Hi Guys,
How are things going lately? I received the Buerklin FE card guides plus the resistor elevator pins from JPS64. If you are interested in a set of guides plus the hardware I can send to you for $20/set to cover the cost of shipping and parts. Send me an email or PM if interested.
How are things going lately? I received the Buerklin FE card guides plus the resistor elevator pins from JPS64. If you are interested in a set of guides plus the hardware I can send to you for $20/set to cover the cost of shipping and parts. Send me an email or PM if interested.
It’s been awful quiet lately guys. How are the verification builds coming along?
Hi Shane (and all beta testers), I have a SSR controlled soft start board to prevent in rush called SFP that I can provide you free of charge for this project. It lets current pass through three 8D-20 NTCs in series (24ohms) for about 2 seconds and then the SSR switches on and bypasses the NTCs. This way, no heat is generated after the soft start ramps up.
https://www.diyaudio.com/community/...ssr-soft-start-circuit-gb.350441/post-6106597
You will have to look around for HV low RDson TO220 MOSFETs. The ones in the BOM are way too expensive. Options exist in the $6ea range. I forget the part number. It’s in the thread somewhere.
https://www.diyaudio.com/community/...ssr-soft-start-circuit-gb.350441/post-6106597
You will have to look around for HV low RDson TO220 MOSFETs. The ones in the BOM are way too expensive. Options exist in the $6ea range. I forget the part number. It’s in the thread somewhere.
Okay great plan.
I'll get this bom ordered.
I am very close. starting to mount everything now.
I'll get this bom ordered.
I am very close. starting to mount everything now.
Hi Shane,
Yes, that one is perfect. Thanks for finding it. Send me your address again in a PM and I’ll get you the SFP PCB.
Yes, that one is perfect. Thanks for finding it. Send me your address again in a PM and I’ll get you the SFP PCB.
I would use a variac if you have one. Then set the trim pot that the bias current to the position that has the minimum current flow. Keantoken will have to tell you which way that is. Have some alligator clips monitoring the current through the source resistors. Another one monitoring DC offset. And another one monitor rail voltage.
Wear safety googles and stand back at least 6 ft away from those big caps when turning on power for the first time.
Make sure there is a fuse in the mains connection for say 6A.
Check to make sure that the MOSFETs are insulated and nothing has ground continuity in the output stage. DGS pins should never be close to ground with ohm meter to ground.
It would be good to test without output stage connected first to make sure mezzanine board works. Not sure if that’s possible.
If turning has no huge current and DC offset is close to zero and trimable. Slowly adjust pot to increase bias current. I forget what Keantoken suggests. But maybe 100mA?
I assume this is not your first discrete Class AB rodeo?
Good luck!
Wear safety googles and stand back at least 6 ft away from those big caps when turning on power for the first time.
Make sure there is a fuse in the mains connection for say 6A.
Check to make sure that the MOSFETs are insulated and nothing has ground continuity in the output stage. DGS pins should never be close to ground with ohm meter to ground.
It would be good to test without output stage connected first to make sure mezzanine board works. Not sure if that’s possible.
If turning has no huge current and DC offset is close to zero and trimable. Slowly adjust pot to increase bias current. I forget what Keantoken suggests. But maybe 100mA?
I assume this is not your first discrete Class AB rodeo?
Good luck!
I’ll get a hold of a variac.
This isn’t my first build but it’s my first beta. So blunter the directions the better.
I built a nirvana, yarra and a FH9HVX.
This isn’t my first build but it’s my first beta. So blunter the directions the better.
I built a nirvana, yarra and a FH9HVX.
To check that the bias will be low on turn-on, you can measure the resistance between the driver transistor bases and turn the bias trimmer so that it is lowest. I always use clockwise=higher for bias, but I usually check with a DMM anyway to be sure.
maybe I'm overly concerned. Is there a chance could you send the exact locations of points that should be monitored?
Measure across the large 0.22R BPR resistors. There are 6 measurements. They should all be similar and abiut 80mA each or 18mV across these resistors:
On the Mezzanine board, measure across here:
On the Mezzanine board, measure across here: