800c's will run hot by hand measurements. 6-7 seconds on the PT is ok. Best to use an infrared or laser Thermometer. Max temp is 190 and then you have a CHERNOBYL Event. Below 150* is good and won't hurt it. Leave some headroom there. I run my EH's @ 33-34ma with plate voltage of approx 430v, and the lamp voltage varies btwn 6.0v and 6.4v depending on wall voltage of 120 -126v. PT gets about 140* with OPT's about 130. No Fan's and in a case or in the case of my 63 Executive's 800c, inside the cabinet. This one is running T-S Reissues and running the same approx values and temps. The T-S's require more bias voltage (more negative) for a given ma level. Both units have either the IBAM or Dave's IBBA board for bias adjustments, or balance and bias adjustments.
I have a Sansui 1000A that runs the same basic setup, but the Sansui runs slightly hotter in stock form. It's been modified to run substantially cooler but still runs about the same as the 800c.
Leave your voltages as is, but get your OP tubes down to 80% of max dissipation with the voltages in spec. This will cool down the unit appreciably, lengthen the life of the tubes, and you won't notice the drop in total wattage. The best way is to build Dave's IBBA board and implement it in the 800c. Then you can balance pairs of tubes, and then bias them all together.
I have a Sansui 1000A that runs the same basic setup, but the Sansui runs slightly hotter in stock form. It's been modified to run substantially cooler but still runs about the same as the 800c.
Leave your voltages as is, but get your OP tubes down to 80% of max dissipation with the voltages in spec. This will cool down the unit appreciably, lengthen the life of the tubes, and you won't notice the drop in total wattage. The best way is to build Dave's IBBA board and implement it in the 800c. Then you can balance pairs of tubes, and then bias them all together.
