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#1
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Deaf Alesis HD24
As I was setting up to record a ~100 voice choir and ~50 piece
orchestra last weekend, I discovered that my HD24 (which I had converted to XR a few years ago) was deaf as a post. Everything else appeared to work just fine, but no analog input or output. (I don't have any way to test digital in/out). I unplugged everything and removed it from the case and opened it up (with my trusty Leatherman tool which hangs from my belt). The daughter-board that plugs onto the interior ends of the analog input and output boards was "hanging by a thread". Of course, there is no mechanical support for this board. It hangs off the lever-arm ends opposite from the input connectors (which are all that hold the analog boards). Now I know why people recommend more gentle transport practices and methods. :-( Alas, after re-connecting the daughter board, the HD24 no longer even recognizes the XR upgrade. In fact it acts exactly the same as if the whole analog section weren't even connected (I tried it). The daughter board powers the analog boards, and the power supply cable to the daughter board appeared to have the voltages that we would expect (although I don't know that it is actually documented publicly?) I re-seated all the ribbon and power connectors. I triple-checked to see that the daughter board was properly lined up with the input and output boards (as cautioned in the XR upgrade instructions) Someone brought a Zoom R16 which records 8 channels to an SD flash memory card. It worked OK, but the metering is really primitive and it was difficult to set decent levels. Dunno what I'm going to do about my HD24. I guess I will try putting the old (non-XR) boards back in to see if I can make a differential diagnosis of the problem location. |
#2
Posted to rec.audio.pro
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Deaf Alesis HD24
On Dec 24, 8:17*pm, "Richard Crowley" wrote:
As I was setting up to record a ~100 voice choir and ~50 piece orchestra last weekend, I discovered that my HD24 (which I had converted to XR a few years ago) was deaf as a post. Everything else appeared to work just fine, but no analog input or output. (I don't have any way to test digital in/out). I unplugged everything and removed it from the case and opened it up (with my trusty Leatherman tool which hangs from my belt). The daughter-board that plugs onto the interior ends of the analog input and output boards was "hanging by a thread". Of course, there is no mechanical support for this board. It hangs off the lever-arm ends opposite from the input connectors (which are all that hold the analog boards). Now I know why people recommend more gentle transport practices and methods. :-( Alas, after re-connecting the daughter board, the HD24 no longer even recognizes the XR upgrade. In fact it acts exactly the same as if the whole analog section weren't even connected (I tried it). The daughter board powers the analog boards, and the power supply cable to the daughter board appeared to have the voltages that we would expect (although I don't know that it is actually documented publicly?) I re-seated all the ribbon and power connectors. I triple-checked to see that the daughter board was properly lined up with the input and output boards (as cautioned in the XR upgrade instructions) Someone brought a Zoom R16 which records 8 channels to an SD flash memory card. It worked OK, but the metering is really primitive and it was difficult to set decent levels. Dunno what I'm going to do about my HD24. I guess I will try putting the old (non-XR) boards back in to see if I can make a differential diagnosis of the problem location. The first thing I would do is to check the analogue power supplies, which should be something around +15v and -15v. (possibly as high as +- 18v) If one or both voltages are not present in the analogue section, the machine may well behave as though there is no analogue circuitry present, while the computing section, running on 5volts, will be unaffected and even unaware the analogue section is not working. If the analogue section uses 8 pin DIL op-amps, this is the easiest place to check - select a convenient chip and carefully meter each of the 8 pins in turn, with the negative meter probe on a ground point. Make sure you don't short 2 pins together with the probe, or you could kill the chip. Gareth. |
#3
Posted to rec.audio.pro
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Deaf Alesis HD24
wrote ...
The first thing I would do is to check the analogue power supplies, which should be something around +15v and -15v. (possibly as high as +- 18v) If one or both voltages are not present in the analogue section, the machine may well behave as though there is no analogue circuitry present, while the computing section, running on 5volts, will be unaffected and even unaware the analogue section is not working. If the analogue section uses 8 pin DIL op-amps, this is the easiest place to check - select a convenient chip and carefully meter each of the 8 pins in turn, with the negative meter probe on a ground point. Make sure you don't short 2 pins together with the probe, or you could kill the chip. Thanks, Gareth. Alas, the analog I and O boards are all small-pitch SMD components, so the trusty method of checking VCC and VDD for +/-15V isn't quite as convenient. Now that I have it back home, I'll do some better troubleshooting ("fault-finding" has a different meaning over on this side of the Pond! :-) I'm going to try to see if I can discover what the nominal voltages on the power harness are supposed to be. The HD24 worked great on the 230V 50Hz in Romania, but now that it is back home here in 120V-land, maybe it has become wimpy? :-) (The switched-mode PS runs on 100-240v, no user control, so I didn't forget to set the power back.) The digital parts of the unit work perfectly, which would appear to indicate that the +5 is good. |
#4
Posted to rec.audio.pro
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Deaf Alesis HD24
On Dec 24, 9:22*pm, "Richard Crowley" wrote:
wrote ... The first thing I would do is to check the analogue power supplies, which should be something around +15v and -15v. *(possibly as high as +- 18v) *If one or both voltages are not present in the analogue section, the machine may well behave as though there is no analogue circuitry present, while the computing section, running on 5volts, will be unaffected and even unaware the analogue section is not working. If the analogue section uses 8 pin DIL *op-amps, this is the easiest place to check - select a convenient chip and carefully meter each of the 8 pins in turn, with the negative meter probe on a ground point. Make sure you don't short 2 pins together with the probe, or you could kill the chip. Thanks, Gareth. *Alas, the analog I and O boards are all small-pitch SMD components, so the trusty method of checking VCC and VDD for +/-15V isn't quite as convenient. *Now that I have it back home, I'll do some better troubleshooting ("fault-finding" has a different meaning over on this side of the Pond! :-) *I'm going to try to see if I can discover what the nominal voltages on the power harness are supposed to be. The HD24 worked great on the 230V 50Hz in Romania, but now that it is back home here in 120V-land, maybe it has become wimpy? :-) (The switched-mode PS runs on 100-240v, no user control, so I didn't forget to set the power back.) *The digital parts of the unit work perfectly, which would appear to indicate that the +5 is good. Well in that case you should measure every pin coming off the Power Supply. If you don't find + and - something around 15 volts, then you have found the problem. I wouldn't even bother trying to establish the exact nominal voltages, they will either be present or absent. Good luck! Gareth. |
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