Anyone using Sansui G-8000 with vintage Polk speakers?

Mystery

I got a Sansui G-8000 monster (yep it's a monster weighing 55 lbs) with a functional issue.
Left channel has issue every few months so that needs fixing.

I have several monitors as well as two pairs of SDA's.
Any experience on how they match up?

Here is a pic. It's so pruddy.

Edit: Right click and view image to see larger version.

boston1450

Beautiful receiver. Id love to hear it on Monitor 10's or sda2's

canadianicon25

Left channel has issue every few months so that needs fixing

what kind of issue is it having?

Mystery

canadianicon25 wrote: »

Left channel has issue every few months so that needs fixing

what kind of issue is it having?

PO said left channel cuts out after few months of servicing.
The technician who serviced it said there are few metal parts that need replacement (not sure what, may be relay or something) but he couldn't find parts so he just cleaned/polished them.
And it works for few months and then again left channel starts to cut out slowly and no output.
Again goes back to servicing and works fine for few months.
It's been like that for last year or so and I worked on a deal with him trading my working Sansui 881 plus some speakers.

I hope it's just deOxit that's all needed but may not be that simple since a tech couldn't fix it.

PolkieMan

Nice wood case too.

boston1450

These g' Sansui's are quite the receiver. They seem to be tough as heck & sound quite well. Ive never heard one like that with that much power but that unit will power a pair of speakers with ease. They dont seem to heat up (the ones ive had) Thats a highly sought one there. Keep us updated on what that bad boy can do. Hope it is a easy repair. Its worth fixing for sure. Enjoy

Toolfan66

If you ever sell it, please let me know!!!

canadianicon25

PO said left channel cuts out after few months of servicing.
The technician who serviced it said there are few metal parts that need replacement (not sure what, may be relay or something) but he couldn't find parts so he just cleaned/polished them.

Maybe try to find out more information about what parts he think he thinks need replacing. Just because he couldn't find parts doesn't mean there isn't something out there that wouldn't work; it just might not be original.

Does cutting out mean it intermittently cuts out or is there no sound from the left channel at all?

canadianicon25

have you noticed the problem re-appearing with a difference in output volume? how about speaker impedance?

canadianicon25

more questions:

does the problem appear when only using the rx. as an amplifier, bypassing the pre-amp section?

Mystery

No idea yet.
I just got it and powered up.
Haven't even hooked up speakers yet.

Not sure about what parts as PO also doesn't know.
All he remembered was the tech said few metal parts inside (not outside switches/knobs) needed replacements but he couldn't find those or that part in ebay or other parts store.
PO said it's not resistor or capacitor but if he had to guess, it's something related to metal switch inside.
So may be dirty relay switch or something that's beyond my head as I've not even opened it yet.

cnh

You can't always get the sound you "want" but if you try sometime, you just might find, you get the "few months" of sound that you "need"!

Whip on a little STONES! And enjoy the Sansui!

cnh

canadianicon25

okay. before you hook them up to speakers measure the DC offset of both channels!

in case you don't know how, forgive me if you do:

get a multimeter. set it measure DC voltage, smallest amount. power on the unit. connect the test leads to the speaker terminals on the side of the receiver. the DC offset should be in the millivolt range preferably less then 50mV.

...few metal parts inside...

this just seems odd that this is the description that a service tech would use. it raises a bit of a flag. inside there aren't many 'metal parts'. also, the failure is occurring over time. most failures in electronics are instant and persistent; not slowly coming on over usage.

Mystery

canadianicon25 wrote: »

okay. before you hook them up to speakers measure the DC offset of both channels!

in case you don't know how, forgive me if you do:

get a multimeter. set it measure DC voltage, smallest amount. power on the unit. connect the test leads to the speaker terminals on the side of the receiver. the DC offset should be in the millivolt range preferably less then 50mV.

...few metal parts inside...

this just seems odd that this is the description that a service tech would use. it raises a bit of a flag. inside there aren't many 'metal parts'. also, the failure is occurring over time. most failures in electronics are instant and persistent; not slowly coming on over usage.

