On the channel I thought was fixed:
It plays but it's very quiet (for this size of amp) and the drivers (MJE150xxs) get hot quick. One of them (the 15030) gets warm with the amp idling. Is that Ok? The 15031 doesn't.
I'm only seeing 0.0001 or 0.0004V dc across any of the emitter resistors. The amp's current draw is only 1.6 to 1.8A, so there can't be a short.
Thanks!
It plays but it's very quiet (for this size of amp) and the drivers (MJE150xxs) get hot quick. One of them (the 15030) gets warm with the amp idling. Is that Ok? The 15031 doesn't.
I'm only seeing 0.0001 or 0.0004V dc across any of the emitter resistors. The amp's current draw is only 1.6 to 1.8A, so there can't be a short.
Thanks!
With virtually no bias current, I wouldn't expect either driver to run hot at idle unless there's a leaking component.
If there is an equal number of outputs on the positive half and on the negative half of the channel, I'd expect to see the same voltage across each one.
Did you measure from the emitter resistor to the secondary center tap (or across the speaker terminals if the relays are engaging) to check for DC offset? Since it produces audio, I assume the DC offset is low but you need to confirm it.
With the gain control set to the maximum, you should see ~20x gain from the RCA input jack to pin 1/7 of IC 101/201. The power amplifier should produce a gain of ~3. Can you confirm that you're getting these gain levels?
If there is an equal number of outputs on the positive half and on the negative half of the channel, I'd expect to see the same voltage across each one.
Did you measure from the emitter resistor to the secondary center tap (or across the speaker terminals if the relays are engaging) to check for DC offset? Since it produces audio, I assume the DC offset is low but you need to confirm it.
With the gain control set to the maximum, you should see ~20x gain from the RCA input jack to pin 1/7 of IC 101/201. The power amplifier should produce a gain of ~3. Can you confirm that you're getting these gain levels?
Would you expect the leaking component to be the driver or an output? An output, right? Especially since the driver passed diode check earlier?
There are equal numbers of outputs on the pos and neg halves. I'm now measuring ~0.0004 volts on each resistor.
DC Offset on this channel: 0.8mV
Gain: Didn't bother to check cause it's obviously working now
There was a hairline break in a solder joint in the EQ standoff, so I re-soldered all of those joints.
Now just to figure out what's causing the MJE15030 driver to be slightly warm (32degC), and this channel will be done.
Question: if you preform a diode check on multiple transistors of the same type, should the reading on each check be close? For example, on each MJE15030 I've tested, the diode check read about 675. If one was to read say 500, could that indicate a potential problem even though it otherwise passes the diode check?
Thanks!
There are equal numbers of outputs on the pos and neg halves. I'm now measuring ~0.0004 volts on each resistor.
DC Offset on this channel: 0.8mV
Gain: Didn't bother to check cause it's obviously working now
There was a hairline break in a solder joint in the EQ standoff, so I re-soldered all of those joints.Now just to figure out what's causing the MJE15030 driver to be slightly warm (32degC), and this channel will be done.
Question: if you preform a diode check on multiple transistors of the same type, should the reading on each check be close? For example, on each MJE15030 I've tested, the diode check read about 675. If one was to read say 500, could that indicate a potential problem even though it otherwise passes the diode check?
Thanks!
Just noticed something odd in the channel that is working. I'm getting 0.7V across R232, which is the emitter resistor for MJE15031. That's not right. I read the resistor 200K!!!
Edit: Fixed it. Now both drivers (MJE15030 and MJE15031) get too warm to hold with the amp idling. About 45deg C.
Edit: Fixed it. Now both drivers (MJE15030 and MJE15031) get too warm to hold with the amp idling. About 45deg C.
Well, I went ahead and put all the outputs on the other side of the amp.
Both channels are working! However I still have 3 things here:
1) there is audible hiss on both channels with the amp turned up but otherwise idling.
2) All 4 MJE150xx parts get to around 42dec C at amp idle.
3) How do I now reset bias to the proper location?
Thanks Perry!!!
Both channels are working! However I still have 3 things here:
1) there is audible hiss on both channels with the amp turned up but otherwise idling.
2) All 4 MJE150xx parts get to around 42dec C at amp idle.
3) How do I now reset bias to the proper location?
Thanks Perry!!!
If the hiss isn't audible more than a few inches from the speaker, it may be normal. If it's louder than that, I'd suspect the crossover module. Pull the crossover module and bypass it (outer pins, jumped top to bottom on riser board). Does the noise stop?
I don't remember them getting hot in the amps I've worked on but doing a few rough calculations, I can see that it may be normal. Since the outputs were passing a very slight current, I assumed that they were on the threshold (probably ~0.4v). 0.4v across 22 ohms would be 0.018 amps through the drivers. With 55v of rail, that's nearly 1w which is enough to make them run hot without a sink.
