Thanks for those options. Both good for scope testing.
Still pondering what to do for production use. When the board is grounded, it pops GFCI circuits. When floating it does not.
Maybe the variac is playing a role in this? Might try to bring the “normal” transformer into the circuit and lightbulb check it. Others have described similar issues with them here:
Variac problems
Still pondering what to do for production use. When the board is grounded, it pops GFCI circuits. When floating it does not.
Maybe the variac is playing a role in this? Might try to bring the “normal” transformer into the circuit and lightbulb check it. Others have described similar issues with them here:
Variac problems
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+ infinity.
I almost did it once, and it was because of a lack of sleep! As I was looking at my test setup I wondered what was missing and why that toroid was sitting by itself in the corner.
No worries Chris, just be safe, cause we care and we want you to make it to the next BAF with all fingers and toes!
Best,
Anand.
Since I have been so graciously enlightened as to the gravity of my improper use of test equipment, I'd like to use this as a learning opportunity for others. Are there any articles herein that describe safe (and proper) use of various types of test equipment we use with our amplifiers and supporting systems? Seems like it would be valuable in cases like this. I for one will be searching safety topics this afternoon to see if I've registered elsewhere on the ZM dodo scale.
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Go to Youtube. Look up Uncle Doug
He has a ton of videos, all well described and he is a methodical teacher who takes his time. Particularly look up Isolation Transformers
Listen. Digest. Understand. And view all the other videos on power transformers, output transformers, various tube topologies, capacitors, resistors, oscilloscopes, etc...
These are the basics. Everything builds up from the basics. A foundation so to speak.
Best,
Anand.
Well, for learning opportunities, there is always the tubes safe practices sticky note.
Safety Practices, General and Ultra-High Voltage
I pretty much learned more on top of what I already was practicing when I was building tube amps from a book before finding diyaudio.com
Some of the information applies (like electrolytic capacitors and physically unplugging from the wall and verifying) and some of the notes have zero meaning here (tubes that have lost vacuum or internally arc). All good reading and reminds me (at least) that electricity is no laughing matter.
Safety Practices, General and Ultra-High Voltage
I pretty much learned more on top of what I already was practicing when I was building tube amps from a book before finding diyaudio.com
Some of the information applies (like electrolytic capacitors and physically unplugging from the wall and verifying) and some of the notes have zero meaning here (tubes that have lost vacuum or internally arc). All good reading and reminds me (at least) that electricity is no laughing matter.
Safety Rule #1: Do not connect your circuit directly to the mains without some form of transformer.
If you go Mains -> Variac -> Transformer, you're good. Now, you can still blow up stuff - including your scope - but you're less likely to do so.
EEVblog has a good video on the issues around oscilloscope grounding: EEVblog #279 - How NOT To Blow Up Your Oscilloscope! - YouTube
Tom
If you go Mains -> Variac -> Transformer, you're good. Now, you can still blow up stuff - including your scope - but you're less likely to do so.
EEVblog has a good video on the issues around oscilloscope grounding: EEVblog #279 - How NOT To Blow Up Your Oscilloscope! - YouTube
Tom
Chris,
I forgot to add Blue Glow Electronics on youtube. He has some safety videos as well, can't recall which but take a look:
Dealing with the DEATH CAPACITOR in Vintage Gear - YouTube
High Voltage Vacuum Tube Electrolytic Capacitor Discharge Probe / Tool - BG074 - YouTube
Audio Test Bench Setup and Dummy Load Build - BG052 - YouTube
How to Make an Electronics Workbench Variac (variable autotransformer) - YouTube
How to find and install a replacement power transformer for your tube amplifer - YouTube
He also has a whole oscilloscope series for audio just type it in the search engine of the Blue Glow Electronics Youtube site.
Much of it is written for newbies as well.
EEVblog is awesome and very entertaining to watch!
Best,
Anand.
