lamp tester
lets not compromise between safety and knowledge.sometimes we need to stop and take a common sense approach to information we get and run with it.
in the case of the homebrew lamp current limiter we're talking about which can be a useful piece of test equipement. one has to stop and ask themselves,"do i understand what this device is and what it is intended to do and how to apply it. do i understand fully any limitations it has." if this is you seek more information.sometimes what we don't know can have disastrous consquences
there is some glaringly obvious bad information in this thread about these devices and how to use them
lets not compromise between safety and knowledge.sometimes we need to stop and take a common sense approach to information we get and run with it.
in the case of the homebrew lamp current limiter we're talking about which can be a useful piece of test equipement. one has to stop and ask themselves,"do i understand what this device is and what it is intended to do and how to apply it. do i understand fully any limitations it has." if this is you seek more information.sometimes what we don't know can have disastrous consquences
there is some glaringly obvious bad information in this thread about these devices and how to use them
New amp startup
So it would be the best to use a lamp (100W)in series with the amp in conjunction with a variac ? If an amp should work on 55V DC after rectification and you start the variac up on a much lower voltage, could some of the semiconductors be damaged due to a too low voltage or should you set the variac to a voltage , say 40Vdc after rectification when you first switch on ? Is it also then necessary to put 100 Ohm resistors in the place of the rail fuses ? Your input will be appreciated.
Regards
Jan
So it would be the best to use a lamp (100W)in series with the amp in conjunction with a variac ? If an amp should work on 55V DC after rectification and you start the variac up on a much lower voltage, could some of the semiconductors be damaged due to a too low voltage or should you set the variac to a voltage , say 40Vdc after rectification when you first switch on ? Is it also then necessary to put 100 Ohm resistors in the place of the rail fuses ? Your input will be appreciated.
Regards
Jan
He he, I was given a bunch of hifi magazines, the first one I started looking through claimed that music sounds better when played through an usb memory rather than a hard disk - and that there were differences in sound between different kinds of usb memories (of course, the more expensive ones sounding better). All in a totally serious (even superior "duh, obviously this is the case" like) tone. This forced me to throw the entire stack of magazines in the trash.
Sorry for going off topic. Just had to share.
Vrystaat
let me begin by stating i don't like the name "lamp tester" i prefer "homebrew current limiter"
in answer to your first question yes it's a good idea to have a series lamp in conjunction with your variac for a few reasons.
let's take a moment to analyze this
in a series connected circuit current flow is determined by the sum of resistances in series
now in the homebrew limiter the wattage of the lamp wattage determines the current (as an example a 100 watt lamp at 120 volts the current would be 0.833 amps a 50 watt lamp the current is 0.4166 amps)so now let's look at how this applies to our limiter and our device under test(your brand new chip amp or that crusty old tube amp you want to revive) if our device under test has a dead short somewhere or a bad fault it's essentially the same as a low value resistor which would change the value of current draw in our series circuit lighting our limit lamp nice and bright because the voltage drop is now across the limit lamp
now using this requires a little estimation of what normal current draw should be in our test device. in a linear solid state amp with no faults at idle it shouldn't be drawing a whole lot the limit lamp would be off or at best a very faint glow in the case of our tube amp we can expect a little more draw because of the heater circuits
to recap a hard short bright light a normal non defective unit faint glow or low intensity
the same principle applies to the substitution of fuses with 100 ohm resistors if you monitor the voltage across them you can exprapolate the current draws in the plus minus rails of the device if there's a big difference watch out there's a problem
as to damage to semi's in current starvation or low voltage i don't see a problem (but i may well be corrected in this instance) i can tell you that using the homebrew limiter with switch mode supplies and sometypes of the newer class d or t amps can problematic as some of these devices can be intolerant of having their operating point messed with
i like using this lamp limiter when i'm going to power up a device in which i've replaced output devices like expensive T03 transistors but can't be sure might still contains a driver stage fault or leaky filters or assess an old tube amp which may or may not be ok because the lamp can give almost instantaneous visual cue from flickering intensity (a sign of instability or breakdown) to monitoring short or long term trends as indicated by changes in the lamp filament intensity
well i hope that this helps to illuminate you (no pun intended)
p.s. you mentioned in your post about an amps voltage after rectification the homebrew because it's ahead of everything would even help show gross diode faults in a supply
let me begin by stating i don't like the name "lamp tester" i prefer "homebrew current limiter"
in answer to your first question yes it's a good idea to have a series lamp in conjunction with your variac for a few reasons.
