Can a Power Tube Bad if It Has Continuity

Does anyone know where I tin obtain plans and use info for the current limiter that uses a lightbulb that some use at offset up????

As well, when checking continuity on my heater wires when I touch on the black lead at the beginning of the path at the kickoff socket and black atomic number 82 at the end of the path at the indicator light I get bespeak. When I touch black at beginning and cherry at the stop, I also get indicate??? If I opposite, and do red brainstorm to red cease I get point and scarlet begin to black stop, I go betoken again?? shouldn't I only get betoken red to cerise and black to black??? Hope I fabricated sense..... The start upwards makes me a petty nervous this is my second build and much more than complex than the 5e7 Bandmaster I did first.

Cheers

Mail by **M Fowler** » Tue Jun 09, 2009 4:10 am

The bulb limiter is in the Trainwreck files section nether the Express build guide has instructions and the BOM file has the parts listing.

Equally far as the continuity tester you are going to get continuity everywhere yous touh fifty-fifty the transformer you cannot become by that type of testing in the amp. Check it, out black to ground and check the heater wiring, jacks and trannies it lights upwardly right?

Just follow your layout and check it against the schematic. Go over your wiring, lead dress and make sure your solder joints are good.

Marker

Post by **Phil_S** » Tue Jun 09, 2009 ane:05 pm

There is also a very good clarification of the dim seedling tester and how to use it here: http://www.antiqueradio.org/dimbulb.htm

As for filament string continuity, I wouldn't be all that concerned. Probably the nigh mutual problem is a bad solder. This happens because you've got a double wire in the pin and lack of experience with it sometimes leaves it with a cold solder. This is easily fixed. When you plug in your tubes, if you have one that doesn't calorie-free upwards, you'll know information technology.

The other fashion to bank check information technology is to power upwardly the amp with no tubes in information technology. Put your meter on ACV and from the superlative side of the tube socket (where the tube goes, not the pins where you solder) and probe the 12AX7 socket at the terminate of the concatenation, one probe to pivot 9 and the other on pin 4, and so pin ix to pin 5. Yous should get the same event, about half-dozen.3vac. Piece of work back towards the first socket in the concatenation. Recall the ability tubes if EL34/6V6'6L6 have filament connections on pins 2 and vii. Don't jam your probes into the sockets. You lot don't desire to open them up so they won't concord the tube pins.

Postal service by **Structo** » Tue Jun 09, 2009 3:15 pm

Hither's how I made mine.

[IMG:800:618]http://i23.photobucket.com/albums/b392/ ... iter-1.jpg[/img]

When you first burn upwards the amp without tubes use a 25 watt bulb.
This limits the current to the amp quite a scrap and helps class the filter caps improve.

Then put a 40 watt, 60 watt and 75 watt.

This gradually builds upwardly the voltage too.

The bulb will flash when you commencement power upward, that'south only the caps charging.
The bulb should go down to a depression glow.
If it stays brightly lit, then yous have a short somewhere and you should ability downwards immediately.

Post by **Structo** » Wed Jun x, 2009 half dozen:03 pm

It really is a nifty and uncomplicated device.
When you start ability upward with a 25 watt bulb you are limiting the current to the amp to around i/4 amp.

Then not only will this warning you to any defective wiring in the ability supply but volition also be a soft power up that will be easy on the filter caps.

Even if it is an old amp that hasn't been turned on in a long time it can help reform the filter caps and help to course new filter caps if you lot gradually increase the wattage of the low-cal bulbs up through the bachelor wattage bulbs.

So I use a 25, 40, 60, and finally a 75 watt seedling.

Midweek Jun x, 2009 9:36 pm

Hijack...
I always employ a Variac which is plugged into an Isobar that has a 15A breaker on it.

But it does non indicate if there is a short.

Beginning power upwards, or very old questionable amp-I pull the tubes and clip two meters on, one to B+, another to the filament leads.

If I don't see 25% voltage on the meters at 30-40VAC
on the Variac, then I don't push it any further and check to see what'due south going on.

I guess if there is a dead short then information technology would pop the fuse on the Variac.

Should I build the light bulb limiter and not utilize the Variac to practice this?
Or is the Variac method good enough?

Post by **Structo** » Thu Jun 11, 2009 ane:09 am

Well I don't own a variac then I use this poor mans device.
Although some day I'll get one.
I had a friends amp that he had congenital on my bench one mean solar day.
He wasn't very knowledgeable and this was his kickoff build.
I had already stock-still a couple wiring mistakes but was a little leery of only powering information technology up without protection.

Certain plenty, when I turned it on the bulb stayed real bright and so I immediately powered down.

There was an under board wire on the power supply that wasn't right.

Once I corrected that fault I was able to power it upward and accept some voltage readings.
Only so did I install the tubes.

And so it earned it's place on my meager bench.
And the ability to limit the current to the amp is a big plus.

Post by **ChrisM** » Sun Aug xxx, 2009 five:47 pm

Deplorable to bump this...

I have fabricated a limiter (finally after building five amps lol). At present I put in a 60W lightbulb.

I plow on the main'south switch and the bulb grows bright. Information technology stays like this. I recollect this is ok as there are no tubes in and all that is in the circuit is the beginning filter cap. Should I flip on the standby switch and see what happens?

ChrisM wrote:Sad to bump this...

I have made a limiter (finally after building v amps lol). At present I put in a 60W lightbulb.

I turn on the principal's switch and the bulb grows bright. It stays like this. I think this is ok as there are no tubes in and all that is in the circuit is the starting time filter cap. Should I flip on the standby switch and see what happens?

Seems like there is something wrong. The bulb should glow briefly, then in one case the first filter is charged it should dim. Something is continuing to draw significant current, then I'd check everything on the PT side of the standby. What voltages do you have for B+, Bias, heater, and relay supply?

MPM

Post by **Phil_S** » Monday Aug 31, 2009 2:45 am

Yes, if the standby breaks the connexion to all filter caps, I guess that bulb is going to glow similar it's in a regluar light seedling circuit. When you close the standby and allow the filter caps to charge, information technology should glow very brightly for a very, very brief moment, and then go dim. The get-go time y'all accuse caps, information technology may take a few extra moments.

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