Amp is going in and out of protect causing the relay to engage and disengage.With all output out of circuit it stays out of protect.
I tried new outputs to rule out leaky once but still protect.
Any ideas?
I tried new outputs to rule out leaky once but still protect.
Any ideas?
Until papaZBill can help...
Check the signal on the output inductors before the relay. You'll likely see a lot of DC offset as the amp tries to power up.
If so, check the 12v Zeners that are in the driver section. Many times they go leaky and they won't provide the 12v for the drive circuit.
Check the signal on the output inductors before the relay. You'll likely see a lot of DC offset as the amp tries to power up.
If so, check the 12v Zeners that are in the driver section. Many times they go leaky and they won't provide the 12v for the drive circuit.
That's a good start. The 12 volt zeners are notorious for becoming leaky.
If you can post pics, It will help determine what version to advice further if necessary.
If you can post pics, It will help determine what version to advice further if necessary.
When you say you replaced all 8 zeners, I think you are referring to the 1N4148's sm you replaced with through holes correct?
The D107,D108,D120,D121 are the 12v zeners Perry referred to. Did you determine if they have approximately 12v across them?
If R215-120 ohm and R204-220 ohm are bad the associated drivers KTA1381 and KTC3503 may be damaged and should be replaced.
Yep,I thought they were the zeners when i found one open.
I will put in the correct parts and change the drivers .
I will put in the correct parts and change the drivers .
I don't have the drivers,can I used the C2690A/A1220A
https://www.fairchildsemi.com/datasheets/KS/KSC2690A.pdf
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https://www.fairchildsemi.com/datasheets/KS/KSC2690A.pdf
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I don’t have any experience with using these devices in this particular application. I believe these devices are more suitable for linear applications, such as Class A/B drivers, not as Class D driver.
Perry or someone else may be able to recommend a better replacement or confirm if they are a good replacement
Perry or someone else may be able to recommend a better replacement or confirm if they are a good replacement
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I can't say that I've used these in this amp but if they don't run hotter than the originals in the other drive circuit, I'd expect them to be OK.
The current rating is higher but they may not perform as well at the switching frequency of the output stage.
When burning the amp in, also make sure that both sets of output transistors operate at about the same temperature. If one side runs hotter, it could be because the drive circuit isn't producing a clean drive signal.
The current rating is higher but they may not perform as well at the switching frequency of the output stage.
When burning the amp in, also make sure that both sets of output transistors operate at about the same temperature. If one side runs hotter, it could be because the drive circuit isn't producing a clean drive signal.
I change the drivers and zeners,also put back the 1n4181s.
The amp is still cycling in and out of protect.All four zeners have 12v across them.
The amp is still cycling in and out of protect.All four zeners have 12v across them.
There is a way to disable protection, which requires lifting a resistor. When I get a chance I will advice.
Lift R35 to disable protection. Monitor the outputs and P.S. mosfets for excessive heat when testing. If necessary remove outputs to test amp.
Protection disable,I see full rail voltage on the output terminals.
Nothing is heating up.The outputs and drivers are new.I see 2 IRF640 on each
side of the board with more 9640s, that is correct?
What to check next?
Nothing is heating up.The outputs and drivers are new.I see 2 IRF640 on each
side of the board with more 9640s, that is correct?
What to check next?
Virtually all of the amps that use this class D circuit have unequal N and P-channel FETs. You can see the grouping by the connections to the rails. The two N-channels have their source legs on the negative rail. The three P-channel have their source legs on the positive rail. You can see the basic circuit by downloading the JBL BP1200.1 service manual which is available at various sites online (or in the JBL folder if you have the tutorial).
If your are seeing full rail voltages(approx. +/-71 volts) on the outside legs of all outputs. (Bank of 2 IRF640's and bank of 3 IRF9640's on either side) the amp is not oscillating.
Check the DC voltages around the LM361 and look at the signal on Pins 4,11 and post.
If you haven't done so, check the +/- 12v regulator voltages. You can check them off the Preamp board header pins. If I'm not mistaken this is a older version and you should have five pins on the preamp board, newer version will have 9 pins. Check all pins and post.
Check the DC voltages around the LM361 and look at the signal on Pins 4,11 and post.
If you haven't done so, check the +/- 12v regulator voltages. You can check them off the Preamp board header pins. If I'm not mistaken this is a older version and you should have five pins on the preamp board, newer version will have 9 pins. Check all pins and post.
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