Marantz 2216 - SOLVED (All inputs & both channels hum\buzz)

[Dingman]

Hiyas guys~ Working on a 2216, serial# U062530

I decided to create a thread on this repair, it's my opinion that good threads can be useful for many years down the road. I've already got several posts in diff threads about this repair and anyone trying to follow - would find it difficult.

Obviously, anyone with advice on this repair should speak up.

Starting out, I only identified the hum and the distorted sound when the volume was turned up. Might be more problems, but both channel outputs seem to be working.

Worked on tracing the hum first. Hums on all inputs, level (loudness) does not change with volume control, Hums with nothing on the inputs.

Using a scope, I could identify the hum as between 100-200 Hz and mostly around 120 Hz. No hum present on the incoming side of tone board PE01 but hum is present on outgoing side of PE01.
So, I rebuilt PE01 with new transistors and new caps - left OEM resistors.
No change on hum.

Additional testing found the hum is being introduced to PE01 by the power supply board P800. Quick voltage tests show that the only transistor 2SC1407 on this board may be bad - ordered a new http://www.mouser.com/ProductDetail...GAEpiMZZMshyDBzk1/Wi2apbjiIOs04CXdH%2bWi22xM=
This board also shows some corrosion on a couple resistors\diodes. If I can get good pics, I'll attach. I can't tell if this corroded "on it's own" or if someone spilled a small amount of something on the board. I did read that possibly the glue on that board (and there is glue in that area of corrosion) was faulty in that it was both corrosive and conductive?
Will replace that 2SC1407 and all caps (and clean corrosion) and I'll report back.

 

[KutzlerTrans]

It sure would be best to replace any diodes you find also

 

[Dingman]

It sure would be best to replace any diodes you find also

Good idea - I'll make sure this board is cleaned up and caps\diodes\trans replaced. I bet that fixes it up just fine. I have a neighbor I'm going to give this to. It's pretty clean and should perform nicely when I'm done.

 

[rBuckner]

The only corrosive glue I've heard about was in Sansui's. Still it's nicer to get the old glue out.

 

[Dingman]

Hum has been eliminated! It was certainly C804 that was the source of the hum. C804 didn't even test on my cheepee chinese tester.
I should mention that I replaced H801 (2SC1407) first. No change, hum still there. I then cleaned up corrosion around resistors R801-R806. No change, hum still there.
Replaced C804 and immediately tested, Hum was gone!

I took some pics, I'll get them posted later - I can't say if the corrosion was caused by the death-glue. I can say that stuff is tough unless it's not. Seemed like some of it dried and was brittle, other parts still firmly gummy.

Has anyone tried some sort of board-safe solvent? Just to soften it all up? I really couldn't get the board very clean and although it now has shiny now caps, the old glue looks like shit. Good thing I'm giving this one away, I don't want my name on it.

Just kidding, it sounds really good now and is pushing some little Klipsch easily.

Oh check this out! On P800 Power Supply board, I replaced all (but one) of the caps - ALL of the Chemi-con caps were BAD. Only ONE even tested - it was the 470uf and tested out at 530. None of the others would even test, one showed up as a resistor.
Not a good sign, IMO.

 

[KutzlerTrans]

Try this next time. Take one of them pocket scales/8 inch steel rulers.
Bend one end upwards, just a little bit and sharpen it real good by sliding it sideways on a piece of 220.
This new scraper will peel that stuff right off as long as you soak it in rubbing alcohol to soften it a bit.
Grind a small 1/8th inch U shape on edge at the other end for scraping between solder joints that are too close.

 

[Dingman]

I have been using a dental pick (a real one, from the dentists office) and it's excellent for breaking and pulling the seal, but I will make a scraper as you describe, I need one.

What do you think of that corrosion? It's on a few other places on the board and in a couple of places went clear thru the hole into the solder joint on the backside.

And what about all the black caps on this board being bad. Are they known to be crap, or this one had a bad batch... Hmmmm.

 

[rBuckner]

It's more old age than anything. I do find that the light purple Panasonic caps are almost always swelling out the end. Also the power supply board's caps are always in the worse shape but that's because they are working harder, doing more ripple current.

 

[Dingman]

Hmm, I see no light purple Panisonics, but I have alot of black "Nippon Chemi-con". And I found two more that have glue on them that have failed. The 2216 now sounds good, hum is gone but if the unit is unplugged (maybe even just turned off for awhile) - when powered back up, there's a low level buzz\hum and the display lights are dim, only for a few seconds. Then buzz stops, display lights go back to normal brightness and unit is fine after that.
I've already rebuilt 95% of the power supply board and double checked that - only one OEM diode and a couple resistors left, everything else is new. So, looked around the amp board - found the two caps in the pictures. Replaced those (and a couple other black Nippons) but startup buzz\hum is still there. Unfortunately, I can't remember if this startup issue was present before I started the original hum repair.

 

[rBuckner]

Power switch with toasted contacts maybe?

 

[Dingman]

Power switch with toasted contacts maybe?

Excellent idea! I will be checking that directly.

I have a question - LOL, should I be worried about this white powder on the top of L206? I think it's L206, tight in there. I have no idea what to do about that.

 

[Dingman]

Yup, the power switch was the culprit. Bypassed it with a "Form C" contact and start up flicker is gone.

Thanks so much, I was too deep in the weeds to think of the power switch.

 

[rBuckner]

Excellent idea! I will be checking that directly.

I have a question - LOL, should I be worried about this white powder on the top of L206? I think it's L206, tight in there. I have no idea what to do about that.

I'd just wipe it off with alcohol on a swab. Glad the switch was the issue.

 

[KutzlerTrans]

Mr Buckner, You are one smart cookie!

 

[mech986]

Excellent repair. Personally, if the power board was suspect, probably would have desoldered everything (with pictures) and then cleaned the board thoroughly then retinned and rebuilt with all new components. As mentioned, its the hardest working board in the whole amp, and everything depends on it, so all new parts would give me piece of mind plus reliability to stabilize voltages for at least another 20 years.

 

[mech986]

I'm actually surprised there isn't an enterprising soul out there making repro power supply boards for various models, then selling those bare or populated for a DIY or fast repair job. Since a lot of Far East board suppliers exist, and can do small runs of say 50-100 easily and relatively cheap, seems like that could be a nice opportunity.

 

[KutzlerTrans]

SHHhhh. Can you translate for our new partnership?

 

[Dingman]

SHHhhh. Can you translate for our new partnership?

I'm actually surprised there isn't an enterprising soul out there making repro power supply boards for various models, then selling those bare or populated for a DIY or fast repair job. Since a lot of Far East board suppliers exist, and can do small runs of say 50-100 easily and relatively cheap, seems like that could be a nice opportunity.

What a great idea - I am in on this as an investor. Seems like a no-brainer.

 

[zebra03]

Sounds about right

 

[mech986]

They do it all the time at DIYaudio.com forums. Now to get extra/spare power supply boards and parts lists (that can come from service manuals). Come to think of it, the service manuals have board and component side tracings, plus parts lists. Would have to compare them to what is really on a board though.