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Post by Tbone81 on Nov 19, 2019 20:35:17 GMT -6
I needs some help troubleshooting a problem. I bought an Ampeg portaflex 210, used. I found a pf-500, b-stock (site stated it was previously owned) on Alto Music for a really good price. I purchased it and upon plugging it in the pf-500 immediately clipped (even though it was at a way low volume), went into protection mode and ceased to work. There is a well known issue with the pf-350/500 that's documented all over the web. Basically the early revisions had this issue. So I returned it, and Alto graciously sent me a brand new pf-500 as a replacement.
Now, heres wear the head scratching begins...I plug the new amp head in and it starts clipping immediately. It doesn't go into protection mode, but it does cut out for a second every time it clips. It happens with the volume and/or gain at very low levels. I was about to loose my shit and curse these new school class D amps but decided to try it on another cab. So I wired up the pf-500 head to two 16 ohm guitar cabs (i don't currently have any other bass cabs), and bam! Works perfectly, doesn't clip, doesn't cut out, its nice and loud at not even half volume. So then I try running a guitar head, at 8 ohms, in the bass cab (which is also 8 ohms), and even with the guitar amp cranked the cab is barely making a sound.
So now I'm left wondering wtf is going on with this bass cab? The speakers are plugged in, all physical connections (both in and outside the amp) feel to be seated securely. But how is it that this cabinet is barely passing any sound? And is the cab that was actually clipping and not my amp? I'm thinking maybe there is something defective in the crossover causing it cut out.
I already ruled out issues with my bass, cables, and speaker cables.
Any suggestions? If I pull the crossover out what should I be looking for?
Thanks in advance.
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Post by johneppstein on Nov 19, 2019 20:47:27 GMT -6
I needs some help troubleshooting a problem. I bought an Ampeg portaflex 210, used. I found a pf-500, b-stock (site stated it was previously owned) on Alto Music for a really good price. I purchased it and upon plugging it in the pf-500 immediately clipped (even though it was at a way low volume), went into protection mode and ceased to work. There is a well known issue with the pf-350/500 that's documented all over the web. Basically the early revisions had this issue. So I returned it, and Alto graciously sent me a brand new pf-500 as a replacement.
Now, heres wear the head scratching begins...I plug the new amp head in and it starts clipping immediately. It doesn't go into protection mode, but it does cut out for a second every time it clips. It happens with the volume and/or gain at very low levels. I was about to loose my shit and curse these new school class D amps but decided to try it on another cab. So I wired up the pf-500 head to two 16 ohm guitar cabs (i don't currently have any other bass cabs), and bam! Works perfectly, doesn't clip, doesn't cut out, its nice and loud at not even half volume. So then I try running a guitar head, at 8 ohms, in the bass cab (which is also 8 ohms), and even with the guitar amp cranked the cab is barely making a sound.
So now I'm left wondering wtf is going on with this bass cab? The speakers are plugged in, all physical connections (both in and outside the amp) feel to be seated securely. But how is it that this cabinet is barely passing any sound? And is the cab that was actually clipping and not my amp? I'm thinking maybe there is something defective in the crossover causing it cut out.
I already ruled out issues with my bass, cables, and speaker cables.
Any suggestions? If I pull the crossover out what should I be looking for?
Thanks in advance.
I'm not totally familiar with the new Mackie ("Ampeg") stuff, but what is the connector used on the speaker cab?
BTW, cabs don't clip in any normal sense (not like amps.). If there's a partial short, that's another matter. Hve you measured the DC resistance across the speaker?
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Post by Tbone81 on Nov 19, 2019 20:49:03 GMT -6
I needs some help troubleshooting a problem. I bought an Ampeg portaflex 210, used. I found a pf-500, b-stock (site stated it was previously owned) on Alto Music for a really good price. I purchased it and upon plugging it in the pf-500 immediately clipped (even though it was at a way low volume), went into protection mode and ceased to work. There is a well known issue with the pf-350/500 that's documented all over the web. Basically the early revisions had this issue. So I returned it, and Alto graciously sent me a brand new pf-500 as a replacement.
Now, heres wear the head scratching begins...I plug the new amp head in and it starts clipping immediately. It doesn't go into protection mode, but it does cut out for a second every time it clips. It happens with the volume and/or gain at very low levels. I was about to loose my shit and curse these new school class D amps but decided to try it on another cab. So I wired up the pf-500 head to two 16 ohm guitar cabs (i don't currently have any other bass cabs), and bam! Works perfectly, doesn't clip, doesn't cut out, its nice and loud at not even half volume. So then I try running a guitar head, at 8 ohms, in the bass cab (which is also 8 ohms), and even with the guitar amp cranked the cab is barely making a sound.
