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TWANG

By TWANG
in Epiphone Amps & Accessories

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TWANG

TWANG

Posted
Posted

so.. I checked again. just because it was ok last check. doesn't mean it was still ok.

 

the wire from Cwhatsit to C5.. little short hop underneath. one loose end.

 

test results are:

with tubes in and bulb limiter connected:

 

R10 259/247

R12 240

R12 225

 

forgot to check R3 in all the excitement, sorry.

 

ax 1.... 157

3... .995

6... 149

8... 1.0

 

6V6

3 ... 235

5.. this buzzes when the probe hits.. 4.8mV..

7.. 3mV .. on the el84 that's up around 300. what gives? bad tube?

8... 13.38.. and again. that seems low..

 

forgot to check the dang heaters.. was too thrilled at finding a loose wire.

 

now what?

switch to other tube and retest?

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TWANG

TWANG

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second test.. other old 6V6 tube..

took about four minutes.. let it warm only seconds.. bulb went dim right away.. but I noticed it was glowing slightly at the end of the test.

pt and ot were relatively cool.. not as cool as not running, but not warm by any stretch.

R10 .....279/270

R12 ........263

R13............245

R3...............168

 

ax

1..........167

3..............1.0

orange to orange 5.5

6.........155.8........no pop when probed

8...........1.1

 

6V6

3......249

4.....251

5..........5.1mV buzzes as probed

7.......5mV

8...........12.18

 

 

gonna go do some reading.

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TWANG

TWANG

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I'm on the wrong pc..no pdf files.. have to switch.

 

took another look..

did a ground continuity check first.. and looked for any tiny wires or other such.

 

grn to 6v6 in 8 gives a squeak.. but not continuous. will do it every time. beep!

 

full signal from ground to pins 1 6 7

 

on the ax full to 4 5 7 and nfb tap

 

all resistor values I could check were on the money.

 

so.. I don't know but it seems to me that I ought to get a pop off pin 6.. but I don't.

glad to know that buzz was normal.

 

I checked all the grounds.. pot input both star.. ground paths are all correct as far I can tell.

had the diagram right there and everything made sense except the squeak on pin8 of the 6v6

what 'hot' pathways I could test also seemed normal.

 

I know there's a ferret, but it must be Lemi Winks.. *south park fans will know... sort of a richard gere joke*

'cause he's sure not in front of me.

 

I'll go downstairs and read that pdf.

right now. I'm still stumped though.

my heaters should be around 7?

and I'm not sure what's happening at pin8. or why.

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cGil

cGil

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Okay, translations... ummm Look at the lower section of this page for the I/O chart.

 

http://www.r-type.org/exhib/aaa0027.htm

 

That I/O chart lists the pins of the 6V6 tube and an abbreviation letter for what they do. The little book icon on the chart will take you to the key to abbreviations. Take note of what the graphic symbols inside the tube look like for the corresponding part in the I/O chart. Then you'll be able to recognize the plates, grids, cathodes and filaments, right away whenever you look at tube data pages like these.

 

http://tdsl.duncanamps.com/show.php?des=6V6GT

http://www.nj7p.org/Tube4.php?tube=6V6GT

 

Yeah, I know, there's gotta be an easier way. I just can't remember where the link was. Arrrgh! [-(

 

Now I remember where the links were... SEwatt! If it ever comes back online, I should probably take time to copy all the FAQ links. Ya think? #-o

 

Gil...

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TWANG

TWANG

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I'm kinda getting it.. I can tell whether or not the test is showing the 6V6 in operating range..

the pins correspond to the symbols and the voltages are listed on that other page for a 6V6..

I see different listings for Class A use, so I assume that's the operating range.

It seems to me, we're going for the third one.. @315V plate.

 

so let's see.

pin 3 is anode.. I'm reading 249

I just don't see anything to inform me of anymore there..

 

pin 4 is screen grid.. range of 180 to 225, I've got 251.. so that's high..

I'll have to look at it a bit and see if I tell how to lower that, I guess.

I do see one of the Class A tables reads 250 for this.. but it's with a 250V at the plate..

 

pin 5 is problematical also.. range of -8.5 to -13 for this control grid.. whatever control grid means..and I've got 12

I don't remember seeing a -, but I'll test again and also see if I can figure out what makes that tick.

 

pin 7 being a heater as is pin 2.. I get .5mV I think that was supposed to be 7.5max?

so I'm not getting much to the heaters. ruh roh.

 

pin 8 is cathode..I've got 12... I don't find anything on this for a range..

 

so I've got something to go on.. better and some cool charts printed out..

and I'll reread some stuff I have which gives different reasons/explanation for voltages. and probably find some values there as

well as be able to trace pathways and decide what to swap.

 

the heater thing bugs me the most right now.

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TWANG

TWANG

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I'm still having some problems figuring out what's what..

