Here's the procedure for discharging the filter caps in a Fender Champion 600.
The video is pretty small so I'll put up another post with pictures so the detail is a bit clearer.
I'll cover the construction of the probe in a later post.
THE UBIQUITOUS DISCLAIMER: AKAVALVE ASSUMES NO RESPONSIBILITY FOR THE SAFETY OF ANYONE IMPLEMENTING THESE INSTRUCTIONS. IF YOU ARE NOT FAMILIAR WITH SAFE PRACTICE IN HIGH VOLTAGE CIRCUITS, DO NOT ATTEMPT THIS YOURSELF.
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7 comments:
What do you think of John Frondelli's method of discharging the caps?:
"Turn the unit on, plug in your guitar, turn up the amp, strum the open strings and let them ring while shutting off the amp. When the notes die out, the caps have used their charge."
Is that an effective method?
That's a simple and quite elegant way of doing it. And for a novice it's a good deal safer than the method I descibed. Thanks for bringing it up.
When you're working inside the amp there can be occasions where that method either won't work or isn't as convienient (when there are tubes or other components removed, the speaker is disconnected or replaced by a dummy load). I'd also encourage people to know where to look for the high voltages and be in the habit of checking for them before they start working.
Also, if you put your amp back together after modding it and it doesn't make any sound you need another way to confirm that the voltage is drained before you set about fixing it.
For starters though John's method really is an excellent one.
This has been the greatest resource. Thank you so much for helping me.
My champ 600 doesn't bleed charge slowly. When I turn the amp off my multi-meter goes from about 375 to 0 in less than 3 seconds. This is happening before I even connect the bleeder wire. Any thoughts?
If the input impedance of your meter if low (possible with some cheap DMM's but always true with an analog meter) then the caps will actually discharge through the meter. It's also possible that Fender added a bleeder resistor in the newer ones so that they discharge themselves.
There is another site that talks about "Let it drain" referring to discharging the caps by allowing the amp to sit for 5 minutes (I assume with it unplugged as well).
Then goes into a second step of "Suck it dry" referring to draining off any residual high voltage.
Akavalve, your method seems to be taking both of those steps into account.
How about John Frondelli's method? Or is there another step with the Frondelli way to help "suck it dry"?
I'm just changing my preamp and power tubes (and some day soon the speaker) but want to be sure I don't die in the process! : )
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