I'll post what I find. I don't think pin 16 should affect the DC output since the wiring is the same for both modes and the IC can switch between them automatically regardless of the status of pin 16.
What is pin 25 connected to?
What is pin 25 connected to?
Would be a real challenge to trace pin 25's destination, but I would believe it ends up somewhere in the system control IC as its purpose is telling the state of the chip (via a 10kOhm pull-up resistor (from 5V line)).
Have a feeling this pin does what it's ment for though - as yesterdays "overheat/5.2Amp draw" test first made the radio turn down its volume, then the vent fan started.
Could that be of significance?
Nevertheless; just finished assembling the unit and it is now under testing: so far so good..
Agree with your saying concerning pin 16 and "same wiring for both modes" IF datasheet actually reflects the truth!
I'm open for the possibility that the design of TDA7454 could have been changed since 2003, yet that would be odd as all datasheets states the same..
Regards
(only half (Vcc) confused at this time 🙂 )
Have a feeling this pin does what it's ment for though - as yesterdays "overheat/5.2Amp draw" test first made the radio turn down its volume, then the vent fan started.
Could that be of significance?
Nevertheless; just finished assembling the unit and it is now under testing: so far so good..
Agree with your saying concerning pin 16 and "same wiring for both modes" IF datasheet actually reflects the truth!
I'm open for the possibility that the design of TDA7454 could have been changed since 2003, yet that would be odd as all datasheets states the same..
Regards
(only half (Vcc) confused at this time 🙂 )
At this point, I'm thinking that there may be a batch if mis-marked ICs. Look at the datasheet below. It's the 7580 and all pins except 25 and 16 are identical. Pin 16 is the filter cap for the audio biasing. If this were grounded on the 7580, I'd expect to see the same problems as you are having. Other ICs like the 7560 are similar except that pin 25 is a 12v output that's active when the IC is switched on.
http://datasheet.octopart.com/TDA7850-STMicroelectronics-datasheet-10837062.pdf
http://datasheet.octopart.com/TDA7850-STMicroelectronics-datasheet-10837062.pdf
-also; in the (highly likely) event datasheet actually matches the truth, IC will switch "back" to high eff mode when temp reaches 100 deg yes, and then what happens?!
Looking forward to your findings! 🙂
Looking forward to your findings! 🙂
hmm.. veeery interesting! It does make sense!
How could one prove that though?
I did order my 4 pcs. of these from 3 completely different sources (one from local store Norway, 1 from England and the latest 2 from Germany). What are the odds?
But as you says; it does make sense!
One cannot be sure that my chips actually are the 7580's either - yet it figures as for the pin 16 function.
Then how about pin 25 if this were the case? It doesn't seem to signalize the same way the 7454 does. Maybe I just leave that one lifted as well and add a 0,47uF in series with pin 16 (if necessary?).
This calls for some further thinking..
How could one prove that though?
I did order my 4 pcs. of these from 3 completely different sources (one from local store Norway, 1 from England and the latest 2 from Germany). What are the odds?
But as you says; it does make sense!
One cannot be sure that my chips actually are the 7580's either - yet it figures as for the pin 16 function.
Then how about pin 25 if this were the case? It doesn't seem to signalize the same way the 7454 does. Maybe I just leave that one lifted as well and add a 0,47uF in series with pin 16 (if necessary?).
This calls for some further thinking..
For the 7850 (typo in previous post), pin 25 has 2 possible functions.
Are the date codes on all of your ICs the same?
Are the date codes on all of your ICs the same?
Not sure how to interpret such, but here are my readings:
Original IC states: "ST G227M0335 MALTA"
IC from Norway states: "ST 220GBHBVb MLT22 545"
IC from England states: "ST 220RUHAVb MLT22 220"
And the IC now in use (from Germany) reads 100% exactly the same as the latter (from England)!
Original IC states: "ST G227M0335 MALTA"
IC from Norway states: "ST 220GBHBVb MLT22 545"
IC from England states: "ST 220RUHAVb MLT22 220"
And the IC now in use (from Germany) reads 100% exactly the same as the latter (from England)!
I finally have the IC and it reads approximately 20k ohms between the two output pins for each channel. I haven't had time to do any other testing with it.
OK, thanks!
Just did a second test here with my "fourth one" IC just received and fresh outta package: 118 Ohms between the same output pins (3-5, 7-9, 17-19, and 23-21).
Seems to be a different batch, yes indeed!
I've handed my repair over to customer though (and no complains so far).
However; if this pin 16 "grounding issue" persist for other IC-replacers as well, it is likely to be a pontentially fire hazard.
Some discredits ought to be in place.. 😡
Just did a second test here with my "fourth one" IC just received and fresh outta package: 118 Ohms between the same output pins (3-5, 7-9, 17-19, and 23-21).
Seems to be a different batch, yes indeed!
I've handed my repair over to customer though (and no complains so far).
However; if this pin 16 "grounding issue" persist for other IC-replacers as well, it is likely to be a pontentially fire hazard.
Some discredits ought to be in place.. 😡
Attachments
hmm.. just did some additional measurements:
Original IC (marked: ST G227M0335 MALTA) and the IC bought here in Norway (marked: ST 220GBHBVb MLT22 545) both read approx. 30kOhms between their output lines.
Output lines resistance then isn't synonymous with chip being bad (my customer now runs the "116 Ohm-resistance version" without complains).
Is there any chance you could test your TDA7454 with pin 16 grounded and see if DC offset occurs?
Is your TDA7454 also a "Malta date code" product?
😱
Original IC (marked: ST G227M0335 MALTA) and the IC bought here in Norway (marked: ST 220GBHBVb MLT22 545) both read approx. 30kOhms between their output lines.
Output lines resistance then isn't synonymous with chip being bad (my customer now runs the "116 Ohm-resistance version" without complains).
Is there any chance you could test your TDA7454 with pin 16 grounded and see if DC offset occurs?
Is your TDA7454 also a "Malta date code" product?
😱
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