Starting Marantz 2325 rebuild

I had seen your pics before and I've seen the 3D repro on eBay. I figured I would need one. Haven't dug deep into mine yet, but at least it doesn't look like a melted mess.
 
Good tip on the main filts. I looked up what I did on one and I had used Nichicon Gold Tunes with solder lug connections.
BlakeH2325 005.JPG
 
Good tip on the main filts. I looked up what I did on one and I had used Nichicon Gold Tunes with solder lug connections.
View attachment 800784
The screw terminals on the UCC's definitely look easier to use than those solder lugs in this application. Glad someone found these caps.

I just finished (well almost) the right P700 Power Amp board. Replaced all of the components listed in Leestereo's rebuild thread, plus I did replace the diodes at H718/719 as noted by hirscwi. I didn't know if the ones present were the later upgrade or not. I felt like they were because they had the glass look, but I had the 1N4148's on hand, so replaced them. This was my first time to replace a differential pair (H701/702). I Hfe matched them, put a dab of heatsink compound on the flat faces and closed them together with shrink wrap. I did find one problem that I will have to go back and fix after I get the part. R746, a 22ohm, 3W resistor had been getting very hot. The plastic lead wrap was totally melted along with the wrap on Diodes H720 and H721. I have two questions about this: Will this 22ohm, 5W wirewound resistor work as a good replacement? http://www.mouser.com/ProductDetail/Ohmite/45F22RE/?qs=sGAEpiMZZMtbXrIkmrvidLMBFxRBS6SAerFClZpPm2U=
And, since I'm going to have to remove diodes H720 and H721 to replace the lead wrap, I'm wondering if I should replace them. They are listed in the SM as 1S2471 (black). I found one place that said a 1N4148 was a substitute for this diode. Does that sound right in anyone's experience? Thanks! Here are a few pics.

Right Power Amp Before
IMG_1682_zpsibxoohhj.jpg


After replacing the recommended parts (still have the hot R746 to replace)
IMG_1687_zpsijza6tqn.jpg


Close-up of the melted plastic lead wraps on R746 and H720, H721
IMG_1686_2_zps5mtat61p.jpg


Parts List:
P700 Power Amp Board (X2)

C701 1µF/250V - Panasonic 1.5µF/250V Mouser 667-ECW-F2155JA
C703 33µF/6.3V - Nichicon ES bipolar 33µF/25V Mouser 647-UES1E330MPM
C710 100pF - Vishay C0G 100pF/1KV Mouser 75-561R10TCCT10
C706/707 10µF/25V - Nichicon PW 47µF/25V Mouser 647-UPW1E470MDD

H701/702 2SA722 - Fairchild KSA992FBU Mouser 512-KSA992FBU
Hfe matched differential pair
H703 2SA722 - Fairchild KSA992FBU Mouser 512-KSA992FBU
H718/719 VD1122 - Fairchild 1N4148 Mouser 512-1N4148
 
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I don't know about the glass diodes but "probably" the 4148 will do. You could try a search for the old one's data sheet. That new 5 watt should be fine as long as it fits. I'd leave it higher off the board to help with heat dissipation but no higher than the Slinky next to it to make sure it doesn't run afoul of something upon reassembly.
 
I don't know about the glass diodes but "probably" the 4148 will do. You could try a search for the old one's data sheet. That new 5 watt should be fine as long as it fits. I'd leave it higher off the board to help with heat dissipation but no higher than the Slinky next to it to make sure it doesn't run afoul of something upon reassembly.
Thanks! That's what I needed to know. I found a second source that says 1N4148 is a sub for the 1S2471 http://english.electronica-pt.com/components-cross-reference?ref=1S2471. I have a question about these big, heat dissipating resistors. Are wire wound resistors common in those applications or is there a better choice of resistor type? I see a lot of use of metal oxide, but wasn't sure if they were good in these hot applications. I've been in this spot before with the same question, so thought I would throw it out there.
Steve
 
Still I wouldn't use a rectifier type diode such as the 1N4004 for use in a signal diode's spot. Even if it worked elsewhere.

The only caution on wirewounds is that they do have some inductance to them and may not be suitable in some usages. The old resistor in the picture looks like it may have been wirewound to begin with. The concern is that the amp will break into oscillation which usually blows up the outputs in a short time and if a speaker is attached the tweeters stand a good chance of being blown open.

