2270 - Serial 11728 - Refurb, mostly caps and diodes, a few transistors

[Dingman]

Ya, I think if you find a ceramic in the signal path, then it's up for C0G.
I bailed on changing all the components at once, but I did go 75%. I'll run it a bit, and then change the rest of the diodes, and the 2W resistor. Transistors are staying.
I fired it up, dim bulb first. No issues there, so then warmed it up, and took the 33.6vdc and adjusted up to 35.05vdc. No speakers attached yet.

 

[Dingman]

And the FLIR shots just for fun.

 

[Dingman]

I let the run all night at low volume and no issues are seen\heard.

I'm waiting on new Mica insulators for the TO-3 outputs, so I think I'll do some work on the phono board. I just can't leave well enough alone.

Fred Longworth says:

This is an easy one. The 2270 phono preamp uses 2SC458 output transistors. These are the highest failure rate, small signal, low noise transistors in the entire history of audio. They leak and cause noise and distortion.
Replace these with 2SC2240.

Note that the 2SC458 pins out as BCE, reading left to right, whereas the 2SC2240 reads ECB.

After the transistors are replaced, put a 400 to 700 Hz sinewave signal into PHONO and turn up the input signal so that clipping occurs within the phono preamp. Adjust the on-card pots for symmetrical clipping, top and bottom of sinewave.

LeeStereo says:

The capacitors C703 and C704 function to block DC in the RIAA feedback loop; with the stock 22µF value, the F3 is ~11.7Hz. It is worthwhile increasing the capacity of these capacitors to obtain a F3 of below 5Hz (to minimize the phase shift within the passband); with a 100µF capacitor, the F3 is ~2.6Hz Also note that later Marantz models used a larger capacitor in this position (e.g., in the 2325, a 47µF capacitor is the stock value).

And from MBuras:

This one is much like the preamp board. Everything was replaced with few exceptions. Original had the big green films that everyone hates. Replaced the 0.47uf films at all 4 corners with Clarity Cap ESA films. Didn't have any experience with them but supposed to be good and my supplier was out of the Solen caps in the same value. Anything is likely better than the greenies. All resistors were documents, mapped, and replaced with metal film equivalents from KOA Speer. C703/C704 tantalums were replaced with Nichicon bipolar caps, increasing the value from 22uf to 100uf. All 4 ceramic caps were replaced with equivalent C0G/NP0 MLCC's and the only electrolytic on the board, C713, was replaced with a Elna Silmic II cap, upping the value from 100uf to 220uf. All 4 SC1000 transistors were replaced with Fairchild KSC1815YTA's and the 2 SC458's were replaced with Fairchild KSC1845FTA's. Both the 1S1212 diodes at H707/H708 were replaced with Fairchild 1N4148's and the single VD1212 at H709 was replaced with 2 Fairchild 1N4148's in series. And lastly a set of Bourns trimmers were used to replace the originals.[\quote]

[/quote][/quote]

 

[Dingman]

Slow but steady, I guess.

I didn't do the phone board yet, but will soon. I did however, get the tone board re-capped. All WIMA MKS2, except C401 & C402, I didn't have WIMA in the .33uf value. I had ordered the OEM value of .22uf but forgot that @Leestereo had raised that value to .33uf. So, a poly type film in those two spots.

http://audiokarma.org/forums/index....grade-of-a-marantz-2270.793805/#post-10978671

I also raised the values of the DC filtering caps per his thread, expect C409 only to 220uf instead of 270uf, simply because I didn't have a 270uf. I installed very low ESR caps.

