This is odd but the base and collector of the TIP31C lower left appear to be tied together intentionally.
I guess that makes it a diode. The emitter is connected to ground.
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Are pins 15 and 16 possibly connected to the output of the rectifiers (via resistors)?
Pin 1 is almost certainly connected to something else. It would be odd to have nothing more than a pulldown resistor to ground on the pin (a direct connection would make more sense).
Pin 1 is almost certainly connected to something else. It would be odd to have nothing more than a pulldown resistor to ground on the pin (a direct connection would make more sense).
Yes. I missed it before. It is connected to pin 3 and a 100K resistor which disappears under an electrolytic capacitor but does not connect to it.
Possible but I don't think so. They each connect to a separate 7K resistor then the two resistor connect together to a lead coonects to the + side of a 22uf cap and then disappears under the TL596.
Pin 3 has a 2.4K pull down to ground and a 100K resistor that leads under one of the electrolytics but does not cennect to it. I have been probing the underside in that area but have not been able to determine where it goes.
You said earlier that the voltage differential between pins 1 and 2 are causing the 594 to shut down. Is 1 too high or is 2 too low?
Pin 1 needs to be lower than 2 and pin 16 needs to be lower than 15.
Are you following the traces through the board to the other side?
I'm not understanding what it means not to be able to see where it goes.
For this IC, the output of pin 3 (determined by the inputs 1, 2, 15 and 16) can be grounded to force the IC to produce output but, if something (like a transistor) is driving pin 3 directly, it could damage that transistor. I was asking what else was connected to pin 3. If no transistor was directly connected, you could jump it to pin 7 on the IC and that should force the supply up so you could see what could be causing the IC to be shut down.
The same could be done with pin 1 (to pin 7). That way, whatever the function of 15/16 is (possibly regulation), they could still function (vs grounding pin 3).
Are you following the traces through the board to the other side?
I'm not understanding what it means not to be able to see where it goes.
For this IC, the output of pin 3 (determined by the inputs 1, 2, 15 and 16) can be grounded to force the IC to produce output but, if something (like a transistor) is driving pin 3 directly, it could damage that transistor. I was asking what else was connected to pin 3. If no transistor was directly connected, you could jump it to pin 7 on the IC and that should force the supply up so you could see what could be causing the IC to be shut down.
The same could be done with pin 1 (to pin 7). That way, whatever the function of 15/16 is (possibly regulation), they could still function (vs grounding pin 3).
Yes I can see both sides. There are leads underneath the electrolytic caps and transformer that I cannot see. I am probing around though.
Pin 3: connects to the 10K resistor then to the collector of a 2n4403. The lead runs a couple of inches over to the STK which is why I missed it before.
Given that there is a 10k resistor protecting the transistor, can I safely ground pin 3?
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If nothing else external to the 594 connects to pin 3, you can jump it to pin 7.
To protect the components, clamp all heatsink mounted components tightly to the heatsink and insert a 5 amp fuse in the B+ line. I doubt that it will draw more than that.
I don't know what the rail voltage is supposed to be and can't see the voltage rating on the rail caps but the STK2240 is limited to ±58v. If you power the amp up and it produces rail voltage, just power up for a second so you can measure the rail voltage to confirm it's not too high. It should be less than the rail cap rating and definitely less than the STK2240 rating.
To protect the components, clamp all heatsink mounted components tightly to the heatsink and insert a 5 amp fuse in the B+ line. I doubt that it will draw more than that.
I don't know what the rail voltage is supposed to be and can't see the voltage rating on the rail caps but the STK2240 is limited to ±58v. If you power the amp up and it produces rail voltage, just power up for a second so you can measure the rail voltage to confirm it's not too high. It should be less than the rail cap rating and definitely less than the STK2240 rating.
Some of the rail caps are 35v and some are 25v. I suspect the 25v are not original to the amp.
Are these connected to the power supply pins of the 2240?
If these are actually on the rails and the rail voltage doesn't exceed 25v, there isn't a problem (with that, anyway). If they have been in the amp and are on the 2240 rails, the rail voltage is likely to be less than ±25.
If these are actually on the rails and the rail voltage doesn't exceed 25v, there isn't a problem (with that, anyway). If they have been in the amp and are on the 2240 rails, the rail voltage is likely to be less than ±25.
The four caps that are directly connected to the 2240 power rails are all 35v.
The other caps on the input side of the transformer are a mix of 25 and 35v.
I put it together with pins 3 and 7 connected and a 5 amp fuse. There is still no power. I measure - 0.44 v on both rails.
I just noticed there are dozens of similar amplifiers listed on Ebay for cheap. Some are new old stock. I may give up and adapt a similar amp from Ebay to fit my connectors.
I just noticed there are dozens of similar amplifiers listed on Ebay for cheap. Some are new old stock. I may give up and adapt a similar amp from Ebay to fit my connectors.
