Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: dpm309 on March 21, 2017, 06:07:25 pm
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Was working on my modified Champ 6L6 and noticed that I do not have any bleeder resistor on the first filter cap located before the standby switch and choke. The other 3 filter caps bleed off in a couple of minutes. If I turn off the amp and leave the standby switch on, all 4 bleed off quickly. My question is what value bleeder resistor should I use for the 1st filter cap? I have used standby switches on all of my builds but this is the first one I did with a filter cap before the standby switch.
On a side note, the reason I opened this up is that I blew a fuse and noticed that I inserted the 5AR4 rectifier tube incorrectly due to a worn guide pin. This is an old Sovtek 5AR4 that I found in the local electronics reclamation store. When I inserted it correctly, everything is working fine. Just a caution to anyone else who has tubes with worn guide pins. Luckily I didn't harm any components.
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Bleed resistor are usually 220K - 330K, 3W will be fine
you can put one on the first cap and one on the other
if you use two bleed resistors you can consider to increase a bit the value to maintain a value of more of 200K when the standby switch is closed
or use only one bleed resistor and close the standby when you shutt off
Franco
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I don't mean to hijack this thread, but I'm curious about adding a bleed resistor to my Vibro champ that I'm slowly working on at a snails (a slow snail) pace. I've seen some people talk about putting in an LED that visually shows when the filter caps are discharged, and was curious if anyone had a good schematic showing how this is implemented? Also for placement, can you just tack the 220-330K 3W resistor on the end of your B+ chain ( far right in the schematic above) and have it go to ground like in the attached picture? My Vibro is standard with no standby switch. Thanks
-Brett
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Would a 2 Watt 220K work? Don't have anything larger on hand.
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Would a 2 Watt 220K work? Don't have anything larger on hand.
yes
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Thanks Sluckey. Would this be the correct place to add the 220k resistor? See schematic below.
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the correct place to add the 220k resistor?
If you leave the stby sw open, the down-stream caps won't discharge as fast n could .bite
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the correct place to add the 220k resistor?
If you leave the stby sw open, the down-stream caps won't discharge as fast n could .bite
No way to fix that when the switch separates filter caps, without having more than 1 bleeder.
There's a simple repair-process step that solves the issue: Keep the Standby closed when powering off (or get rid of it); even if there's no Standby or bleeder, a jumper with alligator clips placed from a preamp plate to ground will drain the B+ through the plate load resistor & B+ dropping resistors. Measure B+ volts before getting grabby.