Nagging intermittent hum on 2285B - want to remedy

pfontherun said:
Mouser.com is still my preferred place (USA). Fistells is great too for Denver residents. Anyway, I too have a 2285B and you can find just about every cap in there I reckon on mouser with exception of the dual section 6800s. Find my post called, if I recall, "2285B recap." I had to replace both of mine with 4 singles. Original replacements are long gone I'm sad to say. Oh-- sometimes dimmer lights do really goofy things on stuff. Is your amp plugged into a circuit in your house with a dimmer light switch? Just a theory.

Ooh hey I read a bunch of your threads. Very informative, thank you very much. If you can coach me a bit on selecting the proper caps, I'd hugely appreciate it.
 
on recapping

This wholesale replacement of capacitors 'recapping' as you guys call it, is on the whole a relatively harmless process but also most of the time completely unecessary. New capacitors are in my opinion pretty ordinary compared to some of the premium capacitors that the japanese used in the 70's and 80's and I can virtually guarantee they will not last anywhere near as long as the old ones. What do I base this on? Thousands of replacements that's what. Caps made from '95 onwards fail more frequently than ones made in the 1970's and 80's. Not only that, often the psu caps were specially made for the particular model- kenwood had Elna make controlled etched foil electros with a THD below -160dB for its monoblock L07's. What are you going to use now some chinese made piece of junk? If you can find an Elna cerafine or a Nichicon Gold...good luck they are gone. Nichicon Fine Golds are nice enough, but give me a NOS ELna RBLL from the 80's and It will last 25 years minimum.
All I am saying is, if you have a stomach ache, you don't get your teeth filled, botox and a heart bypass when all you needed was an antacid. Blanket replacement is a BAD IDEA until you know what caused the problem exactly in the first place, otherwise you will never find out. Also, it is a plain lazy tech who replaces every cap because resistors, diodes, thermistors and especially transistors all develop problems as well but the 'recap' is something the average hobbyist thinks he can 'have a go at'. I scratch my head everytime I see a mess caused by a clown with a soldering iron and a bunch of caps mismatched and cheap ruining what was a lovely piece of gear.
Think twice before you take an original piece of gear and fill it full of new caps.
 
John,
I think I have a different opinion based on a different experience and facts.

restorer-john said:
... 'recapping' as you guys call it

That's the accepted term among people who deal with vintage equipment.

restorer-john said:
...
New capacitors are in my opinion pretty ordinary compared to some of the premium capacitors that the japanese used in the 70's and 80's
...

That may be your opinion but it's not supported by either the manufacturer's datasheets or by simple logic.

Electrolytic capacitor technology has evolved since the 70's and 80's and modern capacitors (I mean the ones you are likely to buy from any reliable source) are specified with an MTBF of twice (at least) as many hours as the ones from the 70's and 80's - from the same manufacturers!

Modern capacitors also have (in general) lower ESR compared to their 70's and 80's counterparts, meaning smaller losses and lower distortion.

restorer-john said:
...
If you can find an Elna cerafine or a Nichicon Gold...good luck they are gone.

Not quite. My regular over-the-counter and mail order supplier has both lines in stock, and although they are more expensive than the regular ones, in some places they are worth using (e.g. feedback loops).

For power supplies modern Panasonics which are quite inexpensive will do a very good job. They are smaller physically and have much lower ESR than the old 70's and 80's capacitors they replace. Of course Chemi-Con and Nichicon are fine too, and many others.

BTW nearly all capacitor factories have moved to cheap-labour countries. So don't expect to buy a capacitor "made in Japan": they are made in China or elsewhere in Asia.

There have been quality issues: read http://www.badcapacitors.org/ for example. They have a very active forum at: http://www.badcaps.net/forum/forumdisplay.php?f=10

restorer-john said:
...
because resistors, diodes, thermistors and especially transistors all develop problems
...
That's true to a certain point, but in my (limited) experience electrolytic capacitors by their very nature (they contain electrolyte which dries up) have an aging process that requires their replacement after some time.
Carbon compound resistors as found in very old equipment also do not age well, but are rarely found in 70's equipment and practically never in 80's equipment, having been replaced by carbon film or even better metal-film resistors. These latter ones age very well.
Transistors and diodes age very well unless exposed to very harsh environmental conditions, or operated beyond specs (as may happen if an electrolytic capacitor fails).

