replace the batteries in your dmm, some testers give hgh readings when battery is near flat or low...or else get a nother dmm and test again...
Open circuit on the other wire ends is good.
You have confirmed the two secondary windings
red/black
yellow/orange.
Now use an insulated terminal block with each wire in a separate terminal.
Power via your Mains Bulb Tester.
Power ON.
Is the Bulb on or off?
Measure the Primary voltage and the two secondary voltages.
IPower OFF.
insert a shorting link from red to yellow
Power ON
Is the bulb on or off?
Measure the THREE secondary voltages
red/black
yellow/orange
black/orange.
You have confirmed the two secondary windings
red/black
yellow/orange.
Now use an insulated terminal block with each wire in a separate terminal.
Power via your Mains Bulb Tester.
Power ON.
Is the Bulb on or off?
Measure the Primary voltage and the two secondary voltages.
IPower OFF.
insert a shorting link from red to yellow
Power ON
Is the bulb on or off?
Measure the THREE secondary voltages
red/black
yellow/orange
black/orange.
lunchtime update
Have replaced battery @ 7.5 v when removed with a 9.0 volt (measured)
Instructions on checking voltages with bulb tester in situ.
The results I have posted are those done that way.
At no time has the bulb lit up (already posted that info?)
I will recheck the voltages this pm with new battery in DMM.
Then I will move on to the check with shorting wire red to yellow.
(Parallel ac in phase)
That is how I originally wired it as per Manufacturers instructions.?
Report back in a few hours as Im moving all the equipment/test gear.
thanks
Have replaced battery @ 7.5 v when removed with a 9.0 volt (measured)
Instructions on checking voltages with bulb tester in situ.
The results I have posted are those done that way.
At no time has the bulb lit up (already posted that info?)
I will recheck the voltages this pm with new battery in DMM.
Then I will move on to the check with shorting wire red to yellow.
(Parallel ac in phase)
That is how I originally wired it as per Manufacturers instructions.?
Report back in a few hours as Im moving all the equipment/test gear.
thanks
Now use an insulated terminal block with each wire in a separate terminal.
Power via your Mains Bulb Tester.
Power ON.
Is the Bulb on or off?
Measure the Primary voltage and the two secondary voltages.
IPower OFF.
insert a shorting link from red to yellow
Power ON
Is the bulb on or off?
Measure the THREE secondary voltages
New battery confirms same readings at 239VAc 38.9v accross as before,
Results
red/black same 38.9 Vac
yellow/orange 38.9
black/orange 0 V
I had lowered the bulb to a 5 watt and it fails to light up under no load.
Power via your Mains Bulb Tester.
Power ON.
Is the Bulb on or off?
Measure the Primary voltage and the two secondary voltages.
IPower OFF.
insert a shorting link from red to yellow
Power ON
Is the bulb on or off?
Measure the THREE secondary voltages
New battery confirms same readings at 239VAc 38.9v accross as before,
Results
red/black same 38.9 Vac
yellow/orange 38.9
black/orange 0 V
I had lowered the bulb to a 5 watt and it fails to light up under no load.
the results confirm that the secondaries are connected out of phase.
Disconnect red from yellow and instead connect red to orange.
Power ON and remeasure the three secondary voltages. r/b, y/o, b/y
Disconnect red from yellow and instead connect red to orange.
Power ON and remeasure the three secondary voltages. r/b, y/o, b/y
Secondaries are now in phase.
Mark the two joined wires as CENTRE TAPs.
This methodology is foolproof.
Does not blow fuses, does not risk damaging the transformer, does not depend on the manufacturer getting the labeling right.
REMEMBER
each time you make any change, you must power ON via the Bulb Tester.
This is what saves your project from destruction when you get tired or distracted and wire something incorrectly.
Mains and PSU error often result in instantaneous destruction. I have done it twice to already working projects.
Mark the two joined wires as CENTRE TAPs.
This methodology is foolproof.
Does not blow fuses, does not risk damaging the transformer, does not depend on the manufacturer getting the labeling right.
REMEMBER
each time you make any change, you must power ON via the Bulb Tester.
This is what saves your project from destruction when you get tired or distracted and wire something incorrectly.
Mains and PSU error often result in instantaneous destruction. I have done it twice to already working projects.
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Thanks for progress so far.....Well its been quite a journey.
BUT
Im now assuming that I must use a single bridge based on previous comment ?.
This means centre tap to star earth.
Black to ac top and yellow to ac bottom.
YES? But I think I have gone full circle...
This just gives me the plus and minus 35.4 V DC when I am expecting and require plus and minus 50 ish V DC. Caps not yet wired in
I have now reverted to looking at other sites and I found this..
http://www.hammondmfg.com/pdf/5c007.pdf
This is the only site that clearly indicates I can get V x 1.41 from bridge and would mean using two seperate bridge.
To do this I would have do as shown in diagram under full wave capacitor load
for the possitive.
I pressume I would have to reverse this for the negative production of 50V dc ???
ie take + from bridge to star earth
and capacitor inverted..using the second of the secondaries
BUT
Im now assuming that I must use a single bridge based on previous comment ?.
This means centre tap to star earth.
Black to ac top and yellow to ac bottom.
YES? But I think I have gone full circle...
This just gives me the plus and minus 35.4 V DC when I am expecting and require plus and minus 50 ish V DC. Caps not yet wired in
I have now reverted to looking at other sites and I found this..
http://www.hammondmfg.com/pdf/5c007.pdf
This is the only site that clearly indicates I can get V x 1.41 from bridge and would mean using two seperate bridge.
