This amp does work on all 5 channels, but is drawing too much current at idle, 5A. Other than that it seems to be working all except the class D sub channel has a pretty bad high pitched whine going on through a 6x9 test speaker, but it does play low frequencies otherwise. The whine could be from my source frequency generator though.
Oh. There is also +0.7vDC across RCA shield to center when no source is connected but that doesn't really seem to be mattering much.
What are these amps supposed to idle at?
Oh. There is also +0.7vDC across RCA shield to center when no source is connected but that doesn't really seem to be mattering much.
What are these amps supposed to idle at?
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Sub channel is oscillating at about 80Khz. My 34401A is also showing that as 0.6vAC. Im not sure if thats drive pulse though.
I believe I located the problem. There are 4 small 22uf non-polar electrolytic caps directly under the speaker wires. I didn't see them last night, but all 4 have busted tops and reading no capacitance. I replaced all 4 with a single 100uf 50v polar cap for testing and now the amp only draws 3A idle, which makes more sense as this is like 2 small amps in 1 chassis. Sub channel sounds clean as well now.
I need to order new 22uv 50v non-polar caps.
Still doesn't explain why RCA shields have about 1vDC on them rerferencing secondary ground.
I need to order new 22uv 50v non-polar caps.
Still doesn't explain why RCA shields have about 1vDC on them rerferencing secondary ground.
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Im back on this amp after replacing the 22uf 50v NP caps. The amp powers and idles at 3A of draw, but the PS fets get very hot within about 20 seconds.
To me, it seems like the primary PS transformer may be shorted across primary and secondary windings, as meter is finding all connections across all points of the transformer as dead shorted... But since this is an MTX PS I'm not totally sure. I dont see any burn marks. Also the PS driver transformer seems to have not overheated - it may be measuring funny though as all 4x points on one side of it are measuring shorted. The PS fets are measuring 62 ohms between gates and source legs. The drive signal on gates looks good for MTX. Any thoughts before I dismount the primary or driver transformer?
I know MTX are different PS altogether so looking for any advice.
To me, it seems like the primary PS transformer may be shorted across primary and secondary windings, as meter is finding all connections across all points of the transformer as dead shorted... But since this is an MTX PS I'm not totally sure. I dont see any burn marks. Also the PS driver transformer seems to have not overheated - it may be measuring funny though as all 4x points on one side of it are measuring shorted. The PS fets are measuring 62 ohms between gates and source legs. The drive signal on gates looks good for MTX. Any thoughts before I dismount the primary or driver transformer?
I know MTX are different PS altogether so looking for any advice.
This (PS FET heating) is normal for some MTX amps.
Some MTX amps have the secondary windings as added windings on the primary so there is no isolation. Here's the patent information.
US5598325A - Series coupled non-isolated bipolar transformer within automotive power amplifier
- Google Patents
Some MTX amps have the secondary windings as added windings on the primary so there is no isolation. Here's the patent information.
US5598325A - Series coupled non-isolated bipolar transformer within automotive power amplifier
- Google Patents