Finally, you seem to recommend replacing capacitors only once they have failed. That is very bad advice. Recapping is as much a matter of safety as it is getting the equipment back to specs. 25~30 years old capacitors, exposed to similar temperatures and operating conditions, will fail within weeks/months of each other. It takes almost the same amount of work to replace a single capacitor as that one and its neighbors, so saving a few minutes but risking a catastrophic failure in a near future is a very bad recommendation. I recommend replacing all the electrolytic capacitors at once.


So all in all I don't agree with your assessment, for the reasons listed above.
:no:
 
jasong said:
Ooh hey I read a bunch of your threads. Very informative, thank you very much. If you can coach me a bit on selecting the proper caps, I'd hugely appreciate it.
Hi Jason,
I am going to write about that in my Recapping HOWTO. I was wondering what kind of issues people would have when choosing replacement capacitors. :yes:
What kind of questions do you have?
 
Gigapod said:
Hi Jason,
I am going to write about that in my Recapping HOWTO. I was wondering what kind of issues people would have when choosing replacement capacitors. :yes:
What kind of questions do you have?

Well, when I go to mouser and look at the selection, I kind of glaze over. :drool:

Even narrowing it to Nichicon still presents a tremendous range of caps.

In my post at 6:32 PM lastnight, I think I asked most questions that I would ask about capacitor specifications. I know enough about EE to get part of the way there, but often draw a blank as to how to proceed.

By the way, I found some interesting things on the full-size schematic yesterday including typos. I now see exactly how those double caps fit into the circuit, and how to wire them with 3 terminals and which wire goes where (positive of one cap joined to the negative of the other, making a T in the circuit). The biggest issue I see is in a mounting bracket; it would be nice to use the original can. I now understand what needs to be done after navigating through some somewhat misleading and incorrect posts about the double caps...it's the actual fabrication that is somewhat daunting to me. I think I can swap out C801 and C802 by myself, but the big boys kind of scare me. :)

I'm seriously wanting to order 4 caps to replace the double cans, and 330 and 470 caps for the power board for starters. So a fundamental cap question is "how do I find the right one out of that haystack on mouser.com?" Assume I want to recap the whole P800 board plus the big guys.
 
jasong said:
...
I'm seriously wanting to order 4 caps to replace the double cans, and 330 and 470 caps for the power board for starters. So a fundamental cap question is "how do I find the right one out of that haystack on mouser.com?" Assume I want to recap the whole P800 board plus the big guys.

OK Jason,
give me some time to look at the selection on mouser and I'll get back to you.
However, for starters, you could draw a list (by hand or using Excel) of the capacitors you want to replace.
Take a look at the list here:
http://gigapod.free.fr/marantz_restoration.html#how_to_recap

Draw a similar list for your 2285B, using the schematics as a base and checking against the receiver if needed.

The list is 9/10 of the work, once you have it, selecting the capacitors from a catalog is easy.
 
Oh yeah I can make a BOM in no time.

2x C003: 6800 uF, 63 V, ES68806310
2x C004: 6800 uF, 63 V, ES68806310
1x C801: 470 uF, 63 V, EA47706310
1x C802: 330 uF, 63 V, EA33706310
1x C803: 100 uF, 16 V, EA10701690
1x C804: 10 uF, 50 V, EA10605090
1x C806: 10 uF, 25 V, EA10602590
1x C809: 330 uF, 50 V, EA33705090
1x C810: 470 uF, 16 V, EA47701690
1x C812: 10 uF, 50 V, , EA10605090
1x C813: 100 uF, 16 V, EA10701690
1x C815: 100 uF, 25 V, EA10702590
1x C817: 4.7 uF, 50 V, EA47505090
1x C818: 47 uF, 16 V, EA47601690
1x C819: 220 uF, 10 V, EA22701090
1x C820: 470 uF, 16 V, EA47701690

So it looks like there are three duplicates for a total of 18 caps.

