• The move to the new server is done. There are some software and database maintenance updates in process. This has us passing the hat around to help out. We appreciate any donations. Seriously, even a dollar helps. The payment page may be found here - https://www.audiokarma.org/support.html

Sansui G7500 HELP.

anderslober said:
Lee.....shall I power ON without the outputs?
Click to expand...

Yes Anders fire it up without the OP's in it.......Lets see if the oscillating goes away then, it will either stop and go dim, or have little change I suspect...

Then could you measure the "rail" voltage and check where the PNP (2SA) goes, that you have -71VDC and where the NPN (2SC) you have +71VDC.
The polarity is extremely important here. Measure where the COLLECTOR connects....

Also note any fluctuating of the voltage......or the voltage being low......

I simply cannot see that you have done anything wrong with the wiring, so we are going to start moving back into the DC supply now.....

You have put new OP transistors in havent you?

I will get up (its early morning) in a minute and go and measure a transistor the way Lee was describing and show you what readings you should get, I have some of those particular Sankens.....NOS never used....
Stay tuned....

OK, the 2SA1106 with the black probe on B you should see, and this will be approx.
B > C = 1.5 megΩ
B > E = 3.0 megΩ
all other measurements with the Ω setting will be OL

the 2SC2581, with the Red Probe on B
B > C = 3.0 megΩ
B > E = 3.0 megΩ
all others will be OL on this too with the Ω setting......

Lastly, can you please identify the driver transistors? I cant read the writing on them from the picture.
Thanks Anders.......
Its Saturday here now, and I am not working today (apart form on that very old McIntosh MC250) so I am good to put some time into this today....
 
Last edited:
No I never had it blow any outputs. But its been years since i used it. I did turn it on before i took it apart wanted to see if the FM worked. didnt have anyspeakers i wanted to try hooking to it though. If ya need to i still have the heatsink with outputs still on it if you need to confirm positions still.
 
jeffj7 said:
No I never had it blow any outputs. But its been years since i used it. I did turn it on before i took it apart wanted to see if the FM worked. didnt have anyspeakers i wanted to try hooking to it though. If ya need to i still have the heatsink with outputs still on it if you need to confirm positions still.
Click to expand...

I'm after the positions of the driver transistors.....
 
Jeff.....yes...please confirm the positions with a picture of your heat-sink.
Kevin.....boy-o-boy...we are using a lot of time on this sucka'! Ok...I'll power ON without the outputs in on dbt. I'll measure the COLLECTOR and note polarity...........and I'll measure the tr's with ohm-setting.....6-ways. Here goes...........

KEVIN!!!! Powered ON with no outputs in......bright....dim....relay clicked! HUH? My outputs.......are they crap? Outputs were brand new and tested!

2sa1106: BCE. Black probe on B.
B>C=OL
B>E=OL.

2sa1106;RED probe on B:
B>C=17.5M ohm.
B>E=17.9M ohm.

I think I am getting the picture now...............outputs ar NOT BCE!!!!!!!

2s2581: BCE. Black probe on B.
B>C=2.35M ohm.
B>E=7.4M ohm.

2sc2581; Red probe on B.
B>C=25M ohm!!!
B>E=OL.

The 2 same outputs measure differently too!!!!!!! C-O-U-N-T-E-R-F-E-I-T-S!!!!!!!!!

With the 6-way tr test all outputs test good!
 
Last edited:
anderslober said:
Jeff.....yes...please confirm the positions with a picture of your heat-sink.
Kevin.....boy-o-boy...we are using a lot of time on this sucka'! Ok...I'll power ON without the outputs in on dbt. I'll measure the COLLECTOR and note polarity...........and I'll measure the tr's with ohm-setting.....6-ways. Here goes...........

KEVIN!!!! Powered ON with no outputs in......bright....dim....relay clicked! HUH? My outputs.......are they crap? Outputs were brand new and tested!

2sa1106: BCE. Black probe on B.
B>C=OL
B>E=OL.