let's take a moment to analyze this
in a series connected circuit current flow is determined by the sum of resistances in series
now in the homebrew limiter the wattage of the lamp wattage determines the current (as an example a 100 watt lamp at 120 volts the current would be 0.833 amps a 50 watt lamp the current is 0.4166 amps)so now let's look at how this applies to our limiter and our device under test(your brand new chip amp or that crusty old tube amp you want to revive) if our device under test has a dead short somewhere or a bad fault it's essentially the same as a low value resistor which would change the value of current draw in our series circuit lighting our limit lamp nice and bright because the voltage drop is now across the limit lamp
now using this requires a little estimation of what normal current draw should be in our test device. in a linear solid state amp with no faults at idle it shouldn't be drawing a whole lot the limit lamp would be off or at best a very faint glow in the case of our tube amp we can expect a little more draw because of the heater circuits
to recap a hard short bright light a normal non defective unit faint glow or low intensity
the same principle applies to the substitution of fuses with 100 ohm resistors if you monitor the voltage across them you can exprapolate the current draws in the plus minus rails of the device if there's a big difference watch out there's a problem
as to damage to semi's in current starvation or low voltage i don't see a problem (but i may well be corrected in this instance) i can tell you that using the homebrew limiter with switch mode supplies and sometypes of the newer class d or t amps can problematic as some of these devices can be intolerant of having their operating point messed with
i like using this lamp limiter when i'm going to power up a device in which i've replaced output devices like expensive T03 transistors but can't be sure might still contains a driver stage fault or leaky filters or assess an old tube amp which may or may not be ok because the lamp can give almost instantaneous visual cue from flickering intensity (a sign of instability or breakdown) to monitoring short or long term trends as indicated by changes in the lamp filament intensity
well i hope that this helps to illuminate you (no pun intended)
p.s. you mentioned in your post about an amps voltage after rectification the homebrew because it's ahead of everything would even help show gross diode faults in a supply
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no.
The Variac usefulness and the bulb tester usefulness are very different.
They do different jobs very well.
They are not interchangable nor are they compatible to conjoined use.
The bulb tester is a fool proof way for checking that gross wiring errors are there, or not there.
The Variac cannot do this effectively.
I completely disagree.
Your explanation that follows does not detail where or how the conjoined bulb tester and Variac offer an advantage.
The Big Advantage of the bulb tester is that it automatically inserts the protection "current limiter", that is Mains voltage rated, to prevent catastrophic damage downstream. I always start with a low power bulb, I have just bought some 25W bulbs specifically for this use and compatible with the bulb holder I have. (my previous 25W bulbs need an e15 holder which I have not found yet.
Normally I start at 40W and progress through to 150W, if necessary, to get the circuit up to almost full operational voltage, checking the circuit at each stage for smoke, smell, voltages, currents, etc. But this progressive increase in bulb power is only required where the quiescent power draw brings on the limiting effect of the PTC inside the bulb envelope, i.e. it start to glow. If the bulb filament stays cold or near so, then the resistance in the primary circuit passes quiescent current safely to the transformer.
You are right in one aspect. Don't use a bulb tester when you are not using a mains transformer. The transformer and it's wiring is what the first line of checking that the bulb tester is useful for !!!!!!
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With buttons and parallel lamps it gets more complicated than it needs to be.
I have built my own with a simple cable like the ones above.
It is really easy to change the bulb if necessary for a project and it is really really easy to remove it and plug the project straight to the wall.
I don t see a reason why to build something with switches etc that are only "convenience" additions and are very likely to create problems if something is overlooked.
If you really need a switch, I would use a switched socket on the wall for the on-off, but I wouldn't wire a bypass switch. We really do not want one extra thing to have to remember when we are dealing with mains ...