If you haven't given up (it's OK if you have)...
What voltages changed from the last time you posted?
What voltages changed from the last time you posted?
It's still on my workbench so I haven't completely given up. I'm just getting ready to attempt to fix the digital odometer on this car and some ignition mis-wiring and only want to have one project open at once.
Pin 1: 0.02
Pin 2: 0.47
Pin 3: 0.02
Pin 4: 0.02
Pin 5: 0.99
Pin 6: 2.17
Pin 7: 0.02
Pin 8: 4.86
Pin 9: 0.91
Pin 10: 0.0
Pin 11: 4.83
Pin 12: 4.81
Pin 13: 3.5
Pin 14: 3.5
Pin 15: 0.46
Pin 16: 0.40
Pin 1: 0.02
Pin 2: 0.47
Pin 3: 0.02
Pin 4: 0.02
Pin 5: 0.99
Pin 6: 2.17
Pin 7: 0.02
Pin 8: 4.86
Pin 9: 0.91
Pin 10: 0.0
Pin 11: 4.83
Pin 12: 4.81
Pin 13: 3.5
Pin 14: 3.5
Pin 15: 0.46
Pin 16: 0.40
Why are you getting less than 5v to pin 12? The IC won't work at that voltage. the 9.5v you had previously was low, but enough. This is too low.
The calibration on the meter is bad (I need to replace it), but not that bad maybe +/- 1.5 volts.
Pin 12 connects to the emitter of 2N3904 NPN transistor via a 47 ohm resistor. The collector connects directly to 12v. The base connects to the enable wire from the head unit in the dash.
I get full voltage on the enable wire. About 5 volts on pin 12. Maybe 6.5-7 volts on the other side of the 47 ohm resistor. There is no heat on the transistor, the 594, or the resistor. The transistor seemed to test OK on the board but I am not sure if I trust the meter anymore.
I am going to stop messing with this at least until I get a better meter.
Pin 12 connects to the emitter of 2N3904 NPN transistor via a 47 ohm resistor. The collector connects directly to 12v. The base connects to the enable wire from the head unit in the dash.
I get full voltage on the enable wire. About 5 volts on pin 12. Maybe 6.5-7 volts on the other side of the 47 ohm resistor. There is no heat on the transistor, the 594, or the resistor. The transistor seemed to test OK on the board but I am not sure if I trust the meter anymore.
I am going to stop messing with this at least until I get a better meter.
If/when you get back to this, confirm that the 47 ohm resistor is with tolerance.
If it is, measure the voltage from the collector to the emitter of the 3904 as well as the voltage measured directly across the 47 ohm resistor and post those values.
If it is, measure the voltage from the collector to the emitter of the 3904 as well as the voltage measured directly across the 47 ohm resistor and post those values.
I have a new multi-meter and still have not given up.
I measure the resistor as 47.4 ohms.
Voltage collector to emitter is 4.2.
Across the 47 ohm resistor is 2.7.
Other voltages against ground:
Enable side of 10K resistor: 12v.
Base of 3904 (other side of 10k resistor) 8.5 volts.
Collector: 12v.
Emitter 7.8 volts.
I measure the resistor as 47.4 ohms.
Voltage collector to emitter is 4.2.
Across the 47 ohm resistor is 2.7.
Other voltages against ground:
Enable side of 10K resistor: 12v.
Base of 3904 (other side of 10k resistor) 8.5 volts.
Collector: 12v.
Emitter 7.8 volts.
Is the 594 heating up?
The IC has low-voltage protection but it should be functioning at 8.5v. The 5v output is out of tolerance but I don't know if it's enough to cause the IC to malfunction.
There are a lot of unknowns here.
Was the amp working perfectly before it just recently failed?
The IC has low-voltage protection but it should be functioning at 8.5v. The 5v output is out of tolerance but I don't know if it's enough to cause the IC to malfunction.
There are a lot of unknowns here.
Was the amp working perfectly before it just recently failed?
The 594 is not heating up. I removed the jumper betweens pins 3 and 7 and the pin 12 input voltage goes back to
This is a long thread, but the amp sounded like it had low power and would eventually shut down after running for 20 minutes. After finding 9v DC on the right front audio output, I removed the front STK 2240 and attempted to run the amp with only the rear STK2240. When I had it put back together there was no power on the power rails.
The 594 is not heating up. I removed the jumper between pins 3 and 7 and the pin 12 input voltage went back to 9.5 volt value that I had before I added the jumper. It seems there is something causing the 594 to draw too much power.
This is a long thread, but the amp sounded like it had low power and would eventually shut down after running for 20 minutes. After finding 9v DC on the right front audio output, I removed the front STK 2240 and attempted to run the amp with only the rear STK2240. When I had it put back together there was no power on the power rails.