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A site where discontinualed schematic diagrams and back dated information can be found on discontinued radios tv's and any electronic equipment can be found. Newer manuals either Service and operating manuals. Radio amateurs should find this site a great source for ham radio equipment manuals. I will return to this site should I need information on any electrical equipment. priced easy to download in a PDF format and print pages need to undertake the repair.
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Quality scan of the original. All the detail necessary to troubleshoot, repair and adjust the unit. I'm sure I will be downloading more manuals in the future as the need arises.
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Exactly as described, a Service Manual complete with the schematics and PCB layout delivered in a timely manner. Many thanks for the great service.
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some of the writing is a bit blur but the part in the schmatic was great and i have fixed the machine thanks
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Well.. I'd searched for this manual and although I found many copies online I was pleased to find your website with a well balanced pricing system and easy to search and follow links. That together with the very quick response time was just what I was looking for.. being a very impatient tech.. ;-) I had the service manual in front of me within a short time.
Bookmarked.. and you can bet I will always come here first for my service & user manuals..
best regards
Ed(Tony) Foley
G7WHK
Power Amplifier
Reference 7520a/7521a
TROUBLESHOOTING
� PROBLEM: No audio (POWER LED is off). CAUSE and SOLUTION: No voltage at BATT+ and/or REM terminals, or bad or no ground connection. Check voltages at amplifier terminals with VOM. � PROBLEM: No audio (PROTECT LED flashes every 4 seconds). CAUSE and SOLUTION: DC voltage on amplifier output. Amplifier may need service; see enclosed warranty card for service information. � PROBLEM: No audio (PROTECT LED is on). CAUSE and SOLUTION: Amplifier is overheated. Make sure amplifier cooling is not blocked at mounting location; verify that speaker-system impedance is within specified limits. � PROBLEM: No audio (PROTECT and POWER LEDs flash). CAUSE and SOLUTION: Voltage less than 9V on BATT+ connection. Check vehicle charging system. � PROBLEM: No audio (PROTECT LED is on). CAUSE and SOLUTION: Voltage greater than 16V or less than 8.5V on BATT+ connection. Check vehicle charging system. � PROBLEM: Distorted audio. CAUSE and SOLUTION: Input sensitivity is not set properly, or amplifier or source unit is defective. Check INPUT LEVEL setting, or check speaker wires for shorts or grounds. � PROBLEM: Distorted audio (PROTECT LED flashes). CAUSE and SOLUTION: Short circuit in speaker or wire. Remove speaker leads one at a time to locate shorted speaker or wire, then repair. � PROBLEM: Music lacks �punch. � CAUSE and SOLUTION: Speakers are not connected properly. Check speaker connections for proper polarity.
STATUS LEDs Clip: Indicates the amplifier is being overdriven, and your speakers may be in danger. This should blink only on musical peaks, and not be on constantly. Power: Indicates the amplifier is on. Protection: Refer to �Troubleshooting� for specific indications. Figure 15. LED status.
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