Marantz 2275 weird protection issue

Dave - transistor that I actually posted as a sub for H711 was KSA1120A, not 1220. I found this part number from another thread. I haven't compared them and don't know if it was that thread OP's typo. KSA1120a is a good part number but no longer available.
 
Dave --
Diodes are H717 & H718 not H718 & H719
Anyway, since replacement of differential pair didn't do anything, next I replaced H703 / H704 pair. Again, no improvement. Somehow, cut-out started to happen every time receiver was powered on. I hope that was not due to new transistors but just a coincidence or whatever was failing was coming to the end of its life.
H405 through H708 - no improvement.
I didn't think that I have an issue in larger transistors, so I went after diodes. I bet it was one of those looking like small Tantalum capacitors. I replaced all 4 diodes and so far no issues. I'll keep forcing it with higher bass and treble just to confirm.
CBS half speed master of 'Wish you were here" and MSFL "Dark side of the moon", both mint are coming my way. Those records seem to keep crazy value.:yikes: Almost worth not playing them and preserve the history, but what the heck! If you have a bag of apples and you always pick one that is about to go bad, you will end up eating almost bad apples every day. Life is too short!:)
 
Sorry about the misinformation on the diodes. So you replaced which diodes, so we can get a good record of what was replaced in this problem?
Since this was Saturday has it held?
Cheers
 
I replaced H717, H718, H720, H721 at the same time. I don't know which one of those 4 fixed the problem but it has been trouble free since Saturday morning. I replaced same 4 diodes in another channel to prevent repeat of this mystery.

While initial problem seems to be gone, another one surfaced. Phono produced low tone rumbling noise after about 4 records. It's possible that it was making this noise earlier but can be heard only while needle is off the record. I briefly looked at the phono amp schematic and will replace H405 and H406 infamous 2SC458 transistors. I recognized this number as I've replaced several dozens of them in Sansui receivers over last few years. I had old sweet Sansui 2000 receiver and KSC1845 took care of the same phono rumble noise. Last time I ordered 50 of them and have only 6 left.
Thanks for your help!
 
Are you testing with the metal bottom off? Most Marantz models will have a hum if the Phono input is selected and the bottom is off.
 
Noise is with both, bottom and top covers installed. I'm aware of the unshielded hum. Noise is very low pitch rumble.
 
Grindfix, what diode numbers did you use to replace H717, H718, H720, and H721? I'm working through my right amp board and have replaced all of the transistors and capacitors with new and it still randomly has one loud pop about once per half hour. Eventually if you listen long enough the protection relay kicks in (like after 2 hours.) This is what sent me down this path in the first place when the relay started to go into protection and ultimately went into protection full time. I'd like to replace these diodes as well, but was not sure what part number to use. By the way, when I was doing my repairs, I got loud hum out of the receiver at zero volume. It turned out to be from the base cover being removed and the receiver sitting on the concrete floor of my basement. With the receiver turned on its side most of the hum went away. With the base cover installed the hum went away entirely.
 
Silverhead said:
Grindfix, what diode numbers did you use to replace H717, H718, H720, and H721? I'm working through my right amp board and have replaced all of the transistors and capacitors with new and it still randomly has one loud pop about once per half hour. Eventually if you listen long enough the protection relay kicks in (like after 2 hours.) This is what sent me down this path in the first place when the relay started to go into protection and ultimately went into protection full time. I'd like to replace these diodes as well, but was not sure what part number to use. By the way, when I was doing my repairs, I got loud hum out of the receiver at zero volume. It turned out to be from the base cover being removed and the receiver sitting on the concrete floor of my basement. With the receiver turned on its side most of the hum went away. With the base cover installed the hum went away entirely.
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Welcome to AK!

I used 1N4148 diodes. Mine was doing similar thing and I have not have that happen after those diodes were replaced. Bottom receiver cover shields all sensitive circuits so hum with cover removed is expected. Good luck with your repair!
 
Update on the phono noise. Replacement of H405 and H406 2SC458 transistors with KSC1845 did not cure the noise. Now that I'm dialed-in on the noise, with headphones on without turntable even connected (in Phono), that noise came from both channels and sounded more like a very dull needle on the record drag. Since the noise is in both channels I'm thinking about replacing VD1212 diode with two 1N4148's in series as a recommended substitute. Can anyone concur?
 
Awesome, thanks! The local hobby shop carries those diodes as a remnant of what's left of Radio Shack. I replaced them in the right board and played the receiver for over an hour with no popping. Out of curiosity I pulled the left amp board which had been mostly re-transistorized by a local repairman in 2013. The bill labor I received when I bought it didn't mention that he replaced those diodes, but someone certainly had. They were different (smaller versions of the originals.) I just replaced them with the 1N4148s as well while I had it apart. All is seemingly well. We're about 1.5 hours into listening to records and nothing has gone awry. Bias is holding at 10mv on both amp boards when warmed up. Both heatsinks are 82 and 83 degrees respectively. Fingers crossed that I am done carrying this thing down and up the stairs to the workbench for a long while!
 
Glad to help.
Seems like everyone is after 2270. I haven't had a chance to hear or work on one but this 2275 is very, very good sounding unit. From technical perspective, it is put together for easy service. It's a pita that it seems to be filled with failure prone semiconductors that cause all these intermittent issues. I ran out of my stash of 1N4148 diodes. Let's see if I'm lucky and my local store stocks them. Will know tomorrow.
 
I agree with your assessment of the 2270 vs. 2275. I have both, and I think the 2275 sounds better. The 2270 has sort of become the mid-high power holy grail. I like it, but I like the 2275 better. It has a little less of that Marantz warmth to my ear, but that translates to a more open sound top to bottom — again, just my impression.
 
Steven Tate said:
I agree with your assessment of the 2270 vs. 2275. I have both, and I think the 2275 sounds better. The 2270 has sort of become the mid-high power holy grail. I like it, but I like the 2275 better. It has a little less of that Marantz warmth to my ear, but that translates to a more open sound top to bottom — again, just my impression.
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Not to de-rail this topic, but it seems that magic is gradually reduced as power level goes up. Sansui 2000 was responsible for for my vintage sound bug. Bit me deep! Just 30 wpc but what an eye opener vs. current average amplification sound.
 
grindfix said:
Dave --
Diodes are H717 & H718 not H718 & H719
Anyway, since replacement of differential pair didn't do anything, next I replaced H703 / H704 pair. Again, no improvement. Somehow, cut-out started to happen every time receiver was powered on. I hope that was not due to new transistors but just a coincidence or whatever was failing was coming to the end of its life.
H405 through H708 - no improvement.
I didn't think that I have an issue in larger transistors, so I went after diodes. I bet it was one of those looking like small Tantalum capacitors. I replaced all 4 diodes and so far no issues. I'll keep forcing it with higher bass and treble just to confirm.
CBS half speed master of 'Wish you were here" and MSFL "Dark side of the moon", both mint are coming my way. Those records seem to keep crazy value.:yikes: Almost worth not playing them and preserve the history, but what the heck! If you have a bag of apples and you always pick one that is about to go bad, you will end up eating almost bad apples every day. Life is too short!:)
Click to expand...

Thank you!
 
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