I'm familiar with DC offset and adjusted quite a few Pioneer SX series to spec (<20mv) but thanks for reminder.
Also, PO was using it until recently so hopefully that part should be okay.

Yes, the problem sounds really weird to me.

canadianicon25

the only thing that comes to mind is the volume pot being really dirty and over time (usage) the grime works its way in again an interrupts the circuit. if that is the case, then it would be hard to find a replacement for it.

output transistors can fail on vintage gear but usually they will fail under heavy loading (high volumes, lower speaker impedance) and will not change over time and would probably work with low volumes just fine.

Mystery

DC voltage:
Speakers System A: Right = -25.9 and Left = -71.6

Speakers System B: Right = -25.7 and Left = -71.9

When I checked again back and forth, I think it's the same reading on both sets.

So the left channel is little off and that causes slightly lower volume but that may not be the only cause.

Need to check service manual to adjust it.

canadianicon25

check hifiengine.com for service manual.

was the DC offset reading the same after the unit had been powered on for 5mins or so?

Mystery

canadianicon25 wrote: »

check hifiengine.com for service manual.

was the DC offset reading the same after the unit had been powered on for 5mins or so?

I have the manual from akdatabase and need to go through it.

Yes, it was powered on for around 20 minutes before I checked DC voltage.
thanks

canadianicon25

good luck.

you could always fire a post to the solid state board at diyaudio.com

lots of good advice over there.

Mystery

Thanks.
Also forgot to mention that pre-amp and amp are not hooked at this moment.
I just have it powered and speaker switch on.

canadianicon25

manual is little vague on that. maybe check the DC offset again this time with the pre-amp connected to the amplifier section.

jim 249

Here is a picture of my G-8000. Bought it new in 1979. I have 2.3TL's but have not hooked them up to it yet. The amp has a hard time trying to drive Carver ALIII's, so I am not sure how well it would drive the Polks. It is old and probably needs a recap. I did notice in the past few years that the phono section will not put out like it used to. I have to really crank the volume up. I split the amp and pre and tried a different pre and all was well again. I have all the paperwork and manual and box including the supplied schematic. If you need any info, please ask. Have fun with it, a really nice receiver!

canadianicon25

The amp has a hard time trying to drive Carver ALIII's

Did you drive these speakers a lot? Those needs serious power. 4ohm with 80 something efficiency. Monoblocks would be great for those.

I did notice in the past few years that the phono section will not put out like it used to. I have to really crank the volume up. I split the amp and pre and tried a different pre and all was well again

Sounds like it could be transistors that are going bad. Generally when it doesn't power like it used to it means that trans. are starting to fail. Sounds like the power amp section is fine though. Problem could be isolated to pre-amp section and/or phono section.

jim 249

Did you drive these speakers a lot?

Not that much. I am guessing not more than 50 hours at the most. I switched to a Nakamichi Pa-5II and it does better, but still not great. Those ribbons soak up a lot of power. I have never had the volume higher than say 48%, less than half. Now it is even less, getting older and have a bit of tinitus. I only listen at less than 90db per my RS sound meter.

Mystery

canadianicon25 wrote: »

manual is little vague on that. maybe check the DC offset again this time with the pre-amp connected to the amplifier section.

I got service manual from here: http://akdatabase.org/AKview/albums/userpics/10004/Sansui%20G-8000%20G-9000%20Service.pdf

1st page has wrong specs. It mentions 120 w for both 8 and 4 ohms. So either it's same for both loads or it's a typo.

I checked with pre and amp hooked up with RCA cables and it's no difference.
Readings were -24 and -66mv.
BTW, what does that do? The receiver works fine without those two connected.
I tested FM, Aux, Tape etc... inputs and works fine as it is.

It looks like the issue is with Volume knob and may be with 4ch/NR Adapter button.
When I first hooked a speaker, there was hardly any sound from left channel.
I had the volume at 50 and still very low high frequency sound.
Then I fiddled the two volume knobs and sound came out fine.
Volume knob may have corroded or something.

