Rewinding will mean freight, and cost too much, as at least one coil will be scrapped.
Expensive.
Better to try this one on load, truck head lamp 100W 24V is enough, and cheap, and if not suitable, get another new transformer.
Expensive.
Better to try this one on load, truck head lamp 100W 24V is enough, and cheap, and if not suitable, get another new transformer.
So I need to build the power supply board. Question is which one LOL.
Only thing Im building is the power supply.
I have to pick between these.
1. https://www.ti.com/lit/an/snaa057c/snaa057c.pdf
Or
2. http://diyaudioprojects.com/Chip/LM3886_CA/lm3886-manual.pdf
Figure 1.3
or
3. https://vaspelectronics.com/35a-power-supply-board
(No stock).
Im confused which one to pick.
Only thing Im building is the power supply.
I have to pick between these.
1. https://www.ti.com/lit/an/snaa057c/snaa057c.pdf
Or
2. http://diyaudioprojects.com/Chip/LM3886_CA/lm3886-manual.pdf
Figure 1.3
or
3. https://vaspelectronics.com/35a-power-supply-board
(No stock).
Im confused which one to pick.
Easy. 2. is a proven design, has a PCB, and many here have build it so can assist if there's an issue (which there will be).
Jan
Jan
Chinoy, Nareshbrd,
got that. It is understandable. I thought the transformer maker was near him.
I was wondering with big transformer and probably large filter cap a soft start is a must or not ?
got that. It is understandable. I thought the transformer maker was near him.
I was wondering with big transformer and probably large filter cap a soft start is a must or not ?
Even if the transformer maker is close, one coil at least would need to be replaced, and depending on how it was made, destruction is possible.
A new coil would also be costly, as at least 1.5 kilos of copper must have been used in building the unit, easily would have cost 4000, if not more of our Rupees. Repair will be less, but still expensive.
Add two trips for delivery and pick up, if local, and freight if not...
That also adds up.
Monsoon, so moisture will get in...one more thing to worry about.
Soft start, I cannot say, big caps may charge slowly or quickly, if NTC is there or not.
A new coil would also be costly, as at least 1.5 kilos of copper must have been used in building the unit, easily would have cost 4000, if not more of our Rupees. Repair will be less, but still expensive.
Add two trips for delivery and pick up, if local, and freight if not...
That also adds up.
Monsoon, so moisture will get in...one more thing to worry about.
Soft start, I cannot say, big caps may charge slowly or quickly, if NTC is there or not.
https://www.salconelectronics.com/p...0-2412-v-ac-current-6a-step-down-transformer/
699.00 INR
24-0-24 + 0-12, 6A...reasonable.
699.00 INR
24-0-24 + 0-12, 6A...reasonable.
There is always an offload voltage that is higher than spec'ed full load voltage.
Its usually just low percentage figure though.
10-15 volts is a lot.
I would be inclined to add a bridge rectifier to the circuit and smoothing caps and measure again.
Maybe even load it with the amp you want to use.
You will lose 2 to 3 volts across the bridge rectifier.
Its usually just low percentage figure though.
10-15 volts is a lot.
I would be inclined to add a bridge rectifier to the circuit and smoothing caps and measure again.
Maybe even load it with the amp you want to use.
You will lose 2 to 3 volts across the bridge rectifier.
Use a headlight bulb, truck electricians would have many with one of the two filaments blown, free supply.
Use that as load, get a few extra if it does blow.
Or use an ordinary filament light bulb, for a few seconds no problem.
For load on DC side.
Will give idea of on load volts.
Though at light loads, which is something I do not think you will use, might be a problem.
But you did say 4 chip amps, so big area to cover, means big load.
You can try, if you feel like.
Use that as load, get a few extra if it does blow.
Or use an ordinary filament light bulb, for a few seconds no problem.
For load on DC side.
Will give idea of on load volts.
Though at light loads, which is something I do not think you will use, might be a problem.
But you did say 4 chip amps, so big area to cover, means big load.
You can try, if you feel like.
Either use a buck transformer or
Fix a +/- 35 volts DC voltage regulator after the main DC supply or
Change the transformer or
Remove the secondary turns from the transformer, if you know how to do it.
There are no other options.
Otherwise this whole topic is going messy.
Regards.
Fix a +/- 35 volts DC voltage regulator after the main DC supply or
Change the transformer or
Remove the secondary turns from the transformer, if you know how to do it.
There are no other options.
Otherwise this whole topic is going messy.
Regards.
In practice it´s higher than "a couple percent".