2sa1106;RED probe on B:
B>C=17.5M ohm.
B>E=17.9M ohm.

I think I am getting the picture now...............outputs ar NOT BCE!!!!!!!

2s2581: BCE. Black probe on B.
B>C=2.35M ohm.
B>E=7.4M ohm.

2sc2581; Red probe on B.
B>C=25M ohm!!!
B>E=OL.

The 2 same outputs measure differently too!!!!!!! C-O-U-N-T-E-R-F-E-I-T-S!!!!!!!!!

With the 6-way tr test all outputs test good!
Click to expand...

Where did you get those outputs from?
They could well be counterfeit....:scratch2:
I have a set of outputs (Sanken) if you want them......they are genuine....I could be convinced to part with them.....

The ones you have there should be BCE if not then they are counterfeit probably...

OR........

get these
NJW3281G (NPN)
NJW1302G (PNP)

they are available and work well you can get them from RS components, Element 14 etc etc, I have them in my G7700.........they TO-3P just like the ones in there....

I think what happened before is you had counterfeits in there that were sort of working but then just let go......
 
I actually got them from a vendor here in SG. I use her quite often for parts and such.

Ok.....I will try the NJW's. Kevin...keep your Sanken's for a rainy day!

The outputs measure as BCE with diode test. How come they measure so differently with the ohm test???

GDI......IF it was the outputs.......shucks....we should have tested those suckers early!
Check out the pics........ohm setting......first 2 pics are 2sa1106....last 4 pics are 2sc2581.
 
Last edited:
They look fake to me.

I have some 2SA1386A and 2SC3519A transistors. The Vcbo is only 180 volts instead of 200, but I think they would work. They are 130 watt as opposed to 100 watts.

Rob
 
Robisme said:
They look fake to me.

I have some 2SA1386A and 2SC3519A transistors. The Vcbo is only 180 volts instead of 200, but I think they would work. They are 130 watt as opposed to 100 watts.

Rob
Click to expand...

All good Rob, he can get these NJW3281G (NPN)
NJW1302G (PNP), I've used them in my G7700.....
I also have a set of Sanken 2581/1106 on offer......:thmbsp:

anderslober said:
Rob....how can you see they are fakes?

What manufacturer is 'SR'? Anybody know?
Click to expand...

Anders, as Rob said, I can almost guarantee those transistors are Chinese fakes.........
I am convinced that is the problem......
 
Ok guys......vented my frustration by busting open a 2sa1106.

See the pic's! I think I have a meeting with my vendor later today!
 
Last edited:
anderslober said:
Ok guys......vented my frustration by busting open a 2sa1106.

See the pic's! I think I have a meeting with my vendor later today!
Click to expand...

HOLY ****!!!! Damned counterfeiters.....:nono:

Seriously Anders you are welcome to grab those Sankens off me I really dont mind.....
 
I am a bit pissed off!@#$%! If all this crap was because of these fake outputs. A first for me! In my naivite, I didn't think they had fakes here in SG. BUMMER! At least now we can get on with the project.

Jeff...post a pic of your heatsink....thanks.
 
anderslober said:
I am a bit pissed off!@#$%! If all this crap was because of these fake outputs. A first for me! In my naivite, I didn't think they had fakes here in SG. BUMMER! At least now we can get on with the project.

Jeff...post a pic of your heatsink....thanks.
Click to expand...

I was pleased to see it fired up and came out of protection without the outputs.....
Yeah, what a complete waste of time eh?
But look, its a lesson we can all do with being reminded of, and certainly you had bought from the person before and you had no reason to suspect anything......
But yeah, I just do not buy NOS, the only time I have is from the Sansui shop because he is a trustworthy source....
Most of the time new subs can be found as in this case the NJW3281G (NPN)
NJW1302G (PNP) devices......
I can wait to see it running Anders!!! At least we know its going to run now!!!
 
You must log in or register to reply here.
Back
Top Bottom