STP
03-28-2005, 05:34 PM
A progress report on ineptness is needed. After replacing the big 47uf cap that leaked all over everything, I replaced some of the surrounding caps and the corroded diodes as well, including the Zener by T2. Thanks for the NTE advice, as it's come in handy. There has been progress, the speaker selection lights come on now and you can hear the speaker solonoids being selected, but the main display board still doesn't come to life. The Sansui schematic is woefull. There are no low voltage references in the output cable from the power supply to the display board. I've checked all the voltages on the power supply board to the schematic references and they're OK.
So I bought a functioning Z-7000, to figure out the Z-9000. I've already got a couple of people who'll reimburse me for the 90 wpc capable Z-7K. Finally, I've also been working on a PL-51 linear tracker. Neat features, like being able to pick a specific track and the needle let-down is so gentle, that you don't even hear it at volume, but it started getting a burning smell. Took it apart and used my old electronic technician skills from a couple of decades back. The back arm-servo driver board was where it seemed to come from, so I started feeling around on the top of the passive components trying to figure out what's hot. I sure found out really quickly. Transistor Q7 was in runaway mode and left a perfect push-tack sized blister on my forefinger. Ouch! The two trannies Q5 and Q6 provide a +15V and -15V to the stepper motor and both tested bad. I'm replacing both tonight.
While I was at it, I found a complete set of electronic schoolbooks on Ebay from Heathkit. I might as well start over in my education from DC electronics and work my way back up. Just enough knowledge to be dangerous, but not enough to figure out what's really going on. Lesson #xxx learned.
Finally, the supposed 'pristine' G-9000 that I got on Ebay last year for a total of $600 still has phono problems. I found a homemade ground running from the audio jack input board. It wasn't hard to miss, comparing it to the good running freight damaged G-9000 that's now my main unit. A 12 inch grey non-Sansui wire ran from the middle of the input jack board to the phono input board! Removed that and now I've got 60 hz hum and still no phono. Thank goodness I own two of these things. And the fun continues. Between all of this, I do have tunes!
So I bought a functioning Z-7000, to figure out the Z-9000. I've already got a couple of people who'll reimburse me for the 90 wpc capable Z-7K. Finally, I've also been working on a PL-51 linear tracker. Neat features, like being able to pick a specific track and the needle let-down is so gentle, that you don't even hear it at volume, but it started getting a burning smell. Took it apart and used my old electronic technician skills from a couple of decades back. The back arm-servo driver board was where it seemed to come from, so I started feeling around on the top of the passive components trying to figure out what's hot. I sure found out really quickly. Transistor Q7 was in runaway mode and left a perfect push-tack sized blister on my forefinger. Ouch! The two trannies Q5 and Q6 provide a +15V and -15V to the stepper motor and both tested bad. I'm replacing both tonight.
While I was at it, I found a complete set of electronic schoolbooks on Ebay from Heathkit. I might as well start over in my education from DC electronics and work my way back up. Just enough knowledge to be dangerous, but not enough to figure out what's really going on. Lesson #xxx learned.
Finally, the supposed 'pristine' G-9000 that I got on Ebay last year for a total of $600 still has phono problems. I found a homemade ground running from the audio jack input board. It wasn't hard to miss, comparing it to the good running freight damaged G-9000 that's now my main unit. A 12 inch grey non-Sansui wire ran from the middle of the input jack board to the phono input board! Removed that and now I've got 60 hz hum and still no phono. Thank goodness I own two of these things. And the fun continues. Between all of this, I do have tunes!