Then I pressed 4ch/NR Adapter button, and no sound. Not sure if that's what it supposed to do without adapter hooked up.
I wiggled that button and some sound and scratchiness.

jim 249 wrote: »

Here is a picture of my G-8000. Bought it new in 1979. I have 2.3TL's but have not hooked them up to it yet. The amp has a hard time trying to drive Carver ALIII's, so I am not sure how well it would drive the Polks. It is old and probably needs a recap. I did notice in the past few years that the phono section will not put out like it used to. I have to really crank the volume up. I split the amp and pre and tried a different pre and all was well again. I have all the paperwork and manual and box including the supplied schematic. If you need any info, please ask. Have fun with it, a really nice receiver!

I got the service manual and brochure but no links for user manual.
May be it's same as service manual.
thanks

MAD

Hope you get it working... maybe deoxit on the pre amp/power amp switch?
It's a handsome looking amp.

I use two cleaners.... electrosol contact cleaner with zero residue and I hit it with nutrol contact cleaner with special lubricants. The local repair guy told me that often you need those special lubricants to prevent oxidation from happening quickly again.
I typically use the zero residue cleaner first... rotate the know 75 times or so... then hit is with the cleaner with special lubricants and rotate a few more times.

Just a thought... I could be totally off or you probably already know about this (does deoxit have lubricants in it?)

I've got a G9700 that does not have that ability to separate the pre and power... it would come in handy.

Mystery

DeOxit has different versions.
DeOxit has 5% cleaning but it does mention lubrication.

Use DeoxIT spray anywhere you suspect heavy oxidation problems on audio/video contact surfaces.
+ Dissolves oxidation & corrosion
+ Reduces intermittent connections
+ Improves signal quality & data transfer speeds
+ Reduces wear and abrasion
+ Cleans, lubricates, and seals connections
+ Reduces arcing and RFI

DeOxit Gold has more protective layer and less cleaning power.
So DeOxit first followed by Gold will ensure longer operation.

But for Pots/knobs, DeOxit Faderlube is better product.

cnh

Wouldn't the FIRST thing any GOOD TECH would DO is check the DC offset? A no brainer for "any" repair guy. So not sure why all the buzz about this above.

DeOxit? Well even a technical incompetent like yours truly can use that on his vintage integrateds and receivers. Am I missing something here? Wouldn't the TECH have DONE ALL OF THAT?

Also, as I understand it, using deoxit is something that might have to be done every six months or so on OLD equipment. So having a little problem with the volume or balance should be a recurring phenomenon that is standard maintenance.

Then again, what do I know? Perhaps mhardy will check in here and correct me if I'm too far afield? Real "wisdom" is always appreciated!

cnh

agfrost

Mystery wrote: »

I checked with pre and amp hooked up with RCA cables and it's no difference.
Readings were -24 and -66mv.
BTW, what does that do? The receiver works fine without those two connected.
I tested FM, Aux, Tape etc... inputs and works fine as it is.

I reserve my right to be a) wrong, or b) pointing out something that isn't your actual question, but the Sansui's pre and amp can be connected internally when in the connected position, or, you can use just the 'Sui's preamp (using RCAs to another amp) or just the 'Sui's amp (using RCAs from an external preamp). Separating the two with the switch should yield similar/near identical sonic results, only you're adding a pair of IC's.

Cool unit. I'm quite fond of vintage Sansui!

Mystery

agfrost wrote: »

I reserve my right to be a) wrong, or b) pointing out something that isn't your actual question, but the Sansui's pre and amp can be connected internally when in the connected position, or, you can use just the 'Sui's preamp (using RCAs to another amp) or just the 'Sui's amp (using RCAs from an external preamp). Separating the two with the switch should yield similar/near identical sonic results, only you're adding a pair of IC's.

Cool unit. I'm quite fond of vintage Sansui!

That confused me too the point of confusion.
Haha...

jim 249

1st page has wrong specs. It mentions 120 w for both 8 and 4 ohms. So either it's same for both loads or it's a typo.

I just checked my user manual and sales brochure and they both say the same as what you have. Seems a bit odd that power would be the same for 4 or 8 ohms. I will check my DC at the speaker outs and post them later tonight.