Teac AG-790 has me stumped...
in [Repair]
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From: William R. Walsh on 26 Jun 2010 20:57 I'm about to give up... I received a Teac AG-790 stereo receiver with burn damage to the PCB underneath resistors 7R41, 7R47, 7R?? (unmarked, next to 7R47) and 7R48. I repaired all of this damage, cleaned up the carbon that had been left behind and soldered to the nearest remaining good portion of the board. Up to this point, the receiver did what it has done since I got it. It played through the right channel only. I kept on looking and found a capacitor at location 7C27 (220uF, 16V) that had blown out the rubber plug at the bottom. So I replaced that. Now nothing works. I know the new cap to be good. The unit will power up just as it always has, there are no blown fuses and my repair job seems to be bulletproof (and correct, per the schematic in the service manual). The audio is gone, replaced only by a faint humming on speakers and headphones alike, in the right channel. Turning the volume dial does not change this. There is still nothing from the left channel. The unit is not in protection and nothing is getting hot, burning up or worse. In addition, the display on the front of the unit will now indicate "E0" (or maybe it's an O...no way to tell). This is not mentioned in the service manual, nor did I find anything in a web search. Operations from the front panel remain possible. I'm beginning to think that it may be too far gone to fix. Anyone out there with an eleventh hour idea? William
From: Jamie on 26 Jun 2010 21:14 William R. Walsh wrote: > I'm about to give up... > > I received a Teac AG-790 stereo receiver with burn damage to the PCB > underneath resistors 7R41, 7R47, 7R?? (unmarked, next to 7R47) and 7R48. I > repaired all of this damage, cleaned up the carbon that had been left behind > and soldered to the nearest remaining good portion of the board. > > Up to this point, the receiver did what it has done since I got it. It > played through the right channel only. > > I kept on looking and found a capacitor at location 7C27 (220uF, 16V) that > had blown out the rubber plug at the bottom. So I replaced that. Now nothing > works. I know the new cap to be good. The unit will power up just as it > always has, there are no blown fuses and my repair job seems to be > bulletproof (and correct, per the schematic in the service manual). The > audio is gone, replaced only by a faint humming on speakers and headphones > alike, in the right channel. Turning the volume dial does not change this. > There is still nothing from the left channel. The unit is not in protection > and nothing is getting hot, burning up or worse. > > In addition, the display on the front of the unit will now indicate "E0" (or > maybe it's an O...no way to tell). This is not mentioned in the service > manual, nor did I find anything in a web search. Operations from the front > panel remain possible. > > I'm beginning to think that it may be too far gone to fix. Anyone out there > with an eleventh hour idea? > > William > > did you put the new cap in backwards? Also, is it possible that maybe the protection circuit is now working since you put the cap in, which is why you are now getting the E0 error. This could be caused by yet, a problem that remains in the bad channel.. Assuming this is like most protection output circuits, you may want to test the output of the bad channel before the relay circuit that joins the speakers. .YOu could have a channel that is outputting DC above the safe point for the initial on cycle. Which would lead to say that you still have a problem, ofcourse!
