The raw PSU board has the return point to mains earth for PSU box and its already floating on 10R. Don't make double return. You can bypass the 10R on the raw board with 0.1uF piggyback if it makes any difference to you.
The Audio Ground to Chassis Safety Earth is there to protect users in event of a serious mains fault that makes the isolated side of the equipment Live.
The Safety is achieved by blowing the Mains fuse.
If you insert a resistor into the route that the Fault Current is trying to find the way out, then the fuse may not blow or could take many seconds or minutes to blow.
The Safe route to allow the Fault Current to escape to the Safety Earth MUST allow kilo Amperes to flow ensuring fast rupture of the mains fuse.
DO NOT insert a resistor into the Audio Ground to Safety Earth connection.
If your amplifier (or equipment) needs a Hum reducing "tweak" then consider using a Disconnecting Network.
ESP has taken our long finished discussions and turned it into a useful Safety paper on how to do this.
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Very valuable info to follow safety percussion! I definitely would follow safety code and do not what to create any intentional troubles. Safety first!!!!
Than you.
Don't include the 1 Ohm resistors in the raw PSU circuit when using such large trafos. Only the 10 Ohm that rides on the yin yang diodes but better use a large current diode bridge with same config and paralleled internal diode legs instead.
So close...
Tonight I only had one thing left, and that was to wire up the umbilical between the two chassis. Got that done and tested (continuity, pin-to-pin, no shorts, shields to chassis on PSU end), so finally hooked everything up to do initial checks and begin biasing. I had already tested the PSU with dummy loads drawing about 120mA from each, so I was confident it was OK and left the lid on.
During testing I noticed one of the transformers had a bit of a hum, while the other was dead silent. I sent an email about it to the folks at Hammond, who simply replied asking for my shipping address so they can send me a new one!
So tonight I connected the umbilical, disconnected the power in from one of the Folded boards (in case anything was wrong I wanted to test each one separately), and powered up. I could hear the transformer humming, I thought maybe a little louder than before. All the LED's lit on the powered board, and I watched the voltage on the power-in connector climb to about 47.5V. Everything looked fine, then I noticed a curl of white smoke coming from the PSU chassis.
So I powered off immediately and disconnected the umbilical (and the power cord from the IEC socket!). Then I had to remove a bunch of screws to get the top off. By then everything in the PSU was cool to the touch, so I don't know where the smoke came from. Nothing was discolored. I had a sniff around, and I thought one of the transformers smelled a bit smoky, but I'm not positive.
When I was doing initial testing, of course, I used a bulb tester, and I had subsequently tested without it and with everything mounted in the chassis. I guess tomorrow night I'll use the bulb tester again, see if there appears to be any unusual current draw, and start measuring.
The only thing different I did this time, other than powering one Folded board, was leaving one raw supply powered up but with no load besides the bleeder resistors. Is it possible that running it unloaded cause an excessive voltage somewhere? Of course, my ideal outcome here is that the smoke came from the noisy transformer and nothing else is wrong, but that seems unlikely to me.
Tonight I only had one thing left, and that was to wire up the umbilical between the two chassis. Got that done and tested (continuity, pin-to-pin, no shorts, shields to chassis on PSU end), so finally hooked everything up to do initial checks and begin biasing. I had already tested the PSU with dummy loads drawing about 120mA from each, so I was confident it was OK and left the lid on.
During testing I noticed one of the transformers had a bit of a hum, while the other was dead silent. I sent an email about it to the folks at Hammond, who simply replied asking for my shipping address so they can send me a new one!
So tonight I connected the umbilical, disconnected the power in from one of the Folded boards (in case anything was wrong I wanted to test each one separately), and powered up. I could hear the transformer humming, I thought maybe a little louder than before. All the LED's lit on the powered board, and I watched the voltage on the power-in connector climb to about 47.5V. Everything looked fine, then I noticed a curl of white smoke coming from the PSU chassis.
So I powered off immediately and disconnected the umbilical (and the power cord from the IEC socket!). Then I had to remove a bunch of screws to get the top off. By then everything in the PSU was cool to the touch, so I don't know where the smoke came from. Nothing was discolored. I had a sniff around, and I thought one of the transformers smelled a bit smoky, but I'm not positive.When I was doing initial testing, of course, I used a bulb tester, and I had subsequently tested without it and with everything mounted in the chassis. I guess tomorrow night I'll use the bulb tester again, see if there appears to be any unusual current draw, and start measuring.
The only thing different I did this time, other than powering one Folded board, was leaving one raw supply powered up but with no load besides the bleeder resistors. Is it possible that running it unloaded cause an excessive voltage somewhere? Of course, my ideal outcome here is that the smoke came from the noisy transformer and nothing else is wrong, but that seems unlikely to me.
If anyone ADDs a resistor to the Fault Current escape route then they are risking their lives.
Your comment has no safety value.
What are you trying to achieve?
Your comment in the next post is safety related
This post is appropriate.
Consider whether post11904 deserves to remain and whether it could be construed as death by misadventure.
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FT-2. But ground its sleeve with some wire. Tends to attract hum when there is a field around.
That post is saying there are yin yang diodes in a board already. States nothing else. Certainly does not elaborate about resistors and fault paths. The other one talks about resistors and paths. What is the problem?
I posted a safety warning referring to NOT impeding the Fault Current Route.
You post a short message implying that all is OK, There are ying yang diodes elsewhere.
It is not OK.
Your next post seems to recognise that the error needs to be attended to.
The first post is misleading at best.
Down right dangerous when read alone as your response to my error message.
You post a short message implying that all is OK, There are ying yang diodes elsewhere.
It is not OK.
Your next post seems to recognise that the error needs to be attended to.
The first post is misleading at best.
Down right dangerous when read alone as your response to my error message.
Certainly a misunderstanding.
The way posts 11902,3 and 4 as displayed, gives the dangerous impression that post11902 can safely be ignored and telling Alex, it's OK, just rely on the Ying Yang.
I think your post11904 tempts some into just ignoring post11902.
You have done this before. Belittling my posts.
On this occasion it appears to be inadvertent. In which case you are forgiven. But the misunderstanding should in my "safety conscious view" still be better if removed.
The way posts 11902,3 and 4 as displayed, gives the dangerous impression that post11902 can safely be ignored and telling Alex, it's OK, just rely on the Ying Yang.
I think your post11904 tempts some into just ignoring post11902.
You have done this before. Belittling my posts.
On this occasion it appears to be inadvertent. In which case you are forgiven. But the misunderstanding should in my "safety conscious view" still be better if removed.
No it was not intended vs. your post. I reply to many practical queries in several build threads everyday I have to attend to in many fast posts. It was just a practical reminder to Alex about parts he already got as far as I am concerned. You don't show to construct an FSP in this thread so I don't read long posts steadfastly all the time when they are of a more general nature. I am not known to hold some personal grudge against any member since my sign up here in 2002. This is not fair to say in my opinion. The other post was triggered by the big trafos photos I saw where 3-5A yin yang diodes or any little resistance in a fault path would not be tolerated since the fuse would have to be big. Different matters in my mind.
You do well advising people for safety in detail, keep it up. You are not opposed or something. At least in my threads.
You do well advising people for safety in detail, keep it up. You are not opposed or something. At least in my threads.
That's only in low signal occasions to attend to with FT series since the aluminum sleeve is not connected to one lead and floats in the breeze. In line level it does not create a problem in general. But in very few mV level if you touch it it hums I have seen several times. Some cut it with the Dremel, dispose it and use tape or large diameter heatsrink, they say its better in general for that cap, but its anecdotal, I haven't tried it, I just ground it in phonos.