Morning 🙂
It's 7.30 am here... I'll be out for a while this morning.
If there's anything else your not sure of ask now 😉
It's 7.30 am here... I'll be out for a while this morning.
If there's anything else your not sure of ask now 😉
Gotta go... just one other thing,
the capacitors in the PSU (those large cans) could retain the full supply voltage... no danger to you but it could easily damage semiconductors if you accidently managed to short it to something such as when removing the IC etc.
So measure across them on DC volts whenever you "work" on the amp... if they are charged up then use another bulb to dab across them to discharge. Never short them out. Or use a resistor of course if you have any, say around 1000 ohms.
Take your time, enjoy and learn.
the capacitors in the PSU (those large cans) could retain the full supply voltage... no danger to you but it could easily damage semiconductors if you accidently managed to short it to something such as when removing the IC etc.
So measure across them on DC volts whenever you "work" on the amp... if they are charged up then use another bulb to dab across them to discharge. Never short them out. Or use a resistor of course if you have any, say around 1000 ohms.
Take your time, enjoy and learn.
OK all occured as it should.
Bulb came on bright, then backed off to very faint orange. Jumpered both fuses to eliminate that factor
Checked rails, -30 & + 30.
Connected woofer no sound
.
Also just on the edit note, the new IC is attached to a heatsink with thermal grease, the heatsink is actually the bit that has it's metal and the base plate of the amp insulated with the plastic
Bulb came on bright, then backed off to very faint orange. Jumpered both fuses to eliminate that factor
Checked rails, -30 & + 30.
Connected woofer no sound
.Also just on the edit note, the new IC is attached to a heatsink with thermal grease, the heatsink is actually the bit that has it's metal and the base plate of the amp insulated with the plastic
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OK... while I think, grab a copy of the data sheet here, it makes it easier to understand as the next step is measuring on the IC
http://www.datasheetcatalog.org/datasheet2/8/0ikk6kzzwhksd02iog4o7s0572ky.pdf
http://www.datasheetcatalog.org/datasheet2/8/0ikk6kzzwhksd02iog4o7s0572ky.pdf
Keep looking at the picture and your circuit seems to broadly follow the standard application, the first diagram on the data sheet.
1. You have confirmed supply present... so that's pins 1 and 5 on the chip with +30 volts and pin 4 with -30 volts.
2. Next measure the DC voltage on pin 3 (the output pin) of the IC. Should be zero volts DC. Can you trace that pin and see where it goes... looks like it goes to a wire connection on your picture... then where... it should go to the speaker... is there a fuse in the speaker line anywhere.
1. You have confirmed supply present... so that's pins 1 and 5 on the chip with +30 volts and pin 4 with -30 volts.
2. Next measure the DC voltage on pin 3 (the output pin) of the IC. Should be zero volts DC. Can you trace that pin and see where it goes... looks like it goes to a wire connection on your picture... then where... it should go to the speaker... is there a fuse in the speaker line anywhere.
OK Pin 3 0v DC, goes direct to the positive on the woofer, no further fuses between it and woofer
Yep, got a bit of time so just have a measure and see if you can trace that connection to pin 3.
Does it go to the speaker directly ?
Does it go to the speaker directly ?
OK... and also confirm that the negative terminal of the woofer actually returns to ground... just to make sure no fuse in the ground connection.
And with the amp OFF and woofer connected you should be able to read on ohms the resistance of the woofer (just to make sure that's OK) between pin 3 and ground. If you then use diode check to do same you should hear the woofer "click"
And with the amp OFF and woofer connected you should be able to read on ohms the resistance of the woofer (just to make sure that's OK) between pin 3 and ground. If you then use diode check to do same you should hear the woofer "click"
It does, there is a sideline to a resistor then back to another pin on the IC, but no interuption between pin 3 and speaker
OK so it clicks... so woofer is good and connected OK.
Is the IC new ?
Now a scary test... with it on and connected to the woofer what happens if you VERY CAREFULLY as in steady hands, touch a metalic screwdriver to just pin 10 of the IC. Make sure you are not touching anything else... there's no shock hazard... we just want you buzzing that input with no other voltages superimposed.
That is attempting to "buzz" the input and see if any response from speaker.
Is the IC new ?
Now a scary test... with it on and connected to the woofer what happens if you VERY CAREFULLY as in steady hands, touch a metalic screwdriver to just pin 10 of the IC. Make sure you are not touching anything else... there's no shock hazard... we just want you buzzing that input with no other voltages superimposed.
That is attempting to "buzz" the input and see if any response from speaker.
3.5 ohms pin 3 to ground of speaker on pcb, very faint crackle in speaker on diode check. Not sure with the grounding qn, where do i put pins to check this have been using speaker ground as ground for all measurements
3.5 ohms sounds correct. The correct ground is the 0 volt line (which will probably be the speaker return as you are using). It's that large area of print above the 1 and 2 in the picture where the two large caps have a common connection. If that reads 0.00 ohms to the speaker negative then it's OK to use that as it will be easier probably.
You have done right but there should be response... so now we have to measure all the pins on the IC for DC voltage and see if anything seems amiss.
What's the DC voltage on pin 8 first though ?
What's the DC voltage on pin 8 first though ?
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