Search found 11371 matches

by Nick
Thu Dec 13, 2018 10:26 pm
Forum: Everyones Projects
Topic: Remember These?
Replies: 210
Views: 3839

Re: Remember These?

Just FYI, I have used these in the past to disconnect HT. Specifically in the ref phono if someone unplugs the connection between the two boxes CE specifies how log a voltage can remain on the pins. I detect the removal and use these to isolate the caps in the power supply while they discharge. Just...
by Nick
Thu Dec 13, 2018 3:50 pm
Forum: Assorted Stuff
Topic: Nothing In Particular
Replies: 10062
Views: 585328

Re: Nothing In Particular

Well, I installed the xmas extensions for the rescue forum and though I would give you guys the benefit as well.
by Nick
Thu Dec 13, 2018 8:53 am
Forum: Everyones Projects
Topic: Remember These?
Replies: 210
Views: 3839

Re: Remember These?

Well, a DC detector and relay wound protect from a failed cap. Not sure how a zener will do any more than a cascode, but I probably don't understand how you suggest using it. I would have thought the rate of cap failure would be low as long as its rated properly. A fast blow Fuse in the B+ would add...
by Nick
Wed Dec 12, 2018 10:48 pm
Forum: Everyones Projects
Topic: Remember These?
Replies: 210
Views: 3839

Re: Remember These?

Mike H wrote:
Wed Dec 12, 2018 3:40 pm

One thought that occurs to me is you could use something that is based on a high Voltage MOSFET. Which won't care if its drain is taken up to HT level.
You could use a mosfet as a cascode above the CCS, but it will eat a bit of the headroom.
by Nick
Wed Dec 12, 2018 12:37 pm
Forum: Everyones Projects
Topic: Remember These?
Replies: 210
Views: 3839

Re: Remember These?

You could try taking the feedback from before the output cap and adding a blocking cap in the feedback loop (can be much smaller). Stops the feedback from working to correct the output cap low pass filter.
by Nick
Tue Dec 11, 2018 3:32 pm
Forum: Assorted Stuff
Topic: Nothing In Particular
Replies: 10062
Views: 585328

Re: Nothing In Particular

Its a Jpeg Image file being displayed on a browser.
by Nick
Mon Dec 10, 2018 1:53 pm
Forum: Assorted Stuff
Topic: Owston meet 2019 >1&2 June
Replies: 36
Views: 1393

Re: Owston meet 2019 >1&2 June

we've had them in November before now - would be much better for me.
Historically though those were less well attended, and the weather made them a bit less fun (IMHO).
by Nick
Mon Dec 10, 2018 12:02 pm
Forum: Everyones Projects
Topic: The Nemesis 813 PP Amplifier
Replies: 191
Views: 3271

Re: The Nemesis 813 PP Amplifier

The fact that you are using a interstage helps a lot for fixed bias, so worth a try.
by Nick
Mon Dec 10, 2018 12:01 pm
Forum: Everyones Projects
Topic: The Nemesis 813 PP Amplifier
Replies: 191
Views: 3271

Re: The Nemesis 813 PP Amplifier

Should have said Andrew not Mark. I know he is working (when he has time) on a high current variant, but not ready yet. 5A should be do able, I did 3A for a gm70 using a three pin reg as a current source, that worked ok, but did generate heat so needed a big heatsink. I had similar startup problems ...
by Nick
Sun Dec 09, 2018 11:39 pm
Forum: Everyones Projects
Topic: The Nemesis 813 PP Amplifier
Replies: 191
Views: 3271

Re: The Nemesis 813 PP Amplifier

Thinking about the hum pots not making a difference (evening dog walk), that may point to the problem being a signal introduced into the cathode WRT amp ground, via the SMPS input from earth and or line neutral. unlike indirectly heated valves, you can't just reference the output directly to 0v. OK...
by Nick
Sun Dec 09, 2018 7:27 pm
Forum: Everyones Projects
Topic: The Nemesis 813 PP Amplifier
Replies: 191
Views: 3271

Re: The Nemesis 813 PP Amplifier

Thinking about the hum pots not making a difference (evening dog walk), that may point to the problem being a signal introduced into the cathode WRT amp ground, via the SMPS input from earth and or line neutral. unlike indirectly heated valves, you can't just reference the output directly to 0v.
by Nick
Sun Dec 09, 2018 7:09 pm
Forum: Everyones Projects
Topic: The Nemesis 813 PP Amplifier
Replies: 191
Views: 3271

Re: The Nemesis 813 PP Amplifier

Worth trying the filters that worked for Mike, just because I never got them to work doesn’t mean you won't.
by Nick
Sun Dec 09, 2018 6:26 pm
Forum: Everyones Projects
Topic: The Nemesis 813 PP Amplifier
Replies: 191
Views: 3271

Re: The Nemesis 813 PP Amplifier

Well that doesn't bode well. What did you do after that didn't work?
I started using Andrews heater supply.
by Nick
Sun Dec 09, 2018 5:06 pm
Forum: Everyones Projects
Topic: The Nemesis 813 PP Amplifier
Replies: 191
Views: 3271

Re: The Nemesis 813 PP Amplifier

I never had much luck getting noise out of SMPS's
by Nick
Sun Dec 09, 2018 1:15 pm
Forum: Assorted Stuff
Topic: Have a look! If this isn't you lot, I don't know what is.
Replies: 11
Views: 275

Re: Have a look! If this isn't you lot, I don't know what is.

Thinking about this, its not us lot at all, we would have built a transmitter as well.