2270 no power

If I didn't know better I'd think you were trying to tell me something. :D I just checked the data sheet and I believe these would work for orientation. I will have to spend some more time testing other parts on that board. I believe I did see the one resistor with a dark ring around it that looks different than its mirror image on the other side that might indicate burning.
 
Just pulled R787 100 ohms, the one that looks like it has a brown/grey ring around it and it measures 97.2 ohms and the opposite side at R786 measures 99.3 but has no grey ring around it. Safe to assume some heat damage??
 

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Is that why it measures less then it's counterpart? At 100 ohms how close to the actual value should they be? How much of a drop would be considered " normal " and not heat damage. Just trying to learn as I go.
 
Is that why it measures less then it's counterpart? At 100 ohms how close to the actual value should they be? How much of a drop would be considered " normal " and not heat damage. Just trying to learn as I go.
All resistors come with a tolerance rating. 1% up to 5% Depends on which ones you buy. Most resistors in the Marantz gear is 5% tolerance. If you measure and it is farther than that. then maybe it needs replacing. Carbon resistors change value with just age. Heat speeds up the value change. Others will chime in with their thoughts.
 
So having said that, at 5% for instance, the reading could be as low as 95 ohms and regardless of the burn mark on the resistor still be within tolerance and realistically could be left in place??? Hmmmm.... I understand that under my circumstances ( and the minimum cost of replacements) knowing that there was a wisp of smoke it's just preventive medicine regardless of the tolerance percentage. Is this an accurate statement?
 
So having said that, at 5% for instance, the reading could be as low as 95 ohms and regardless of the burn mark on the resistor still be within tolerance and realistically could be left in place??? Hmmmm.... I understand that under my circumstances ( and the minimum cost of replacements) knowing that there was a wisp of smoke it's just preventive medicine regardless of the tolerance percentage. Is this an accurate statement?
When in doubt ...throw it out..or at least keep the old component just in case you want to put it back in.
 
Tried the search feature on here but had no luck finding a BOM list for Mouser for a 2270. I thought there was one so must have been thinking of another unit so if anyone has one I'd appreciate it. I would like to order the other necessary replacements for the damaged parts but would also like to order everything at once to avoid extra shipping cost. Because I've removed all the transistors on the right side for testing I would assume just as well to replace them instead of installing the old ones?
Will order the outputs as suggested earlier in this thread with the ones suggested by Mr Buckner as well as the driver transistors ,and other transistors at H754/755/766/767. Would these replacements be suitable? If I remember correctly 755 tested bad the other day when I checked it.
H754/5..2SC735.....>>>2N3904
H766/7...2SA562....>>>2N3906
Also need to replace that burnt resistor at R786/7 so I have to find a suitable replacement for it. Original is a Carbon 100 ohm 1W but I'm having a hard time to find that same value in a carbon. Would a Metal Oxide one suffice or no....660-MOS1CT52R101J ?
 
https://www.manualslib.com/manual/906440/Marantz-2270.html?page=2#manual

Its not a list, but it has some schematics.

Don't use a carbon. As Randy said, they drift. MO is very good choice.

Before you install any substitute transistor, Make darn sure the EBC legs are in the same location:yikes:

Did you try digital docs for a parts list in the manual there? There should be a list towards the back.
As far as transistors go, its good if you can stick to the closest hfe and match the set you put in.

As far as changing all the transistors, Don't do it. Just change the bad one and its mate with a hfe matched pair. You could end up with a bias issue or unbalance in the amp if you put a bunch of subs in.
Original new parts are OK, But substitutes can make you pull your hair out if your amp will not adjust afterwards.

Heres a good post to read.
http://www.audiokarma.org/forums/index.php?threads/marantz-2270-bias-wont-go-below-15mv.322206/
 
https://www.manualslib.com/manual/906440/Marantz-2270.html?page=2#manual

Its not a list, but it has some schematics.

Don't use a carbon. As Randy said, they drift. MO is very good choice.

Before you install any substitute transistor, Make darn sure the EBC legs are in the same location:yikes:

Did you try digital docs for a parts list in the manual there? There should be a list towards the back.
As far as transistors go, its good if you can stick to the closest hfe and match the set you put in.

As far as changing all the transistors, Don't do it. Just change the bad one and its mate with a hfe matched pair. You could end up with a bias issue or unbalance in the amp if you put a bunch of subs in.
Original new parts are OK, But substitutes can make you pull your hair out if your amp will not adjust afterwards.

Heres a good post to read.
http://www.audiokarma.org/forums/index.php?threads/marantz-2270-bias-wont-go-below-15mv.322206/



Kutzler ... Thanks for both links , I have the manual printed from Hifiengine but what I meant I was looking for was a recap list. I will follow your advice and order a few extras on that one Transistor to match the HFE as close as possible and avoid replacing any others as you suggested. Would you say the replacement part numbers I posted would be ok as replacements just the same for that transistor and one resistor?
That link for the Bias adjust is interesting but it had my uneducated little brain swimming. There is so much to try to take in and understand that it will take me years ( if I have that many left) to understand all this. I envy those of you that do so easily.
 
Quad .... Thanks ...yes that will certainly help a lot. Funny thing is I started to read that thread earlier in the week while at work and have no idea why I didn't realize it was a recap list. Crazy busy at work and night shift has me firing on less than all cylinders I'm guessing in fact I'm just getting in now from work since yesterday at 7pm so I will read the links in depth when I get some sleep. Hoping it will be clearer then. o_O
 
It seems that the very first item ( filter caps) on the list for Mouser is now not available. Is there a recommended replacement. I've been on the mouser site but at 10,000uF the highest Voltage I can find in 40 mm dia is a 63v.
 
Checking the data sheet on some of these it seems the first one would fit the bill as far as diameter, volts, and capacitance. Only difference being 3 dummy pins which I assume can either just be left alone or cut off correct?
 
Correct. Dummy pins are of no concern unless you're actually board mounting the capacitor. Mouser seems to be running short on viable 40mm caps last I checked. Having to search more and more. Hope this isn't a sign of things to come.

As far as specs for filter capacitors you'll just want the biggest ripple current numbers you can buy that will fit in the space and your budget.
 
The spec sheet denotes the ripple current at 4.77A. Not sure if that's suitable but all things equal it seems to be the best option so far. Just wondering Mike .... Going back to post # 49 I asked if 2N3904 would be a suitable replacement for the one transistor ( 2SC735 ) that tested bad but never did get a response. Is this a replacement that you would say is ok and if so I assume that it's mirror image on the other side of the same board should be replaced even if it tested ok? Just trying to get all the ducks in a row before placing an order.
 
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