Bright light, NO idea :-)

[jdg123]

Hello guys,

I have done quite a few recaps of working units of multiple brands but that only speaks to reading carefully and solder skills. NOW I have been given a Marantz 2275 that, "just quit working one day". Why would/could I say no?

Unit is not too dirty. Everything looks fine, no bulging caps, no runny goo.

First attempt at power immediately blows a fuse. Read some threads and guessed maybe the bridge rectifier, changed it...now the DBT stays lit bright and fuse stays intact (this may be because the new bridge is way over spec, I don't know...I don't know a lot! ) Can anyone point me in the proper direction?

There are NO lights coming on, no click for the protection circuit just an apparent short not, enough to blow a 5A fuse...

 

[EchoWars]

I would have suspected blown outputs long before I started looking at the rectifier. If the new bridge is installed correctly, then I'd pull the driver boards & heatsink assy. out one-by-one (couple of connectors on the bottom of the board, and four screws holding the heatsink). Pull one of 'em, and try the DBT test again. If that's a fail, pull the second one and try again. If you still get a bright bulb, then it's time to look for something odd like incorrectly installed bridge, or a shorted filter cap.

 

[jdg123]

Thanks! That was easy. Right channel board is the culprit.

Now, how much is smart to order: Should I, according to your experience EchoWars, order say 4 pr of MJ21195,6 just to test for a good matches? (I will change both pairs, left and right channels.)

Is there anything else I should change out, just because...Of course the three tiny electrolytics on the power boards...

Many thanks Echo Wars!

 

[KutzlerTrans]

Change out your h720/721 vd1122 diodes with 1n4842 diodes and maybe change out the differential pair (h701/702)

I would recap the power supply while your in there. There are a few threads floating around about it. These are nice units. If you plan on cranking the snot out of it then put new filter caps in it and go through the pre amp and re-grease all of the transistors mounted on heat sinks.

 

[jdg123]

KutzlerTrans, thank you! I will give the Marantz its due as suggested. I have been reading around this forum (and others) but have not run across an alternative for the 2SC1327 for H701, 2 differential pair. Any assistance in this would be greatly appreciated. I have found the differential pair to be key to good stereo imaging!

Cheers!

 

[jdg123]

Thank you both for your assistance, very much. I feel like I can move forward. I'll start a new search and maybe a new thread about the differential pair. Oh the problem with parts!

Cheers!

 

[rBuckner]

... I have been reading around this forum (and others) but have not run across an alternative for the 2SC1327 for H701, 2 differential pair. ...

KSC1845, most likely KSC1845FTA's. MJ21193/4 will also be just fine and are still overkill. Don't use the silver thermal grease - it's conductive. Good luck and keep us posted!

 

[jdg123]

You guys are great! I will indeed post my results...I know you'll all be patient Thanks especially for the heads up on "arctic silver" and its conductive copies - I already made that mistake on a receiver long ago. It made me crazy until I figured it out! Here is my takeaway from the last three days of reading and direct help:


To review: I'm trying to keep alive and well a Marantz 2275, it has great personal value and history as it was a catalyst for a long lasting friendship that continues to enrich my life.

It has blown outputs. I'm advised to buy MJ21193 and MJ21194 from Digikey or Newark to replace the outputs. Utsource is quite 'iffy".

While I'm inside and on the power boards might as well replace H720, H721 with 1n4842, maybe the differential pair H701,H702 with KSA1845FTA if I can get a good matched pair * - do the tone board electrolytics CE09 - CE14 and CE33 - CE39.

Obviously clean all switches, might as well do the big power filter caps...

The above seems pretty doable and reasonable. The rest is more of a "If it isn't broke, don't fix it!" kind of thing…Yes?

 

[jdg123]

Hey guys I'm getting conflicting information about replacing H720 and H721 listed as vd1122 in service manual for Marantz 2275.
NTE thinks VD1122 is a standard 600V/1A diode, alldatasheets thinks it a 27V Zener. The recommended 1n4842 IS a 27V zener but no longer available...NTE thinks that replacement is NTE146A...whats the scoop?

 

[rBuckner]

Look at the parts on your board. If they have a rectangular glass body with orange inside they are a better part the factory used and can be left along. If they are small round "blobs" with a paint dot at one end those are the VD (!) parts. I thought it was a double diode used for temperature compensation! If you do have the blob diodes, measure them with the diode function on your meter and I'm expecting about 1.2V. In that case use two 1N4148 or 1N4448 diodes in series with cathode to anode at the mid joint to replace them. If it's 0.6V only one 1N4148 is used but I don't think it's these.

