You might also want to get some SMD training kits before resuming your fight, similar to these:
41Hz Audio:Sounds Good to Me!
Thanks heinz1 for the link. I will ask if they can ship to korea but look like they have a server problem
I damage the PCB trying to desolder the U6 during debugging without a desoldering station and a magnifier. I can get the des. station and waiting for the magnifier
About the bias... Now I am at 1A per device and is really hot. I can't stay with the hand in the srink for more then 10 seconds. How can I go to 2A with the ampli still to be closed?
Thanks
Enrico
I damage the PCB trying to desolder the U6 during debugging without a desoldering station and a magnifier. I can get the des. station and waiting for the magnifier
About the bias... Now I am at 1A per device and is really hot. I can't stay with the hand in the srink for more then 10 seconds. How can I go to 2A with the ampli still to be closed?
Thanks
Enrico
Wait till I am done with my electrostatic headamps.
Comes in two favours. One is known, the other is secret.
Patrick
I'll stay tuned
my Stax need a new companion
This measure was taken after 2h "on" with the amp close, open just for take the measure. But I didn't found a great difference close or open, not like the regular F5 with thermistors.
Thanks Ramallo and Patrick.
Now is more clear how I can proceed.
Btw, tonight I have bias one channel at 2A per FET (435mV at the gate resistor) to test also the trasformers and the regulators. The transformers from Todoidy are very well done... absolutely silent. The regulators now give me -15,97 and + 15.95. I take also some temperature. I have misured 76 degree in the bolt of 1 FET and 64 degree in the regulator.
Regards
Enrico
Now is more clear how I can proceed.
Btw, tonight I have bias one channel at 2A per FET (435mV at the gate resistor) to test also the trasformers and the regulators. The transformers from Todoidy are very well done... absolutely silent. The regulators now give me -15,97 and + 15.95. I take also some temperature. I have misured 76 degree in the bolt of 1 FET and 64 degree in the regulator.
Regards
Enrico
We measured ~67°C at the MOSFET at 22°C room temperature.
The junction to case Rth of the FET is 0.83K/W.
At 32W dissipation, this makes ~25°C above heatsink.
So you are still just around 100°C junction temperature.
But to be on the safe side, I suggest you lower bias to 1.6A.
This will reduce your MOSFET case temperature to ~65°C.
AND you should check whether you have tightened the bolt properly.
The difference between MOSFET case and heat sink immediateky next to it should not be > 5°C. More like 2°C.
However, when increasing bolt tension, you should cross check electrical insulation between heat sink and FET.
Those Kerafol are somewhat fragile.
Patrick
The junction to case Rth of the FET is 0.83K/W.
At 32W dissipation, this makes ~25°C above heatsink.
So you are still just around 100°C junction temperature.
But to be on the safe side, I suggest you lower bias to 1.6A.
This will reduce your MOSFET case temperature to ~65°C.
AND you should check whether you have tightened the bolt properly.
The difference between MOSFET case and heat sink immediateky next to it should not be > 5°C. More like 2°C.
However, when increasing bolt tension, you should cross check electrical insulation between heat sink and FET.
Those Kerafol are somewhat fragile.
Patrick
Thanks Patrick for your advices.
I will recheck tonight the difference between the mosfet and the heatsink immediately near.
About the bolting I don't tight too much because I need to dismantle the ampli to float it. As far I know when the kerafol are tight one time are very dangerous to be re-used.
I will recheck tonight the difference between the mosfet and the heatsink immediately near.
About the bolting I don't tight too much because I need to dismantle the ampli to float it. As far I know when the kerafol are tight one time are very dangerous to be re-used.
I am not saying that I will keep the bolt "loose". What I am saying is that I will tight properly the bolts when I will float the ampli.
Is not a matter of cost but of availability. I am in Korea and the last time that I ordered the Kerafol in the AudioStore cost me more in shipping and time than the cost itself.
Thank Patrick, this is very kind from you
but still I have 6 of this kerafol in the pocket.Last time I order 40 of them from the AudioStore and I use 16 for the bridges, 4 for the regulators and 8 for the 2 channel. I will need 6 for the protection board.
The ones in the bridges and in the regulators are well tight and I hope by the end of the week to float both of the channel at 1.5A. At that time I will check the kerafol. If I have any doubt I will change them and I will use the used ones for the protection that is not so critical.
Regards,
Enrico
Fully agreed... but I can't find it here
Today I try to find some probes for the fluke in the only shop in the island... they have to order oversea! 4 weeks to delivery
Believe me, anything here is a problem. The other chance is to take the car and drive 500km for go in one place in Seoul where you can find "almost" everything.
I was there already 2 times but I have to leave in friday evening, sleep there and be in the building by 9.00... at noon everything is closed!
Is not easy be a DIYer in Korea but I will survive
Today I try to find some probes for the fluke in the only shop in the island... they have to order oversea! 4 weeks to delivery
Believe me, anything here is a problem. The other chance is to take the car and drive 500km for go in one place in Seoul where you can find "almost" everything.
I was there already 2 times but I have to leave in friday evening, sleep there and be in the building by 9.00... at noon everything is closed!
Is not easy be a DIYer in Korea but I will survive