Discussion in 'Marantz Audio' started by Osibisa, Dec 29, 2017.
Happy New Year!!!
Not seeing 2SC496 at Mouser or Digi-Key, can you recommend a source
I circled back to deal with this module removing and testing every semi on the board.
With my DMM each component tested good which is a bummer, so time to evoke shotgun methodology since I can't replicate what seems to be a thermal failure.
All parts are on order, expected to arrive this weekend.
Guess I'll miss out on the joy of finding and correcting the specific source of the problem.
Parts arrived early so was able to replace caps, diodes, and resistors above 1/4 watt.
Powered up yesterday afternoon and it came to life ... success!!!
Two other issues cropped up which should be minor:
Stereo light went dim and FM signal strength dropped to zero, light stays dim on other modes as well even though the actual mode lights illuminate correctly . If I cycle power the stereo light will illuminate as normal.
From reading an older thread with the same issue, it appears that replacing H801 & H802 (2SD331) brought resolution. Looking at the board one of the D331's was replaced with a D613.
Regarding the replacement, I've read conflicting part subs - MJE15030 vs. MJE15032G for the D331 ... which is more suitable in this application?
Second issue although now not really an issue was that when listening the audio in the left channel would drop out.
After pondering for a while, I inserted and removed a RCA cable into the left pre-out jack and the sound came back ..... jacks are dirty.
Having never heard this model before I have formed a very positive impression.
Lots of work still to be done, needs complete cleaning, replace a few missing screws (one shown in above photo), vellum, yada yada yada.
Focus is to get receiver operational, and once I get those two D331 subs in place I can clean this baby up.
Thanks to MBZ & Catrafter for your input.
The 030's will be fine and the 032's will work if that's what you have. They latter have a higher voltage rating and the 030's have plenty of room there.
While waiting for some parts to arrive I've been working on the faceplate, bezel, and lens that separated when the faceplate was removed.
This also gave me the opportunity to replace the vellum which actually wasn't in too bad a shape.
To reassemble I found some 1/4" double sided tape (Aleene's Instant Tacky) at Michael's Craft Store which is working well. This was followed by a bead of clear E6000 adhesive.
I realized late last night that 1/4" is wider than the original and the glue bead is bonded to the tape instead of the faceplate, so it was corrected this morning.
So on to the left amp ... want to re-cap in order to be uniform with the now operational right.
Does it make sense to touch the differential pair when it is not causing any issue?
Also, my modules have two .33uf films (C719 & C720), the modules I've seen posted here have a single cap at that location. Has anyone replaced these?
I would always suggest replacing the diff pair if you’re already working on the board. Cheap & easy to do and might eliminate a future fix. Lots of threads on AK with bad/noisy diff pairs. I know there are a few others that would say no. Guess it falls into the everyone has opinions category.
^^^ I say yes! Replace the diff pair with a matched set that is.
Took the advice given and replaced the differential pair, also swapped out the tantalums, cleaned and re-greased the large silicone. I'm not liking the way one of the large resistors look, so all of them will be replaced as I did in the right module.
After some testing through headphones, I did notice that the right channel (no signal in Aux) was quieter at near max volume, perhaps it is because that channel was completely rebuilt.
Tomorrow I'll move the left module over to the right to confirm if it is in fact the module or preamp. If it is the module I'll replace the small transistors and retest, then I'll tackle the rectifiers in the power supply.
The phono preamp has more noise in the left channel as well but it is more noticeable. Haven't looked too closely at the board since I am focusing on another part of the receiver, and I would venture to guess that the '458's are still in place.
This is taking some time but that is the enjoyment of the hobby (at least for me!!!)
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