The white emitter resistors at the top of the board are the cement filled type but I'm not sure what the element inside is, wire wound or not. On those I'd stick with the cement filled ones just to feel like I was being safer. I certainly would never change them unless there was an issue.
 
Yeah I'm not sure why I used those 1N4004 because my standard cross reference for a 1S2471 is 1N4148 general purpose diode. Probably read it somewhere but can't for the life of me find any notes indicating where. I'll go back and edit my original post to avoid future problems.

As for your issue with R746, there has to be something else at play there. I replaced with a 3 watt metal oxide component and it's relatively cool with no heat damage in the area after hundreds of hours of play. And my original never looks beat up like that either. I'll take a temp reading in a bit and tell you exactly how hot it gets.
 
Still I wouldn't use a rectifier type diode such as the 1N4004 for use in a signal diode's spot. Even if it worked elsewhere.

So what is your recommendation on these diodes? Leave them alone? 1N4148?

The only caution on wirewounds is that they do have some inductance to them and may not be suitable in some usages. The old resistor in the picture looks like it may have been wirewound to begin with. The concern is that the amp will break into oscillation which usually blows up the outputs in a short time and if a speaker is attached the tweeters stand a good chance of being blown open.

The white emitter resistors at the top of the board are the cement filled type but I'm not sure what the element inside is, wire wound or not. On those I'd stick with the cement filled ones just to feel like I was being safer. I certainly would never change them unless there was an issue.
I thought about replacing all of the resistors over 1/2 watt, but I studied all of them carefully and didn't see evidence of heating anywhere except that 22 ohm 3W, so that's the only one I''m changing. I ordered a Vishay/Dale wire-wound 22 ohm 5W, so hope that does it. Will I get any kind of audio warning if trouble is brewing where I could turn it off before damage occurred?
 
After 30 minutes of moderate volume radio the R746 resistor is steady at 30.5C. By comparison that big resistor on the power board is reaching upwards of 80C!
 
As for your issue with R746, there has to be something else at play there. I replaced with a 3 watt metal oxide component and it's relatively cool with no heat damage in the area after hundreds of hours of play. And my original never looks beat up like that either. I'll take a temp reading in a bit and tell you exactly how hot it gets.
A couple more pieces of info -- the same resistor in the left channel has been hot, but not AS hot. The wire sleeve is completely melted next to H720 and the sleeve on H720 is a little melted, but not as much as the right side. Also, the right channel (one with most damage) has clearly been worked on. The output transistors had been pulled, and replaced. There is no Marantz logo on them like the left side. That right side heat sink compound might have been getting hot, too because it was pretty hardened and hard to clean off. The board looked original except H715 that hooks to the heat sink appeared to have been replaced. I'm wondering if that amp had a problem and a tech fixed it properly or just got it back working with the problem still there. Anybody have any ideas from these clues?:dunno:
 
OK, I put the amps back in and fired it up moderate volume for about thirty minutes. The hot resistor on the PS board measured 70C at the hottest point. R746 measured 33C on the left channel and 34C on the right. Maybe there was a problem on that right board that was fixed. Not sure. Maybe I should just remove R746 from both boards, put some more heat resistant sleeve on them and put them back in. Or do you think replacing them with a 5W might be the way to go. I'm going to leave it running for a while and see if temps rise any.
 
I'd go with your theory that there was a problem in the past, it was fixed, and they just didn't clean up very well. Putting new wrap on the old ones should work just fine.
 
I'll think on whether to leave them or replace them until I get the new parts I ordered. Hey, Mike, when you did your 2325 did you recap the PU01 board that has speaker/loudness/filter switches? While I had the tone board out, I decided to go for it. About 2/3 of the way through, I regretted even starting, but I had gone that far...might as well finish. It was a mother to get access to, and I'm lucky I didn't damage any wires - at least I think I didn't. Anyway, got 7 or so caps replaced and got it back in, and everything seems to work. Hope I don't have to get back to it again. It had two of the long grey 1uF caps that I normally would replace with the Panasonic EWC's, but I was out, so I decided to leave them. Turns out both Mouser and Digikey have them on back order. I ordered some similar Kemets, but I don't plan on going back to that switch board. Better part of valor and all that.
Steve
 
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