From: stratus46 on 27 Jun 2010 02:31 On Jun 26, 5:57 pm, "William R. Walsh" <newsgrou...(a)idontwantjunqueemail.walshcomptech.com> wrote: > I'm about to give up... > > I received a Teac AG-790 stereo receiver with burn damage to the PCB > underneath resistors 7R41, 7R47, 7R?? (unmarked, next to 7R47) and 7R48. I > repaired all of this damage, cleaned up the carbon that had been left behind > and soldered to the nearest remaining good portion of the board. > > Up to this point, the receiver did what it has done since I got it. It > played through the right channel only. > > I kept on looking and found a capacitor at location 7C27 (220uF, 16V) that > had blown out the rubber plug at the bottom. So I replaced that. Now nothing > works. I know the new cap to be good. The unit will power up just as it > always has, there are no blown fuses and my repair job seems to be > bulletproof (and correct, per the schematic in the service manual). The > audio is gone, replaced only by a faint humming on speakers and headphones > alike, in the right channel. Turning the volume dial does not change this.. > There is still nothing from the left channel. The unit is not in protection > and nothing is getting hot, burning up or worse. > > In addition, the display on the front of the unit will now indicate "E0" (or > maybe it's an O...no way to tell). This is not mentioned in the service > manual, nor did I find anything in a web search. Operations from the front > panel remain possible. > > I'm beginning to think that it may be too far gone to fix. Anyone out there > with an eleventh hour idea? > > William 'blown plug' usually means the acid is out and quite possibly eating away the traces near by. Replacing the cap may have finished off a nearly gone trace. Do you have the prints so you can 'ohm it out' and verify the connections are actually there? G²
From: Baron on 27 Jun 2010 11:34 William R. Walsh Inscribed thus: > I'm about to give up... > > I received a Teac AG-790 stereo receiver with burn damage to the PCB > underneath resistors 7R41, 7R47, 7R?? (unmarked, next to 7R47) and > 7R48. I repaired all of this damage, cleaned up the carbon that had > been left behind and soldered to the nearest remaining good portion of > the board. > > Up to this point, the receiver did what it has done since I got it. It > played through the right channel only. > > I kept on looking and found a capacitor at location 7C27 (220uF, 16V) > that had blown out the rubber plug at the bottom. So I replaced that. > Now nothing works. I know the new cap to be good. The unit will power > up just as it always has, there are no blown fuses and my repair job > seems to be bulletproof (and correct, per the schematic in the service > manual). The audio is gone, replaced only by a faint humming on > speakers and headphones alike, in the right channel. Turning the > volume dial does not change this. There is still nothing from the left > channel. The unit is not in protection and nothing is getting hot, > burning up or worse. > > In addition, the display on the front of the unit will now indicate > "E0" (or maybe it's an O...no way to tell). This is not mentioned in > the service manual, nor did I find anything in a web search. > Operations from the front panel remain possible. > > I'm beginning to think that it may be too far gone to fix. Anyone out > there with an eleventh hour idea? > > William Just asking, you did put the cap in the right way round ! -- Best Regards: Baron.
From: Arfa Daily on 27 Jun 2010 12:47
"Baron" <baron.nospam(a)linuxmaniac.nospam.net> wrote in message news:i07qvk$dja$1(a)news.eternal-september.org... > William R. Walsh Inscribed thus: > >> I'm about to give up... >> >> I received a Teac AG-790 stereo receiver with burn damage to the PCB >> underneath resistors 7R41, 7R47, 7R?? (unmarked, next to 7R47) and >> 7R48. I repaired all of this damage, cleaned up the carbon that had >> been left behind and soldered to the nearest remaining good portion of >> the board. >> >> Up to this point, the receiver did what it has done since I got it. It >> played through the right channel only. >> >> I kept on looking and found a capacitor at location 7C27 (220uF, 16V) >> that had blown out the rubber plug at the bottom. So I replaced that. >> Now nothing works. I know the new cap to be good. The unit will power >> up just as it always has, there are no blown fuses and my repair job >> seems to be bulletproof (and correct, per the schematic in the service >> manual). The audio is gone, replaced only by a faint humming on >> speakers and headphones alike, in the right channel. Turning the >> volume dial does not change this. There is still nothing from the left >> channel. The unit is not in protection and nothing is getting hot, >> burning up or worse. >> >> In addition, the display on the front of the unit will now indicate >> "E0" (or maybe it's an O...no way to tell). This is not mentioned in >> the service manual, nor did I find anything in a web search. >> Operations from the front panel remain possible. >> >> I'm beginning to think that it may be too far gone to fix. Anyone out >> there with an eleventh hour idea? >> >> William > > Just asking, you did put the cap in the right way round ! > > -- > Best Regards: > Baron. Agreed on that, but seems to me that the fundamental question is not being asked. In what part of the circuit is the replaced cap ? Can you determine its exact function from the schematics ? Knowing that may be helpful to assess whether there may be an immediated connection between the previous and current symptoms, or whether we're in 'red herring' territory here ... Arfa |