Yes I have drive pulses. With the scope set to 5V/Div, Pin 9 and 10 of the 494 look the same and like this:
Heres what is on Leg 1 of the power fets, scope set to 1V/Div:
Heres what is on Leg 2 of the power fets. Scope set to 10V/Div:
Theres also a square wave on the large rectifier legs 1&3 measuring 110vAC. These rectifiers and the output transitors have nothing more than about +-1vAC on the scope; looks more like noise to me though and very similar to the above first photo.
Heres what is on Leg 2 of the power fets. Scope set to 10V/Div:
Theres also a square wave on the large rectifier legs 1&3 measuring 110vAC. These rectifiers and the output transitors have nothing more than about +-1vAC on the scope; looks more like noise to me though and very similar to the above first photo.
What is the DC voltage when you place one probe on the center leg of one rectifier and the other probe on the center leg of the other rectifier?
With the black probe on either of the non-bridging speaker terminals, what is the DC voltage to the center legs of the rectifiers?
I measure -77vDC from non-bridging terminals to Leg 2 of the Rectifier next to transformer wires 12&13 (Rectifier 'arrows' pointing outward).
Also measure -1.4vDC on Leg 2 of rectifier next to transformer wires 9&10 (Rectifier 'arrows' pointing inward).
Again, still seeing -18 to -20vDC across speaker terminals.
Also measure -1.4vDC on Leg 2 of rectifier next to transformer wires 9&10 (Rectifier 'arrows' pointing inward).
Again, still seeing -18 to -20vDC across speaker terminals.
Do you read the same AC voltage to the outer legs of both rectifiers (one probe on non-bridging terminal)?
If so, the positive rectifier is open.
If not, there is a broken connection between the transformer and the positive rectifier.
If so, the positive rectifier is open.
If not, there is a broken connection between the transformer and the positive rectifier.
Yes. 113vAC across all 4 outer legs (both rectifiers).
I actually think both rectifiers might be bad. This amp has the transformer leads attached via screw terminals. I unscrewed leads 9/10/12/13 from the board... I think that is sufficiant for removing the transformer from the equasion.
Testing a rectifier is like testing two diodes right?? If thats the case, then both the rects are failing this test. I'll look up how to formally test these to be the case.
I actually think both rectifiers might be bad. This amp has the transformer leads attached via screw terminals. I unscrewed leads 9/10/12/13 from the board... I think that is sufficiant for removing the transformer from the equasion.
Testing a rectifier is like testing two diodes right?? If thats the case, then both the rects are failing this test. I'll look up how to formally test these to be the case.
Yes. You test them like individual diodes. ~0.5 one direction and open when you swap the probes.
You nailed it - FMG-33S is open on the ohm meter and fails diode check It was hard to determin with the transformer connected, but now I'm sure. What could be the cause of this, and, would there be some protection circuit which wasnt letting the amp power up? I'm just seeing if there might be more than one problem with this amp at this point.
It's an old amp. It could have been a random failure.
The DC may have been preventing it from powering up.
The DC may have been preventing it from powering up.
Heres what happened when I de-soldered the rectifier. I sure hope the rest of the transistors are OK and dont come off like this... What is a good equivalant rectifier for replacement of this one? Should I replace the one on the other side at the same time? FMG-33S and FMG-33R.
EDIT: I actually will need to replace both rectifiers. I just found the 33R to have it's 3rd leg detached from the body also.
EDIT: I actually will need to replace both rectifiers. I just found the 33R to have it's 3rd leg detached from the body also.
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Wow and they want $10 for S/H...
Im almost temped to borrow the rectifiers from the other Alpine 3435 just to sorta of see if this amp has any more faults before paying that much to repair. The other alpine's rects are good... Im going to start working on the other alpine (new thread) shortly.
Im almost temped to borrow the rectifiers from the other Alpine 3435 just to sorta of see if this amp has any more faults before paying that much to repair. The other alpine's rects are good... Im going to start working on the other alpine (new thread) shortly.
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These amps are relatively valuable, I'd think that it would be well worth spending $30 on.
If you have the MUR1620CT and MUR1620CTR, you can use those to allow further testing.
If you have the MUR1620CT and MUR1620CTR, you can use those to allow further testing.
The closest I think I've got to MUR1620CTx are a set of U1620x OnSemi rectifier transistors from a Bazooka EL1500 parts amp. They are TO-220 casing. They are cross-referencing to a NTE6240. Heres datasheet:
http://pdf1.alldatasheet.com/datasheet-pdf/view/10599/NTE/NTE6240.html
http://pdf1.alldatasheet.com/datasheet-pdf/view/10599/NTE/NTE6240.html
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Would this rectifier from ST work in place of the FMG-33x series? Digikey stocks these for about $3 each.
FMG-33R:
FMG-33R pdf, FMG-33R description, FMG-33R datasheets, FMG-33R view ::: ALLDATASHEET :::
STTH60P03S
http://www.st.com/internet/com/TECHNICAL_RESOURCES/TECHNICAL_LITERATURE/DATASHEET/CD00045915.pdf
FMG-33R:
FMG-33R pdf, FMG-33R description, FMG-33R datasheets, FMG-33R view ::: ALLDATASHEET :::
STTH60P03S
http://www.st.com/internet/com/TECHNICAL_RESOURCES/TECHNICAL_LITERATURE/DATASHEET/CD00045915.pdf
I don't know if that one will work. It appears to be a more specialized diode. I'd expect this one to work for the positive rectifier:
MUR3060WTGOS-ND
You'll still need the negative rectifier. It would likely cost less (when shipping is included in the cost) to simply order the two $10 rectifiers. Has the owner decided that $30 for the parts is too much?
MUR3060WTGOS-ND
You'll still need the negative rectifier. It would likely cost less (when shipping is included in the cost) to simply order the two $10 rectifiers. Has the owner decided that $30 for the parts is too much?
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