So now I'm left wondering wtf is going on with this bass cab? The speakers are plugged in, all physical connections (both in and outside the amp) feel to be seated securely. But how is it that this cabinet is barely passing any sound? And is the cab that was actually clipping and not my amp? I'm thinking maybe there is something defective in the crossover causing it cut out.
I already ruled out issues with my bass, cables, and speaker cables.
Any suggestions? If I pull the crossover out what should I be looking for?
Thanks in advance.
I'm not totally familiar with the new Mackie ("Ampeg") stuff, but what is the connector used on the speaker cab? 1/4", TS. You think its as simple as a bad contact? |
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Post by johneppstein on Nov 19, 2019 20:54:49 GMT -6
I'm not totally familiar with the new Mackie ("Ampeg") stuff, but what is the connector used on the speaker cab? 1/4", TS. You think its as simple as a bad contact? Well, I'd say it's worth checking with an ohmmeter, for sure. Might not be a bad contact - could also be a partially blown speaker with the VC shorting out. Or bad solder/frayed wire on the jack creating a partial short.
I'd do a thorough examinalion of the cab. That may or may not be it, but it's a good place to start. I was taught to start at the end and work back from there.
The old Portaflex cabs had a 4 pin xlr with the two middle pins wired so that if a speaker wasn't connected it put the amp into standby, but you're obviously isn't one of those.
The amp going into protect suggests at least a partial short.
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Post by svart on Nov 19, 2019 20:55:59 GMT -6
What's the bass cabinet? A lot of bass cabs are 2 or 4 ohms.
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Post by Tbone81 on Nov 19, 2019 20:58:26 GMT -6
What's the bass cabinet? A lot of bass cabs are 2 or 4 ohms. The Cabinet is a portaflex pf-210, 8 ohms. The amp (a pf-500) also runs at 8 ohms (or 4ohm). |
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Post by Tbone81 on Nov 19, 2019 21:00:26 GMT -6
1/4", TS. You think its as simple as a bad contact? Well, I'd say it's worth checking with an ohmmeter, for sure. Might not be a bad contact - could also be a partially blown speaker with the VC shorting out.
I'd do a thorough examinalion of the cab. That may or may not be it, but it's a good place to start. I was taught to start at the end and work back from there.
Thanks, from looking inside the amp it appears the speakers are fine, but I think I'm going to have to pull them out to be sure. I'll try that. |
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Post by svart on Nov 19, 2019 21:05:37 GMT -6
Is it clearly clipping, or could it be the voice coil chattering against the magnet assembly?
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Post by johneppstein on Nov 19, 2019 21:09:12 GMT -6
Have you tried the cab with a different amp?
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Post by Tbone81 on Nov 19, 2019 21:12:42 GMT -6
Have you tried the cab with a different amp? Yes, I don’t have another bass amp so I tried a 30watt guitar head, at 8ohms, into the cab. Sound barely came out. |
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Post by Tbone81 on Nov 19, 2019 21:14:29 GMT -6
Is it clearly clipping, or could it be the voice coil chattering against the magnet assembly? At this point I’m not sure. It sounds like clipping to me. When it happens all sound completely cuts out for a second. |
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Post by svart on Nov 19, 2019 21:17:52 GMT -6
Hmm. If the voice coil is hitting, it could be shorting and causing the amp to go into current limiting for a second.
Sometimes I've seen some magnet assemblies come free from being glued to the basket or otherwise shift slightly if they were dropped and aren't welded or bolted. Can you see if the magnets look centered, or maybe see if you can move one of them?
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Post by Tbone81 on Nov 19, 2019 22:10:16 GMT -6
Hmm. If the voice coil is hitting, it could be shorting and causing the amp to go into current limiting for a second. Sometimes I've seen some magnet assemblies come free from being glued to the basket or otherwise shift slightly if they were dropped and aren't welded or bolted. Can you see if the magnets look centered, or maybe see if you can move one of them? Just pulled both speakers. They both appear to be fine. Magnets are secure and centered, no obvious signs of being blown. |
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Post by Tbone81 on Nov 20, 2019 14:41:36 GMT -6
I needs some help troubleshooting a problem. I bought an Ampeg portaflex 210, used. I found a pf-500, b-stock (site stated it was previously owned) on Alto Music for a really good price. I purchased it and upon plugging it in the pf-500 immediately clipped (even though it was at a way low volume), went into protection mode and ceased to work. There is a well known issue with the pf-350/500 that's documented all over the web. Basically the early revisions had this issue. So I returned it, and Alto graciously sent me a brand new pf-500 as a replacement.
