Global Specialties 1310 power supply

[bluefox616161@hotmail.com]

I have a global specialties 1310 power supply that has 3 outputs... output one is a 5v @ 1 amp output and is not adjustable it seems to work fine... output 2 and 3 are both 1.3 - 20 volt @ 1/4 amp. they have separate potentiometers   to adjust the  output .   output 2 is 1.306 v at min setting. 10.37 at half way up.....but then i only get 10.50 volts from half to full not 20v like it should be.  output 3 is the same thing.... also the built in voltage display seems to be off a tad... my snapon eedm504d shows 1.307 at min and built in screen on power supply shows 0.08  full power shows 10.48 on snapon meter and 10.1 on built in power supply screen....they have the manual for this on global specialties website
id like to use this if i can fix it

[tom66]

My guess would be the tap changer isn't working, maybe the relay supply is missing?
Tap changer will select the closest tap on the transformer to minimise power dissipated in the pass transistor.

[Andy Watson]

Is the mains voltage setting correct for your country?

[bluefox616161@hotmail.com]

yes it is a 110 input voltage. i live in the US so im good there.  it has 2 transformers inside a med size one with 6 wires coming out (in pairs of 2) and a smaller transformer with 3 wires coming out... this big one is unmarked and i get 9.69 volts ac from one set purple and brown, 9.68 volts ac from the green and blue set, and 12.03 from the black and white set... the small transformer is labeled mouser transformer
41 fg 100
pri 115 black
sec 12.6 red
c.t white
it has 3 wires coming out of it 2 red and one white i get 7.25 volt ac from either red wire to white and 14.58 from red to red.

[bluefox616161@hotmail.com]

copied from the manual

VARIABLE SUPPLIES :
Since the operation of both variable supplies is identical, the following
discussion will deal only with the B variable supply.
The transformer secondary is rectified by the full-wave bridge
comprising D13 through D16’ and is filtered by capacitors C14 and
C15’. This serves as the unregulated input to U3’ an LM317 adjustable
three-terminal regulator. The output of U3 is set by fixed resistor R16
and variable resistor R17 the B ADJUST control. Capacitors C16’ C17’
and C18 accomplish additional filtering for the output, and improve the
transient load response. Diode D19 protects the regulator from the
current flow that would occur into its adjust pin if the output becomes
shorted, and diode D20 protects the regulator from the condition of its
output being raised above its input voltage.
Resistors R9 and R10 sense current flow through the supply, creating
a voltage drop that ultimetaly is used for the current reading on the
digital display. As there is a constant current flowing in the supply
circuitry even when there is no load attached, it is necessary to subtract
this so that the display shows true load current. This is done by the
constant current sink made up of transistor Q2' resistors R13' R14' and
R15' and diodes D17 and D18' Resistors R8' R11' and R12 scale this
resulting voltage to supply a 0.1mV / mA signal to display circuitry.
Similarly, resistors R18' R19' and R20 scale the final supply output
voltage to procedure a 1mV / V signal for the display circuitry.

[Andy Watson]

There is something odd about the output of the big transformer. There should be two output pairs that supply at least 16V AC (each). Is it possible to disconnect the transformer outputs from the circuit board and measure them unloaded?

[bluefox616161@hotmail.com]

the transformor leads clip on to the main board so it was simple to unplug them and test them unloaded..... purple and brown pair is the input for output 2 on front panel of power supply.. i get 9.7 volts ac unloaded
green and blue is input for output 3 and i also get 9.7 ac volts unloaded...
white and black is the input for output 1 (its the fixed 5 volt 1 amp output) and i get about 12.2 volts ac... now they all share the same plug type so i plugged the white and black pair into the input for 2 and i get 13.5 volts dc out not just the 10.3 that i was getting... plugged the white and black pair into 3 and i get the same voltage out  13.5... (and its adjustable on both 2 and 3 from 1.3 to the 13.5 with the front dial.

seems as if my transformor is not putting out the corect input voltage to my board?
it has no markings on it other than
41-01-0095
jun 7 1995
on the top.
it has 4 mains wires  brown and yellow to the hot (black) and red and yellow to the neutral  (white)
and the 3 sets of secondary outputs

[Andy Watson]

The 12.2V is in line with what the manual claims, i.e. it is the 10V winding, which, when unloaded rises to 12.2V. Looks very much like there is a problem with the two 9.7V windings.  These should be delivering 16-17V minimum.

[bluefox616161@hotmail.com]

iv contacted global specialties to see if they will give me a part number for the transformer but if they are unwilling to send me one do you know how i might find a replacement?

[Andy Watson]

Global Specialist are still selling the 1310 - I would approach them first to see if they will sell you a spare transformer at a reasonable price.

Do you know the history of this unit? Is it possible that somebody has already attempted to repair it? I find it strange that both windings are faulty and yet apparently delivering the same output voltage. Does the transformer get hot if powered-up for a few minutes?

[bluefox616161@hotmail.com]

it came from a tattoo shop and it was used to power a tattoo machine. it is in very good condition everything looks like new inside no dust. the transformers has a slight hum but it stays cool looks nice as well... i would bet that i am the first person to open it