For the biasing, I'd set it with the amp meter on your power supply. After you clamp all of the transistors to the sink, turn the biasing up until you see a VERY slight increase in current draw. If you want to set it with the voltage across the emitters, I'd set it to about 1mv. Run a high frequency (10-20k) signal at low voltage (~1v on the speaker outputs) and look for signs of notch/crossover distortion on the output. If it's clean, the bias is high enough.
I don't remember them getting hot in the amps I've worked on but doing a few rough calculations, I can see that it may be normal. Since the outputs were passing a very slight current, I assumed that they were on the threshold (probably ~0.4v). 0.4v across 22 ohms would be 0.018 amps through the drivers. With 55v of rail, that's nearly 1w which is enough to make them run hot without a sink.
For the biasing, I'd set it with the amp meter on your power supply. After you clamp all of the transistors to the sink, turn the biasing up until you see a VERY slight increase in current draw. If you want to set it with the voltage across the emitters, I'd set it to about 1mv. Run a high frequency (10-20k) signal at low voltage (~1v on the speaker outputs) and look for signs of notch/crossover distortion on the output. If it's clean, the bias is high enough.
Ok, that Kicker also had some bad SMPS output caps that would intermittently short. Replaced them and it works great so far.
Now I have another ZR1000. This one also had burned SMPS FETs. Replaced them and the SMPS works fine. I then had excessive current draw on the +15V rail. It's seemed like it's a short...
I found that U101, U201, U9, U102, and U202 were all getting hot so pulled them. After that I hooked power back up to check current draw. It went up to about 2 amps, something went pfft, and it only pulls 1 amp now, which is about right for just the SMPS... Except that I'm feeling some of the SOT23 transistors in the audio section warm up, which I never noticed in the other amp. Could that be because it's powered up without the opamps in place? I didn't think it would be a problem to do that, but maybe it is?
Thanks!
Now I have another ZR1000. This one also had burned SMPS FETs. Replaced them and the SMPS works fine. I then had excessive current draw on the +15V rail. It's seemed like it's a short...
I found that U101, U201, U9, U102, and U202 were all getting hot so pulled them. After that I hooked power back up to check current draw. It went up to about 2 amps, something went pfft, and it only pulls 1 amp now, which is about right for just the SMPS... Except that I'm feeling some of the SOT23 transistors in the audio section warm up, which I never noticed in the other amp. Could that be because it's powered up without the opamps in place? I didn't think it would be a problem to do that, but maybe it is?
Thanks!
When you pull components, you should be very cautious when powering up the amp. In some cases, the amp can become unstable and oscillate which can cause more damage.
Have you checked to see if the amp is oscillating with no input?
If not, there's a good chance that there is significant DC on the output.
Have you reinstalled all of the op-amps?
If so, does it produce audio? Check signal on the emitter resistors if the relays aren't engaging.
Was the voltage across the power supply pins of the op-amps more than 30v total?
Which IC is U9?
Have you checked to see if the amp is oscillating with no input?
If not, there's a good chance that there is significant DC on the output.
Have you reinstalled all of the op-amps?
If so, does it produce audio? Check signal on the emitter resistors if the relays aren't engaging.
Was the voltage across the power supply pins of the op-amps more than 30v total?
Which IC is U9?
Where do I check for oscillating? On the output of the final power amp stage?
Before doing any of the previously mentioned stuff, I pulled the MJE150 drive transistors so that the final output stage wouldn't be a cause of any problems. I've done that before on these amps with no problem...
I've got DC on one channel (I always forget to check for that), but the other one the MM goes crazy. Jumps from positive to negative voltage constantly. The output is oscillating without the MJE150 drivers installed.
The fuse on the inputs was blown.
I've not yet reinstalled the op-amps. Will do so later.
No, the voltage across the op-amps power pins was not more than 30V.
U9 is the TL074. It looks like U8 in the schematic, but the PCB says U9. This one is obviously bad. The others I'm not sure about. What's the easiest way to test the opamps? It's not like I can socket these SOIC packages... Or should I just replace them?
Are the fuses on the rca's gnd fast acting or slow blow type? And would it hurt anything if I ran wire and used a fuseholder and mounted it on the amp's side panel for easy replacement?
Before doing any of the previously mentioned stuff, I pulled the MJE150 drive transistors so that the final output stage wouldn't be a cause of any problems. I've done that before on these amps with no problem...
I've got DC on one channel (I always forget to check for that), but the other one the MM goes crazy. Jumps from positive to negative voltage constantly. The output is oscillating without the MJE150 drivers installed.
The fuse on the inputs was blown.
I've not yet reinstalled the op-amps. Will do so later.
No, the voltage across the op-amps power pins was not more than 30V.
