Help with power transformer identification

[tubehead99]

Hello all on this great forum,

...after having typed miles of words and having lost them in the form of the forum asking for loggin when i was sure i was logged in i will go now for the short version :)

I am tring to fix after along time on the shelf my Guyatone GA 1000 head i remember that some smoke came out of th PT.

I have some spare PT all unknown and without identificaition but i remember this one coming from a guitar amp of same rating(100W) and tubes (4 6l6)

Leads coming from one sidea are soldi colors:

Blue
blue
yellow
yellow
black

form the other hole come out solid:

red
red
brown
brown
purple
black


Can some one help identify the wirings for this unkown POWER tranny? or at least some one can link me to a step by step or well explained tutorial for identifing the leads with a multimeter and or variac?

searched long time in the years info over the internet for the guyatone GA - 1000 head but cant find also any schematic on the web some one has a link or something?

will 3  47Mfd caps tied togheter on the negative pole work as replacement of the original 50+50+50 MFd ?

Thanks for reading and Cheers.

(the first 4 pics are of the replacement "unknown" transformer.. the latter one is of the old original PT of the head just for documentation :))


http://i716.photobucket.com/albums/ww170/psychedelicwarlord/PICT0813.jpg

http://i716.photobucket.com/albums/ww170/psychedelicwarlord/PICT0812.jpg

http://i716.photobucket.com/albums/ww170/psychedelicwarlord/PICT0811.jpg

http://i716.photobucket.com/albums/ww170/psychedelicwarlord/PICT0814.jpg

http://i716.photobucket.com/albums/ww170/psychedelicwarlord/PICT0815.jpg

[stratele52]

Blue
blue
yellow
yellow
black


I'm sure those are primary wire . With ohmeter test lead on the black wire , IMO the black is the common.

1- Take mesurement from the one blue ; ........ohms
2-                                       other      ; .........ohms
3-                                        one yellow;..........ohms
4                                        other yellow; .......ohms


Tell us the result .
__________________________________________________
What I think ;

The more ohms between the black and the other wire mean this for a 240 volts.

Little less ohms ; 220 volts

Less ohms 120 volts

and less is for 110 volts
_________________________________________________

After that , you can put few AC volts ( 10 to 24 ) between the black and the other wire you need maybe a 220 if you are european ?

With this small AC volt , you can take some AC mesurement on secondary side to find wich wires are B+, Heater  ......

Good luck

[tubehead99]

:)
Black > any yellow =0,3
Black > any blue = interrupted
yellow > yellow =0,3
blue > blue = 0,2
Any blue > any yellow = interrupted

sure the PT is coming from some unfixable EU wreck.

so as you say i have to figure that black and one of the two yellow are the  two mains 240 or 220  right? and what i have to do with the other yelllow? :)

but i argue that readings of 0,2 - 0,3 ohms seem to me very low and also is strange that blue between them show continuity and between black not..

sure i will put some 12 ac on the primary once identified and take readings so in proportion of the voltage applied i can figure the other outputs am i right?

but just let me ask two things: if you can check the pics you cans ee the original PT has also a 60v out will i be able to get it if not from the socondary outs from one or half of the unused primary?

and about the caps dp you think coupling 3 47 mfd by the grounds in substitution af the  50+50+50 originals?

i know the ripple thing but just for firing it up and seeing it working after that i can order some better caps.. i also have some other trannies that i ll do better use in some kit thantaking dust on the shelf. :)

i really thank you for the help.

[stratele52]

Your mesurments are very low , too low IMO.

Black and any yellow 0,3
0,3 is ohm or kilohms ?  What is your meter ?

I have a power transformer here in Canada and for AC wall input , I have two black wire . Between them I mesure 4,7 ohms with fluke voltmeter . These are for 120 volts AC , your PT should mesure more if for 240 AC ; 8 ohms between your black and another wire.

I can't go farther without more information or test.
_____________________________
About your filter caps 47 or 50 mfd is the same

[tubehead99]

Yeah i tought so also..
0.3 ohms not kilo..
 i ve taken the reading in the scale of 200 ohms with my digital multimeter.. (not a fluke but seem to always  work )

Strat i am thinking that's not the side of the primary maybe is the other side..

ill take some readings on the other side before i put some current in the two yellows (so the higher resistance corresponds to the higer voltage handling of the winding ..so 220).

could it be that the other side with more wires color include the primary?

thanks for the caps hint.

