Marantz 2235 Restoration

MarantzRefrb

MarantzRefrb

Super Member
A 2235 from eBay has been patiently awaiting its turn:

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Had never been opened before - Clean!
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I had not seen a side mounted dial-cord before:
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2235 allows the use of face feet:
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Clean?
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Full rebuild kit with all options from iRebuildMarantz.com:
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Time to get started.
 
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Stock P800 Power Supply board:
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New parts going in:
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Completed:
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Set Output voltage - black J805 red J804 - set R806 for 35vDC:
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As easy as this 2235 looks like it would be to rebuild, that P800 board is difficult to move, even with all of the screws out of it, the caps are down low, and the board moves maybe a 1/2" left to right. This P800 took me longer to do, and was more difficult than a 2275, 2245, and 2230. The 2235 wins the most difficult P800 award, IME.
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Thanks, Jonstigator! I have read that too, that the 105C is the way to go in the PS. This little 2235 won't be in a wood case, so it's likely to never run anywhere near 85C/185F.

I soldered those Elna Silmic II's in there at about 400C, and they lived, so I have a hard time understanding the temp ratings on these.
 
IMHO the temp rating is a bit of an overhyped factor in selecting caps for power supply. A standard Marantz power supply will never see near 220 degrees Fahrenheit. At least I hope not! What that temp rating does get you is longevity. The cap was tested for longevity at or near its rating so if used in a lower temp environment it’ll last even longer.

The key in a power supply capacitor is low esr and high ripple current capacity. Almost all modern capacitors provide a decent spec on both but some specialized series like Nichicon UPW are especially good while also giving the the 105c rating. And some AK members will tell you they hear a difference using Elna Silmic II or Nichicon UFG in the power supply. Maybe. Any which way they’re all better than the tired caps you pulled out. Just a matter of taste.

p.s. some will even tell you that pulling out the old caps is a bad move. so there, all bases covered for opinions. Follow your gut.
 
I can believe that changing the coupling caps in a cap-coupled model, like the 2230, might make more of an impact on the original sound, and could possibly harm it (I can believe this for the moment, haven't tested it yet).

But after 3 months of solid focus on restoring 3 different receivers, with the same cap complement, and listening to every board along the way - taking care to listen with the same headphones, output volume and as many other factors as I could control - I personally found that replacing the capacitors improved the sound in every model, and in every case I tested. I couldn't say whether Nichicon or Elna II's sound better, just that Marantz used Elna in the original design, and if I'm now able to replace caps myself, why not go audio-grade.

I have not replaced the filter cap or coupling caps in my 2230 - am seriously worried about harming what I have there.
 
UPW - miniature sized, low impedance, high reliability for switching power supplies. Elna or Nichicon audio series are better in liniar PS.
 
MarantzRefrb said:
I have not replaced the filter cap or coupling caps in my 2230 - am seriously worried about harming what I have there.
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I have replaced those caps in several 2230's and have always seen an improvement in sound with the overall rebuild. It's hard to say what effect each segment had, but I certainly have never felt that the large cap replacement caused a loss of the "Marantz Sound" that is often referred to.
 
Well I did not want to start a **** storm. I have always sworn by Panasonic FC for all my general positions including all in the power supply. I lean the other way on that debate. I am not sure if you can hear the difference in quality caps. I simply opt to use the best cap I can where it was designed to be used.

All electrolytic caps have a self life. Even if unused they will go dry just like granny but in half the time. So going through and replacing caps in really old units is needed before one pops. This is not a rebuild rather a refresh with a clean face. Kind of like an oil change.

I always replace the coupling caps. I have used Mundorf, Elna LAO, Nichicon KZ and Gold Tune then many others. Does it sound better than when it was new? I don't know I was not there. Does it sound better than it did 2 days ago? Oh Hell yea!

