Direct Coupled B-1 Buffer - Hypnotize troubleshooting

[Pboden]

Been away from diy audio for years and yesterday I ran through some old stuff in the attic and found an old project that never was finished - among the B1 Buffer.

I started up the B1 buffer today, but I can not get it running - that is no music.
I see that there are some leds that do not start.

Appreciate any help on troubleshooting.

 

[Rodeodave]

Looks like the V+ side of the regulator doesn't turn on. I'm saying that because the 5 LEDs stay dark. Check part orientation and solder joints.

 

[AndrewT]

if you are really careful you can measure the voltage across each LED.
You may find that one has a very high voltage indicating it has been inserted in reverse.
Can you see the flat edge indicating the -VE side of the pair of lead outs?
All the good ones should have around 1.7Vdc to 1.8Vdc across them. That is the Vf when current is passing.

 

[Pboden]

Well I just removed the leds on the "faulty" side and there are no voltage on the pcb.
Where/what is the source for those five leds ?

Thanks

 

[AndrewT]

do you still have the schematic?

 

[Pboden]

Yes, found it - Mezmerize B1 Buffer – diyAudio Store

Trying to locate the possible culprit so I believe I have to start messure somewhere, so any tips would be appreciated.

 

[AndrewT]

start at the AC input.
Then move to the rectifier in and out.

 

[Pboden]

I get no voltage on one of the irf9240. Around 6Vdc on the other.
Just made a order for new ones.

 

[Pboden]

What is actually accepted AC input (range) on the board ? My previous problem may be due to a faulty transformer.

Thanks

 

[AndrewT]

The DCB1 needs at least 5V and preferably 7V across the CCS part of the regulator.
This is required when the mains voltage is at it's lowest.
You can use a dual 15Vac secondary wired as a centre tapped secondary and in normal operation you will measure 20Vdc to 22Vdc on the main smoothing capacitors.

 

[Pboden]

I solved the PSU and I finally got music coming out, but the 5 leds on one side(IRFP9240 side) do not work. There is no 1.8v on these diodes.
Can't figure it out, but as long the its works it should´t matter - right ?