Hi,
I need some help with a EV 7100 Power amplifier. I can't seem to get it out of protection. I must be overlooking something but I'm unable to see what it is.
On pins 2 and 3 of the TA7317 protection IC I show no voltage. Its been over 5 or 6 years since I have had to look at something like this.
If it was working correctly what should I be seeing on the pins?
I need some help with a EV 7100 Power amplifier. I can't seem to get it out of protection. I must be overlooking something but I'm unable to see what it is.
On pins 2 and 3 of the TA7317 protection IC I show no voltage. Its been over 5 or 6 years since I have had to look at something like this.
If it was working correctly what should I be seeing on the pins?
Attachments
2 and 3 are the signal inputs, so you should be seeing <+/-100 mV to ground on both.
Let's stare at the datasheet:
Pin 6 is an open-collector output, it gets pulled to ground (pin 4) and thus engages the relay. If this happens, check the two thermal fuses (T.S 1 and 2) for continuity, as well as the 1k5/1W series resistor, R126.
Pin 1 (overcurrent detection) should be somewhere in the negative range, definitely no higher than +0.5 V. If it does get pulled up, inspect the protection circuitry around Q16/17 and what comes before that (0.33R emitter resistors etc.).
Turn-on delay seems to be coupled to pin 8. Voltage here should be going up slowly after powering on, up to a few volts or so. A leaky C26 could sabotage that; also check R54 for correct value.
The IC should obviously be receiving positive (pin 9) and negative (pin 5) supply voltages.
I'm not yet sure how the power-off circuitry (pin 7) works.
BTW, no need to photograph that schematic, EV provide it online in the manual! 🙂
EDIT:
The bias pots should be checked and cleaned if necessary, the circuit used here is not inherently safe. Otherwise, pretty nice amp.
Let's stare at the datasheet:
Pin 6 is an open-collector output, it gets pulled to ground (pin 4) and thus engages the relay. If this happens, check the two thermal fuses (T.S 1 and 2) for continuity, as well as the 1k5/1W series resistor, R126.
Pin 1 (overcurrent detection) should be somewhere in the negative range, definitely no higher than +0.5 V. If it does get pulled up, inspect the protection circuitry around Q16/17 and what comes before that (0.33R emitter resistors etc.).
Turn-on delay seems to be coupled to pin 8. Voltage here should be going up slowly after powering on, up to a few volts or so. A leaky C26 could sabotage that; also check R54 for correct value.
The IC should obviously be receiving positive (pin 9) and negative (pin 5) supply voltages.
I'm not yet sure how the power-off circuitry (pin 7) works.
BTW, no need to photograph that schematic, EV provide it online in the manual! 🙂
EDIT:
The bias pots should be checked and cleaned if necessary, the circuit used here is not inherently safe. Otherwise, pretty nice amp.
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Thanks
I will post my readings. I guess I will extend the TA 7317 so I can measure voltages without shorting any pins.
Your correct in the bias circuit sucks and I should just replace the bias pots to maintain good contact. This is a hard amplifier to work on because everything is so compact.
I will post my readings. I guess I will extend the TA 7317 so I can measure voltages without shorting any pins.
Your correct in the bias circuit sucks and I should just replace the bias pots to maintain good contact. This is a hard amplifier to work on because everything is so compact.
Ok,
My readings on the TA 7317 IC
1.) -.4vdc
2.) 0
3.) 0
4.) 0
5.) -.769vdc
6.) .969vdc
7.) 0
8.) 1.3vdc
9.)3.1vdc
The readings are after replacing C27,C28,C25, and C26
The resistors R149, R55, R56, R59, R58, R53, and R52 all check as normal listed resistances.
The problem being it takes 10 minutes or so to come out of protection with no DC offset on pins 2 and 3 over about 15mv.
I also replaced the TA 7317 with a new one from my drawer.
So, resistors seem to check out, caps replaced, IC replaced, no DC offset above acceptable levels, no excessive current draw in output stage.
Amp will play music fine but won't latch up the relay until aproximately 10 minutes have passed.
Will post pin voltages before it latches up.
My readings on the TA 7317 IC
1.) -.4vdc
2.) 0
3.) 0
4.) 0
5.) -.769vdc
6.) .969vdc
7.) 0
8.) 1.3vdc
9.)3.1vdc
The readings are after replacing C27,C28,C25, and C26
The resistors R149, R55, R56, R59, R58, R53, and R52 all check as normal listed resistances.
The problem being it takes 10 minutes or so to come out of protection with no DC offset on pins 2 and 3 over about 15mv.
I also replaced the TA 7317 with a new one from my drawer.
So, resistors seem to check out, caps replaced, IC replaced, no DC offset above acceptable levels, no excessive current draw in output stage.
Amp will play music fine but won't latch up the relay until aproximately 10 minutes have passed.
Will post pin voltages before it latches up.
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My non-working voltages
Pins
1.) 22mv
2.) 2.3mv
3.) 3mv
4.) 0
5.) -.780
6.) 58vdc
7.) 0
8.) .277
9.) 3.2vdc
any help would be appreciated. I've looked and probably overlooked and can't seem to see it. Its probably something simple and I just don't see it.
Pins
1.) 22mv
2.) 2.3mv
3.) 3mv
4.) 0
5.) -.780
6.) 58vdc
7.) 0
8.) .277
9.) 3.2vdc
any help would be appreciated. I've looked and probably overlooked and can't seem to see it. Its probably something simple and I just don't see it.
I believe I have it.....
I thought I would check Pin 1 voltages again. Looked at the schematic and thought what would happen if C207 was leaky. Replaced it and the amp came out of protection within 4 seconds of turning it on.
Will let things cool down and check the amp again later.
I thought I would check Pin 1 voltages again. Looked at the schematic and thought what would happen if C207 was leaky. Replaced it and the amp came out of protection within 4 seconds of turning it on.
Will let things cool down and check the amp again later.
My thanks to sgrossklass for his help in making me see what was happening in the protection circuit.
Great to hear you found the culprit. 🙂 Taking ages to come out of protection usually is a dead giveaway that some time constant related electrolytic is leaky.
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