Pororo

If I'm not mistaken, on Rev 0.4 a pair of 50k resistors have to be "crossed" with one mounted on the underside. There's also at least one additional resistor between 0.4 and 0.6.

I have 2 offboard amp PCBs that LilKnight sent me. The problem is that one is Rev 0.4 and the other is 0.6. I'm guessing it would be a bad idea to build one channel with 0.4 and the other with 0.6? Does anyone have a spare single PCB either 0.4 or 0.6? Thanks.

Thanks Birgir. Got the PCBs in the mail today.

Ahhh, that makes sense. I just checked pin 1 on the Raytheon 6S4A and pin 1 is not connected to anything. Thanks. And thanks to Kevin for introducing the mod many years ago.

Cool, thanks. Just adjusted the balance and offset 006t style to +/- 1V. Is there a sonic difference between connecting pin 9 directly to the lead of the plate resistor as you did above, versus connecting with one resistor in between as you did in the previously posted mod? Here's a pic of Justin's mod below. I copied his example and shorted pins 1 and 9. I can't tell 100% but it looks like he initially cut the traces to pin 1 and then restored them with a solder bridge. It also looks like he left all traces to pin 1 intact. This really confused me. I thought maybe he knew some details about the inner construction of the tube that made this logical. In your old photo, it looks like you cut the traces to pin 1 and then wired pin 9 to the traces from 1 and 6... which makes sense. Anyway, I'm probably making this sound way more complicated than it actually is. I like the looks of your mod above, nice and simple. So basically, I should cut the short between 1 and 9, isolate 1, and use just one wire directly from 9 to the leg of the plate resistor. Right?

6S4A Mod of 007T Following the nice high rez photos previously posted by Justin and Spritzer, I rewired my 007T (the first version from the 1990s with one normal bias and 2 pro bias). Not only is the PCB annoyingly black, but it's also a bit different from the 007TII. For example I did not see any Q15,Q16,Q17, or Q18. It looks like a simple bit of wiring, but it took all damn afternoon what with troubleshooting and comparing pinouts and comparing to Justin and Spritzer's photos. Anyway, I fired it up and the relay clicked and all 4 LEDs lit up. I played around with TVR1,TVR2,TVR3, and TVR4, but if I'm not mistaken, after the mods, the adjustment process is different. Should I adjust for balance and offset using the procedure for the 006T and adjusting only TVR1 and TVR2? As it is now I get the following readings from the PRO jack: Bias 277V R+ 6.3V L+ 4.5V L- 54V R- -24V

Got the boards. Thanks Tran.... Now the Adventure Begins.

Waiting here in Chicago. Boards are stuck in customs at JFK for almost a week too.

If using a matched pair 2SK170 rather than LSK389, should the pair be thermally coupled? If so, is thermal grease and shrink wrap sufficient (assuming they are close enough on the board)?