IMG_3355

Sansui G-8000 Monster Receiver Service & Repair

Visitors will know how much I love classic hi-fi electronics. One special category is monster receivers from the ’70s and ’80s. The Sansui G-8000 Pure Power DC Stereo Receiver is one of the biggest monster receivers.

The Sansui G-8000 receiver was created at a time when Japanese manufacturers were competing to produce the meanest hi-fi beasts, like this Pioneer SX-1250 I restored. The G-8000 is not quite as mean as the SX-1250, but make no mistake, the big Sansui is a real monster. A quick look at the specs over at Hifi Engine shows that this receiver puts out 120 watts per channel into 8 ohms. More information can be found at Classic Receivers.

The Sansui G-8000 features great build quality, something we normally associate with gear of this vintage and price, no surprises so far. All major circuit blocks are located on separate boards and some inside shielded boxes, as per Sansui tradition. This is a nice touch that appears a lot in the gear from this period. Sadly, we rarely see it now.

Specifications thanks to HiFi Engine

Tuning range: FM, MW
Power output: 120 watts per channel into 8Ω (stereo)
Frequency response: 5Hz to 50kHz
Total harmonic distortion: 0.03%
Damping factor: 60
Input sensitivity: 6mV (mic), 2.5mV (MM), 150mV (DIN), 150mV (line)
Signal to noise ratio: 78dB (MM), 95dB (line)
Channel separation: 60dB (MM), 70dB (line)
Output: 150mV (line), 43mV (DIN), 1V (Pre out)
Speaker load impedance: 4Ω to 8Ω
Semiconductors: 104 x transistors, 70 x diodes, 11 x FET, 7 x IC, 10 x LED
Dimensions: 560 x 201 x 475mm
Weight: 24.6kg
Finish: simulated walnut grain

Considerations

One thing worth noting with this design is that Sansui uses a lot of board-to-board interconnects. These are nicely executed with gold-plated pins in most cases, but the connectors were quite loose in this receiver. Also worth noting is the incredible complexity of a piece of analogue engineering such as this. There are so many switches, rotary controls and wiring, all of which accumulates dust and dirt over time and can cause problems.

The issues with this Sansui G-8000 related to these connectors, controls and dirt, as well as some not very clever previous repair work. According to its owner, one channel was cutting out intermittently and the controls were noisy. I found loads of dirt, excessively high DC offsets in both channels and idle currents set to almost zero in both channels.

Service

Servicing the big Sansui involved cleaning and lubricating all of the switches and controls. It’s important to use quality cleaners and lubricants for this. I use a range of products that suit different types of controls. These include solvents like isopropyl alcohol, Kontakt 40 and 60, and Caig DeoxIt.

I systematically remade every board-to-board interconnect I could get to and some of these were clearly very loose. I then power the receiver up and let her idle for an hour or so, before adjusting DC offsets to zero in each channel and setting bias to 16mV.

She is certainly a pretty old girl…

Now inside the chassis and we see that some engineering has gone into the G-8000. In the top centre, there’s a large toroidal power transformer, flanked by two banks of four large filter capacitors per channel. The vertical boxes near the filter capacitors are the associated power supply circuits. Along the top, there is a heatsink, to which all the output transistors are attached. Front and centre, we have the tuner board and front end, and to the left, we have a smaller secondary regulated power supply, probably for the tuner and preamp circuits.
Detail of one channel’s power supply filter capacitors, power supply circuit board and in the foreground, the driver and bias circuit for one channel, inside a little shielded can – very nice touch. Adjustments for bias and offset are made through those holes in the top edge of the shielding box.
Same arrangement for the other channel, except that this time someone has managed to lose the lid to the bias and driver board box – you can see where the three screws held the lid in previously. I never understand how people can lose parts like this when working on equipment. I mean – how do you lose an entire metal lid and screws??
IMG_3350
Flipped over and you can now see the underside of several boards and a bird’s nest of wiring and connectors. You will also see at the rear, the regulation and protection circuit board, with associated relays. These often go bad and this was going to be my next step if what I did initially did not repair the old G-8000…
IMG_3351
Close-up of that regulation and protection board. I remade all those connections you can see, probably a dozen just in the area covered by this photo!
IMG_3352
This looks like a preamplifier board to me, nice use of discrete components only, no op-amps here…
Right, down to business. After zeroing out the DC present in both channels, it was time to set bias current. The number we are looking for here is 16mV across the measurement point you can see me clipped into.
And here she is, working perfectly again, all ready to go back to her loving owner!
Bring back backlit meters I say…

Results

This stunning Sansui G-8000 certainly sounds much better than she did, with bias current correctly set and no DC biasing the speaker voice coils as it was. The intermittent channel issue has gone, along with the other gremlins and she now works smoothly and sounds great.

9 thoughts on “Sansui G-8000 Monster Receiver Service & Repair”

  1. Thanks suppose your right there i’ve Seen the magic smoke, even ducked a volcanic capacitor (and yes after a day of slow rise on a variac) perhaps if it’s just a board traveling 7,000 miles it might be a good idea to consider if I see any more relay blinks. Will certainly let you know and do indeed appreciate your consideration and attention. Just testing a cassette deck with a kinks tape, life’s good.

  2. I’ve been in Perth believe it or not. bout as far from home as every ive gotten and be buggered if i ever would haul this sweetheart that far. Still you never know. Anyway before dismantling i gave her the old Italian tune up. Rode her bucking, worked out I didn’t need to listen, shut down all speakers to avoid DC dumps. went on off a bit. Then left her to herself without input for two days, on. Been running now another day all inputs check out no issues. Life of Riley.

    1. Good news Anthony, fingers crossed she keeps running nicely. Don’t neglect the inevitable though which involves board removal for service at some point and before what has happened to a stunning Yamaha receiver I’ve just received for repair. It was doing similar things until the last time her owner turned her on. At that point, the magic smoke was released! We always want to get to equipment like this before that happens as it prevents further/more significant damage.

  3. Thanks for posting this. I have an 8000 I picked up last year in a flea market. It sounds so good I’ve been running it since then. It has a protection shut off problem that initially was very intermittent but has become more consistent. Will take your cleaning and lub advice and check for dc and bias, though when up it is quite silent and sounds great. In case it’s relays I will need more advice or your hand. Wanted to ask where you are, I’m upstate NY. Thanks again.

    1. Hi and no problem, I’m glad you found the article. Be aware that cleaning, lubricating and adjusting things, whilst very important, will probably not resolve the protection issue. This needs to be addressed separately, as part of an overhaul and repair, something the unit will certainly need at this age. I’m in sunny Perth, Western Australia, so logistically we have a problem! I’d love to assist you with this course, but perhaps there is a good local technician you can try?

  4. I have a sansui receiver G 8000 and my right Channel went out. I need a new speakers input board.

    1. Hi Rayay, thanks for commenting. I would need your receiver in for inspection and repair. Are you local and able to bring her in?

Feel free to share your thoughts and leave a comment!