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Old 07-31-2017, 11:30 AM
Shibby Shibby is offline
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Join Date: Mar 2017
Posts: 31
So I have finally gotten around to trying to fix this thing. A beautiful thrift store Sansui 661 got in the way among other things. So I went over every board and documented each and every through hole capacitor and sent the order out through Digikey. I have gotten the vast majority of the caps replaced except for some of the super tiny ones under the shields. I will get to these soon. The larger board that is directly connected to the tube seemed to have the most damage. Several leaky caps with electrolytic goo all over the board. the corrosive damage from this was seemingly minimal be there were certainly a few components that had suffered a bit of damage to their solder joints. I was able to get these joints cleaned up and fixed but i can say it certainly wasn't easy. I had never had the opportunity to work on a damaged bard such as this before so it was certainly a learning experience. I checked continuity between each solder joint and the next component down the line and everything looked good.

After getting the majority of the new caps in and fixing some ugly joints (it appears that someone has been in here before) I went to reassemble her on the bench to see if I would get anything out of her. In a temporary laps of brain power I stacked the main board connected to the tube (D1?) on top of the shield of the power board forgetting to place the cardboard spacer in between to prevent shorts. well I plugged her in and of course got nothing. Until about 10 seconds later the smoke came. I quickly unplugged the power supply and tried to see where it was coming from. After plugging it in a couple more times I was able to see that the smoke was coming from the B734 transistor on D1.

I pulled everything back apart and had a closer look. All three legs were burnt and she had a hole blown right through her. I have to admit it was kind of cool . I went ahead and desoldered the transistor and sure enough there is a short between the collector and emitter pins. I had a look at everything else on the board and it doesn't seem as if anything else had suffered any damage. Heres hoping. I have a couple new transistors on the way from ebay so hopefully I'll be able to have another go here soon. I did try powering everything up again with the cardboard spacer in place and as expected did not get any smoke so I am certain that I am to blame for this and not a component on the board.

Anyway in the mean time I would like to look into running the boards through the ultrasonic (something I should have done first). Does anybody have any advice for disconnecting the D1 board from the tube? Also other than the flyback is it ok to leaving everything else on? Cables, Plugs, pots, chips and soldered in daughter boards?
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