Hi all,
I will document on this thread the repair of my K1800FX, which died suddently on my last gig.
There was no hint of it going to die nor it was being abused.
I got this 2009 unit used, just a couple months ago, but it was in very good shape and with low hours on it.
![Click image for larger version
Name: IMG_20230514_090717.jpg
Views: 444
Size: 2.39 MB
ID: 982556](filedata/fetch?id=982556&d=1684400634&type=medium)
![Click image for larger version
Name: IMG_20230514_101121.jpg
Views: 452
Size: 3.20 MB
ID: 982557](filedata/fetch?id=982557&d=1684400649&type=medium)
Accessing to the PA electronics through the speaker hole:
![Click image for larger version
Name: IMG_20230514_102747.jpg
Views: 454
Size: 3.45 MB
ID: 982558](filedata/fetch?id=982558&d=1684400732&type=medium)
![Click image for larger version
Name: IMG_20230514_102742.jpg
Views: 444
Size: 2.72 MB
ID: 982559](filedata/fetch?id=982559&d=1684400754&type=medium)
The LPA1180 Rev. J amplifier:
![Click image for larger version
Name: IMG_20230514_104440.jpg
Views: 459
Size: 2.51 MB
ID: 982560](filedata/fetch?id=982560&d=1684400781&type=medium)
A general view of my main workbench, with the amplifier on it;
![Click image for larger version
Name: IMG_20230514_104859.jpg
Views: 446
Size: 3.47 MB
ID: 982562](filedata/fetch?id=982562&d=1684400803&type=medium)
This is the PCB, trace side:
![Click image for larger version
Name: IMG_20230514_105513.jpg
Views: 452
Size: 2.38 MB
ID: 982563](filedata/fetch?id=982563&d=1684400860&type=medium)
Only hint so far I have found that may explain the failure,,, If you enlarge the picture, you can see some embedded metal part on the silicone grease of that transistor:
![Click image for larger version
Name: IMG_20230514_105528.jpg
Views: 454
Size: 1.05 MB
ID: 982564](filedata/fetch?id=982564&d=1684400917&type=medium)
The PA with the drivers and power transistors removed. Both power transistors are shorted. Drivers measure fine on my PEAK DCA75:
![Click image for larger version
Name: IMG_20230514_112021.jpg
Views: 448
Size: 1.93 MB
ID: 982565](filedata/fetch?id=982565&d=1684400946&type=medium)
I have checked all the diodes and capacitors (for ESR and capacity), and all measure OK. I have also powered the amplifier without the power transistors, and the +5, +15 and -15Vdc rails are present and the control panel LEDs light nicely.
So I have ordered replacement transistor and will replace and set BIAS on them.
More to come!
Jose
I will document on this thread the repair of my K1800FX, which died suddently on my last gig.
There was no hint of it going to die nor it was being abused.
I got this 2009 unit used, just a couple months ago, but it was in very good shape and with low hours on it.
Accessing to the PA electronics through the speaker hole:
The LPA1180 Rev. J amplifier:
A general view of my main workbench, with the amplifier on it;
This is the PCB, trace side:
Only hint so far I have found that may explain the failure,,, If you enlarge the picture, you can see some embedded metal part on the silicone grease of that transistor:
The PA with the drivers and power transistors removed. Both power transistors are shorted. Drivers measure fine on my PEAK DCA75:
I have checked all the diodes and capacitors (for ESR and capacity), and all measure OK. I have also powered the amplifier without the power transistors, and the +5, +15 and -15Vdc rails are present and the control panel LEDs light nicely.
So I have ordered replacement transistor and will replace and set BIAS on them.
More to come!
Jose
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