 

[Dingman]

I did the pre-tone board yesterday. I did change it up a bit, I had also just re-capped the pre-tone on a different 2270 (serial 9006) and I sure feel like it lost most, if not all, of that Marantz "warmth".
I do brief listening sessions after each board and although subjective, I am using the same source, same material and same speakers so it should be somewhat comparable.
On the 9006 unit, seemed like it changed the most with the pre-tone and not so much with the actual tone board.
On this #11246 unit, I was hearing about the same - tone board changed the SQ slightly - seems less warm, less muddled. But overall, fairly well balanced. I think these old Marantz run a little on the muddled (warm, blanket over speakers, etc) anyway, so I like having a little better "clarity".
But not so much, like the way the #9006 turned out - as I said, it seems to have totally lost the warmth and while testing on some Cervin-Vegas, I almost felt like I needed to turn up the bass. Don't get me wrong, I think this #9006 sounds great - very clear, low noise floor, good separation - it's good SQ. But not warm by any means now.

At any rate, on this #11246, I decided not to use all C0g caps, four of them were swapped to Nichicon Poly Foil Type Film Capacitor's (these are the yellow ones in the pics). I *think* it made a favorable difference compared to the other unit. Quick listening test, seems like it maintained a little of the warmth. I'll have to bounce the units back and forth for a bit and see if I'm sure about what I think I hear.
Oh, and the 1uf's aren't C0G either, they are a normal poly cap. I didn't have a WIMA or C0G to fit.

 

[Steven Tate]

Some thoughts about the Marantz “warmth”: I bought three units new in the 70’s - a 2230, 2245 and 2270. I listened to them over many years. While there may have been some suggestion that they had a warm sound in those days, I believe it was only relative to other brands that stressed treble over the mid ranges. But Marantz had no shortage of all frequencies. I just considered it more balanced. I had a friend with a Sansui that he thought was superior, but it was too brilliant for me. Now, fast forward 40 years. I got back in the hobby after a 25 year absence and bought several working 22xx units. All of them - and I mean all of them - were lacking in the high end. Compared to original Marantz,they sounded muffled and, yes, blanket-over-the-speakers is a good description. This sound is definitely not the original warm sound of Marantz. When I refurbished these units, it opened up the top end tremendously, but this was not a loss of original Marantz warmth. It was a return to the original broadly reproduced soundstage. I believe in the modern era, people who didn’t have originals often mistake the sound of the aged Marantz with poor high frequency reproduction as the “Marantz warmth”. It isn’t. I still have all of my vinyl records from the 60’s and 70’s and I can tell you my refurbed units sound very much like my original units when I play those records. Very subjective, I know, but here is my method: when I bought my new 2245 around 1972, I also bought a Dual 1229 turntable and the first album by a new group called The Eagles. The first song on that album is “Take It Easy”. I set the system up with some great speakers I already had, put the album on, and the first sound was that awesome acoustic guitar chord, full of brilliance, that starts that song. I’ve never been more thrilled with a sound in my life, and I have used that chord to compare systems ever since. On an unrestored 22xx, that chord will be seriously lacking. Replace those old caps, and that brilliant sound of acoustic strings jumps right out. Bottom line - I’ll bet your 2270 sounds more like the original than you think. Beautiful job! Those boards and pot look like brand new. I really enjoy your rebuild threads.
Steve

 

[Dingman]

Some thoughts about the Marantz “warmth”: I bought three units new in the 70’s - a 2230, 2245 and 2270. I listened to them over many years. While there may have been some suggestion that they had a warm sound in those days, I believe it was only relative to other brands that stressed treble over the mid ranges.
CLIP TEXT
Replace those old caps, and that brilliant sound of acoustic strings jumps right out. Bottom line - I’ll bet your 2270 sounds more like the original than you think. Beautiful job! Those boards and pot look like brand new. I really enjoy your rebuild threads.
Steve

Those are really good, thoughtful comments. That all really makes sense to me. The #9006 does sound really good at this point - very clear, high and mids almost overpower the bass - but of course, I'm mentally comparing to how it was sounding before the new caps - and it was certainly on the muffled side. So, although it "feels" bright right now, I'd bet after getting used to it, then if you were to make me go back to the pre-recap sound, I'd be "No way! No Blankets!".
Ya, I'm thinking you're correct - these units are now sounding much like when they were new, and no so much like the "40 year old blanket" sound we tend to associate with this era Marantz.

