Phoenix Gold Xenon 1200.1

[chrisg4]

i noticed that the KA7500BD chip is heating up quite a bit on below board

is that normal?

NB: i didn't have the FQP65N06 so i used IRFZ44N's to test. Also used lower voltage drivers on the driver board. Have ordered the originals.

 

[Perry Babin]

It appears that the IC is driving two 220 ohm pulldown resistors. This is a low value and may make the IC run at a bit higher temperature than in most other amps. It shouldn't be so hot that it's about to desolder itself from the board.

 

[chrisg4]

I'm unable to touch it. Just worried that it would cause some damage.

 

[Perry Babin]

I don't think it should be that hot. It's possible that it's defective. It doesn't happen often but they can fail. Don't replace it yet.

What transistors did you use as subs for the drivers?

 

[chrisg4]

I used 2sb1124

 

[Perry Babin]

I would expect those to be OK.

Do you read ~5v DC on the gate leg of all of the PS FETs?

 

[chrisg4]

0.01v on gate leg

 

[Perry Babin]

Are the FETs shorted from leg 1-3?

no power applied

 

[chrisg4]

no they are not shorted

 

[Perry Babin]

DC voltage on the base and emitter of the driver transistors on the driver board?

 

[chrisg4]

0.01v on both base and emitter

 

[Perry Babin]

That means that there is no output from the 7500, assuming that there aren't any bad connections between the 7500 and drivers.

Resistance from base of drivers (or pins 9 and 10 of the 7500) to ground.

 

[chrisg4]

i replaced the ka7500 with a tl494

resistance is 2.2 ohms base to ground

the tl494 is not heating up

 

[Perry Babin]

That IC cannot drive 2.2 ohms. What else did you replace on that board besides the drivers and the 7500?

 

[chrisg4]

the other 2 transistors Q2, Q3

 

[chrisg4]

Update, i had the pnp and npn mixed up... also put back the KA7500

psu side is working now and got rail voltages but no output

 

[chrisg4]

I have replaced both IR21844s on the audio driver board, amp makes weird sounds when a speaker is connected

 

[chrisg4]

i have output now after replacing TL072 and the LM311.

 

[chrisg4]

driver board

This is much harder to check without a scope.

The following test can tell you if you have a damaged IC but isn't definitive to tell if the ICs are 100%.

Hi Perry Pabin,

the is outputting weird sounds through the speakers with no input.

i've replaced both ir21844s, the tl072, lm311, lm293, Q1,Q2,Q3,Q7

what else can i check?

 

[Perry Babin]

What sort of weird sound? Describe, I don't want a sound of video file.