Hifonics BRX 3016.1D waveforms

[bl4ckw1d0w]

Ok so story on this one was blown power and audio section.

Right now the rectifiers are pulled and a 2 ohm resistor in series with 12v power. No current draw.

I am trying to understand what the attached waveforms are telling me, if they are ok and how to clean them up if they're not.


Replaced R106 and R107 on the Pwm card.

I didnt have any irf064ns but i did have a ton of IRFP3206's on hand.

8 Mosfets in power section changed to Irfp3206.

Gate resistors changed to 10Ω down from 22Ω.

8 drivers replaced with bd139 and bd140. Originally were the C3228 and complimentary pnp.

8 power supply Fets replaced from IRFP064N'S to IRFP3206.

4 pulldown resistors reduced from 470Ω to 220Ω which helped pul back down to ground.

 

[Perry Babin]

Were those waveforms with the scope probe ground on the source leg and the probe on the gate leg. If not, repost with that configuration.

 

[bl4ckw1d0w]

I am gone from the shop for the day but i believe the source of the 3206 is connected directly to ground and the ground lead wad clipped to the ground rail. I am not positive ill have to check tomorrow and clip it to the source leg.

 

[bl4ckw1d0w]

The waveforms were taken with probe on gate leg.

 

[Perry Babin]

Use the short ground lead that clips to the end of the probe.

 

[bl4ckw1d0w]

Probe on gate of IRF16_2
Ground lead of probe on source.

See attached.

 

[Perry Babin]

Is that scope reading right? Only about 4v of amplitude?

 

[bl4ckw1d0w]

I removed the 2ohm current limiter.

Here is the correct waveform with B+ voltage at 12.05V.

See Attached.

 

[Perry Babin]

The amplitude is still low. What is the DC voltage on the collector of the NPN driver transistors?

 

[bl4ckw1d0w]

Im getting 12.18 volts on the collector.

 

[Perry Babin]

What does the amplitude on the base of the drivers and the output of the driver IC look like?

 

[bl4ckw1d0w]

I did re-insert 2 ohm current limiter so i did not slip the probe and blow components.See attached.

 

[Perry Babin]

That's a LOT of drop. What's the resistance between the base of the drivers and pins 9 and 10 of the 494?

 

[bl4ckw1d0w]

Pin 9: 1.277kΩ

Pin 10: 263.2Ω

 

[Perry Babin]

Are you saying that there is a difference in the resistance between the output terminals of the 494 to their respective driver bases?

 

[bl4ckw1d0w]

Yes. I am assuming you mean pin 10 is driving this pair of NPNs i am referencing at 262Ω.

If i measure pin 9 of TL494 to the base of the other set of NPNs i am getting 263.8Ω.

I have been taking measurements from the drivers group driving the bank of irf3206 i referenced with low amplitude. I cant see the designations on the board because of the limited space.

 

[Perry Babin]

Each output (9/10) drives one NPN and one PNP in an emitter-follower configuration. The attached diagram may be similar.

 

[bl4ckw1d0w]

This amp is driving 2 NPN/PNP pairs per 9/10 pin. I have an NPN/PNP combo driving 2 IRF3206's. I have a total of 8 mosfets with 2 drivers per 2 mosfets. Its more similar to the AQ20 schematic.

 

[bl4ckw1d0w]

Should I be reducing the reistors between the base of the driver pair and pin 9/10?

 

[Perry Babin]

Why are the values different?