Question about R1 and R2 temperature
I started my F6 over the weekend and both channels seem to be working fine. I set the bias measuring 0.5V across R2 and the offset at the speakers terminals below 10 mV. It played music for a couple of hours until I decided to turn it off to install the face plate and cover. While disconnecting the probes from R2 I noticed it was really hot. I turned it on again and measured the temperature after 30 minutes. It was 134˚ F. Am I overlooking something?
I started my F6 over the weekend and both channels seem to be working fine. I set the bias measuring 0.5V across R2 and the offset at the speakers terminals below 10 mV. It played music for a couple of hours until I decided to turn it off to install the face plate and cover. While disconnecting the probes from R2 I noticed it was really hot. I turned it on again and measured the temperature after 30 minutes. It was 134˚ F. Am I overlooking something?
What resistor did you use for R2? Normal idle dissipation for this part is about 1.1W, with correct bias.
It should be a 3W rated part.
That should be fine, if mounted spaced above the board and away from other parts.
I always use a wooden coffee stirrer as spacer when soldering power resistors. That way their bodies don't touch the PCB and the air can circulate around it.
Reviewing the ERX series datasheet, it seems as if my concern is unfounded. The graphs show expected temperature range for the 3S up to about 180˚ C!
Reviewing the ERX series datasheet, it seems as if my concern is unfounded. The graphs show expected temperature range for the 3S up to about 180˚ C!
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Legit and reliable. You need to specify whether you want idss matched or curve matched. For the F6, IDSS is sufficient.
Thanks for the reply, it's encouraging, after reading posts about counterfeits. I ordered matched (4) nn mosfets, and 2 pairs of matched jfets for an f6, but I did not specify ldss or curved (ignorance). I am hoping they will restock the transformers for the f6 kit, but I won't wait too long, as I feel I am late to the party, and wouldn't want to miss out on the boards. The jensen site shows the transformers with no (not that I saw) minimum.
I would suggest you get back to Calvin ASAP and specify IDSS..... they are not the same as curve matching.....
Starting PCB redesign.
first schematics, waiting for comments...
Replacement for Jensen, Edcor?
JP
first schematics, waiting for comments...
Replacement for Jensen, Edcor?
JP
Why replace the Jensen? They are fantastic transformers.
Look into making pads for multiple choices. Most transformers have similar layouts.
Look into making pads for multiple choices. Most transformers have similar layouts.
Output mosfets need to be symmetrically placed about the midline of ums pcb to account for split heatsinks.
Second add option for trimpots across source resistors to tweak distortion.
Option of cascode on input to allow turboing amp or using Idss parts greater than 8mA.
If you are designing an all singing all dancing PCB then you could add connections for the PCF mod as well.
I think it would be valuable if the transformer is mounted on a daughter board (mounted directly over main board sitting on standoffs) which can be configured with links and transfered between different circuits, eg transfer between F6 and Hockey Puck Amp.