This #11246 doesn't seem as bright, but I've only had a short listen on test speakers and so.. maybe it is just as bright, or maybe it isn't. It sure has a different set of caps on the pre-and-tone boards tho, so I do expect it to sound differently... and all the old OEM transistors\diodes\resistors are still in there, so that's probably a crap-shoot on how they've all aged.

 

[Dingman]

I'm fixin' to do the phono board today (and probably the big filter caps, upgraded to 15,000) and I noted that someone has had to repair this board already.
One cap and looks like 3 transistors replaced with 1345's. So, I'm gonna replace all transistors with 1845's and 992's.

 

[Dingman]

I did get that phono board re-done. All transistors (I used 1815's and 1845's) replaced as well as the most caps and diodes.
For C703/C704, Leestereo used bipolar 47µF/35V Nichicon ES capacitors; I also used the bumped up value of 47uf but I used polarized Audio Grade Nichicon KZ Muse.
The filtering/decoupling capacitor, C713, was a 100µF/50V was replaced with a 220µF/50V (Leetereo used a 270uf) low ESR (mine is panasonic).

 

[Dingman]

I started on the right amp board. Naturally, I found I'm lacking the 4.3K 1\2 watt resistor and the 15v zener diodes.
But I did get a little work done on it - got the flyback diodes installed - couldn't get it looking as nice as Leestereo, but they do have good mechanical connection.


And just because I got nuthin' else, here some pics of solder pads cleaned, leads folded down against the pad. C751 ready for soldering.

 

[Dingman]

I've got the right amp board done. I'll put it back together, install outputs with new goop.
I try to get the solder joints just right, sometimes have to re-do them if they go "cold" or don't seem to wick out well. I don't clean rosin off, so still looks like crap. Do you guys clean up after soldering?

 

[Dingman]

Crap, I realized I installed 1\2 watt zener's and I should have installed that 1.3 watt listed in Leestereo's thread.

Grrr, another order to Mouser and another delay.

 

[catrafter]

I think the 1/2 zeners will be fine. According to some quick calculations the zeners are dissipating less than a quarter of a watt.


Tom,

 

[Dingman]

I think the 1/2 zeners will be fine. According to some quick calculations the zeners are dissipating less than a quarter of a watt.


Tom,

You are correct on the load for those, but I had intended on installing the bigger ones just to stick with the leestereo build. LOL, but my brain forgot and ordered the 1\2 watts. And then my brain installed the half watts.
Since I don't have the big ones, I might just leave the 1\2 in there.

 

[catrafter]

I would leave the zeners be and not look back.

Tom

 

[Dingman]

I would leave the zeners be and not look back.
Tom

I'm sure they would have been fine, but I had already ordered the larger zeners, so I did install the 1.3 watt versions.
I've got the amp back in, and it dialed in to 1mv dc, and 10mv across both emitters.

 

[Dingman]

Geesh, I told you guys that I was slow. Just got the right amp done, and while waiting for it to warm up, I polished up the pre\amp jumpers.
Hey, whats the consensus on the bare metal jumpers vs the black ones, which also jump the shield side?

 

[Steven Tate]

I have seen several experts that don’t approve. I believe their basis was that there is no shielding over the length of the jumper which could result in low level hum. I”m not sure if the black jumpers are well shielded or not. But if you get some high quality 6” RCA jumper cables,you’re good.

 

[catrafter]

2230 and 2270 (2245?) receivers do NOT have the shield side of the pre-main jacks connected together, there may be hum problems if you use jumpers that only connect the center contacts.

Tom

 

[Dingman]

2230 and 2270 (2245?) receivers do NOT have the shield side of the pre-main jacks connected together, there may be hum problems if you use jumpers that only connect the center contacts.

Tom

Well, isn't that interesting. I'll just fab up a couple of RCA jumpers of my own.