krustyoldsarge Posted November 11, 2002 Share Posted November 11, 2002 My Marantz 2220b was sounding a bit tired and restrained. Worse yet, passages with a lot of bass were producing clipping in my Klipsch Kg4s. Distinct lack of soundstage, too. You might ask "what was I expecting from 20wpc, anyway". Better than this, these are Klipsches, after all! So I open the receiver up, look at the power supply card and notice r805 (330ohms) is discolored, and ask myself "what else is going bad here?" Probably some caps and tired diodes, too. I replace r805, and decide to do some other upgrades while I'm in there. Out with about half of the filter electrolytics on the power board, back with double the value and voltage rating whenever physically possible. Caps in general are significantly smaller than when our beloved Marantz's were made, seems you can usually double your capacitance and voltage rating for the same case size. Now for some controversy, out with c003 and c004 (6800uf @ 35v) and in with 2 each SamHwas at 10000 uf @63v. If you use SamHwas, you could probably go to even bigger values since the SamHwa's case at this value is too small for the clamp. My neighbor helped me rig something out of an old racket ball to stabilize them in the clamp. Good thing he's an old farm boy! Beware of polarity, mark the orientation of the original cans on the chassis with a Sharpie pen. I mention this because the schematic seemed to mislead me here. Unless you enjoy fireworks! Heard a lot about fast recovery diodes on the web, so out with h801 and h802 and back we go with four FR607 diodes. The board's inside track lead holes had to be drilled out (carefully!) a smidge to allow the FR607's fat leads through. After all, they're rated pretty hefty: 7amps at 1000 v. To duplicate the original diodes bridge I soldered about a 2" jumper of 7strand teflon insulated silver audio wire to each outer lead. Bypassing each individual diode with a .1uf @600v film cap gives them the humorous appearance of possessing te****les! My neighbor (and test audience) got a good snicker out of that mod! We're not done yet. A look at the main amp board and horrors! Electrolytic couplers in the signal path (c701 and 702, 3.3uf @ 25v)! I could tell this was gonna be a tricky mod because the original caps are tiny and the board is crowded. With much effort i swap the teeny-tiny (aarrrgh) electrolytics out for yellow tootsie roll style polys, 3.3uf @ 100v. I mounted these on the back (bottom) of the amp board, leads shrink tubed and bent away from the power transistor's heat sink. Don't try this if you're in a hurry! That's quite enough modding for now. We reckoned if we tried changing anything else, we'd have a h**l of a time isolating a problem to a particular mod. However, we weren't going to just power the unit up and wait for sparks, so we put together a "dim-bulb tester" out of junk lying around my place. Ever watch the movie "Joe's Apartment" That's enough, off to bed! We hook the 2220b up to the dim-bulb tester and test it early the next morning. No bright bulbs, great! "Enough of your screwin' around, let's hear some tunes!" says my buddy. The moment of truth! Sounds great! No smoke (always a good thing)! While playing Aerosmith's "Walk this Way" my buddy gets his ear right next to the tweeter and reports back "Damn, I can hear the drummer cutting in with the brushes, I know this tune by heart and ya can't catch that brush on every system!" Detail checks good. Check for soundstage with Aqua's "Dr. Jones". My hair nearly stands on end! Dynamic response with Van Halen's "Dreams" is noticeably improved. Vocals and harmony checked with Level 42's "Leaving me now". Really smooth and open. So far so good. Can it work hard? Pulled up a club mix of "Better off alone" (forgot the artist). Jaw-dropping, and the Marantz ain't even clipping or heating up! I've been running the Marantz for six hours straight with no problems. This is also a testimony to the Klipsch kg4's ability to reproduce music without inducing fatigue. Next, I intend to upgrade the parts in the kg4's crossover. For the Marantz, the next downtime will probably see h803 and h804 swapped out for UF5408 ultrafast diodes. Also read on the web where it isn't a bad idea to upgrade the small transistors with tophat types from Motorola. In the meanwhile, I'll continue cannibalizing caps from tossed computer power supplies..... Some of you will doubtless say, switch to tubes. See below! My buddy's thinking of retiring his Blahse 701's now.... Quote Link to comment Share on other sites More sharing options...
fini Posted November 11, 2002 Share Posted November 11, 2002 Sarge, I'm truly in awe of you (and others here) who have the knowledge (and the guts) to jump in and fix these old beasts. I've acquired many audio fixer-uppers, thinking, "How hard could it be?" Well, I've come to realize there's lots to know about electronics repair. I'm a (semi-retired/retarded/retreaded) carpenter, and would have clients tell me how amazed they were at what I could build with wood. I'd think to myself, "Man, woodworking is so basic and forgiving...can't EVERYONE do this?", and it was basic, to me, a 25-year veteran woodbutcher. Truth is, you can't learn carpentry JUST by watching Norm on Saturday afternoons, so I know I'll never get it together enough to fix my stuff, just by reading this forum. I wish there was a vintage electronics equivalent of a Home Depot (albeit on a local, more homey scale), where interrested folks could stop by for some basic, hands-on soldering and troubleshooting experience. My wife quilts, my daughter "scrapbooks," each has a friendly and helpful group of similar-interrested women that regularly meet, freely and happily exchanging info, and encouraging each other. I want something like that! We guys tend to guard our knowledge, and waggle it in front of others (which isn't the same as sharing). More like showing off, I guess. We all do it, to some extent. Still trying to attract mates and propagate... Maybe I need a therapist, not a soldering coach. fini Quote Link to comment Share on other sites More sharing options...
Clipped and Shorn Posted November 11, 2002 Share Posted November 11, 2002 fini, (semi-retrofitted capenter) What did you say you were waggling in front of others? Is that why you were asking about raincoats the other day? A few years back, guys would learn electronics from mail order courses (check some of those old Popular Mechnics mags). I will bet there are a bunch of those old guys living around here who are retired. Also I think it is possible to learn some things by jumping in with some basic equipment and then asking questions of these old guys. Also maybe we could find some of those old courses or some cool old diy books. I am going to buy a Variac and a good slobbering Iron today. -c7s Quote Link to comment Share on other sites More sharing options...
krustyoldsarge Posted November 12, 2002 Author Share Posted November 12, 2002 Hey, I?m just an old hacker who had a couple years of electric shop in high school. Never stopped enjoying tinkering with electronics, though. Used to drive my parents crazy, but they had a kid who could replace the tubes in their Admiral electric clock radio. But I?ve never been a great woodworker. Man, do I wish I could master dovetailing, joints, finishing and all that good stuff! Now, you?re really on to something with that ?Audio Depot? idea! There?s a void in America that needs to be filled! I can see myself now with an apron, workbench and solder sucker showing soccer moms and the kids how not to test a power electrolytic. A Tim Allen kind of life indeed! Waggling my knowledge and diode bypass caps! There?s some good stuff for free out on the web if you want to seriously hack around with electronics, though. Check out: http://www.repairfaq.org Quote Link to comment Share on other sites More sharing options...
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