I found

http://www.electronicrepairguide.com/testing-transformer.html?gclid=CO3CucHOrpUCFQEuxwodZlsaag

and

http://acapella.harmony-central.com/archive/index.php/t-1042093.html

but the first seems over my head and I don't know where to get a small 6.3 V filament transformer.

rat shack?

 

 

I'll go over the solder joints.. but I'm leaning also toward an ot problem.

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TWANG

TWANG

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we don't get many hurricanes up here... but now and the corn blows over pretty good.

got a way to test the ot's now.. so that will be handy..

I never was positive I fried any.. but I had some resistors fry so.. it'll be nice to check them all and know what I've got

as well as what I've got in this.

 

amps on the side until I get my tester made.. guitars getting done pretty fast.

 

TWANG

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cGil

cGil

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Never give up' date=' never surrender...!!! [/quote']

 

I have that movie! :)

 

Ahh, don't worry. At the moment, these guys http://www.nhc.noaa.gov/ say all the models are in agreement that Gustave is only pointed a bullseye in your general direction!!! Plus or minus 300 miles, of course. 8-[ And at the moment they all agree it'll still probably go west of the projected target? According to the models? What the hell are they doing? Did somebody pull NOLA out of a hat and say dat's it? :^o

 

Gil...

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TWANG

TWANG

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I just wanted to add the if you have the current limiting light bulb in while testing voltages your voltages may appear low.

It's only used to make sure you're not going to fry anything' date=' then once you've got that, don't use it anymore.[/quote']

 

I guess it's not really going to protect the ot.. if that's part of the problem.. anymore than it has.

So yeah I think I will.. but then. I'm going to set up the ot test stuff after I go to radio shack tomorrow, so I may as well wait and test the ot first.

 

Got four guitars done. 'cept one needs a bit more fret polishing.

two to go, two were done already. soon, I'll be going broke on ebay!

or.. making enough to build another amp.

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TWANG

TWANG

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Sorry man. Had to do the shopping thing... went with my son and caught Hamlet2..

I laughed so hard, my nose started running and spent the last 20 min of the movie trying not to snot on people..

 

that url said a neon bulb.. rat shack said.. they must be nuts, that would be expensive.. which I thought, too. so I just got a lantern bulb..

will that work?

Seems to me it ought to but.. d'oh!

 

So. tomorrow for sure.. but I have to get at least one guitar finished up first.

 

But yep. test the ot's tomorrow and I'll reflow solder first, too...

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cGil

cGil

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Sorry man. Had to do the shopping thing... went with my son and caught Hamlet2..

I laughed so hard' date=' my nose started running and spent the last 20 min of the movie trying not to snot on people..

 

that url said a neon bulb.. rat shack said.. they must be nuts, that would be expensive.. which I thought, too. so I just got a lantern bulb..

will that work?

Seems to me it ought to but.. d'oh!

 

So. tomorrow for sure.. but I have to get at least one guitar finished up first.

 

But yep. test the ot's tomorrow and I'll reflow solder first, too...

 

 

[/quote']

 

Lantern bulb for a transformer test? Nope. Lantern bulbs will work on DC or AC. Sorry. It's gotta be a neon bulb. Neon bulbs only work on AC, not DC, and that's what's being taken advantage of to test the windings. When you apply the battery to the transformer, it creates a field. When you remove the battery, the field collapses. But transformers being transformers, it resists that change, IF, the windings are intact. If so, the neon bulb will light up for a split second. But, if the windings are shorted there will be no momentary 1/4 wave of "AC", and the bulb won't light up at all. It's gotta be a neon bulb to be able to determine if the OT works or not.

 

Gil...

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Eracer_Team

Eracer_Team

Posted
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remember this bulb is only a short little thing maybe 1/2~1" long, we're not talking Vegas here.

 

maybe this might work: http://www.radioshack.com/sm-120vac-neon-lamp-assembly--pi-2062374.html

 

 

R-Shack has 7 matches in thier search and all rated at 110 or 120vac.

I remember reading that "secret transformer test" article like sometime last year, can't remember what voltage they recommended.

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cGil

cGil

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Yeah, never trust a Rat Shack clerk to know anything about anything. Okay, maybe they know what batteries my cell phone needs, but that's about it.

 

Oh yeah, as to the recommended battery for a transformer test, who cares. I just use one of the 9volts I have scattered about the bench.

 

Gil...

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TWANG

TWANG

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connect a common neon lamp like the venerable NE-2 bulb

 

that's all the info they gave.. the pic looks like the ET RShack bulb..

http://www.premierguitar.com/education/images/200704_techviews_1.gif

 

I use a 6V lantern battery, but any DC supply will work as long as it will not be damaged by being connected to a low-resistance transformer winding.

 

sez he.. as if I'd know if it would be damaged.. I'll go with Gils 9V.

 

But... should I have the kid pick up that "120VAC Neon Lamp Assembly (2-Pack) "

??

 

 

link

http://www.premierguitar.com/Magazine/Issue/2007/Apr/The_Super_Secret_Transformer_Tester.aspx

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