Pioneer GM-D8400M

[RiLoWa]

Does anyone have a copy of the service manual they could pass along for one or similar?

 

[RiLoWa]

Should the TC74AC14F get warm to almost hot?

 

[Perry Babin]

Those are not typically used in a way that will cause them to get hot. Confirm that the supply voltage feeding it isn't too high. I'd guess that it should be about 5v.

 

[RiLoWa]

I do have 5V on it

 

[Perry Babin]

I'd think that it's defective but that's only based on the fact that logic ICs that I've seen in car amps typically don't get hot.

 

[RiLoWa]

Ok replaced the TC74AC14F (IC303) and the NJM311M (IC302) in front of it. The new logic IC gets hot also.

This amp had extensive damage to all of the voltage regulators so it didn't seem out of line that this IC could be defective.

I have clean audio signal up to the input of the NJM311M I replaced so the only other IC I suspect damaged is the TND505MD drive IC.

I have the service manual if you want / need a copy.

 

[Perry Babin]

If the logic IC that you're referring to is IC303, it's possible that whatever it's driving is defective.

Send me a copy of the manual if you need more help with it.
babin_perry@yahoo.com

 

[RiLoWa]

An update to this repair - I finally received a new TND505 (IC305) and installed it tonight along with a new IMT4 (Q301). The TC74AC14F (IC303) still gets hot and no audio is reaching the speaker output terminals.

The last place I see audio is Pin 2 of the NJM311M (IC302).

 

[Perry Babin]

What's the DC voltage across the resistors R319-R322?

If you have a multimeter that can read high frequency AC, post the AC voltage as well.

 

[RiLoWa]

Not sure how reliable the ACV readings are. I checked each several times and each time the ACV and Frequency were slightly different but here is what I get:

R319: 000.0mVDC ~81.5mVAC ~60KHz
R320: 000.0mVDC ~82.0mVAC ~60KHz
R321: 000.0mVDC ~25.8mVAC ~52KHz
R322: 000.0mVDC ~28.0mVAC ~52KHz