On the "if it ain't broke" thing... I'd say "if it's an electrolytic cap and not replaced, it will break in time". They're way past the time they were expected to be in use and I see about 25-50% of caps in this era equipment swollen to some degree. Nice that the 2275 has given you more than just great sounds!

 

[EchoWars]

Hey guys I'm getting conflicting information about replacing H720 and H721 listed as vd1122 in service manual for Marantz 2275.
NTE thinks VD1122 is a standard 600V/1A diode, alldatasheets thinks it a 27V Zener. The recommended 1n4842 IS a 27V zener but no longer available...NTE thinks that replacement is NTE146A...whats the scoop?

Look at the schematic...the collector supply also powers the front end of the amp (47V). The voltage is given at the base of H711 (44V). So H720 sure as hell isn't a 27V zener. FYI, pls ignore the NTE substitution charts. Nothin' but grief there.

In any event, I have a spec sheet for the VD1122 diode, and electrically it's basically the same thing as a plane-Jane 1N4148, but in a radial 'bead' package.

 

[jdg123]

OK, easy to understand. Clarity Thanks! On my board they are the orange-in-clear package so I won't mess with them. Had a good evening just cleaning the boards, ordering the right parts and being thankful for this forum and the good people helping me out!

Cheers!

 

[EchoWars]

OK, easy to understand. Clarity Thanks! On my board they are the orange-in-clear package so I won't mess with them. Had a good evening just cleaning the boards, ordering the right parts and being thankful for this forum and the good people helping me out!

Cheers!

Sounds like they've already been replaced. "Orange-in-clear" seems to indicate a glass encapsulated diode, which the VD diodes are not. You don't mention if the parts you see are axial or radial devices, but I'm guessing they're axial, like any common small-signal glass diode.

 

[jdg123]

Yes, someone has been inside this unit, only one electrolytic on one board is new but the outputs are Faichild I think.


Ive ordered caps for preamp, power and main filter as well as mj21193,4. In for a penny, in for a pound

 

[rBuckner]

Those orange/glass diodes are about the size of 1W zeners. Make sure to take pictures of boards / wiing before starting work, that's saved my bacon more than once! Good luck and post your progress.

 

[jdg123]

Progress Report: both power boards have new matched differential pairs, new electrolytic caps and both power transistors have been replaced with MJ21193,4s.

Now because I am completely new to diagnosis I need advice about what to move on to...and going back to the warning in the service manual:

"Caution: because the driver and output stages are direct coupled, several components may fail as a direct result of a single initial component failure. If a shorted transistor or zener diode is found or a control or boas diode, Be sure to check the remaining driver and output components for shorts or open circuits before reenergizing the amplifier."

I'm thinking I should replace the driver transistors because I have close replacements: I have 2sb536 instead of 2sb537 and I have 2sd381 instead of 2sd382.

So far, so good.

Service manual specifically says to check things for which I have no replacements H709, (2sc496) replacement (NTE295?) and the bias diode H710 (S33016R) replacement (NTE601 that pesky varistor) Should I go on a hunt for replacement parts for these two and just change them out or can these be tested?

 

[jdg123]

I wanted to add for clarity's sake: two photos of the H710 area (can find no evidence for H709, just empty holes) and restate this is a Marantz 2275. (almost all the data I find in thread form is for 2270)

 

[jdg123]

Oh, and one pic of recap and differential pair

 

[jdg123]

Feeling a little foolish here...

Obviously I don't have H709.

The P700 board is YD2917003-5 and the serial number of the Marantz is 9605J4 (an inside sticker says Plant Cord 7021) I downloaded the manual from HiFi Engine.

What I DO see is a resistor leaning up on the heat sink of H711 (2SA794). I'm guessing this is for thermal adjustment? Anyway, still looking for advice of what to do next so that I don't let out the magic smoke when I fire up the unit (with DBT .

 

[KutzlerTrans]

2SC496, Use BD135(corrected) Be very careful to have these installed right side up. Check before installing.
2sB537, Use MJE15031
2sD382, Use MJE15030
H710.... Do not mess with it.
H711, 2SA794, use ksa1220a
H712, 2sc1567 usa ksc2690a