You're right of course...I get +/- 25.5V when PS is connected to the Aleph J boards. However, I'm having a problem with the PS where the positive rail drops out completely. This is odd because this same PS worked properly before while powering a different amp. I'm going to post my issue in an SLB thread and hopefully you guys can help me figure this out.
Hi,
while I am waiting for the original pcb I bought a non-original board here in Italy and after having mounted it it seems to me that the trimmer r27 on the pcb is marked opposite. This is because, after mounting it, instead of reading 68k ohms I read 32k ohms. Also I tried to adjust it and to increase the ohms I have to rotate counterclockwise. Now I would like to know if the resistive trimmer is placed in the opposite position, are there problems or does it work anyway?
while I am waiting for the original pcb I bought a non-original board here in Italy and after having mounted it it seems to me that the trimmer r27 on the pcb is marked opposite. This is because, after mounting it, instead of reading 68k ohms I read 32k ohms. Also I tried to adjust it and to increase the ohms I have to rotate counterclockwise. Now I would like to know if the resistive trimmer is placed in the opposite position, are there problems or does it work anyway?
Well I sure did not know that! I thought both were in use, they just put one on both sides. Learn something new everyday.
Russellc
I have a bit of a problem. Way before I started the project I ordered a Transformer, 400VA 18V Dual Seconndaries. Took it out today and I noticed that it only has three wires out aside from the primaries. I measured it and it is
Wires > Red Black Red
Red > Black +18V
Red > Black +18V
So it doesn't seem like it is centre tapped, but dual secondaries sharing a single -
Any ideas on how I would wire this sucker up to the bridges for the PSU.
Wires > Red Black Red
Red > Black +18V
Red > Black +18V
So it doesn't seem like it is centre tapped, but dual secondaries sharing a single -
Any ideas on how I would wire this sucker up to the bridges for the PSU.
Hi,
I'm in the process of building the power supply section for an Aleph J, using Antek Toroidal transformer 600VA with 18V secondaries (input voltage used will be 240V)
Unfortunately, many of the components listed in the BOM for filling up the universal power supply board (DIYaudio) are either out of stock or phased-out.
So far. here are some of the components that are available from Mouser:
Here are some of the components that are out of stock:
Can someone recommend me other (brand/model) substitutes, better if still in Mouser.
Thanks!
I'm in the process of building the power supply section for an Aleph J, using Antek Toroidal transformer 600VA with 18V secondaries (input voltage used will be 240V)
Unfortunately, many of the components listed in the BOM for filling up the universal power supply board (DIYaudio) are either out of stock or phased-out.
So far. here are some of the components that are available from Mouser:
- (2 PIECES) Vishay GBPC3502-E4/51 Bridge Rectifier 35 Amp 200 Volts
- (8 PIECES) Nichicon LGU1V223MELC Aluminum Electrolytic Capacitors - Snap In 35volts 22000uF 105c 35x50x10L/S
- (2 PIECES) Amphenol CL-60 Inrush Current Limiters 5A 10ohm Straight leads
Here are some of the components that are out of stock:
- (8 PIECES) Panasonic ERX-3SJR47 Metal Film Resistors - Through Hole 0.47ohm 3W 5%
- (2 PIECES) Panasonic ERG-3SJ223 Metal Oxide Resistors 22K OHM 5% 300PPM 3W
- (1 PIECE) Vishay WKP332MCPEJ0KR Safety Capacitors 3300pF 20% X1 760VAC/Y1 500VAC
- Led Resistors?
- Other needed components (If I missed some)?
Can someone recommend me other (brand/model) substitutes, better if still in Mouser.
Thanks!
The 0.47R Panasonic is still available in very limited quantity:
https://www.mouser.ca/ProductDetail/Panasonic/ERX-3SJR47A?qs=9gtMhpKs0nGq/yRIAj967g==
It's the same part used in the Aleph J itself so I recommend getting a bunch.
The 22K 3W resistors in the BOM are bleeders. I personally use a lower value and wattage rating. For concreteness, something like this will do : https://www.mouser.ca/ProductDetail/YAGEO/MFR1WSFTF52-4K7?qs=xZ/P%2Ba9zWqbU/6djJccuig==
Safety cap. This should be fine:
https://www.mouser.ca/ProductDetail/KEMET/C941U332MVVDAAWL45?qs=xIpY4gsFVQErsX59LFZqIQ==
LED resistors: Any 1/4W resistor 10K to 50K will probably be fine. The resistance value is quite arbitrary. I tend to use a higher value since I don't like the LEDs too bright.
Hope this helps.
https://www.mouser.ca/ProductDetail/Panasonic/ERX-3SJR47A?qs=9gtMhpKs0nGq/yRIAj967g==
It's the same part used in the Aleph J itself so I recommend getting a bunch.
The 22K 3W resistors in the BOM are bleeders. I personally use a lower value and wattage rating. For concreteness, something like this will do : https://www.mouser.ca/ProductDetail/YAGEO/MFR1WSFTF52-4K7?qs=xZ/P%2Ba9zWqbU/6djJccuig==
Safety cap. This should be fine:
https://www.mouser.ca/ProductDetail/KEMET/C941U332MVVDAAWL45?qs=xIpY4gsFVQErsX59LFZqIQ==
LED resistors: Any 1/4W resistor 10K to 50K will probably be fine. The resistance value is quite arbitrary. I tend to use a higher value since I don't like the LEDs too bright.
Hope this helps.
Thank you for your inputs! I will check them out.
With regards to the bleeder, what will a lower value and lower wattage have an effect on the power supply?
Oh ok. As per the link above (substitute part), the Yageo Metal Film Resistors - Through Hole (BLEEDER) has:
4.7Kohms
1W
1% tolerance
100PPM / C
Is that okay (safe) for use on the Aleph J power supply?
The bleeder puts a small load on the power supply that helps slowly drain it after the amp is powered off. This is viewed as a safety feature.
A lower resistor will drain it faster, though at 4.7K, the load is still less than 6mA ( 25V/4700R). With 22K resistor,
the load is proportionally less.
One could argue that the bleeder may not really needed. Your LED and resistor combo is also a drain on the PS, though
it might be a very light one with a large LED resistor. Note also that once the amp channels are attached, a good chunk
of energy in the power supply will be quite quickly drained by the amp boards on power down.
Since the loads from the bleeders are wasting power, you try to balance how quickly the power supply gets drain to a safe voltage level vs how much power you want the bleeders to burn during regular operation.
For an Aleph J (less than 25V rails), the dissipation of a 4.7K bleeder is ~ 25*25/4700 < 0.14W. At 22K, it's < 0.03W. So 3W is definitely not needed.
A lower resistor will drain it faster, though at 4.7K, the load is still less than 6mA ( 25V/4700R). With 22K resistor,
the load is proportionally less.
One could argue that the bleeder may not really needed. Your LED and resistor combo is also a drain on the PS, though
it might be a very light one with a large LED resistor. Note also that once the amp channels are attached, a good chunk
of energy in the power supply will be quite quickly drained by the amp boards on power down.
Since the loads from the bleeders are wasting power, you try to balance how quickly the power supply gets drain to a safe voltage level vs how much power you want the bleeders to burn during regular operation.
For an Aleph J (less than 25V rails), the dissipation of a 4.7K bleeder is ~ 25*25/4700 < 0.14W. At 22K, it's < 0.03W. So 3W is definitely not needed.