I forgot to add Blue Glow Electronics on youtube. He has some safety videos as well, can't recall which but take a look:
Dealing with the DEATH CAPACITOR in Vintage Gear - YouTube
High Voltage Vacuum Tube Electrolytic Capacitor Discharge Probe / Tool - BG074 - YouTube
Audio Test Bench Setup and Dummy Load Build - BG052 - YouTube
How to Make an Electronics Workbench Variac (variable autotransformer) - YouTube
How to find and install a replacement power transformer for your tube amplifer - YouTube
He also has a whole oscilloscope series for audio just type it in the search engine of the Blue Glow Electronics Youtube site.
Much of it is written for newbies as well.
EEVblog is awesome and very entertaining to watch!
Best,
Anand.
When I was an experimental physicist, we routinely did work with multi-kilovolt equipment, sometimes tens of kilovolts.
(among a lot of other things, in our Plasma Physics Institute we did operate a lightning lab, and we were one of the only two facilities in Europe that could certify aircraft parts for safety from lightning strikes)
I got enough respect that way that in my diy endeavours, I'm not going above, say, 450V for tube amps - no 211 or 845 for me, thanks.
And whenever I come near an open amp, after all those years I still find my left hand automatically gone into a pocket and staying there ...
Regards, Claas
(among a lot of other things, in our Plasma Physics Institute we did operate a lightning lab, and we were one of the only two facilities in Europe that could certify aircraft parts for safety from lightning strikes)
I got enough respect that way that in my diy endeavours, I'm not going above, say, 450V for tube amps - no 211 or 845 for me, thanks
. And whenever I come near an open amp, after all those years I still find my left hand automatically gone into a pocket and staying there ...
Regards, Claas
I understand the safety concern now. I presumed the variac was a proper variable transformer. It’s not.
Do I need an isolation transformer when using a VARIAC?
Appreciate the other references. Looking forward to reviewing them.
Do I need an isolation transformer when using a VARIAC?
Appreciate the other references. Looking forward to reviewing them.
Chris,
I promise to stop posting these safety videos so you can carry on with your build!
Watch Carlson’s explanation on isolation transformers. Pay close attention to the diagram he draws:
Tech Tips Tuesday, Isolation Transformer and Variac Safety - YouTube
And Uncle Doug’s basics of how AC mains wiring came to be and why isolation transformers exist:
Isolation Transformers - YouTube
Best,
Anand.
I promise to stop posting these safety videos so you can carry on with your build!
Watch Carlson’s explanation on isolation transformers. Pay close attention to the diagram he draws:
Tech Tips Tuesday, Isolation Transformer and Variac Safety - YouTube
And Uncle Doug’s basics of how AC mains wiring came to be and why isolation transformers exist:
Isolation Transformers - YouTube
Best,
Anand.
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I recognized one of my boards in a post here. Glad to see some are still playing around . I am routinely using my two AlephP v.1.7 builds to drive anything balanced, even if the gain is not needed since they come with the volume attenuators. They sound their best set to a high internal gain even if the attenuator has to take that back down. Also use the input attenuator to reign in hot sources. Check out old builder's thread for pointers.
. I am routinely using my two AlephP v.1.7 builds to drive anything balanced, even if the gain is not needed since they come with the volume attenuators. They sound their best set to a high internal gain even if the attenuator has to take that back down. Also use the input attenuator to reign in hot sources. Check out old builder's thread for pointers.
Very enlightening and total clarity has been achieved! Thanks a million for sharing that video. Here’s hoping it helps others avoid my mistakes as well! 
I recognized one of my boards in a post here. Glad to see some are still playing around
Yep! That was my P1.7... I also built a second one for a friend and he still has that one. Since I retired and moved to an apartment, I have drastically down scaled my system. But am thinking of building another P1.7 and F5 as an integrated amplifier to drive my LS-50's. That would replace an Arcam integrated I am using now.
Do you still have any boards available?
Mark
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