape 1,2 are working with no issue, but AM/FM gives me nothing, the right lights come on, including the dial light. If I press the Dolby button, the associated red light will come on, but no sound. Even the signal strength meter will not move as I turn the tune gyro.

I checked all cable connectors and they all seem fine. the tone controls respond perfectly when not in bypass mode. Any ideas what to look for?

 

[Golanr]

I'm getting 3.4V at J806 on the power supply. It is supposed to be 13.4v. It then feeds all the tuner boards as @EchoWars explained.
Tracing to H804, I get the same on the Emitter of the new MJE15030G and 3.76V at the base. I will continue to trace but welcome any idea you can offer.

 

[Golanr]

I traced the cable from J806 to the the star splitter in the bottom. I disconnected it from the splitter and tested again. 13.66V which is close enough. So I'm assuming the problem is further down the line. The question is, which of the cables leaving the splitter is connected to the board causing the issue. More tracing is needed...

 

[Golanr]

OK, this is really strange . I got all 4 cables disconnected from the 13.4v star. Got 13.66v on the cable coming from J806, so far so good. Now I connected each cable separately and tested voltage. The cable going to J304 showed 6.66v. OK, I thought this was it, but I also tried (separately) the other 3 cables and they all showed funny numbers. The grey cable going to the input selector showed 5.95v. Connecting (again Separately) the cable going to P200, it showed 5.70v. I can't believe all these boards are bad. Is it possible that my P800 has an issue where it shows the right voltage but can't sustain it under load? All other inputs work perfectly. Suggestions?

This is what I replaced on P800
C801 to 470uF 63V UPW1J471MHD3
C802 to 220uF 50V UPW1H221MPD
C804 to 47uF 50V UPS1H470MED
C805 to 680uF 50V UPW1H681MHD6
C806 to 470uF 35V UPW1V471MPD
C807 to 10uF 50V UPM1H100MDD
C808 to 47uF 25V EKY-250ELL470ME11D
C809 to 220uF 35V UPJ1V221MPD6
H808 to Dual Diode BYQ28E-200,127
H811 to Dual Diode BYQ28E-200,127
R807 to 150 ohm 7W W221500JRLF
L801 to MY2-02DC24
H801, H804 to 863-MJE15030G

 

[Jailtime]

Here's a totally stock power supply board from my 2275 so you can check your work.

You tried every board fed by the 13V supply, one at a time? I would have thought a board pulling the power supply down, but not if each and every one pulled it down on it's own. I'm kinda throwing darts here, but are all the grounds good? No wires pinched or nicked?