So in order for the ODS to discharge, doesn't the standby have to be closed? For the other filter caps to drain
Yeah!! usually if your working on it you can leave the Stby off... flip the power switch while you hit a chord on the guitar and let it fade will usually do the trick.. I say usually...It won't damage the tubes doing it that way..
In reguards to those balancing resistors I checked and they will eventually bleed off if you run the RC time constant on the 2 220's (total resistance here being 440K in that configuration) should specify the amount of time it takes to discharge...(With the Plate caps being 50uf I got 21 seconds)If the other caps don't have bleeders that may very it a bit as well...Hope some of this makes sense..
I sort of got into the habit of clipping a test lead from V1 plate resistor to ground because I was working on other amps that did not have the balancing or bleeder resistors.
It's a good technique but be sure to take it off before powering up.
tictac wrote:Here's the way I do it, no thump @ turn on...
When you put the standby before all filter caps the switch sees all the current charging the power supply; put the switch after the first filter cap (the largest value in the amp) and you eliminate the current charging those large caps, the switch is less stressed in this position...
TT
Is there danger to the tubes if the screens are left floating and the plate has full voltage?
In your diagram you are showing main filter caps, B+1 going to OT, then the 3 way standby switch (choosing either sag resistor or choke).
This kinda OT but hey this whole thread has been OT...
I am working on a D amp and the standby is after the first (primary) filter caps. I am not worried about my switch as it is a nice hefty Carling and the primary caps are rated at 700V.
Anyways...I have a 220K 3W bleeder in parallel to the primary filter. That is I have a 220K in parallel to the 220mF/220mF/270K/270K combo. I already have those balancing resistors, is it bad to have added the bleeder?
I realize the bleeder will only drain the first filter caps when the amp is shut off.
Are you saying you put the 220K resistors in parallel with the 270K balancing resistors?
All that will do is lower your total resistance in that parallel branch to 121K.
Or if you have the 220K in parallel with the two 270K resistors that would bring it down to 156K.
Well like on my D'Lite that has the stby switch before the first filters, it has the balancing resistors on the two 100uf caps.
I'll repeat that it has always bled down to a safe level within a minute or two.
In an amp where the switch is after the first plate filters, if you leave the stby switch in the play position, then I would think it would drain all the caps through the resistors to ground.
But you can always put a test lead from V1 plate resistor to ensure that it drains.
The Carling switches are alright but they are rated for AC current and voltages.
When you apply a big DC voltage to them, they can arc over time.
That's why some guys put the cap across it, to keep that from happening.
