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 Post subject: Re: LKB 2103 Electrophoresis Power Supply Schematic/Advice
PostPosted: Jun Wed 12, 2019 2:15 pm 
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likchtar wrote:
What is a way to bypass this ground leakage safety.

At 3 KV, there isn't a safe way to do that. Instead, you must insulate your art installation sufficiently to remove the ground leakage. You are dealing with quite lethal voltages.

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 Post subject: Re: LKB 2103 Electrophoresis Power Supply Schematic/Advice
PostPosted: Jun Thu 13, 2019 1:31 pm 
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Location: Long Island
I don’t think the OP came here for a lot of “pine box” admonitions. Yes it is high voltage with enough current behind it to warrant extreme precaution. Hopefully he understands that now if he didn’t previously. He did not understand electrophoresis power supplies, nor did I the first time I saw one.

The interlocks on the output jacks, which disable the supply if a plug is not present, are to prevent accidents should the open jacks get splashed while the high voltage is on. The rear interlocks are sometimes connected to the benches so moving a supply while it is on disables it. They are also used in some labs as keys so students or junior techs cannot turn the supplies on until more senior staff has checked things over.

Neither of these features are likely to matter for a power supply that is no longer in lab service, and they do have to be bypassed in order to use the supply for anything else. Those who blithely advise others to go ripping the neutral-ground connections out of medical isolation transformers without a second thought of what that might do if somebody uses the transformer in a medical application in the future, should not get their feathers in a ruffle over defeating the interlocks of an old electrophoresis supply for experimental use.

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 Post subject: Re: LKB 2103 Electrophoresis Power Supply Schematic/Advice
PostPosted: Jun Thu 13, 2019 3:54 pm 
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I don't think he was asking about defeating the interlocks. I think he's asking about defeating a ground-fault safety feature in the supply. I think that would be a bad idea, and it would be vastly preferable to remove the ground-fault instead.

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 Post subject: Re: LKB 2103 Electrophoresis Power Supply Schematic/Advice
PostPosted: Jun Thu 13, 2019 7:50 pm 
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Joined: Sep Thu 23, 2010 6:37 am
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Location: Powell River BC Canada
On our cable tv community interest channel they featured an artist making
products with electric wood burning. I did watch it because it was something
people might want to do.

There was a very brief instant, once, where I glimpsed precisely how it was done.

If that artist wanted to instruct an adult in all aspects, of what it was, the methodology
would be the responsibility of the student.

On line advice is not one on one.

The query here was tacked on to a similar situation with different equipment.

A forum on the hobby of radio repair should veer away from questions concerning
equipment that is clearly dangerous.

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 Post subject: Re: LKB 2103 Electrophoresis Power Supply Schematic/Advice
PostPosted: Jun Thu 13, 2019 8:49 pm 
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Location: Long Island
Quote:
I don't think he was asking about defeating the interlocks. I think he's asking about defeating a ground-fault safety feature in the supply. I think that would be a bad idea, and it would be vastly preferable to remove the ground-fault instead.


Did you even read the thread? The OP's handle is NantachieRat. He had a power supply that would not turn on due to interlocks. Somebody else five or six posts later had a different model power supply with a ground fault circuit.

Quote:
A forum on the hobby of radio repair should veer away from questions concerning
equipment that is clearly dangerous.


A 9-volt transistor radio battery is clearly dangerous, if you connect it through your skin, across your heart. So what's left to talk about?

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 Post subject: Re: LKB 2103 Electrophoresis Power Supply Schematic/Advice
PostPosted: Jun Fri 14, 2019 12:29 am 
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Chris108 wrote:
Did you even read the thread? The OP's handle is NantachieRat. He had a power supply that would not turn on due to interlocks.

Yes, I've read the thread. Twice, in fact, once back in 2013 when NantachieRat started the thread, and again this week when likchtar revived the thread.

Chris108 wrote:
Somebody else five or six posts later had a different model power supply with a ground fault circuit.

While likchtar mentioned that he or she had already defeated the interlock, likchtar specifically asked for assistance in defeating the ground fault circuit. I assumed that subsequent posts referred to that request, since NantachieRat abandoned the thread in 2013 and hasn't logged in to ARF since April of 2015.

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 Post subject: Re: LKB 2103 Electrophoresis Power Supply Schematic/Advice
PostPosted: Jun Fri 14, 2019 2:06 pm 
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Location: Erie, PA
The ground fault sensing on these LKB's is the same detection circuit for an output short, and even if it could be internally defeated you wouldn't want to do it as you risk destroying the supply in a very quick manner or making it even more unsafe.

The optical or mechanical safeties on these particular LKB power supplies must be bypassed to use them as bench supplies or anything else aside from their original intended purpose. Being a good idea or not is up to the end user. Understand the margin for error and the trust level you have in yourself as a service technician or experimenter.

-Mark-


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 Post subject: Re: LKB 2103 Electrophoresis Power Supply Schematic/Advice
PostPosted: Jun Fri 14, 2019 7:45 pm 
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Joined: Jun Fri 19, 2009 6:34 pm
Posts: 8542
Location: Long Island
Quote:
While likchtar mentioned that he or she had already defeated the interlock, likchtar specifically asked for assistance in defeating the ground fault circuit. I assumed that subsequent posts referred to that request, since NantachieRat abandoned the thread in 2013 and hasn't logged in to ARF since April of 2015.


Little wonder there! :lol: I agree with you and Mark that there is no good way to disconnect or defeat a DC ground fault circuit on the output of one of these supplies as it ties into too many other things.

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