I don't mind buying them all, but I'd probably only start on 801 and 802 when soldering by myself. I am going to crack the baby open again today and have a look at it, the full schematic shows some weird stuff I want to look at.
 
I opened it up again today and had a good look at the top and bottom (and cleaned the bottom plate, yecch). It looks like someone has done some soldering on the tone board, and on the relay on the power board P800. There are relatively tall, recent-looking gobs of solder on the relay's feet that stand out from the rest of the board.

But what caught my interest was looking at the solder joints on the C801 and C802 caps. It's kind of hard to see from the pictures, but it appears as if there are ring fractures around the caps' feet, especially C801 (circled in attached picture). They look different than the other solders on that board. I don't know if that would be a possible source of my hum problem, but it's interesting anyway.

If I had a good pencil iron handy, I'd be inclined to try and touch up those joints just for the heck of it.

The huge black double caps look very good cosmetically from the bottom at least :) It seems like it'll be a rather large job to replace them...:\ quite a gaggle of wires around and attached to them.
 
And now after I opened it and wiggled C801 and C802 a little bit, it's humming again...if the hum doesn't go away I will be pretty certain that those caps have bad joints. It's not going away like it usually does...perhaps my slight wiggling of the caps fractured a fragile connection.

If anyone has any last minute tips or advice or cautions about touching up those joints, fire away soon. :) They're accessible from the top of the unit and should be easy little dabs to make.
 
jasong said:
And now after I opened it and wiggled C801 and C802 a little bit, it's humming again...if the hum doesn't go away I will be pretty certain that those caps have bad joints. It's not going away like it usually does...perhaps my slight wiggling of the caps fractured a fragile connection.

If anyone has any last minute tips or advice or cautions about touching up those joints, fire away soon. :) They're accessible from the top of the unit and should be easy little dabs to make.
Hey Jason,

Definitely redo these solder joints. Just heat up the (30W recommended) soldering iron and apply it to each solder joint with a very small amount of resin core solder. Let it melt for 4~6 seconds, take it off, let the cap cool down for a minute, do another solder joint, etc.

The top left solder joint on your pic definitely looks like it needs resoldering.

BTW don't use a 15W pencil iron for this kind of job, it's not hot enough. 30W is OK, regulated is better.
 
jasong said:
Well, when I go to mouser and look at the selection,
...
OK, just checked their site, it seems they have a nice selection filter that will make it easy to get the list of capacitors you want.
Here is how to select:

  1. Product = General Purpose Electrolytic Capacitors
    [*]Tolerance = +/- 20 %
    [*]Voltage = (select according to BOM)
    [*]Temperature Range = - 40 C to + 85 C
    [*]Termination Style = Radial

Once you have selected these, select the capacitance and you are done, just pick the first Nichicon on the list that they have in stock.

I recommend ordering one more of each capacitor than the quantity in the BOM (except for the big ones). The extra cost is negligible. :yes:
 
Thanks, everyone--interesting thread. Found out a lot I didnt know by reading it. Good luck with your 2285B.:thmbsp:
 
All I have on hand at the moment is a silver solder. I found my old pencil iron (my dad adopted it :)). I know I shouldn't use acid flux, so it's either wait to get some resin core solder or try some kind of miracle with the silver solder and no flux. I'll try and wait until tomorrow and get the proper solder. :)
 
jasong said:
...it's either wait to get some resin core solder or try some kind of miracle ...

Jason,
I too would wait until tomorrow to get the resin core solder and a proper 30W soldering iron. Miracles are hard to come by these days. ;)
 
Gigapod said:
Jason,
I too would wait until tomorrow to get the resin core solder and a proper 30W soldering iron. Miracles are hard to come by these days. ;)

*sigh* the iron I have is 45W. I do, however, have a rotary dimmer switch that I made for my air heat gun that I can plug the iron into lower the heat a bit.

The pictures aren't very clear, it was difficult to focus the camera on the power board, but as you can see, the solder joints look very suspect. Also, wiggling the cap earlier resulted in humming for a long time when I turned it back on. I'm very suspicious about C801 and C802.

