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PostPosted: 10 Nov 2009, 04:30 
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Joined: 08 Nov 2009, 20:05
Posts: 7
Location: Nr. Manchester. UK
Quoting Admin...
Quote:
By increasing the bulb, you can increase the power to the equipment

Yes, yes I forgot that, done it myself, and another little ol trick, using 115V equipment on 240V you got an illuminating voltage dropper..... just like them resistive cords you get on some shavers and AC/DC radio's which I've seen swapped for standard electric cord .... and then a earthing job - with a spade!

Dave


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PostPosted: 10 Nov 2009, 15:27 
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Joined: 14 Oct 2008, 17:35
Posts: 901
Location: Dartmouth, Nova Scotia
RiGuy wrote:
Whats up with all the jacks ?
What can we do with your version that we can not with the original. Do tell!

The tester I made, may be very scary looking but it has saved many stereos from total destruction and with the addition of some terminals, a momentary switch and an AC voltage meter, it is perfect for testing and measuring voltages on power transformers, and by adding a diode in series after the light bulb it can even be used as a lead acid battery charger. :D

And obviously it may not be a good idea building this tester in the same setup as I have! :!: :eek: :!: :tombstone:

I think it may be time for me to upgrade to a proper case with heavy gauge wire too..... :firefighter:

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PostPosted: 21 Jan 2010, 18:57 
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Joined: 14 Nov 2008, 09:09
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Hi guys - so I finally rigged one of these up and they are pretty neat -- so far all of the amps I've tried on it have passed the initial test -- that is -- none of them immediately lit the lamp, as in a slapper from the blue line of a short.

I understand that you can use the dim bulb tester with all the tubes out of an amp, correct? all tubes out, power on - no bulb glow, no short -- a good thing.

next just the rectifier tube -- power on - and a nice low glow -- good --

next all of the the tubes -- here I get confused -- all the tubes in, power on... and bulb glows bright and then backs off to a bit less bright -- what's going on here to drop back the brightness?

another question: I recall reading about how people can kind of "reform" electrolytics using the dim bulb tester -- I know a lot of people don't put much stock in reforming capacitors - but I guess if I have a dbt (dim bulb tester) it's worth doing a little reforming while I wait to recap the amp...

What do you guys think?

Thanks,
Reed
Minnesota


(edit 6:20 CST after checking dbt on amp with all tubes in)


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PostPosted: 21 Jan 2010, 20:35 
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Joined: 14 Oct 2008, 17:35
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Location: Dartmouth, Nova Scotia
I must say, the circuit has many bizarr uses that I don't fully understand, like you can revive and charge lead acid batteries with it by just adding a diode (have yet to really experiment with this).

With tube amplifiers it is very strange, I think the bulb goes bright because of the tubes warming up, it has to do with the high voltage applied Vs the heat up time and it also takes a moment for the bias to stabilize. With class "A" tube amplifiers, I find the bulb seems to stay semi lit.

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PostPosted: 21 Jan 2010, 21:50 
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Joined: 28 May 2008, 21:53
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Location: Winnipeg, CANADA
Hi Reed, what is the power rating on the bulb you are using? Sounds like you are using a low wattage bulb and the intensity change of the light is the cold heater draw.

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[ DIY Mains AC Power Cable Cord ] - [ Gobo LM1875 Amp Kit ] - [ Tang Band D4-1 Horn Speaker Kit ] - [ Monoblock Push-Pull KT88 Tube Amp Kit ]


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PostPosted: 22 Jan 2010, 12:03 
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Joined: 14 Nov 2008, 09:09
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Hi Gio -

yeah - I think you're right - 40 watt bulb - powers up dims down -- I think that's good ---

if I run the dim bulb tester with say a 100 watt bulb does this mean the current is limited to 100 watts?

Is that what's going on? the bulb acts as a limiter? as in, does not allow more power to get through than the lightbulb wattage?

R


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PostPosted: 23 Jan 2010, 10:46 
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If the device you want to test consumes about 20W, use a bulb with about double the power (40W) and it should power up and then dim down to about half brightness. If it lights up brightly you have a short. Do you know the power rating of what you are checking?

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[ DIY Mains AC Power Cable Cord ] - [ Gobo LM1875 Amp Kit ] - [ Tang Band D4-1 Horn Speaker Kit ] - [ Monoblock Push-Pull KT88 Tube Amp Kit ]


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PostPosted: 23 Jan 2010, 19:51 
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Joined: 14 Nov 2008, 09:09
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ah! ok - thanks Gio - that helps --
one more question - is it ok to use the amp -- as in run the amp with speakers to test it ect -- while powered through the dim bulb tester?


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PostPosted: 25 Jan 2010, 19:08 
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The other thing is, if it plays undistorted audio, then it is usually working properly.... although in the case of my Heathkit EA-3, it works and sounds perfect on the tester :twisted: , but when off the tester, it still sounds fine but the output tube plates turn and uneaven orange! :evil: The original tubes that came with the amplifier work ok but have slightly warped plates because of this.

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PostPosted: 25 Jan 2010, 22:30 
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Joined: 14 Nov 2008, 09:09
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hey guys -
I have just finished recapping my fisher 480a tube amp -- the amp used diode rectifiers and I replaced the old diodes with hexfred diodes --

can I test this type of a diode rectified amp with the dim bulb tester? If so, should I test it with or without any tubes in it -- the device does not have a rectifier tube - but is diode rectified --

Reed


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