U9 is the TL074. It looks like U8 in the schematic, but the PCB says U9. This one is obviously bad. The others I'm not sure about. What's the easiest way to test the opamps? It's not like I can socket these SOIC packages... Or should I just replace them?
Are the fuses on the rca's gnd fast acting or slow blow type? And would it hurt anything if I ran wire and used a fuseholder and mounted it on the amp's side panel for easy replacement?
In an amp that will power up, you would generally use a scope to confirm that the output signal on the op-amps is clean.
If you don't have a scope, you can use a multimeter to check the voltage on the two inputs of each op-amp. On an op-amp that's being used for audio, the voltage on the inverting input will match the voltage on the non-inverting input (within ~0.01v). There are rarely exceptions to this, especially when the output of the op-amp is not within 3-4 volts of the power supply voltage. If the op-amp has swung as far as possible the inputs may not match because the op-amp has run out of headroom/rail voltage or because the feedback loop is open.
If you have a scope, with no signal, the output on a class A, AB or B amp should be a perfectly clean straight line, generally at 0v DC. If you see any waveform that's more than ~1vp-p, the amp may be oscillating. Low voltage waveforms may be seen on the speaker outputs if power supply noise is entering the audio chain. If the waveform on the outputs is swinging rail to rail, it's definitely oscillating.
It's difficult to test for high frequency oscillation with a DMM unless the DMM has a wide bandwidth. If it does, you'll read significant AC voltage with no input signal.
For low frequency oscillation, you can sometimes see signs of oscillation (as you did here).
You check for oscillation on the speaker output terminals in most cases. In this amp, if the speaker protection relays are not engaging, you need to check for oscillation on the emitter resistors.
The DC and oscillation are likely due to the fact that the input of the power amplifier has no DC path to ground and is essentially floating. If you ground the open end of R107/207, the amplifier may idle at 0v DC with no oscillation. You'd have to replace the drivers. Monitor the temp of the outputs or set the bias to the minimum position to prevent the outputs from heating up.
Since the DC servo op-amps have been removed also, the DC may not drop to 0.000v (or whatever it would be with the op-amps in the circuit) but it should be well below 1v.
Mounting the fuse in a fuse holder shouldn't cause any problems. What were the markings on the fuse that was blown?
If you don't have a scope, you can use a multimeter to check the voltage on the two inputs of each op-amp. On an op-amp that's being used for audio, the voltage on the inverting input will match the voltage on the non-inverting input (within ~0.01v). There are rarely exceptions to this, especially when the output of the op-amp is not within 3-4 volts of the power supply voltage. If the op-amp has swung as far as possible the inputs may not match because the op-amp has run out of headroom/rail voltage or because the feedback loop is open.
If you have a scope, with no signal, the output on a class A, AB or B amp should be a perfectly clean straight line, generally at 0v DC. If you see any waveform that's more than ~1vp-p, the amp may be oscillating. Low voltage waveforms may be seen on the speaker outputs if power supply noise is entering the audio chain. If the waveform on the outputs is swinging rail to rail, it's definitely oscillating.
It's difficult to test for high frequency oscillation with a DMM unless the DMM has a wide bandwidth. If it does, you'll read significant AC voltage with no input signal.
For low frequency oscillation, you can sometimes see signs of oscillation (as you did here).
You check for oscillation on the speaker output terminals in most cases. In this amp, if the speaker protection relays are not engaging, you need to check for oscillation on the emitter resistors.
The DC and oscillation are likely due to the fact that the input of the power amplifier has no DC path to ground and is essentially floating. If you ground the open end of R107/207, the amplifier may idle at 0v DC with no oscillation. You'd have to replace the drivers. Monitor the temp of the outputs or set the bias to the minimum position to prevent the outputs from heating up.
Since the DC servo op-amps have been removed also, the DC may not drop to 0.000v (or whatever it would be with the op-amps in the circuit) but it should be well below 1v.
Mounting the fuse in a fuse holder shouldn't cause any problems. What were the markings on the fuse that was blown?
The fuse says TH. I know it's 1 amp from reading somewhere.
I have a scope, I'll replace the opamps and do the testing.
Thanks Perry, it would take me forever to fix these on my own. I'm hoping to learn enough on these (and a couple other broken amps I have) so I can graduate to a stack of broken Phoenix Gold Xenon amps I got from a guy on eBay, which I have plans to use on my own system. It's just those amps sort of worry me
They are so much more complicated, and none have visible problems and they have those blasted daughter cards! I don't want to screw them up more than they already are.
Side note: do you offer free updates to your repair tutorial? Or maybe shipping only charges? And do you have any Xenon specific data in there?
I have a scope, I'll replace the opamps and do the testing.
