Anyone using Sansui G-8000 with vintage Polk speakers?
Comments
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DC speaker voltage: Left 85mv Right 6mv
Was the same with the amp connection switch in both modes.
Industry standard is 50mv or less on each channel. Guess I need to try and adjust if it is adjustable. Some amps require parts replacement to get to spec. -
i have confused this thread by replying to two different posters.
i will stick to the opening poster no offense jim 249.
mystery,
the DC offset in left channel and right channel are high when compared to the 0-5mV the service manual specs. the service manual has instructions on how to adjust this.
what i was hoping you would do is move the selector switch on the side to the separated position, capacitor coupled (to be safe). then connect a pre-amp of some kind to the power amp in jacks. this will bypass all the other stuff but the power amp section of the sansui, if your volume problem doesn't appear again then we know the power amp section is okay.
if the problem seems to be in the volume knob, the potentiometer needs to be cleaned and lubricated or possibly replaced. do the former first. for a pot that is really bad, do a double whammy on it. clean it with lube free cleaner. this will dry it out hopefully getting rid of grime. then hit it with lubricated cleaner to lube the sliding contacts again. disassemble the rx. as needed. -
canadianicon25 wrote: »what i was hoping you would do is move the selector switch on the side to the separated position, capacitor coupled (to be safe). then connect a pre-amp of some kind to the power amp in jacks. this will bypass all the other stuff but the power amp section of the sansui, if your volume problem doesn't appear again then we know the power amp section is okay.
if the problem seems to be in the volume knob, the potentiometer needs to be cleaned and lubricated or possibly replaced. do the former first. for a pot that is really bad, do a double whammy on it. clean it with lube free cleaner. this will dry it out hopefully getting rid of grime. then hit it with lubricated cleaner to lube the sliding contacts again. disassemble the rx. as needed.
Will test that in the weekend.
However, the main suspect is volume knob.
This morning, I was listening to music with just left speaker hooked up and it worked fine for around 1/2 hour.
Then no sound, nothing like the amp turned off.
I only had left speaker so the right channel may be working.
I turned/pushed volume knob few times and there was no scratching sound but it came on when I moved it past half volume few times and scared the crap out of everyone as the sound was really loud at that level.
And it worked for another 15 minutes fine before I headed to work.
So volume knob could be the issue but it's so weird that it just cut off completely and no scratchy sound when moved.
Klipsch RB81, KG3.5, B&W DM602.5, Polk.
Subwoofers: Klipsch RW10, Triad ProSub Bronze. -
I had a similar issue that turned out to be a fuse on a speaker. My Carver receiver back in the 80's would play fine, sound good, etc. for a while and then all of a sudden the the left channel would either get real quiet or cut out altogether.
If I turned the volume knob up and back down quickly the would sound come back and everything would be fine, sometimes for a few minutes, sometimes for hours. I finally discovered the culprit accidentally: one end of the fuse on one of the speakers was only partially seated in the holder. I pushed it all the way in and, Voila! problem solved. Haven't had the issue since
Your issue sounds similar in that resistance to passing the signal slowly builds until the signal won't pass at all. Any fuses in the speakers or inside the amp? I would check placement or even install a new fuse. Sometimes they can look good when they're not."Science is suppose to explain observations not dismiss them as impossible" - Norm on AA; 2.3TL's w/sonicaps/mills/jantzen inductors, Gimpod's boards, Lg Solen SDA inductors, RD-0198's, MW's dynamatted, Armaflex speaker gaskets, H-nuts, brass spikes, Cardas CCGR BP's, upgraded IC Cable, Black Hole Damping Sheet strips, interior of cabinets sealed with Loctite Power Grab, AI-1 interface with 1000VA A-L transformer -
No fuse on the speakers but I assume there are few inside the amp.drumminman wrote: »Any fuses in the speakers or inside the amp? I would check placement or even install a new fuse. Sometimes they can look good when they're not.
Klipsch RB81, KG3.5, B&W DM602.5, Polk.
Subwoofers: Klipsch RW10, Triad ProSub Bronze. -
LOL! I 'm sorry, I had to laugh at the part about scaring the crap out of everyone when you had the volume pot at half way and the speaker came on.:eek: I think I've done something similar to that at some time or other, makes a funny visual.:cheesygrin: Hope you find it's something minor and easy to fix!Will test that in the weekend.
However, the main suspect is volume knob.
This morning, I was listening to music with just left speaker hooked up and it worked fine for around 1/2 hour.
Then no sound, nothing like the amp turned off.
I only had left speaker so the right channel may be working.
I turned/pushed volume knob few times and there was no scratching sound but it came on when I moved it past half volume few times and scared the crap out of everyone as the sound was really loud at that level.
And it worked for another 15 minutes fine before I headed to work.
