Keyboard Shortcuts
ctrl + shift + ? :
Show all keyboard shortcuts
ctrl + g :
Navigate to a group
ctrl + shift + f :
Find
ctrl + / :
Quick actions
esc to dismiss
Likes
Search
Re: reviving my sbitx v3
开云体育
Yes, so I've removed D7, I have a direct short to ground, somewhere. I haven't even thought of plugging a pi into it since this began. Right now, even if I apply only 2-3v, the fat trace running from the main switch then around the edge of the board to the
PA xformer is VERY hot. I don't have a component tester at the moment, to examine whats going on with the individual transistors. Any suggestions are welcome.
From: [email protected] <[email protected]> on behalf of Gordon Gibby KX4Z via groups.io <docvacuumtubes@...>
Sent: Saturday, March 1, 2025 3:47 PM To: [email protected] <[email protected]> Subject: Re: [BITX20] reviving my sbitx v3 ?
If you have a current limited supply at about 2Amps
OR?
a variable voltage supply,
Then you could do a preliminary test after replacing D7 so you again have SOME reverse polarity protection.? ?We have had MULTIPLE radios severely damaged by good friends of mine in Northern
Florida by accidentally getting the polarity backwards.? ?It only takes a blink of an eye.
I use a "wall wart" that ONLY puts out 12V and can't put out more than 1-2Amps for initial?testing of some of my radios.
Alternatively, I have a MFJ power supply that is adjustable.? ??
With the Raspberry Pi DISCONNECTED, you?can very carefully apply current limited source, or else use a variable voltage source of about 5V and see what current flows -- there should?be VERY
LITTLE if the raspberry isn't connected.? ? Then if you can get the voltage up to 12V without having current more than 1/2 amp or so -- you might be in OK shape.? ? But at that point I would carefully measure the output of the 5V regulator and see if it was
damaged BEFORE CONNECTING ANY RASPBERY?TO IT.
If you are lucky, not all the 2n2219s were damaged.? ?By measuring the voltage across their emitter resistors you can calculate the current through them annd?see what is happening, or else
see which ones are getting HOT.? ??
On Amazon, there are multiple sources for 2219a's and they aren't that expensive.....
One of the things I try to always put together now,....is some form of polarit?protection on anything expesnsive that I buy.? ? ?I built a mosfet protection circuit and did a printed circuit
board which is shared as a project on ? ? Lots in our group have used it.? ? I put it on EVERY radio down at our EOC becuase?it is SO EASY to damage radios when people are stressed out or tired.
Let usknow?how it goes!
Gordon KX4Z
On Sat, Mar 1, 2025 at 5:33?PM Michael Bales via
<mikebales73=[email protected]> wrote:
-- Mike - K8MCB? |
to navigate to use esc to dismiss