[stratele52]

Yes take some measurement on the other side. But normally ,red wires are for B+ , on secondary , but we never know....

[tubehead99]

ok i've taken the remaining readings:

red > red 85,6
brown > brown 6,7
purple > one red 49,7
purple > other red 26,2
black > purple 6,3
black > any brown interrupted
black > one red 44
black >other red 42

i also checked all the wires from the other side to this side and all are interrupted continuity (this is good sign :) ?)

i paste the previous readings of the previous tested side:

Black > any yellow =0,3
Black > any blue = interrupted
yellow > yellow =0,3
blue > blue = 0,2
Any blue > any yellow = interrupted

What you think Strat ?

[tubehead99]

Yes take some measurement on the other side. But normally ,red wires are for B+ , on secondary , but we never know....

Strat can you tell me why and if the 0 common on the output must be tied with the 0 at the input of the original transformer?

sorry for the many questions ...but i have checked it and seem to work ( at least disconnected)

anyway i ll shut up after this :D

original PT:
http://i716.photobucket.com/albums/ww170/psychedelicwarlord/PICT0815.jpg

[stratele52]

Sorry tubehead99 , I'm too busy to study your mesurements and give answer. Did you write how many volts you put on transformer ?

I'll come back later

[drgonzonm]

I did an internet search on 'guitar power transformer standard wire colors' and found radioremembered.org.  This explained some of the color coding.  (Please note not all transformer manufacturers followed standard wiring practices.)  Please also note that standard wire colors changed over the years.   

[Shrapnel]

I PM'd you an email address... I think this guy here may be of some service to your problems. Graydon over at http://gdsamps.com/ since I think he's responsible for that amp in the first place (or inherited it by purchase, Can't quite remember.)

[stratele52]

Hi tubehead99,

With your mesurements i can say that your transformer primary is the black with one yellow probably for your eropean wall outlet voltage.
The two blue are for Noth America voltage ?

In both case you have to put some low voltage ( ta save your transformer in case of wrong winring ) to do some voltage test.
Applied ,lets say 12 AC volts , at the black an one yellow and mesure what you have on the other side of transformer ; the secondary.
Do these test   with each primary wire.
1- Black and one yellow
2- Black with other yellow
3- Blue and blue

Each time you have to take some mesurment at the secondary, you have to do 3 test, like I write before.
_____________

The secondary of your transformer with your mesurements is ;

1-Two  red  wire is for B+ , to solid state rectifier
2- Black wire is B + center tap
3- Purple is bias voltage
4- Two brown wires are for tubes heater

DON'T FORGET like I write , a low voltage test must be done to be sure. Those test are very easy to do but not esy to explain by e-mail. Be sure you  know what you do to not burn your Power transformer.
_________________________________________________________________________________

i also checked all the wires from the other side to this side and all are interrupted continuity (this is good sign :) ?)   
----tubehead99
Answer;
Yes this is normal , secondary and primary are electricaly separate, interrupted

[tubehead99]

stratele52 thank you very much i am doing the low voltage test his evening so i can make use of the transformer .. you know is not a junk item is a fine big transformer well worth the hassle ( i know MY hassle and not yours ;))
So thank you for taking the time to address me in a more certain way :)

in the meanwhile i did try the amp again with the old original power trans. seem not to be in great shape the trans or the amp i will probably try to make it sound putting some good signal right at the in of the power stage so i can guess if is the pre or post stage that sound bad .. and if is the power stag ei will try the new trans (that you helped find out) in after that. if it will work at least the power stage in worst case i will keep it as power amp. in the worstest case i am left with at least a good PT to make some other easy project.
I really thank you for the infos :)

Sharpnel: thank you got the email but dont really think the amp is worth some professional repair work. even if i have to say is very well built with great caps. thanks. :)

Drgon: i've checked somewhere over ..and also that website but seem to be some strange make transformer. thank you too. anyway.

Cheers all.