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Fuse Resistors - The where's, why's and how's

Hi, I'm new here. I got my fathers old 317-II which worked "until removed like 8 years ago" :)
classic: red light is on, the click is present after like 4-5seconds, but no output sound whatsoever.
Checked:
-Loudspeakers work on another amp
- Fuses are not blown
- visible check ok!?

Now i've seen that there are MANY resistors, but in the first posts only 4 + 2 resistors 82 and 68 ohm should be replaced.

Should they ALL have their appropriate resistance when the amp is turned on ? Should I only check those or like ALLLL ?

Plus: my measure device can't mesure capacitors. They do not have "blown heads", seem fine.

I'll be going to the electro-shop tomorrow and will get the 6 resistors, what could I need else ?

thx in advance :)

I'll add some pics:

 
Hi Jigo. Welcome to AudioKarma, Sansui forum. You really should start a new post with a title that describes your issue. Many more people will see it as a stand alone thread rather than tacking it on to a thread that is several year old.

- Pete
 
ok I'll move it; I am used to post similar problems to similar threads, as many forums want it so ;)
 
Anyone have any pictures of the 517 circuit board? I've found some schematics but if anyone's taken one of these apart and has some tips I'm all ears! Glad I found this thread because the distortion I'm hearing in the right channel seems like it could very much be this problem exactly, but I'm also pretty new to amp repair. (If I feel at all in over my head I'm just going to take it in to a local shop, but I have a friend who's an electrical engineer who is going to look at it with me). If anyone has any more info on hand on exactly what resistors to replace, or values / numbers on the schematic that would be amazing! Thanks for all the info in this thread either way, super helpful.
 
skippy124 said:
Hi,

After working on quite a few Sansui amps and encountering the dreaded fuse resistors on many of them, I thought it might be worthwhile to post up some information on where they are in various amps and receivers, what symptoms are typically present when these go faulty, and what to do about replacements.

Contributions are welcomed from other AK'ers, and I will index these in this first post.

Starting at the end.... it has been well documented by others here that the typical 1/4W fuse resistor used by Sansui in many of their amps and receivers can be replaced by either good quality 1/4 or 1/2 Watt Metal Film resistors, and that is the path I have taken on many occasions and have yet to encounter any problems with this approach.


The typical fuse resistor that gives problems can a light grey , greyish blue or light green colour, and looks like these ones shown below

fuseresistors003sm.jpg


The following posts will show the position of fuse resistors in the AU117 through AU717, plus the AU 2900/3900/4900 series. As stated above posts are welcome on other amps/receivers, and any comments are more than welcome.

Some of the typical symptoms of out of spec (high resistance) or open circuit fuse resistors are (in the affected channel) - distorted output, low bias reading and/or inability to set correct bias, low gain and pops/crackles/noise.

I hope this is of use and gives a little back to the excellent Sansui fraternity we have here on AK.

AU117

AU217II

AU417

[URL="http://www.audiokarma.org/forums/showpost.php?p=5544295&postcount=18]5050[/URL]


Cheers

John
Click to expand...
I hate to complain but I can't see any photo bucket pics I guess I'm not a member of their club..
 
Willy6 said:
Everybody should drop photo bucket like a hot rock.
Click to expand...

Exactly, however I just re-enabled the Photobucket Hot-Fix in my browser and got the pictures showing again - but there are none for AU-517/717 in this thread - just a marker post for this info.

(I disabled the fix because of some weird AK thread/post permissions issues I was getting).
 
Regarding AU-517 & AU-717 fuse resistor positions:-
Here are the driver board layouts from the SM - with fuse resistors ringed in red, R23 & R25 (on each board) all 150Ω

Note: these are 'Track Side' (=conductor side) diagrams.

AU517_717 Left driver.JPG AU517_717 Right driver.JPG

Here is the AU-717 Tone Control Board, R37 & R39 + R38 & R40 all 82Ω - (Note: the AU-517 - F-2673 Tone Control Board has no fuse resistors).

AU-717 F-2720.JPG

And lastly the EQ Board (=Phono inputs) R47 & R49 + R48 & R50 all 82Ω.

AU517_717 EQ board.JPG

Note: the PSU Protector Board for the AU-517 (=F-2765) and AU-717 (=F-2663) have no fuse resistors.
 
