Sansui G7000 redo .

anderslober

Yikes...not again!
While I wait for some parts to arrive for 2 other projects......I thought I would start this little G7000 thread. The big 'G' series are some of my favourite receivers. They are built well and perform excellently:thmbsp:

Anyway......I bought this unit a while back. I bought it very cheaply, as the main transformer was missing, 2 knobs were missing......other than that, the unit is in great condition.

I was lucky to find another transformer with all wiring intact! Should be a drop-in! I do however have one question......does it matter how the colored wires are connected? For example......the 2 yellow wires(with connectors) from the tranny go to the PS board....I know which pins to use on the PS....but how do I know which wire goes on what pin? Is there a 50-50 chance of messing it up? Or doesnt it matter, as long as the connectors go to where the originals were? I did check the SM......but the copy I have has no scat'........

New transformer and wires with connectors.

Voltage selector.

Tuner board/section.
 
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I found a scat' on the 'net.......... ..the new tranny is all connected up now. Now for the recap......
 
As long as the wires are the same diameter , and same colour , I don't see the reason to be toasted. Did you check the voltages and are the same ?
 
I found a scat' on the 'net.......... ..the new tranny is all connected up now. Now for the recap......

You are going to test the newly installed transformer first aren't you Anders?

I would power up on a DBT first, and if no smoke signals (check 1 or 2 AC voltages), then give it the 'full beans' :D - and measure every AC voltage output, followed by all DC voltages...

I personally wouldn't be committing any shiny new parts until I knew the transformer was ok.

Remember the rule, 'never recap a faulty unit'? ;)
 
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John......good'un!..........I havent done anything to the unit.....except for the installation of the tranny..........You can bet your $&@# that I will DBT!
 
Are there any fusible resistors on the driver board? R41/42?
The SM didn't say much......the value of the resistors wasn't even listed. On the scat' they are indicated as 10 ohm.
 
The easiest part of the operation....the driver board: Before and after.
 

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Nice work, those trimmers actually don't look too bad, but I would still replace them.
 
Well, well.......I managed to finish recapping the whole unit. When checking and re-greasing the main outputs, I found the main outputs on the right were blown. I sub'ed in mj21193/21194. I desoldered the drivers/pre-drivers...they all tested ok.

Now.......I proceeded to hookup up everything again.....prepared for DBT.....DBT'ed....NO POWER....NOTHING:yikes: WTF??!

I checked all the simple stuff first...fuse....cable...socket....I do have power at the units' terminals. I checked the scat'.....could the 2 big 8.2 ohm resistors be open?
The power switch AND transformer are ok.
 
Just desoldered the 2 8.2 ohm/7w resistors.....one was OL......one was 34 Megaohm!
Gotta get some new'uns.......and hopefully all will be ok!
 
Nice soldering job.. but I wonder why you didn't replace the trim pots ... the old ones are not good.

This.
Changing the bias trimmers on G-7000 (and 7500) is not optional, it is mandatory. If that trimmer scritches just a little while you are setting the bias, it will smoke the output transistors and drivers almost instantly.
 
Ok....the big 7W resistors arrived. I popped them in, powered up on DBT......massive brightness!! At least I had power.......! I turned of the unit.....took the driver board out....DBT'ed again.....still bright......GULP!......checked both main output sides.....DBT'ed....still bright.........DARN...NOW WHAT? Anyway, I proceeded to ohm the tranny again......all good....guess what.....I SCREWED UP BIG TIME!.....lucky this was on DBT! I had swapped the lamp power supply for the left main output supply! Jeeeezzzz...
The lamps were getting 36v........the main output section was getting 7.5v.....anyway....I swapped the supplies around....DBTed......all good!! Initially the relays didnt click......I tapped them both......and the clicked. They must have been sticky.
Now to bias and dc-offset............I will change the trimmmers........
 
The unit works! Although, I am not out of the woods just yet. The tuner tunes fine and the stereo light works........I am just using a dipole antenna........when I depress the muting(muting ON)....the sound disappears. Also when I select MONO, the signal meter goes down to almost zero. I still have output, just not stereo of course.

Damn tuners!
 
I managed to tweak vr11 and vr12 on the muting VERY slightly. Now I have good signal indication and stereo light. FM Muting function seems to work normally.
When the unit is STEREO, I have a bit of background distortion/hissing.........when I put the unit in MONO this distortion of course disappears. Can anything be done to get the distortion/hissing down a bit?
 
Check where the tuning cap is soldered to the board. Cracked solder joints there will cause all kinds of headaches.
 
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