LC Audio Zappulse 2.1 Issue

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#42
Now that I have changed the burnt resistor on the one module from 1K ohm to 68 ohm (I did not have an 82 ohm available) the DC at output is more like positive 10V.

I can get an 82 ohm resistor and try. But still have no sound at the output with the 68ohm.

The module with 1 ohm is still at -35V on output.
 
#44
The modules worked at one time.

I beleive I had misconnected the power GND and -V rail a while back. Saw some smoke, so I disconnected the module. The only damage I saw was the 80 ohm resistor in front of the caps. They were charred, so I removed them. I was unable to dterermine their value. I sent an emauil to LCAudio, and afetr a few emails they said it was 1K, but I knew they were thinking of another resistor.

None of the MOSFETS are not shorted to each other. Both square caps seem to be fine (show 22uf on my LC meter). the Rifa caps below also seem fine (caps not open, or shorted). On the Rifa caps below, the two closest to power/output connections shoe .22uF in circuit and teh back ones show 2.2uF in circuit)

What have I connected to the Gate Drive Supply? Sorry, I don't understand. All connections to the modules are +V, -V, V GND, Sig in, Sig GND, Out, Out GND.

I have no other connections on the modules.
 
#46
OK, measure the three MOSFETs. A MOSFET that is not shorted can still be bad. This is what I was hoping.

MOSFET Tab (or drain) to Source Pin should be 12VDC with no connection on input or output...Got it...will try tonight.

I just ordered six IRF640 MOSFETS the other day thinking this is what needed to be replaced. Hopefully this will be the issue.

Mr Clausen, I really appreciate your assistance.

I have a Tripath TA3020 Amp, a UCD400 amp and was hoping to get the ZAP working so I can do my own personal review.

Thanks again.
 
#47
Here are the voltages I get across the MOSFETS - all voltages are grounded to tab/drain

Module #1
MOSFET #1

Source -23.5V (+V Rail Side)
Gate -23.5V

MOSFET #2

Source -43V
Gate -43V

MOSFET #3 (-V Rail Side)
Source -22V
Gate -18.5V

Module #2

MOSFET #1(+V Rail Side)

Source -70V
Gate -70V

MOSFET #2

Source 0V
Gate +12V

MOSFET #3 (-V Rail Side)
Source -23V
Gate -19.4V

All six appear bad? Maybe MOSFET #2 on Module 2 is OK?
 
#48
After thinking about it further, I do not believe I miss connected the GND and -V rail, but either the GND or -V rail may have not been securely soldered onto the connection. Would this cause the problem losing the GND or a rail?

Anyway, the Voltages should read:

Module #1
MOSFET #1 (+V Rail Side)

Source -23.5V
Gate -23.5V

MOSFET #2

Source -43V
Gate -43V

MOSFET #3 (-V Rail Side)
Source -22V
Gate -18.5V

Module #2

MOSFET #1(+V Rail Side)

Source -70V
Gate -70V

MOSFET #2

Source 0V
Gate +12V

MOSFET #3 (-V Rail Side)
Source -23V
Gate -19.4V
 
#51
OK, once again Voltages referenced from Power Ground:

Module 1

MOSFET #1 (V+ Side)
Vs = +10V
Vg = +10V

MOSFET #2
Vs = -36.3V
Vg = -36.3V

MOSFET #3
Vs = -24V
Vg = -20.2V


Module #2

MOSFET #1 (V+ Side)
Vs = -36V
Vg = -36V

MOSFET #2
Vs = -36.5V
Vg = -24.3V

MOSFET #3
Vs = -24.2V
Vg = -20.4V

Hope this helps.
 
#53
i think you must clear fet pins..Soldier relic is much unfavorable for low signal and high frequency applications..
Click to expand...

Clear FET pins? I do not understand.

I have received six new IRF640 MOSFETs. I can replace them if need be.

I also took these voltages with no connections to input and output. Was I supposed to have a dummy load across the output for these Gate/Source/Drain voltages to be real/accurate?

Sorry for all the lame questions.

I am beginning to think these modules are KAPUT... thinking of getting another UCD400 or finish my AMP2. But then again I need another amp ilke I need a hole in my head.
 
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