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GB for DC coupled B1 buffer with shunt PSUs

AlanElsdon said:
Same here on my Hypnotize - no heat problems using small heatsinks on all devices.

Alan
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Ack, no problems with 2 x 15, and heat on those fets. I would suspect lowering the first resistors 2 x 68 down would have more impact. I just dont think there is enough juice in this design to usually be a problem, but that's a laymans answer.😛
 
I think we need to learn that over time. Uriah blew one < .5amp but .5 amp okay, I think slight alterations in current and tranny on this design might present a different load. I would feel comfortable with 1A, but will ask Salas if he has any thoughts on that.
 
Tea-Bag said:
I think we need to learn that over time. Uriah blew one < .5amp but .5 amp okay, I think slight alterations in current and tranny on this design might present a different load. I would feel comfortable with 1A, but will ask Salas if he has any thoughts on that.
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OK I'll wait.
Is it a Slow Blow fuse or not ?
 
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 ?
 
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.
 
korben69 said:
Here's the Final BOM v4.2.
Thanks to all Salas and the Beta Tester's Team 😉
Enjoy 😎

PS : As usual report for mistakes...
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Thanks korben69,
Resistor 470R Farnell order code - 1357858 is metal oxide film resistor. Carbon type resistor order code is - 1265115.
 
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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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.
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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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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.
 
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?
 
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 ?
 
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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