But it is your receiver. Do what sounds best to you. That's Karma
 
Jonstigator said:
Does it sound better than when it was new? I don't know I was not there. Does it sound better than it did 2 days ago? Oh Hell yea!
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Unfortunately, I WAS there. Unfortunate, because that makes me older than I feel. But my first Marantz was a new 2230 in 1972 when I was 22. I didn’t have a golden ear, I just knew I liked it better than my friend’s Sansui. It was stolen six months later, and I bought a new 2245 that I kept for 20 years. To me, a fully recapped 2230 doesn’t sound any brighter than that original. I don’t believe that famed warmth is a fragile thing. I think it is built into the design. Just opinion with no evidence.
 
I understand the argument on both sides of using the 105c longevity, vs. 85C reported audio-grade. I can replace these if and when they fail, is the best part of all though. Might as well investigate for myself, as was mentioned. And yes, any new caps are better no matter what - point taken.

Regarding the coupling caps on a 2230, these have a carbon composite resistor on both channels, and small coils:
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If you guys wouldn't mind helping me figure these components out, in my 2230 thread:https://audiokarma.org/forums/index.php?threads/marantz-2230-restoration.924022/ - I'd really appreciate the knowledge and would also like to keep this thread dedicated to the 2235 - it was my fault for bringing that up in here.

Thanks for weighing in all!
 
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Steven Tate said:
Unfortunately, I WAS there. Unfortunate, because that makes me older than I feel. But my first Marantz was a new 2230 in 1972 when I was 22. I didn’t have a golden ear, I just knew I liked it better than my friend’s Sansui. It was stolen six months later, and I bought a new 2245 that I kept for 20 years. To me, a fully recapped 2230 doesn’t sound any brighter than that original. I don’t believe that famed warmth is a fragile thing. I think it is built into the design. Just opinion with no evidence.
Click to expand...

Yuppers! I had a near new 2225 as a teenager. The more I loved it the more my mother hated it. She sold it while I was in boot camp. I still was not lucky enough to listen to other models. But I know a fully recapped 2220b and a 2225 sound just as good as my first 2225. Simply put, caps age and leak and go dry.

You are right when you say it comes down to circuit design. Marantz kept them simple and sweet. Recapping just brings them back into spec.
 
I would go ahead and reuse the carbon resistor and coil and reconnect them just as you found them I also like to take pics and hand draw all my wiring with wire color indicated. Try to undo at the cap and leave every thing else as is. I am not sure what they do but I have seen these jumped by other caps too.

In do apologize for hijacking your thread.

MarantzRefrb said:
If you guys wouldn't mind helping me figure these components out
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It has been so hot here, I was only able to work on this 2235 after midnight last night!

Begin P700 Output amplifier L&R board:
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Remove all screws from P700, ground strap preventing removal of board:
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Remove wire post from board that connects ground strap:
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Remove output transistors:
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Access to rear of stock P700 board:
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Stock P700:
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Recapped:
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Back together for testing:
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When I went to set DC Offset and Bias, I noticed that the SM does not line up with my 2235. According to the SM:
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None of my resistors are the same numbers listed above:
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If the manual is correct, and my board numbers are wrong, that would mean:
R747=R756
R748= R757

R729=R766
R730=R767

Bias
Translated to my 2235:
Across R756 - Set R766 for 7.5 mV
Across R757 - Set R767 for 7.5 mV

DC Offset
R723=R713
R724=R714

Would this be an accurate assumption?

Thanks!
 
It's impossible to get your grabbers to connect across the resistors, because there is shielding on the legs of each resistor:
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In looking at the schematic, there are test points that will allow an easier connection with grabbers:
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Can confirm the above jumpers, and these numbers are correct for some 2235's:
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Bias
Across R756 = J713 to J715 - Set R766 for 7.5 mV DC
Across R757 = J14 to J16 - Set R767 for 7.5 mV DC

DC Offset
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For the DC offset, I have no scope. Is this model different from the other direct-coupled amps, where you set 0mV DC across the speaker terminals?
 
You're exactly right Steven, I was looking at the wrong manual. What a waste of time :eek:.

I forgot about the AK database, thanks so much for reminding me, very glad that database exists! That cleared this all up:
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I'll readjust the settings to the correct specs. Thanks again!
 
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