May have been an insect that found a new home...Too bad.
I am trying to help my brother repair his amplifier , it powers speakers by his pool. Its in an enclosed sun porch and he brings it in the house for winter. He hooked it up this summer and no sound quickly followed by smoke. We connected up a cheap amp and things sound ok so i do not believe it was a wiring or hook up issue. I attached a picture and control board 27-01-044590-6 has a burnt spot and output board 27-01-044591-6 is charred also. I am an elecronics technician by trade but do not typically work on vintage equipment. It looks like I may be better off trying to purchase used boards as the traces and parts of the output board are heavily damage. The control baord may be able to be salvaged. I am able to follow and interpt schematics and have all the test equipment to fix this, just looking for advise from more knowledgable people here who have experience with this gear. Thank you for all replies !!
May have been an insect that found a new home...Too bad.
Try Iratech
Ira Tec Pro Audio's Homepage
Your neighbors called. They like your music.
You may have chlorine deposits on the PCBs. Scrub everything with soap and water and let it dry in the sun for a week. Test the output and driver transistors for shorts. Isolate the power supply from the rest of the unit and see if the power supply comes up. When a PCB burns and arcs over you need to replace the board or grind away the carbon trails. If you have a Variac bring the AC line up slow and monitor the current or power draw to keep from causing more damage.
Don
Thank you for the replies !! the room its in is away from the pool with widows that are never opened , none the less a good cleaning of the boards is needed , I belive this maybe the first time it was opened up. Don yes I have a Variac and thats a great idea to power it up like that. luckily he has a cheap amp working for now so I actually have till next spring to get it working again. That will give me time to identify on the schematics what burnt and hunt for replacements. Thanks agian and if there are anymore ideas I certianly appreciate it.
Did this amp take a lightning strike ?
Did the large cap on the right short ?
I am guessing the supply voltage is +/_ 50 VDC
Did you find a free schematic on line ?
Don
DonOriginally Posted by donaldpatten
No lightning strike as weather has been great up here, the amp was moved from the house from winter storage to a sun room for powering pool speakers. This is the same way my brother has done it for six years. He wooked it up as normal , turned on and no sound then saw smoke coming from the vents. Its possible a pair of speaker wires were shorted but could not be confirmed. Work is busy and I do not get to look at it every night but I will check the large cap , and yes I found a schematic. Don please check the thread when you can as I will post info as I troubleshoot.
Did some more investigating on the amp..........its getting worseThe large caps do not appear to be shorted but I have found burnt spots on three boards the control board (front panel VU meters) the driver board, and the output board. I attached pics, I guess I will be lokking for a donor amp , at least for the output board. I tested the good and bad output boards per the manual and all test good except pins 1-5 Emitter Collector resistance of 4 transistors was 25 Ohm on burnt board and 500K on the good board. Not sure if an output transistor shorted to start this mess , Why would the spots on other boards burn ? I know Im asking alot but thank you for looking at my mess !!!
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