Restoring G-9700

[walleye man]

Hi, I've been viewing and reading post for over a year. Having recently restored a QRX-7001, which turned out very good and am finishing up a G-8000 for my younger brother. I recently purchased a G-9700 however it was damaged during shipping. I would like to know if anyone here has or knows who might have a rear chassis bracket that the bumpers and heat sinks mount to? That is what was damaged in shipping. I am constantly amazed by the knowledge of the members of this group. I have learned a lot already and hopefully will learn a lot more as I really enjoy restoring vintage receivers.Thanks!

Bob
G-9700, G-8000, QRX-7001

 

[walleye man]

Audiokarma member Kale,
he also sells on ebay

Thanks!
I have contacted him.

 

[lbcgav]

I bought a G8000 off of eBay that arrived damaged. I removed the rear bracket and was able to straighten it pretty well with some blocks of wood and a hammer. It came out very nicely.

 

[walleye man]

I have straightened it out with wood blocks and hammer. I might try to straighten it a little more. It doesn't look real bad
and it will not be seen by anyone other than myself until I try to sell it. (Ha I doubt I ever will if it sounds as good as members
say!) I am really impressed with the G8000 that I have. I do need different speakes as I have a pair of Sansui SP2500-X.

 

[Tom B]

As far as the G-9700, be aware of an issue I ran across with one. This unit uses contacts of the Function switch. (FM AM etc) to supply DC for the Tuner boards, as well as DC switched for the Display (AM and FM). These contacts can burn internal, causing intermittant AM and FM, usually keeping the display from lighting up. This function switch is big, has 6 or 7 positions, and I think 4 rows of contacts. A total of 24 or 28 contacts. The switch is impossible to find, except in another G-9700. I assume I could have dismantled the switch and tried to replace the burnt small removable contacts, but would not have been able to replace the larger stationary contacts. I was able to find unused contact positions that I was able to jumper in parallel with the bad ones. I also had to parallel a few of the DC positions for FM and AM to get the switch fully functional. So if you get the G9700 running, and have radio problems, check and clean that switch .

 

[LBPete]

Hi walleye man, welcome to AudioKarma Exclusively Sansui. Straightening it is your best bet. If you were able to find another, it would't be cheap. That steel is pretty soft and will respond well to a block of wood and a hammer. I'm a big fan of the 9700. Tons of clean, clear power. Just be careful setting bias current. It's very sensitive to miss-adjustment.

Please post the serial number for the database. Click on the link in my signature block.

- Pete

 

[walleye man]

Thanks Pete, that's what I'll probably do is try and straighten it out some more. I will add it the G-8000 and a QRX-7001 to the database. Is it safe to replace the main filter caps (12,000uf 100v) with 15,000uf 100v ones?

 

[Willy6]

Thanks Pete, that's what I'll probably do is try and straighten it out some more. I will add it the G-8000 and a QRX-7001 to the database. Is it safe to replace the main filter caps (12,000uf 100v) with 15,000uf 100v ones?

Yes it is.

 

[walleye man]

Thanks you! I am so looking forward to restoring my G9700!

 

[LBPete]

Thanks for the serial numbers. You could actually go more than 15k if you have room for them. The G-9700 has a soft start circuit so it can handle quite large filter caps. These receivers were built in a period of cost cutting when the yen/dollar exchange rate was sinking and there was decreasing demand for monster receivers. The 12k filter caps were probably a price point they could make work financially.

- Pete

 

[walleye man]

Serial numbers have been entered into the database!

 

[LBPete]

Thanks!

- Pete

 

[nosirrah]

a reminder, please no links to ebay in the forum.

 

[walleye man]

Ok. Now that the holidays are over I have been working on my G9700 checking things over and have found some issues. The main fuse was 12 amps but only 32 volts. I have replaced it. Found R34 and R28 open on the left driver board. Have ordered replacements for them, TR09/TR10 and both pots. Is there anything else I should replace on the driver boards? 2 of the output transistors were bad and will replace all of them. The right side has Saken (don't know if they are real). I would like to replace the 2 0.0047uf/500v caps, that are across the 12,000uf caps, but am unsure what to replace them with. Are they film capacitors? I think that they are but am unsure. Should I replace them with the same size or something else since I increased the size of the main caps from 12,000uf to 15,000uf? I will replace all the electrolytic caps and clean all switches and pots also.

Thanks

 

[LBPete]

As a rule, its better to do repairs and get it working before doing the recap. When you are disturbing as many solder joints as you do replacing all the caps, it's easy to make mistakes. That will make troubleshooting a lot harder if you add new problems to your original issues.

The caps across the filter caps are film caps. You can up the size a little if you want. It's unlikely you will be able to find genuine original outputs so for symmetry you should replace all the output transistors. That way you won't have a miss match left to right. Save the original transistors. They have real value.

- Pete

 

[walleye man]

Thanks Pete,

That is great advice to get it working before trying to completely recap it. I did turn it on with a DBT, 75w first then 150w, with the driver boards removed before stating to recap it. It turned on and all indicator lights illuminating, tuner readout and first two lights on the power meters lighting up. I am planning to replace main caps and all the caps on the F-3070 Power Supply Circuit BD, F3071 RF Power Supply Circuit BD, F-3072 Protection Circuit BD and F3073 Pre Power Supply. Then turn it back on with the DBT to make sure I recapped those boards correctly. Next repair driver boards and turn it on again with the DBT and without the output transistors. Set the bias and offset and leave the receiver powered on for a couple of hours to make sure all is well. Continue to recap the other boards one a time testing after each one. When this is complete replace all the output transistors as you suggested and recheck bias and offset again. I hope this is the correct approach to completing the restoration on my G-9700. I will hang on to the Saken transistors and attach a photo, when I return home, to see if you think they are originals.

Bob

 

[walleye man]

Here is a picture of the Sanken transistors.

 

[Hyperion]

Here is a picture of the Sanken transistors. View attachment 1084337

They look original to me, but a look underneath at the bottom of the transistor usually confirms.

 

[LBPete]

You need to see the bottom, especially the insulation where the leads go through the plate.

- Pete

 

[ManyMoonsAudio]

Look really legit to me. Matching date codes on the pairs and the look of them is definitely right.

 

[Kale]

It seems to me genuine Sanken, but today fake production is better than before... here one example,


that is output stage of one AUX1 what I had on restoration... so those transistors looks genuine Sankens, buuut!...
look at the next picture:

There should be number 2, not letter Z... and when I see the bottom of transistor, it was a fake!
So, we really need to see bottom of those transistors to be sure.

 

[walleye man]

So it's been quite awhile since I updated my progress of restoring my G-9700. I can proudly say that it is complete! But not without a lot of searching this very valuable forum for tips and answers to lots of questions. I have attached a pictures of the other side of the Sanken transistors and a couple of others. I replaced the original speakers connectors with binding post but I am trying to repair the original connectors. Thanks to all who have asked and those who shared their knowledge of restoring and repairing vintage receivers! It looks and sound awesome! Plenty of clean clear power! Some day I will upgrade my speakers to something a little better but right now I am just going to sit back and crank out some long over due tunes! Lots of them! One final question - is it possible to output 48 volts RMS without clipping from a G-9700? What has anyone else's G-9700 achieved?

Thanks again for all the knowledge and skill of the members of this group!