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Hyperion said:
Regarding AU-517 & AU-717 fuse resistor positions:-
Here are the driver board layouts from the SM - with fuse resistors ringed in red, R23 & R25 (on each board) all 150Ω

Note: these are 'Track Side' (=conductor side) diagrams.

View attachment 1110733 View attachment 1110734

Here is the AU-717 Tone Control Board, R37 & R39 + R38 & R40 all 82Ω - (Note: the AU-517 - F-2673 Tone Control Board has no fuse resistors).

View attachment 1110746

And lastly the EQ Board (=Phono inputs) R47 & R49 + R48 & R50 all 82Ω.

View attachment 1110748

Note: the PSU Protector Board for the AU-517 (=F-2765) and AU-717 (=F-2663) have no fuse resistors.
Click to expand...

Wow thank you so much! I'm switching 'em out on Tuesday with the help of a friend.
 
Hyperion said:
Exactly, however I just re-enabled the Photobucket Hot-Fix in my browser and got the pictures showing again - but there are none for AU-517/717 in this thread - just a marker post for this info.

(I disabled the fix because of some weird AK thread/post permissions issues I was getting).
Click to expand...

I had to drop the photobucket add-on as it was chewing quite a bit of CPU cycles...maybe it was just my specific case.
 
One thing I just found out with sony tape decks and their servo motor controls... on the servo control PCB, right under the multi-pin input is a small white micron 1/4 watt resistor, which acts as a fuse if anything bad happens in the circuit. They are only a ten ohm resistor... often I jumper them and adjust the tape speed to compensate. But they DO serve a purpose, as I've found out. But anyway... just an FYI.
 
Fantastic thread, deserves a bump. I have two questions.

1) Does an AU-G77X have any fuse resistors? The SM mentions them in the table of abbreviations on P1., but I can't see any indication of them in the schematic. (This is an '80s amp, and it sounds like fusible resistors are "old" technology....)

2) Even if the schematic doesn't indicate a resistor as being fusible, are there typical applications that indicate (at the schematic level) that a resistor is meant to be fusible?
 
js22 said:
This is an '80s amp, and it sounds like fusible resistors are "old" technology....)
Click to expand...
You can still buy fusible resistors, they are still a thing.
They are used in applications where if there is excessive current, serious damage can occur. So they use a fusible which will let go before your amplifier goes critical mass.
 
js22 said:
are there typical applications that indicate (at the schematic level) that a resistor is meant to be fusible?
Click to expand...
Anyone competent at electronics who can read a schematic, could suggest potential candidates to be fusible resistors in the vintage amplifier designs that are commonly discussed here. It isn't a case of their presence being 'meant', in very many cases where used in vintage audio gear it is best to replace those found with modern 'flame resistant' standard resistor type alternatives. This is because they can be very unreliable, drifting in value as they age, so it seems. The crucial caveat here being do not increase the power rating of the resistor being replaced. If it was originally ½ or ¼ watt - whichever, then match the power rating with the replacement. As Kev says above you wan't the resistor to burn and open (in a fault situation), rather than survive and allow more extensive damage to occur.
 
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SoundOfSound said:
There are some cases out there were a fusible resistor is the only protection you have. There are also unobtainable parts with these little guys trying to protect them.

I think the new technology has gotten much better.

Here are some fusible resistors to use if you need fusible replacements. They are metal film and flame proof.

Vishay 1/3W and 1/2W with a prefix of NFR25 for 1/3W and NFR25H for 1/2W.
http://www.mouser.com/ds/2/427/nfr25-239840.pdf

Yago 1/4W to 3W with a prefix of FRM.
http://www.mouser.com/ds/2/447/Leaded-R_FRM_2011-12977.pdf
Click to expand...


After re-reading this thread I realized that the MF resistors I previously used were lacquer coated and potentially dangerous in this application. I was not able to find any of the above with the 150 ohm 1/4 specs I need on an AU 317, so I am going with these ones now instead for their flame retardant epoxy coating. https://www.mouser.com/ProductDetai...GAEpiMZZMu61qfTUdNhG8/%2BBUtNJ2QbfguQoEij0fg=

(bump, this thread should be a sticky) :beerchug:
 
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