Thanks Perry, it would take me forever to fix these on my own. I'm hoping to learn enough on these (and a couple other broken amps I have) so I can graduate to a stack of broken Phoenix Gold Xenon amps I got from a guy on eBay, which I have plans to use on my own system. It's just those amps sort of worry me
They are so much more complicated, and none have visible problems and they have those blasted daughter cards! I don't want to screw them up more than they already are.Side note: do you offer free updates to your repair tutorial? Or maybe shipping only charges? And do you have any Xenon specific data in there?
The Littelfuse 468 series has a 1 amp marked TH. It's a slow blow.
http://www.littelfuse.com/data/en/Data_Sheets/468.pdf
What are the model numbers on the Xenon amps.
Email me directly about the tutorial.
babin_perry@yahoo.com
http://www.littelfuse.com/data/en/Data_Sheets/468.pdf
What are the model numbers on the Xenon amps.
Email me directly about the tutorial.
babin_perry@yahoo.com
Ok all op-amps are back in and I replaced the known bad and two others that looked possibly damaged. They were replaced with pulls that looked ok. I've got to make an order to digikey&mouser for new parts.
The amp is pulling high currents again. I've got current limited to 1.4A at the input. U102, U202 gets hot. The others don't.
No input on RCA. Tests as follows:
Output of U101: 15V clean line
Output of U201: 0V clean line
Output of U102: 7V clean line
Output of U202: 10V clean line
Output U9.A: 12.5V clean line
Output U9.B: 11.9V clean line
Output U9.C: 11.9V clean line
Output U9.D: 9V clean line
The amp is pulling high currents again. I've got current limited to 1.4A at the input. U102, U202 gets hot. The others don't.
No input on RCA. Tests as follows:
Output of U101: 15V clean line
Output of U201: 0V clean line
Output of U102: 7V clean line
Output of U202: 10V clean line
Output U9.A: 12.5V clean line
Output U9.B: 11.9V clean line
Output U9.C: 11.9V clean line
Output U9.D: 9V clean line
If you've jumped the input shield to the secondary center tap (or replaced the fuse), it looks like the op-amps are defective.
Pull the 2 that are getting hot to see how the others react.
There are 2 outputs for U101 and 201.
Are you sure you're using the correct pins for the output?
Pins 1 and 7 for the 072
Pin 6 for the 071
Are you using the secondary center tap on the power transformer for the reference (black meter lead)?
Pull the 2 that are getting hot to see how the others react.
There are 2 outputs for U101 and 201.
Are you sure you're using the correct pins for the output?
Pins 1 and 7 for the 072
Pin 6 for the 071
Are you using the secondary center tap on the power transformer for the reference (black meter lead)?
>If you've jumped the input shield to the secondary center tap (or replaced the fuse)...
Yes I did.
>There are 2 outputs for U101 and 201.
I used Pin 7 on both. Double checked. Same results.
>Are you sure you're using the correct pins for the output?
Yes. Double checked U102 and U202. Same results.
>Are you using the secondary center tap on the power transformer for the reference (black meter lead)?
Yes
I put audio to the input. U201 output audio with gain. U101 output nothing but a flat line. Since U201 worked, I checked U202. Nothing but a 10V flat line. Safe to say U101 and U202 are bad. I think I'll have to shelf this one until parts arrive.
I don't understand what U102 and U202 do? They invert the output from the power with what, a low pass filter? And feeds that to the input of the amp section? For what purpose? And I can't find where the "<" connector goes to.
THX
Yes I did.
>There are 2 outputs for U101 and 201.
I used Pin 7 on both. Double checked. Same results.
>Are you sure you're using the correct pins for the output?
Yes. Double checked U102 and U202. Same results.
>Are you using the secondary center tap on the power transformer for the reference (black meter lead)?
Yes
I put audio to the input. U201 output audio with gain. U101 output nothing but a flat line. Since U201 worked, I checked U202. Nothing but a 10V flat line. Safe to say U101 and U202 are bad. I think I'll have to shelf this one until parts arrive.
I don't understand what U102 and U202 do? They invert the output from the power with what, a low pass filter? And feeds that to the input of the amp section? For what purpose? And I can't find where the "<" connector goes to.
THX
kicker ZR360
Hey!!! i don't mean to interupt but i have a kixker ZR360 2 channel amp that plays tunes out of one channel and the other just gives out such a weird signal that makes my speaker move in and out weird. its not music its some kind of voltage. My 5th period teacher told me it could be a bad transistor. I keep thinking maybe its the module but that same module works good in my DX350 amp. Thanks
Hey!!! i don't mean to interupt but i have a kixker ZR360 2 channel amp that plays tunes out of one channel and the other just gives out such a weird signal that makes my speaker move in and out weird. its not music its some kind of voltage. My 5th period teacher told me it could be a bad transistor. I keep thinking maybe its the module but that same module works good in my DX350 amp. Thanks
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