Now, heres wear the head scratching begins...I plug the new amp head in and it starts clipping immediately. It doesn't go into protection mode, but it does cut out for a second every time it clips. It happens with the volume and/or gain at very low levels. I was about to loose my shit and curse these new school class D amps but decided to try it on another cab. So I wired up the pf-500 head to two 16 ohm guitar cabs (i don't currently have any other bass cabs), and bam! Works perfectly, doesn't clip, doesn't cut out, its nice and loud at not even half volume. So then I try running a guitar head, at 8 ohms, in the bass cab (which is also 8 ohms), and even with the guitar amp cranked the cab is barely making a sound.
So now I'm left wondering wtf is going on with this bass cab? The speakers are plugged in, all physical connections (both in and outside the amp) feel to be seated securely. But how is it that this cabinet is barely passing any sound? And is the cab that was actually clipping and not my amp? I'm thinking maybe there is something defective in the crossover causing it cut out.
I already ruled out issues with my bass, cables, and speaker cables.
Any suggestions? If I pull the crossover out what should I be looking for?
Thanks in advance.
I'm not totally familiar with the new Mackie ("Ampeg") stuff, but what is the connector used on the speaker cab?
BTW, cabs don't clip in any normal sense (not like amps.). If there's a partial short, that's another matter. Hve you measured the DC resistance across the speaker?
Resistance across each speaker appears to be normal. I pulled the speakers. I'm going to bypass the crossover and hook up the amp to the speakers directly to see how they perform. |
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Post by svart on Nov 20, 2019 14:47:22 GMT -6
Have you tried the cab with a different amp? Yes, I don’t have another bass amp so I tried a 30watt guitar head, at 8ohms, into the cab. Sound barely came out. Oh I didn't see this post. That's a smoking gun that there's something wrong with the cab. It should be as loud as any other speaker/cab with the guitar head. My final guess is that the crossover probably has a bad solder joint or something that's arcing or vibrating and touching occasionally.. |
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Post by johneppstein on Nov 20, 2019 16:16:08 GMT -6
Have you tried the cab with a different amp? Yes, I don’t have another bass amp so I tried a 30watt guitar head, at 8ohms, into the cab. Sound barely came out. That's not good - you should get a good level with a 30 watt head, guitar or not. I'd suspect a partial short somewhere, possibly a frozen voice coil. If you have an ohmmeter check the DC resistance - for an 8 ohm cab it should read about 6 ohms. Look over the wiring, make sure nothings touching where it shouldn't. If you don't have a meter, test the speakers with a 9 volt battery. If the cones don't give a healthy jump they're bad. |
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Post by johneppstein on Nov 20, 2019 16:19:48 GMT -6
I'm not totally familiar with the new Mackie ("Ampeg") stuff, but what is the connector used on the speaker cab?
BTW, cabs don't clip in any normal sense (not like amps.). If there's a partial short, that's another matter. Hve you measured the DC resistance across the speaker?
Resistance across each speaker appears to be normal. I pulled the speakers. I'm going to bypass the crossover and hook up the amp to the speakers directly to see how they perform. Good idea. I forgot about the crossover - could be a shorted cap. If the speakers are still out of the cab, press gently on the cones to make sure one or both are not frozen or scraping. Keep the pressure balanced and be gentle. |
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Post by Tbone81 on Nov 20, 2019 16:36:59 GMT -6
Resistance across each speaker appears to be normal. I pulled the speakers. I'm going to bypass the crossover and hook up the amp to the speakers directly to see how they perform. Good idea. I forgot about the crossover - could be a shorted cap. If the speakers are still out of the cab, press gently on the cones to make sure one or both are not frozen or scraping. Keep the pressure balanced and be gentle. Thanks for all the help guys, I hooked up the amp directly to the speakers (bypassing the crossover) and it works and sounds great. So that narrows it down to the crossover. The crossover pcb has silicon poured over all the metal legs of each resister/cap etc. this makes it hard to test out each component with my multi meter. I’ve tried testing the solder points on the underside of the pcb but it’s difficult to get good contact and since I can’t see the tracings from underneath, it’s a pita. Any suggestions? |
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Post by johneppstein on Nov 20, 2019 17:07:04 GMT -6
Good idea. I forgot about the crossover - could be a shorted cap. If the speakers are still out of the cab, press gently on the cones to make sure one or both are not frozen or scraping. Keep the pressure balanced and be gentle. Thanks for all the help guys, I hooked up the amp directly to the speakers (bypassing the crossover) and it works and sounds great. So that narrows it down to the crossover. The crossover pcb has silicon poured over all the metal legs of each resister/cap etc. this makes it hard to test out each component with my multi meter. I’ve tried testing the solder points on the underside of the pcb but it’s difficult to get good contact and since I can’t see the tracings from underneath, it’s a pita. Any suggestions? Nothing that shouldn't be obvious. I hate it when they do that, but it's probably to try to keep parts from breaking loose when the cab gets banged around - or to make people buy a new crossover if it goes bad.
