Hi folks, long time no see! I moved about 5 years ago and I just finally finished enough of a remodel to get my electronics lab back in some semblance of order.
I started to tinker with some of my basket case amps this summer (I have a horrible habit of buying nearly any broken amp I find that has a reasonable price). I have a pair of Directed 1100d's, the newer case style, that I bought from the same guy. Both amps have the same issue, they power up fine but have no audio.
These amps are physically in perfect condition, but I have been holding off on working on them because I don't have a lot of experience with class D amps. I did buy Perry's repair tutorial probably 6 years ago now and armed with that I started troubleshooting these amps.
From what I can tell they both have exactly the same problem and I think it is in the pre-amp section. According to the amp tutorial, I have the proper square and triangle wave, however, what I have found is that I have no audio on pin 3 of the differential op amp. I have a rock solid triangle wave on pin 4, but I get what looks like a ghost of a 80khz sine wave on pin 3. I've seen this sine wave elsewhere while probing as well and I am 99% certain it is rf noise from some electronically ballasted lights.
Anyhow, questions, can I drive pin 3 of the dif op amp directly? Does anyone else have any pointers for what to look at in the pre-amp section? The pre-amp seems to have a floating ground, there is no connection between the RCA shield and the secondary center tap. Also, I can probe the first few op amps in the pre-amp and follow audio with the amp powered down, but with power on I can not get audio on any pins of the op amps. I know that feedback could make it impossible to see the audio on an input, but there is nothing resembling audio on the outputs either. I don't have a schematic to work off from and even though the pre-amp is fairly simple, it is all packed into a small area and has a lot of junk I normally don't mess with, like the master/slave functionality-- I guess that switch reconfigures the inputs for different behavior and very well might be the source of these issues. I am pretty sure these amps were either a strapped or bridged pair before I got them.
Any help would be greatly appreciated. Thank you all in advance!
Sincerely,
Jason
I started to tinker with some of my basket case amps this summer (I have a horrible habit of buying nearly any broken amp I find that has a reasonable price). I have a pair of Directed 1100d's, the newer case style, that I bought from the same guy. Both amps have the same issue, they power up fine but have no audio.
These amps are physically in perfect condition, but I have been holding off on working on them because I don't have a lot of experience with class D amps. I did buy Perry's repair tutorial probably 6 years ago now and armed with that I started troubleshooting these amps.
From what I can tell they both have exactly the same problem and I think it is in the pre-amp section. According to the amp tutorial, I have the proper square and triangle wave, however, what I have found is that I have no audio on pin 3 of the differential op amp. I have a rock solid triangle wave on pin 4, but I get what looks like a ghost of a 80khz sine wave on pin 3. I've seen this sine wave elsewhere while probing as well and I am 99% certain it is rf noise from some electronically ballasted lights.
Anyhow, questions, can I drive pin 3 of the dif op amp directly? Does anyone else have any pointers for what to look at in the pre-amp section? The pre-amp seems to have a floating ground, there is no connection between the RCA shield and the secondary center tap. Also, I can probe the first few op amps in the pre-amp and follow audio with the amp powered down, but with power on I can not get audio on any pins of the op amps. I know that feedback could make it impossible to see the audio on an input, but there is nothing resembling audio on the outputs either. I don't have a schematic to work off from and even though the pre-amp is fairly simple, it is all packed into a small area and has a lot of junk I normally don't mess with, like the master/slave functionality-- I guess that switch reconfigures the inputs for different behavior and very well might be the source of these issues. I am pretty sure these amps were either a strapped or bridged pair before I got them.
Any help would be greatly appreciated. Thank you all in advance!
Sincerely,
Jason
The JBL BP1200.1 service manual (in the JBL folder of the tutorial) is a good reference for most of the amp beyond the preamp circuit.
There have been some problems with the solder connections of the preamp boards. That should be checked.
Using the BP1200 diagram as a reference, point 'A' is the input to the class D amp. You need to find the corresponding point in your amp. If that's the point you're referring to as 'pin3' and you have no audio there, the problem is likely before the class D section.
There have been some problems with the solder connections of the preamp boards. That should be checked.
Using the BP1200 diagram as a reference, point 'A' is the input to the class D amp. You need to find the corresponding point in your amp. If that's the point you're referring to as 'pin3' and you have no audio there, the problem is likely before the class D section.
Well, I got one working. It was the crossover cards. I had resoldered them once because it looked like a couple of the solder connections had cracked. This time I desoldered them completely and checked the boards for cracks. No cracks, but one of the pads had lifted from the board, I think it was the issue. I cleaned out the via and made a jumper wire and put it back together and we have audio now. In fact, I blew a little 8" driver because I wasn't really expecting it to come up full tilt. Note to self, check gains before applying power...
Thanks for the help Perry. I will tackle the other one on my next days off, but I suspect it is going to have a similar failure.
Sincerely,
Jason Campbell
Thanks for the help Perry. I will tackle the other one on my next days off, but I suspect it is going to have a similar failure.
Sincerely,
Jason Campbell
the original bbq case 1100d's are my favorite..... that being said, the 2 biggest things i've seen with them, are problems from rca grounding (they seem to be able to pass a good deal of current for a while over others) and fragile solder joints throughout..... it's been years, but i wanna say it has been simple as a burned up case ground inside. one of the next amps i'm working on when i get some time is a 2nd gen case 750d (essentially a gen 1 600d) so, i'll try to get on it and let you know what i find, since i know for a fact it ran for weeks on virtually no chassis ground current before i got a hold of the car.
I remember those ones. I couldn't believe they packed that much power for the size. At the same time as we installed a pair of those in a guys blazer, I had just bought a brand new Phoenix Gold MS1000TA. I remember thinking that there was no way these little cheesy looking amps can put out more than twice the power of my MS1K in a quarter of the footprint.
Turns out they could... Man, times were really changing quickly back then.
Anyhow, I fixed the other one the other day. It was the same failure. I took a few pics with a usb microscope of the connections. There were more broken than these two, but they all look about the same...
Later,
Jason
Turns out they could... Man, times were really changing quickly back then.
Anyhow, I fixed the other one the other day. It was the same failure. I took a few pics with a usb microscope of the connections. There were more broken than these two, but they all look about the same...
Later,
Jason
Could u please give me some onsite on my problem. 1100d will not switch back from slave I got a pair of 1100d from a scrap mantle other seemed to work didn't play much until I got my scooter hooked up.input RCA's nothing butthe slave rca it makes some thing of a sound but controls dont work.
Please don't post in a repair thread that was started by someone else unless you are trying to help them.
Start a new thread if you need help with a repair of your own.
Start a new thread if you need help with a repair of your own.