28-11-2015, 07:34 PM
(28-11-2015, 06:08 PM)Yorkie Wrote: In my earlier post on restoring the KB MK1 FB10, I remarked on what seemed to me to be an odd HT feed arrangement - two 8K2 resistors in parallel, (making 4K1), then a 1K8 in series with those, giving a total resistance of 5K9. Why not, I ask, instead, using either a single 5K6 of 6K2, either of which would be +/- 5%, given that the three resistors would in any event have been 10% tolerance carbon composition types?
I can only assume that this was about power dissipation. There's 110V across those resistors, which equated to around 2 watts of heat to lose. It's shared between 3 resistors presently. If they'd used just one, perhaps it would need to be bigger and more expensive. I'm guessing that it was cheaper to use 3 separate ones, even when taking labour costs into account.
The 1k8 dissipates 0.625W, and the 8k2 resistors will dissipate 0.8W each.
Lovely job. The cabinet repair is amazing!