To do this I would have do as shown in diagram under full wave capacitor load
for the possitive.
I pressume I would have to reverse this for the negative production of 50V dc ???
ie take + from bridge to star earth
and capacitor inverted..using the second of the secondaries
Last edited:
NO ! Centre tap goes to the smoothing capacitor junction point.
This assertion is a complete fabrication. Everyone with any knowledge knows that sqrt(2) is the peak voltage of a sinewve and that tells you the smoothed voltage stored on the capacitors when there is no load. Expect considerably more than +-50Vdc, your unloaded voltage has been around 38.5Vac and that should give around +-54Vdc
No ! two bridges are used when a dual secondary feeds the bridges separately. Once the dual is converted to centre tapped one MUST use a single bridge rectifier.
This last para is all mixed up. Forget all that and just wire up a centre tap to a single bridge rectifier.
Add the smoothing caps to the rectifier bridge, still with no load.
The bulb should flash briefly at start up and then remain unlit as the caps charge up.
recheck AC and DC voltages.
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HALLEYLOOYA
At last,many many thanks, I now have the plus and minus DC of 54.2V.
The right way around.A very quick less than a second lighting up.
Wow I never would have believe that this was the way to wire this up and I am sure not alone.
I will now rewire the original 4 caps for 20k per rail and re install the 2 x 100 Nf accross the 39v ac leads.
I note in the TNT article it also shows a third 100nf .How important is that?.
Each of the 10k BHC is also already bypassed with 1 100nf.
Finally (I hope) I think I have seen enough advice stating the is should really operate with a soft start circuit.
.Anyone disagree.
This I will order asap.
One again many thannks
At last,many many thanks, I now have the plus and minus DC of 54.2V.
The right way around.A very quick less than a second lighting up.
Wow I never would have believe that this was the way to wire this up and I am sure not alone.
I will now rewire the original 4 caps for 20k per rail and re install the 2 x 100 Nf accross the 39v ac leads.
I note in the TNT article it also shows a third 100nf .How important is that?.
Each of the 10k BHC is also already bypassed with 1 100nf.
Finally (I hope) I think I have seen enough advice stating the is should really operate with a soft start circuit.
.Anyone disagree.
This I will order asap.
One again many thannks
Don't add any small caps across the secondary windings. The ~~ are also the secondary windings.
Sometimes these extra capacitors can cause some ringing of the supply if there is a step change in current demand.
You can test for this with a scope on the main smoothing.
If you have ringing, then you need a snubber.
A snubber is a resistor to damp the ringing. But a resistor alone will overheat due to the DC, so you need a series capacitor to protect the resistor from overheating.
The result is that we see an R+C across the secondary, IF YOUR PSU NEEDS such a device.
Sometimes these extra capacitors can cause some ringing of the supply if there is a step change in current demand.
You can test for this with a scope on the main smoothing.
If you have ringing, then you need a snubber.
A snubber is a resistor to damp the ringing. But a resistor alone will overheat due to the DC, so you need a series capacitor to protect the resistor from overheating.
The result is that we see an R+C across the secondary, IF YOUR PSU NEEDS such a device.
A soft start depends on your views of what fuses you need to stop your home burning down.
If you want a close rated fuse then you need a soft start.
If you fit a fuse that is 3times the size that your transformer needs to run at full power, then you can manage without a soft start.
Close rated Fuse = VA/Vac
Use a T rated fuse for transformers and motors.
If you want a close rated fuse then you need a soft start.
If you fit a fuse that is 3times the size that your transformer needs to run at full power, then you can manage without a soft start.
Close rated Fuse = VA/Vac
Use a T rated fuse for transformers and motors.
Nearly there.
If you want a close rated fuse then you need a soft start.
If you fit a fuse that is 3 times the size that your transformer needs to run at full power, then you can manage without a soft start.
Close rated Fuse = VA/Vac
Yep I think thats clear enuff....Its on order and I consider in hindsight I am rather fortunate that I only ordered a 35V traffo to replace the 38V one which gave up the ghost.
The 54v is sailing close to the wind.(Im Using 63V Caps)
Wiring up the rest tomorrow and will go for the 3.15 rated fast blows.
I think anyone reading this thread might be a little concerned about some of the rather misleading postings of information around the web including some posted here.The TNT article I considered almost a bible.
Havent had a scope for nigh on 20 years since retiring and had access to one locally before I moved house recently.
Will have a listen after the whole kit has run in for a few weeks.
Once again many thanks and I hope others may find the thread usefull.
If you want a close rated fuse then you need a soft start.
If you fit a fuse that is 3 times the size that your transformer needs to run at full power, then you can manage without a soft start.
Close rated Fuse = VA/Vac
Yep I think thats clear enuff....Its on order and I consider in hindsight I am rather fortunate that I only ordered a 35V traffo to replace the 38V one which gave up the ghost.
The 54v is sailing close to the wind.(Im Using 63V Caps)
Wiring up the rest tomorrow and will go for the 3.15 rated fast blows.
I think anyone reading this thread might be a little concerned about some of the rather misleading postings of information around the web including some posted here.The TNT article I considered almost a bible.
Havent had a scope for nigh on 20 years since retiring and had access to one locally before I moved house recently.
Will have a listen after the whole kit has run in for a few weeks.
Once again many thanks and I hope others may find the thread usefull.
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