First time poster, long time reader! I searched this board six ways to Sunday and didn't find a reference to the anomaly I observed during my repair. I'm wondering if I just missed it.
The unit came to me for repair from another guy who was unsuccessful fixing it. In the intervening time between him and me, the owner powered it up and said he let smoke out of some more of the parts! The short version of my successful repair was to redo the driver board and replace all 8 output transistors and switch to 6A fuses. I bought the f-2624 rebuild kit off ebay(highly recommend this approach and it comes with great docs) and the recommended output transistors from Mouser and Newark. Replaced every semi, elec cap, fuse resistor, and some other resistors that were toast. [It's worth noting this unit has the newer version f-2624 board with the bias varistors]
The anomaly was that when I went to adjust the bias, the pots referenced in the manual (4-2-2) were backwards. IOW, adjusting the current through F04 was accomplished via VR04, NOT VR03. Likewise, F05 current was adjusted with VR03. Anyone else have this? Is it mentioned in a post I missed? (This was not mentioned in the docs that came with the rebuild kit) Perhaps the older version of the board is as noted in the Sansui manual?
With the board removed, I wanted to share that every single semi and fuse resistor on the f-2624 can be successfully tested in-circuit (except the STV3Hs which I tested by pulling a leg and using a power supply and dropping resistor). I tested the output transistors in-circuit as well so I didn't have to pull off the heat sink. I used an Agilent bench DMM in diode mode to test the semi's and the fuse resistances were spot on as well in-circuit. For giggles and grins, at least for those of you with grey hair like me, I pulled out the dusty trusty Sencore Super Cricket and double checked all semi's in-circuit and it worked perfectly!
When I first went to adjust the bias and before I knew the pot references were backwards, I set them at midpoint resulting in a 500mA bias on both channels which I couldn't change. I didn't think to try the other pot at the time! Old-man moment I guess! I pulled the board thinking something was still wrong and that's when I did all the in-circuit testing again. When I put it back in is when I discovered that adjusting the opposite pot got me dialed in to 30mA.
This 9090 is purring like a kitten now!
The unit came to me for repair from another guy who was unsuccessful fixing it. In the intervening time between him and me, the owner powered it up and said he let smoke out of some more of the parts! The short version of my successful repair was to redo the driver board and replace all 8 output transistors and switch to 6A fuses. I bought the f-2624 rebuild kit off ebay(highly recommend this approach and it comes with great docs) and the recommended output transistors from Mouser and Newark. Replaced every semi, elec cap, fuse resistor, and some other resistors that were toast. [It's worth noting this unit has the newer version f-2624 board with the bias varistors]
The anomaly was that when I went to adjust the bias, the pots referenced in the manual (4-2-2) were backwards. IOW, adjusting the current through F04 was accomplished via VR04, NOT VR03. Likewise, F05 current was adjusted with VR03. Anyone else have this? Is it mentioned in a post I missed? (This was not mentioned in the docs that came with the rebuild kit) Perhaps the older version of the board is as noted in the Sansui manual?
With the board removed, I wanted to share that every single semi and fuse resistor on the f-2624 can be successfully tested in-circuit (except the STV3Hs which I tested by pulling a leg and using a power supply and dropping resistor). I tested the output transistors in-circuit as well so I didn't have to pull off the heat sink. I used an Agilent bench DMM in diode mode to test the semi's and the fuse resistances were spot on as well in-circuit. For giggles and grins, at least for those of you with grey hair like me, I pulled out the dusty trusty Sencore Super Cricket and double checked all semi's in-circuit and it worked perfectly!
When I first went to adjust the bias and before I knew the pot references were backwards, I set them at midpoint resulting in a 500mA bias on both channels which I couldn't change. I didn't think to try the other pot at the time! Old-man moment I guess! I pulled the board thinking something was still wrong and that's when I did all the in-circuit testing again. When I put it back in is when I discovered that adjusting the opposite pot got me dialed in to 30mA.
This 9090 is purring like a kitten now!