I have built my own with a simple cable like the ones above.
It is really easy to change the bulb if necessary for a project and it is really really easy to remove it and plug the project straight to the wall.
I don t see a reason why to build something with switches etc that are only "convenience" additions and are very likely to create problems if something is overlooked.
If you really need a switch, I would use a switched socket on the wall for the on-off, but I wouldn't wire a bypass switch. We really do not want one extra thing to have to remember when we are dealing with mains ...
A 40 watt bulb is great for just powering up class AB and D amps.
But the bulb will come on if any serious power is taken.
I found for SMPS testing at least a 100 watt bulb is required or the SMPS keeps resetting itself under load.
I have a test rig for testing new amplifiers and I just put in a low current transformer so it will overload before blowing up transistors. If there is a problem I can almost always hear hum in the speaker.
But the bulb will come on if any serious power is taken.
I found for SMPS testing at least a 100 watt bulb is required or the SMPS keeps resetting itself under load.
I have a test rig for testing new amplifiers and I just put in a low current transformer so it will overload before blowing up transistors. If there is a problem I can almost always hear hum in the speaker.
Just click on "quote" and it will do it automatically.
You can then edit the text in quotes if you like.
amplifier testing
AndrewT,
So what you are saying is not to connect the variac and lamp tester in series with the amplifier and not to increase the AC voltage gradually ? I must just use the lamp tester starting with a 40W bulb and change it to 60 and then 100W when they don't light up brightly ? What about 100 Ohm 5W resistors in the place of the rail fuses at the same time with a DMM to monitor the current being drawn ? Should any load be connected on the speaker outputs ? If so, what would a safe idle current reading be if a load of 4/8 Ohm was connected. My power supply is (400VA) 54-0-54 V DC linear. Sorry for all the questions, I'm just trying to figure out the best and safest way to do it. I'm using lateral 2sj162/2sk1058 output devices and they do not come cheap !
Regards
Jan
AndrewT,
So what you are saying is not to connect the variac and lamp tester in series with the amplifier and not to increase the AC voltage gradually ? I must just use the lamp tester starting with a 40W bulb and change it to 60 and then 100W when they don't light up brightly ? What about 100 Ohm 5W resistors in the place of the rail fuses at the same time with a DMM to monitor the current being drawn ? Should any load be connected on the speaker outputs ? If so, what would a safe idle current reading be if a load of 4/8 Ohm was connected. My power supply is (400VA) 54-0-54 V DC linear. Sorry for all the questions, I'm just trying to figure out the best and safest way to do it. I'm using lateral 2sj162/2sk1058 output devices and they do not come cheap !
Regards
Jan
AndrewT,
This is my first project from the bottom up and we all need advice. Everyone makes mistakes sometime. People who does nothing makes no mistakes. I'm so sorry that I wasted your precious time , plse do not reply or act on any of the posts that I might post in the future on this forum.I'm sure there are plenty of other people who are willing to help.Life is too short to live with bitterness and regrets.Sometimes its better to say nothing than to degrade people.
Thanks for the superb advice and you should have a great day too.
Cheers
Jan
This is my first project from the bottom up and we all need advice. Everyone makes mistakes sometime. People who does nothing makes no mistakes. I'm so sorry that I wasted your precious time , plse do not reply or act on any of the posts that I might post in the future on this forum.I'm sure there are plenty of other people who are willing to help.Life is too short to live with bitterness and regrets.Sometimes its better to say nothing than to degrade people.
Thanks for the superb advice and you should have a great day too.
Cheers
Jan
You most certainly, most unequivocally were not stupid to be offended by a bully. Your response was very level headed and appropriate.
Guess the Name
I have read this thread w/ some interest. This instrument has a name and not one person has named it properly. It has been around for at least 70 years. There were commercial produced units with embellishments before the WW II . It's called a Dim Bulb Tester. If one were to Google that name you would be reading for the next week or more.
I have read this thread w/ some interest. This instrument has a name and not one person has named it properly. It has been around for at least 70 years. There were commercial produced units with embellishments before the WW II . It's called a Dim Bulb Tester. If one were to Google that name you would be reading for the next week or more. 