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GB for DC coupled B1 buffer with shunt PSUs

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cedricb

Member
Joined 2008
Salas said:
2X12VAC transformer is the recommendation for the DCB1S, it can handle 2X15VAC with some sinking for long term reliability though. 2X12VAC ends up to about +/- 16-17VDC after rectification depending on mains power potential, and I guess it can provide for both you need. The 2X15VAC was a recommendation based on some double bridge PCB plan that never saw the light of day, also some had already such transformers. 2X12VAC will be in the BOM.
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So I could use a bridge rectifier between the transformer and the voltage regulator ?
 
Salas

Salas

diyAudio Chief Moderator
Joined 2002
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cedricb said:
So I could use a bridge rectifier between the transformer and the voltage regulator ?
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The DCB1S in both guises has a 4 diode bridge and filter capacitors on board. For your other application you can build other rectifier and filter system. My recommendation is to use individual transformers for each application, with different bridge and filter caps. Its better.
 
Salas

Salas

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korben69 said:
OK I'll wait.
Is it a Slow Blow fuse or not ?
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Make it 750mA T type (slow) for 115VAC and 500mA T for 230VAC when with 50VA trafos so not to have problems with more efficient cores or bigger capacitors that some may experiment with. Anyway, if a fuse aint enough because someone wants to hear what a 500VA might do, he may exchange some till OK. This is beyond the scope of a BOM.
 
jean-paul

jean-paul

Disabled Account
Joined 2002
The LEDs are 1003207 in the BOM which happen to be red low current LEDs. The green version is 1003209. The typenumber of these is HLMP-1790.

But these are low current 3 mm LEDs with a max. If of 7 mA . Are you sure these are the right ones ??

Panasonic TS-HA are snap in caps. They won't fit on the PCB AFAIK. The PCB is layed out for standard 7,5 mm pitch caps with lead wires. In 25 V Panasonic FC 4700/25 is a good choice, in 35 V Panasonic FC 3300/35 of 3900/35 will fit. Obviously 25 V caps won't survive 2 x 15 V transformers !!!! I would advice to use 105 degrees capable low ESR caps for audiophile reasons but also for longevity.

When using 2 x 15 V transformer United Chemicon 4700/35 is a good choice. Farnell stocks these as 1692334.
 
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korben69

Member
Joined 2006
jean-paul said:
The LEDs are 1003207 in the BOM which happen to be red low current LEDs. Thegreen version is 1003209. The typenumber of these is HLMP-1790.

But these are low current 3 mm LEDs with a max. If of 7 mA . Are you sure these are the right ones ??
I haven't been reported those parts to be wrong.

Panasonic TS-HA are snap in caps. They won't fit on the PCB AFAIK.
Corrected
The PCB is layed out for standard 7,5 mm pitch caps with lead wires. In 25 V Panasonic FC 4700/25 is a good choice, in 35 V Panasonic FC 3300/35 of 3900/35 will fit. Obviously 25 V caps won't survive 2 x 15 V transformers !!!!
Transformer recommandation is 2x12v not 2x15v. BOM is based according to this value.
I would advice to use 105 degrees capable low ESR caps for audiophile reasons but also for longevity.

When using 2 x 15 V transformer United Chemicon 4700/35 is a good choice. Farnell stocks these as 1692334.
Click to expand...
 
jean-paul

jean-paul

Disabled Account
Joined 2002
Panasonic FC 3300/35 is partnumber 9692355 at Farnell. Panasonic FC 4700/25 is 9692231.

BTW the yellow LEDs have partnumber 1003208 at Farnell. They are listed with a Uf of 1.8V. Their typenumber is HLMP-1719.The red and green ones are listed with 2/2.2 V Uf which seems inappropriate for our purposes.

I have tried Kingbright green LEDs but those are all 1.99 V and they're terribly precise. In a string of 5 I had 8 mV difference when testing 24 or so LEDs. So the voltages went too high and I ordered other LEDs.
 
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K

korben69

Member
Joined 2006
jean-paul said:
BTW the yellow LEDs have partnumber 1003208 at Farnell. They are listed with a Uf of 1.8V. Their typenumber is HLMP-1719.The red and green ones are listed with 2/2.2 V Uf which seems inappropriate for our purposes.

I have tried Kingbright green LEDs but those are all 1.99 V and they're terribly precise. In a string of 5 I had 8 mV difference when testing 24 or so LEDs. So the voltages went too high and I ordered other LEDs.
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HLMP-K101 datasheet shows 1.8v typical, 2.2v Max, Red Led ,Farnell 1003205.
Same specs for HLMP-K105, Farnell 1003200.
For those who have tried, let me know the correct ref.
 
Salas

Salas

diyAudio Chief Moderator
Joined 2002
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jean-paul said:
Obviously 25 V caps won't survive 2 x 15 V transformers !!!! I would advice to use 105 degrees capable low ESR caps for audiophile reasons but also for longevity.

When using 2 x 15 V transformer United Chemicon 4700/35 is a good choice. Farnell stocks these as 1692334.
Click to expand...

15*1.41=21.15V without subtracting 2 diode Vf. 35V caps will last longer, especially if 105c with 2X15VAC. But 25V not surviving at all?
 
Salas

Salas

diyAudio Chief Moderator
Joined 2002
Paid Member
jean-paul said:
Most transformers will give higher voltages with this light load. I would not be surprised to see a 2 x 15 v transformer give 2 x 17 V with this load. So 24 v at the caps. That is not a large margin.

Salas, coul you comment on the low current LEDs ?
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Being conservative is good. Good thinking.

About leds, a 10mA idss BL will give 7mA max at that position. 7-9mA idss gave 5-6mA. 7mA leds maybe will have lowest dc impedance, but better be conservative here too and use higher. On the other hand, is it a real max, or just the nominal Vf is rated there?
 
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