BOSOZ Troubleshooting

[kennethrl]

I have just completed assembling my BOSOZ. It is based on the Colony pcb boards.

The power supply appears to be working I am getting 50volts output.

I connected the preamp to my system and not sound is coming out.

If I turn off the preamp while the CD player is still on I get a some sound bleeding through. With the preamp on no sound.

I would appreciate any advise.

[wuffwaff]

Hi,

maybe you could provide us with some voltages? Plus, minus, at the drains, at the gates, at the sources......

This would certainly help giving you some advice

William

[kennethrl]

Here are some voltages:

Power supply V+ Q101- D=60v, G= 0 S=10V
V- Q102 D=90v G= 6v, s=6v

Main Board Q1 D=0, S=5, G=3
Q2 D=0, S=5, G=5

Q1 D=5, S=5 G=0
Q2 D=5 S=5 G=0

Is it a blown MOSFET?

[moe29]

...hmmm, i can't make much sense of your measurements.

Be very careful taking these measurements! All standard
precautions should be taken.

Measure the Vgs of each FET on the main board. You do this by putting
one probe on the Gate and one on the Source pin. The pin out is
G - D - S as you look at the FET from the front. You should get a
reading like 3.8 or so.

Also, take a measurement at the Drain, like the article says.

This is real easy to do, just put the negative probe of your meter to
ground and the positive on the metal part of the case of each FET.
You should get a reading of 30 volts or so.

You should be getting a reading of 60 Volts at the + and - PSU connection
points on the main board.

All your heatsinks should be toasty warm too!

This is a starting point for toubleshooting.

Good luck, let us know.

[moe29]

...one more thing.

I think i've read that there is some kind of mistakes on the silkscreen
of the Colony boards... I can't remember which part was involved.

Check the schematic against what the parts silkscreen says on the board.

maybe someone else can remember if this is right...?

[kennethrl]

Originally posted by moe29
...hmmm, i can't make much sense of your measurements.

Be very careful taking these measurements! All standard
precautions should be taken.

Measure the Vgs of each FET on the main board. You do this by putting
one probe on the Gate and one on the Source pin. The pin out is
G - D - S as you look at the FET from the front. You should get a
reading like 3.8 or so.

Also, take a measurement at the Drain, like the article says.

This is real easy to do, just put the negative probe of your meter to
ground and the positive on the metal part of the case of each FET.
You should get a reading of 30 volts or so.

You should be getting a reading of 60 Volts at the + and - PSU connection
points on the main board.

All your heatsinks should be toasty warm too!

This is a starting point for toubleshooting.

Good luck, let us know.

I did some measurements...

Gate to Source was ~3.8

The Drain measurement is 12V

PSU is 20V

The heatsinks are not warm

I checked the PSU and not loose connections. The wiring appears correct. The main board has not loose connections...but I haven't traced out the wiring.

The only posting on the colony boards I found was a mislabeled ZEN amp board.

[moe29]

Concentrate on the PSU. You should be measuring +60, -60 volts under load.

Be sure that you've wired your transformer(s) correctly.

Take a close look at the Zeners. They seem to pop at times. Make sure
the polarity is right on all of them. If in doubt, and you have the parts,
heck replace them all.

Let us know how it goes!

[kennethrl]

Ok..... after rewiring the transformer on the 120V side I finally got 60v +/-

Still I don't have any output signal. I hooked up a CD player to the preamp and no signal. The interesting thing is if the preamp is turned off while the CD player is still going, the output signal comes on full volume before fading off.

any suggestions?

[moe29]

Are you getting 30 volts on the drains of each FET?

Gates at ground and 3.5 volts or so on the Sources?

If the main board is running right the heat sinks get toasty, along with
the 3 watt resistors.

If you're not using balanced inputs, be sure to ground the Input of
the unused polarity.

If all of that is working right, then recheck how you've wired your
Inputs, Outputs, and Volume Control(s).

There's a lot more places to make a mistake on a preamp then your
normal amplifier - so recheck everything.

Maybe one of the more experienced members could chime in with a
suggestion I think i've reached the limit of what i can suggest,
and don't want to make things harder for you!

Keep working on it, i'm sure we can get this working for you.

[jh6you]

This never means that I am an expert more experienced.

Anyhow, I would include the following check points:

1. Check whether the 60+ supply line goes through the resistors to Drain of Mosfet.
2. Check whether the 60- supply line goes through the resistors to Source of Mosfet.
3. Check whether the 60- supply line goes through the resistors and comes back to the 60- supply line.
4. Check whether the +/- input lines go through the resistors to Gate of Mosfet.

Good luck.

Happy New Year !!!