So volume knob could be the issue but it's so weird that it just cut off completely and no scratchy sound when moved. -
sounds like physical damage to the pot. the contacts are contacting until half-way around.
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Will test that in the weekend.
However, the main suspect is volume knob.
This morning, I was listening to music with just left speaker hooked up and it worked fine for around 1/2 hour.
Then no sound, nothing like the amp turned off.
I only had left speaker so the right channel may be working.
I turned/pushed volume knob few times and there was no scratching sound but it came on when I moved it past half volume few times and scared the crap out of everyone as the sound was really loud at that level.
And it worked for another 15 minutes fine before I headed to work.
So volume knob could be the issue but it's so weird that it just cut off completely and no scratchy sound when moved.
Sounds like you have a dirty protection or speaker relay. It might be the fuses as drumminman suggested, but I'm suspecting the relays as I've had personal experiences with them. Could even be a combination of both as well. If you are up to it, go ahead and de-solder the relays and clean up the contacts inside them, then try it again and see what happens. The fact that the sound comes on when you turn it way up sounds exactly like dirty relay contacts.
Edit: Do this: Try turning it up again until it comes on, then turn it down really low. If it cuts out again after a bit, it's very likely the relay(s) -
canadianicon25 wrote: »what i was hoping you would do is move the selector switch on the side to the separated position, capacitor coupled (to be safe). then connect a pre-amp of some kind to the power amp in jacks. this will bypass all the other stuff but the power amp section of the sansui, if your volume problem doesn't appear again then we know the power amp section is okay.
I set to separated (1) direct coupled.
For some reason, the button doesn't move to (2) capacitor mode.
May be it's really dirty not to move there.
Then I used external source and used this G-8000 as amp only.
Voila, there is sound on both sides.
So now starting to clean the button without taking any boards out as taking boards out is not comfortable for me.
Will adjust bias while I'm there.
Hopefully, this top board has everything for bias/dc adjustments.
Also what is that black switch on the board on lower left?
Klipsch RB81, KG3.5, B&W DM602.5, Polk.
Subwoofers: Klipsch RW10, Triad ProSub Bronze. -
Before I go for bias offset, I want confirm this.
Manual says, set VR01 and VR02 to center position.
Then, for the purpose of proceeding the accurate adjustment, set the voltage to 0 volt by VR01 first and VR02 next.
Confusion is, if voltage is set by VR01 to 0, how to adjust VR02?
It'll already be at 0 from VR01 adjustment.
Edit: Bias adjusted to .2mv/.3mv on both channels.
Not adjusting dc for now.
Next, cleaning the button.
Klipsch RB81, KG3.5, B&W DM602.5, Polk.
Subwoofers: Klipsch RW10, Triad ProSub Bronze. -
Before I go for bias offset, I want confirm this.
Manual says, set VR01 and VR02 to center position.
Then, for the purpose of proceeding the accurate adjustment, set the voltage to 0 volt by VR01 first and VR02 next.
Confusion is, if voltage is set by VR01 to 0, how to adjust VR02?
It'll already be at 0 from VR01 adjustment.
Edit: Bias adjusted to .2mv/.3mv on both channels.
Not adjusting dc for now.
Next, cleaning the button.
You adjusted the DC offset not the transistor bias current. -
Hehe... okay.canadianicon25 wrote: »You adjusted the DC offset not the transistor bias current.
After cleaning the button with few shots of DeOxit, toggled for 100 times.
Again shot of DeOxit, toggled for 100 times.
Did that 4 times.
Then sprayed lube and toggled for 100 times.
I let it dry and just got back.
So far playing for last 15 minutes without any hiccup.
I'll let it run for an hour or so before putting the top back.
If it was just the dirty button, I got a good deal.
Thanks
Klipsch RB81, KG3.5, B&W DM602.5, Polk.
Subwoofers: Klipsch RW10, Triad ProSub Bronze. -
right on. hopefully that fixed the problem.
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to answer your question about the little black switch:
the board you are looking at is the FM tuner board. the little black switch is for de-emphasis. probably on/off. best to just leave alone i would think as it is probably set to on. -
canadianicon25 wrote: »to answer your question about the little black switch:
the board you are looking at is the FM tuner board. the little black switch is for de-emphasis. probably on/off. best to just leave alone i would think as it is probably set to on.
It has 50uf --> 75uf on the button and it's set at 75uf.
Also, I left the receiver on for around 2 hours and it worked great.
Hopefully, that's all it was.
Thanks for all the suggestions.
I'll have to store it for now until I get a stand or something that can hold it's weight.
My stereo stand will fall apart if I put this on top of it. :eek:
Klipsch RB81, KG3.5, B&W DM602.5, Polk.
Subwoofers: Klipsch RW10, Triad ProSub Bronze.
