Orion XTR2500.1D IR2110s Output Driver Card Issues

Hi all

I have an XTR2500.1D that I seem to be having a head-scratching issue with.
The output drive card will have great signals all the way through to the IR2110s HIN and LIN pins when the IR2110s is NOT installed.
Once I install the 2110s I lose the square wave to HIN and pin 5 of the 393 goes to 3.6v.
The 4.7-ohm resistors are lifted from the HO and LO pins to isolate the output.
Relay does engage, rail voltage is present, 12.8v across c156 and 12.8v to VDD ref from VSS.
Diodes are good to go all resistors have been verified.
I am not familiar with this card so I am not sure if a mute circuit is active.
 

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Sorry for the delayed reply

Do you have DC on the input to the output inductor when the 2110 is in the circuit?
Yes, there is -5 volts slowly raising to -5.2v DC on both sides of the inductor chain and at the speaker terminal. The voltage is present and slowly drops after the power is removed and relays disengage.
This voltage is not present if the drive card is removed. Should I remove the 2110 keeping the card in circuit to test for this voltage again?

Does it do the same with the outputs in or out of the circuit?
Yes, output placement does not change the results.

Does the LIN drive signal change when you lose the HIN drive?
LIN is only present if the 2110 IC is removed. When removed, a LIN sawtooth wave is present. I am not sure if a sawtooth is a correct signal for LIN. Again, I am not familiar with this card.

I have been through this card more times than I can shake a stick at trying to figure out where this fault is originating from.
 
Would you like the results with or without the 2110 IC installed on the board?
Like I had mentioned pin 5 will go from having the sign wave from the 072 with the 2110 IC removed to having 3.6v positive DC with the 2110 IC installed.
Thank you, Perry, I know you are always busy with this stuff and I do appreciate your input.
 
Yes, I am referring to pin 5 of IC172 the LM393. Pin 5 is correct to the zip file if the 2110 is removed.
Pin 1 - correct to zip file
pin 2 - correct to zip file
pin 3 - correct to zip file
pin 4 - correct to zip file (12.8v)
pin 5 - not correct to zip file = 3.4v positive
pin 6 - correct to zip file with slight horizontal fluctuation
pin 7 - not correct to zip file = long dead time short pulses negative
pin 8 - correct to zip file (12.8v)
 
Thank you for the direction Perry. This did change the signals on the LM393 with SD connected to B+
I hope the images are ok for you.
The image number is the pin number
 

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This is with a 50hz input signal.
You will see a change in the timebase on a few pins.
 

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Here are the signals at the input pins of the IR2110s
Also, what is the feasibility of having the right, but wrong transistors on the board based on the datasheet from Mouser? They produce transistors with different package size has a different base, emitter configuration but has the same identifier.
For the HIN it looks to be around 12v above the negative rail and I don't have a clue what is going on with LIN. I had to move the vertical to get this into view without switching to AC coupling.
These will go away if I put the SD pin back in place.
 

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Thank you Perry
Yes there is a 12v square wave (riding negative supply) on the emitter of Q171
I did verify that the BR transistors are original so the base-emitter should be correct.
These signals are still with the SD tied to 12v
So I am looking for the reason as to why there is no square wave on the LIN pin?
If I connect the SD pin back to its pad I lose both HIN and LIN to determine if the 2110 if faulty.
 
When you enable the 2110, you lose signal because the amp is driving everything to the extreme to try to correct for a faulty output.

You, you need to find why there is a bad LIN signal.

The drive from Q171 has to be on the collector, driving from the negative rail up to about 12v.
 
Thank you for the input and help Perry.
I may do some hunting around to find another drive card/amplifier to keep on hand to help troubleshoot this issue.
I get the feeling of a diode leaking or a transistor leaking as I get a good square wave on the base of Q156 which then the square wave turns into a mess, as you see above, going to the LIN pin from the emitter of Q156. I did replace Q156 with the same result so there is more happening in the circuit.