In other news, a local parts store advertises a multimeter that supposedly reads capacitance. The specs on the capacitance scales are something like "20 uF to 2 nF" but I think nF might be a misprint of mF. Sounds like it could potentially be useful for electronics, if that nF is a misprint of mF (other specs usually read low to high).

Anyway, those 4 solders have gaps that are visible. Also, the old dried out brown glue holding those caps to the board looks like it may have stressed the leads. I will repair those joints as soon as possible, and see if the mysterious humming failure mode returns.
 
Well, I successfully soldered the joints.

First I tried with a 30 W iron. I had lots of trouble getting solder to flow onto the posts. I could get solder to bond with the dab on the PCB, but not the posts or in the joint. Heating up the solder around the bad joints exposed a definite annulus between the posts and the board holes, on C801 especially. I could also see dark grey material on the posts farther inside, close to the board. After several tries, I got nervous and didn't want to heat the posts too many times, and just about gave up and put the cover on. I did NOT want to turn it on at that point, with the clearly visible gaps around the posts.

Then I started composing a defeatist post to this thread, and while thinking about it I realized that the leads were probably not getting hot enough...so I tried with a well-tinned old 45 W iron and FINALLY got it to all to flow together into nice trumpet-shaped beads that clearly bonded the posts to the PCB paths. A lot of black flaky crap floated up from the joints on C801...perhaps this was the dark grey oxidized material that I could see on the leads.

So I plugged it in, and it WORKS and sounds GREAT! :banana:

I really think those solder joints were bad, and were causing the problem that Gigapod associated with C801 and C802. Thank you so much Andre for all your help, I hugely appreciate it! Je te remercie MERCI MERCI MERCI! (/pas Zawinul). :)

I still want to recap the power board, but if this resoldering fixed the humming, it will be a huge victory. Coincidentally, a new needle arrived today, and it sounds AWESOME. That cheapo copy replacement for the Stanton D6800 stylus was CRAP! This needle is not as good as the 681EEE stylus, but it sounds fantastic, I'm hearing way more definition and high end than I was with the other stylus.

THANKS EVERYONE. Now back to crossing my fingers that it stays fixed. :)
 
Oh wait wait wait! DO NOT wire the big 6800 caps in parallel. on the schematic they're done like (sorry for the ANSI) this: -ll--ll- aka series. There are 2 "inside" each therefore 4 total. Orientate the new ones so one (-) from one cap goes to one (+) of the other. Then repeat again for the other 2. You'll then have the mysterious 3rd lead which is where the 2 are joined. On the bottom of the originals this explains the "extra" leg.
 
pfontherun said:
Oh wait wait wait! DO NOT wire the big 6800 caps in parallel. on the schematic they're done like (sorry for the ANSI) this: -ll--ll- aka series. There are 2 "inside" each therefore 4 total. Orientate the new ones so one (-) from one cap goes to one (+) of the other. Then repeat again for the other 2. You'll then have the mysterious 3rd lead which is where the 2 are joined. On the bottom of the originals this explains the "extra" leg.

Sorry sorry sorry, I said the wrong thing there. :)

It is series as shown on the schematic. I posted in the other thread about how they are set up after I looked at the schematic and a guy's crude MS Paint wiring diagram. I know for sure how those caps are set up now, they are wired in series and both dual caps are joined between the caps in series by solders underneath where they sit in the receiver. So looking at the schematic, one line feeds two parallel sets of two capacitors such that the current flows to the positive terminal of one cap and the negative terminal of the other cap in each of the two pairs of capacitors. So basically the circuit is two Ts that are joined at the bottom, and where the caps are in the top parts of the Ts. Thanks for the warning though. :thmbsp: I wouldn't jump into that without the schematic, I think when I wrote that, I just had read that they could be replaced, and not looked into it much.
 
jasong said:
So I plugged it in, and it WORKS and sounds GREAT!

I have been lurking on this thread since it started, as I have a 2285B which which should be here tomorrow.

Good to see you fixed her.:thmbsp:
 
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