Harman-Kardon-ServiceNews_02-2004-Article 电路图 维修手册.pdf

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1、Hi. Tech Support Specialist Andy Andersen here again to help you with any repair issues for Harman/Kardon, JBL Consumer and Infinity products that may have developed since the last issue. For those of you who arent familiar with my background, I was a senior technician for a large service center and

2、 also an owner of my own audio/video service center. As a consequence, I have a very clear picture of the challenges that come across your bench. Its my job to help techs out there in the field, like yourself, troubleshoot and successfully resolve any difficult repair issues that you may be facing.

3、Feel free to contact me at for help and information. Technical Issue of Note In each edition, I include whatever significant technical issues that may have recently come to light. This issue, Id like to highlight a technical problem common to both the AVR 520 and AVR 525 receivers. Shutdown Problems

4、 There are some AVR 520 and AVR 525 units that spontaneously shut down. In cases where there is no obvious cause and the unit shuts down immediately, there could be two reasons for the problem. AVR 520 C554 Above figure shows that this circuit is for over-current and DC Detect of the amp. It could b

5、e due to either over-current, or to a defective DC detect cap. On the AVR 520 the culprit would be the C554. On the AVR 525 the culprit could be the C432. DC sense has a delay normally due to the R/C time constant. Protect is faster than most DMMs. NOTE: If the amp shuts down immediately, look at th

6、e over-current part of the protect. Your DMM is slower than the protect system of the AVR. Micro will sense protect faster than your DMM can track. Use your scope to check the protect lines. Set your scope to DC, slow sweep and you will very quickly see any protect problems. The DC protect checks fo

7、r average voltage over a short time. If the cap is open, the response time would be too short and will trigger protect for almost transit voltage. Well, thats all for now. Till next time, remember, you can always contact me at 516.682.6435 for assistance. Harman Service News Issue 2 2004A newsletter

8、 for the HCG service center network 250 Crossways Park Drive, Woodbury, NY 11797 516.496.3400 Important E-Mail Addresses Repair Questions it is merely in a standby mode. All of the opamps are running and any problem with their supply voltage will cause the amp to behave very badly. You Throw The Bal

9、l +/- Voltage in our opamps is the most important voltage. It must track within .7 volts. Most of our audio stages are DC coupled. In our bass amps, even though the amp checks out fine, the customer could experience some strange problems. Checking the +/- voltage is a very good way to determine the

10、health of the opamps used in the pre-amp output drivers. Any deviation is usually caused by a defective component such as an opamp, an open or shorted filter cap, a shorted or leaky decupling cap (0.1uf SMD) Even though the amp works now, it could be harboring that tech-gnome, so check the dual supp

11、ly and check it often. More Than A Mystery Harman International designs and manufactures some of the finest quality audio equipment available today. Many of our products have unique design and engineering characteristics. Therefore, it is not only advantageous, but necessary that our authorized serv

12、ice technicians acquire this special knowledge for these products in order to repair them correctly. Gain From Training We are proud to continue our tradition of ongoing training for Harman/Kardon, JBL and Infinity service technicians, to keep their skill levels state of the art. When service center

13、s take our trainings they not only improve their technicians skills, but they also improve their repair-time productivity, that in turn leads to increased revenue and profits. Thats why we strongly encourage all authorized service centers to take our product training classes. For three months we off

14、ered training on our Class H BASH amplifiers. Currently, we are offering training on our Analog Class D amps. Even if you do not sign up for the training, there is another way to benefit from the class. We are making the curriculum materials available in both PowerPoint and PDF on our website. Class

15、 H Amplifier, IL BASH Amplifier and Class D Amplifier training information can all be found at Harman Service.Com (). We urge you to pass this valuable training experience along to your technicians. Have them contact Andy Andersen at , or call him at 516.682.6435 to find out how they can sign up and take the trainings. Editors Note: Please dont forget to pass this newsletter along to your technicians, so that they can also directly benefit from its information. Service Tip of the Month by Andy Andersen