Redoing the 6.8K resistors and the Can Caps on these. Are they 1 watt or 1/2 watt?
3 posters
6.8K MK4 Can Cap Resistor 1/2 or 1 Watt?
bubbasweet- Posts : 95
Join date : 2016-03-14
Bob Latino- Admin
- Posts : 3271
Join date : 2008-11-26
Location : Massachusetts
bubbasweet wrote:Redoing the 6.8K resistors and the Can Caps on these. Are they 1 watt or 1/2 watt?
Personally, I always used 2 watt resistors on the quad cap.
Bob
WLT- Posts : 189
Join date : 2013-07-13
Location : Rochester NY
Using the published Dynaco MK III manual. Page 15 the B+ is 480VDC. Page 14 lists point 5 as 445VDC. So current thru the 6800 ohm resistor is I=V/R or .00514 amp. Power is IxIxR. Which comes out to 1 watt. Derating should be at least 2 or 3. So Bob’s comment about 2 watt is reasonable. Each of our amps have slightly different voltages so you can measure yours to verify this calculation but it should be close. From a practical/historical view. Many of these older 6800 ohm resistors have gotten hot and aged out to much higher values. These were two watt carbon composition types so that is not surprising. Replacing with a 2 or 3 watt carbon film or metal film should give good long term results.