- Joined
- Jan 14, 2011
- Messages
- 75,036
- Location
- Gillette, Wyo.
- Tagline
- Halfbiass...Electron Herder and Backass Woof
nelsress begins his WOPL 400 project
- Thread starter nelsress
- Start date
- Joined
- Jan 14, 2011
- Messages
- 75,036
- Location
- Gillette, Wyo.
- Tagline
- Halfbiass...Electron Herder and Backass Woof
- Joined
- Jan 14, 2011
- Messages
- 75,036
- Location
- Gillette, Wyo.
- Tagline
- Halfbiass...Electron Herder and Backass Woof
Those damn big ass caps - they'll bite you if you're not careful. I've been bit a time or two so I built a simple circuit that has a three position switch - it is either open, has a 20 ohm or 50 ohm 10 watt resistor that is switched between two leads that I connect one to the capacitor plus side that I want to discharge and the other lead I connect to ground. I do this when the leads are open so no arc - just connect the two leads and throw the switch to one of the resistor positions to drain the cap. I also have two .080" jacks to plug a multimeter into so I can verify the voltage across the cap(s).
I've had test leads turn into plasma so I'm a bit shy about high voltage/high current. My last episode that turned metal into plasma was about 20 years ago but it's still fresh in my memory. I stayed from the test setup for the rest of that test day but was hard at it the following day.
I've had test leads turn into plasma so I'm a bit shy about high voltage/high current. My last episode that turned metal into plasma was about 20 years ago but it's still fresh in my memory. I stayed from the test setup for the rest of that test day but was hard at it the following day.
B+ test points
Using a 4700 ohm, 3 watt resistor that I found in my stash I discharged the capacitors, added wires from the positive PS cap connection to the positive supply fuse tip and one from the negative PS cap connection to the negative supply fuse tip. While I was in there I decided to re-route the black B- and the green B+ wires from the top to the bottom of the chassis along with the two white negative output wires.
After making these changes I decided to power up again. This time I had voltage at both rail fuses and had good test readings on the B- but was not getting reading on the B+ test points. Thinking that I might not have had a good solder joint where I removed the B+ and re-soldered it so I removed the power, discharged the capacitors again and did some continuity testing. Everything seemed to pan out except there was no continuity from the any of the B+ attachment points to the B+ test points. I did however have continuity between the B- attachment points and the B- test points. I can't really come to any logical conclusion why this might be so but I'm new at this so there may be one. Later I'll go out and make sure the B+ rail fuse is intact, I didn't think to check that.
Anyway, the good news is that once again I got no odors, smoke or sparks when powering up!!
I'm guessing that the good news will be that there's a simple explanation for the lack of B+ voltage at the B+ test points-perhaps a fuse?!?
Using a 4700 ohm, 3 watt resistor that I found in my stash I discharged the capacitors, added wires from the positive PS cap connection to the positive supply fuse tip and one from the negative PS cap connection to the negative supply fuse tip. While I was in there I decided to re-route the black B- and the green B+ wires from the top to the bottom of the chassis along with the two white negative output wires.
After making these changes I decided to power up again. This time I had voltage at both rail fuses and had good test readings on the B- but was not getting reading on the B+ test points. Thinking that I might not have had a good solder joint where I removed the B+ and re-soldered it so I removed the power, discharged the capacitors again and did some continuity testing. Everything seemed to pan out except there was no continuity from the any of the B+ attachment points to the B+ test points. I did however have continuity between the B- attachment points and the B- test points. I can't really come to any logical conclusion why this might be so but I'm new at this so there may be one. Later I'll go out and make sure the B+ rail fuse is intact, I didn't think to check that.
Anyway, the good news is that once again I got no odors, smoke or sparks when powering up!!
I'm guessing that the good news will be that there's a simple explanation for the lack of B+ voltage at the B+ test points-perhaps a fuse?!?
- Joined
- Jan 14, 2011
- Messages
- 75,036
- Location
- Gillette, Wyo.
- Tagline
- Halfbiass...Electron Herder and Backass Woof
Using a 4700 ohm, 3 watt resistor that I found in my stash I discharged the capacitors, added wires from the positive PS cap connection to the positive supply fuse tip and one from the negative PS cap connection to the negative supply fuse tip. While I was in there I decided to re-route the black B- and the green B+ wires from the top to the bottom of the chassis along with the two white negative output wires.
After making these changes I decided to power up again. This time I had voltage at both rail fuses and had good test readings on the B- but was not getting reading on the B+ test points. Thinking that I might not have had a good solder joint where I removed the B+ and re-soldered it so I removed the power, discharged the capacitors again and did some continuity testing. Everything seemed to pan out except there was no continuity from the any of the B+ attachment points to the B+ test points. I did however have continuity between the B- attachment points and the B- test points. I can't really come to any logical conclusion why this might be so but I'm new at this so there may be one. Later I'll go out and make sure the B+ rail fuse is intact, I didn't think to check that.
Anyway, the good news is that once again I got no odors, smoke or sparks when powering up!! I'm guessing that the good news will be that there's a simple explanation for the lack of B+ voltage at the B+ test points-perhaps a fuse?!?
After making these changes I decided to power up again. This time I had voltage at both rail fuses and had good test readings on the B- but was not getting reading on the B+ test points. Thinking that I might not have had a good solder joint where I removed the B+ and re-soldered it so I removed the power, discharged the capacitors again and did some continuity testing. Everything seemed to pan out except there was no continuity from the any of the B+ attachment points to the B+ test points. I did however have continuity between the B- attachment points and the B- test points. I can't really come to any logical conclusion why this might be so but I'm new at this so there may be one. Later I'll go out and make sure the B+ rail fuse is intact, I didn't think to check that.
Anyway, the good news is that once again I got no odors, smoke or sparks when powering up!!
I'm guessing that the good news will be that there's a simple explanation for the lack of B+ voltage at the B+ test points-perhaps a fuse?!?
I will add this note to the release notes as an errata.
Thanks again.
- Joined
- Jan 14, 2011
- Messages
- 75,036
- Location
- Gillette, Wyo.
- Tagline
- Halfbiass...Electron Herder and Backass Woof
Hi Joe,
Okay, that makes sense as I did get continuity between the B+ rail fuse tip and the Bias+ test point and forgot to mention it! Okay, I'll run the test using the bias test point instead of the B+ point. You're welcome, glad to have helped in some way, pay back for all the help I've been getting!!
Okay, that makes sense as I did get continuity between the B+ rail fuse tip and the Bias+ test point and forgot to mention it! Okay, I'll run the test using the bias test point instead of the B+ point. You're welcome, glad to have helped in some way, pay back for all the help I've been getting!!
Last edited:
- Joined
- Jan 14, 2011
- Messages
- 75,036
- Location
- Gillette, Wyo.
- Tagline
- Halfbiass...Electron Herder and Backass Woof
Thanks Nav, I've always heard about the jolt those big f-in caps can put out, your switch mechanism is a good idea! I might have to build one of those myself for future builds. The alligator clips worked okay this time but I like your idea better. Thanks for stopping in, always good to see your avatar, I mean you.