I'd start by going over each solder joint, heating it up and adding a little fresh solder.
As far as removing the goop, I'd need to know what kind of goop it is. If it's silicone caulk style goop you can probably get a start on it by cutting it off with an X-Acto knife but I'm not sure what to do about the thin residual left on the surface. Speaking of silicone caulk - you should avoid using garden variety silicone goo you get at the hardware store because it oucasses acetic acid for a long time after curing and that's bad for circuitry. There are versions available specifically for electronics to avoid that.
If it's epoxy based, good luck. There are many types of epoxy and while there are solvents for some they don't work for all and may be bad for electronic components.
If you can get at the leads on the component side - if they're not totally covered in gunk - and you find a part that tests bad you can use an old service tech trick to replace it - clip the leads above the board, leaving enough to be able to form a tiny loop or hook with your needlenose pliers. Install the new part by making complementary little hooks in the leads interlocked with the ones sticking out of the board. Crimp the hooks tight around each other and solder. A bit messy looking but it works. You'll want to heat sink both the component lead (obviously) and the stubs sticking out of the board to maintain integrity of the joints between stub and board.
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Post by Tbone81 on Nov 20, 2019 19:42:40 GMT -6
Thanks for all the help guys, I hooked up the amp directly to the speakers (bypassing the crossover) and it works and sounds great. So that narrows it down to the crossover. The crossover pcb has silicon poured over all the metal legs of each resister/cap etc. this makes it hard to test out each component with my multi meter. I’ve tried testing the solder points on the underside of the pcb but it’s difficult to get good contact and since I can’t see the tracings from underneath, it’s a pita. Any suggestions? Nothing that shouldn't be obvious. I hate it when they do that, but it's probably to try to keep parts from breaking loose when the cab gets banged around - or to make people buy a new crossover if it goes bad.
I'd start by going over each solder joint, heating it up and adding a little fresh solder.
As far as removing the goop, I'd need to know what kind of goop it is. If it's silicone caulk style goop you can probably get a start on it by cutting it off with an X-Acto knife but I'm not sure what to do about the thin residual left on the surface. Speaking of silicone caulk - you should avoid using garden variety silicone goo you get at the hardware store because it oucasses acetic acid for a long time after curing and that's bad for circuitry. There are versions available specifically for electronics to avoid that.
If it's epoxy based, good luck. There are many types of epoxy and while there are solvents for some they don't work for all and may be bad for electronic components.
If you can get at the leads on the component side - if they're not totally covered in gunk - and you find a part that tests bad you can use an old service tech trick to replace it - clip the leads above the board, leaving enough to be able to form a tiny loop or hook with your needlenose pliers. Install the new part by making complementary little hooks in the leads interlocked with the ones sticking out of the board. Crimp the hooks tight around each other and solder. A bit messy looking but it works. You'll want to heat sink both the component lead (obviously) and the stubs sticking out of the board to maintain integrity of the joints between stub and board.
Thanks, for now I'm going to wire a normal TS jack to the cab and bypass the crossover...that'll be a project for another day, and honestly I dont give a shit about using the horn.
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Post by johneppstein on Nov 20, 2019 21:48:39 GMT -6
Nothing that shouldn't be obvious. I hate it when they do that, but it's probably to try to keep parts from breaking loose when the cab gets banged around - or to make people buy a new crossover if it goes bad.
I'd start by going over each solder joint, heating it up and adding a little fresh solder.
As far as removing the goop, I'd need to know what kind of goop it is. If it's silicone caulk style goop you can probably get a start on it by cutting it off with an X-Acto knife but I'm not sure what to do about the thin residual left on the surface. Speaking of silicone caulk - you should avoid using garden variety silicone goo you get at the hardware store because it oucasses acetic acid for a long time after curing and that's bad for circuitry. There are versions available specifically for electronics to avoid that.
If it's epoxy based, good luck. There are many types of epoxy and while there are solvents for some they don't work for all and may be bad for electronic components.
If you can get at the leads on the component side - if they're not totally covered in gunk - and you find a part that tests bad you can use an old service tech trick to replace it - clip the leads above the board, leaving enough to be able to form a tiny loop or hook with your needlenose pliers. Install the new part by making complementary little hooks in the leads interlocked with the ones sticking out of the board. Crimp the hooks tight around each other and solder. A bit messy looking but it works. You'll want to heat sink both the component lead (obviously) and the stubs sticking out of the board to maintain integrity of the joints between stub and board.
Thanks, for now I'm going to wire a normal TS jack to the cab and bypass the crossover...that'll be a project for another day, and honestly I dont give a shit about using the horn.
IMO they sound better WITHOUT the horn. But I've been getting a lot of flak about being hypercritical (sorry, everybody), so I'm trying to not be. Which is why didn't mention it before... |
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