An "unwritten rule" but which appears in transformer winding manuals , go figure, is overwinding secondaries by 5%, which I also follow myself.
Some go higher, which is show in that table, for example 1176057 , nominal 2 x 24V, specs 2x26.4V, a full 10%, go figure.
And it is a toroid, supposedly having better regulation than cheaper EI ones.
Notice it meets a strict British Standards rule:
BSI - BS EN 61558
That said, chinoy´s 38VAC instead of 26VAC difference is GROSS, 46%,WAY above any "safety extra" usually accounted for, way above mains voltage variation,etcI am certain that a wrong transformer was supplied and it must be exchanged, at factory or seller´shop by the proper one.
In fact I suggest carrying a meter with you to the shop and get a proper voltage one (which should be around 28VAC per secondary, absolute maximum 30VAC).
Not kidding.
Yours is not a "Math" or "capacitors" or "regulators" problem, it´s simply the wrong part, period.
Do not search for kludges or bandaid, go to the core of the problem and replace it.
It is not YOUR job to use bucking transformer or Variacs or anything on a new fully paid for product, bought at a "reputable" shop.
If you put a larger inductor in your PS you can lose a couple volts, as in making a CLC, storage and smoothing of the DC.
Inductor will reduce a few volts only when loaded. At idling conditions the output will still be same as full DC voltage. Just enough to destroy anything that exceeded the rated voltage. There is no protection against overvoltage.
A custom built transformer usually cannot be returned for a user mistake. Just get get a new one so this topic can be closed 🙂 .
Regards.
For my power amp supply, 2400 VA transformer, 780,000 uf capacitance, 3 mh inductor, in CLC, the loaded and unload voltage is the same. The load at idle is 8 amps for the Bias. The inductor created a 2 vdc loss. Voltage went from 49 vac to 47 vdc after the bridge rectifier, and 45 vdc after the inductor. Sad to lose so much voltage but plenty of current. 🙂
From what I read above this was not a custom wound transformer at all but an over the counter one based on salesman recommendation.
Who obviously picked the wrong one or it was mislabeled, none of those buyer fault, they should replace it at no cost.
UNLESS buyer asked for a "38V transformer" thinking 38VDC rails and salesman obviously offered a 38VAC one.
In which case it was buyer mistake, big time.
My suspicion gets reinforced by the 1.46X voltage "error", perfectly matching 1.41X or 41% difference between peak/rectified and RMS , plus usual 5% overwinding, which by itself is not a problem.
A GROSS error which can not be solved by bucking, adding chokes, etc.
What does the sales slip say?
IF 26V, ask for replacement-refund transformer is NOT what you ordered.
If 38V, YOU asked for the wrong one, not their responsibiity.
Can you please upload a transformer picture, showing any labels on it?
Is the cardboard box labelled?
What about the sales bill?
Who obviously picked the wrong one or it was mislabeled, none of those buyer fault, they should replace it at no cost.
UNLESS buyer asked for a "38V transformer" thinking 38VDC rails and salesman obviously offered a 38VAC one.
In which case it was buyer mistake, big time.
My suspicion gets reinforced by the 1.46X voltage "error", perfectly matching 1.41X or 41% difference between peak/rectified and RMS , plus usual 5% overwinding, which by itself is not a problem.
A GROSS error which can not be solved by bucking, adding chokes, etc.
What does the sales slip say?
IF 26V, ask for replacement-refund transformer is NOT what you ordered.
If 38V, YOU asked for the wrong one, not their responsibiity.
Can you please upload a transformer picture, showing any labels on it?
Is the cardboard box labelled?
What about the sales bill?
oops, typo in my last post:
The inductor created a 2 vdc loss. Voltage went from 49 vac to 47 vdc after bridge rectifier
should be 34 vac. , at 49 vac would have given me around 69 vdc, which would have been too high for the front end. 🙁
The inductor created a 2 vdc loss. Voltage went from 49 vac to 47 vdc after bridge rectifier
should be 34 vac. , at 49 vac would have given me around 69 vdc, which would have been too high for the front end. 🙁
I checked, generic populated transistor amplifier PCB, with heat sink, for 36-0-36 V, is INR 1350 (Less than $20) here.
You can use this for your transformer.
For your antique sound, use an equaliser to remove highs and lows from digital files while playing, and find some OLD speakers made out of planks or plywood, the result will be 70s Akai amp sound.
You can use this for your transformer.
For your antique sound, use an equaliser to remove highs and lows from digital files while playing, and find some OLD speakers made out of planks or plywood, the result will be 70s Akai amp sound.