For a quickie, you could power it up without a cap and use a voltmeter or scope to determine the polarity. You might use reduced line voltage JIC. Jerry Silverman Greentron Inc 4 Newland Ave Greenville SC 29609 864 232 3889 Fax 271 2080 mailto:greentron@xxxxxxx ----- Original Message ----- From: "Don Cohen" <bond007d@xxxxxxxxxxx> To: <techassist@xxxxxxxxxxxxx> Sent: Wednesday, July 09, 2003 11:55 AM Subject: [TechAssist] HELP! Goldstar VCR Model #GHV-1233M - Correct PS cap orientation? > Hello, > > This is an old 1986 model that customer really likes and wants fixed= > regardless of cost (to a point). Left side deck gears (looking from front)= > were broken, so I replaced the whole deck with one from a newer model= > junker with same deck - gears looked fine. I did all the usual maintenance= > and also replaced 3 caps on the power supply board. When I plugged unit in,= > it looked like it was doing a reset operation, but something seemed= > binding, with the mode motor continuing to turn when it should have shut= > off. After about 5 seconds, there was a horrific pop and one of the caps I= > had replaced blew up. There was no previous problem with VCR other than= > maintenance and broken gears. That cap was C112 on the power supply board= > and is a 100uF/16V. I tested it before I put it in with an ESR meter and it= > tested fine. Since the whole outer case blew right off, I am not able to= > check to make sure I even put it in correctly (polarity), but I am pretty= > sure I did, as I always check that before finishing. I did not make note= > when I pulled it out if the part marking matched the silk screen info. I= > know that sometimes they are marked wrong. The silk screen on board says= > that the + leg goes to the center pin of IC102 (positive 9 volt regulator= > AN78M09). That pin is ground. Also according to the silk screen, the= > negative leg is supposed to go to pin 1 of IC102, which is Vin. On the= > newer unit that I robbed the deck from, the power supply is designed= > differently, but the same regulator and cap are there (except the voltage= > on the cap had apparently been upgraded to 25v) and the orientation is= > reversed for the cap - neg leg of cap to center IC pin and positive to pin= > 1. That is what I would expect. > > So, does anyone have an old schematic or service bulletin that they could= > verify that the silk screen info is indeed wrong? If not, does it sound= > correct that the cap's + leg should not go to the IC's (and board) ground= > pin? Obviously I could just try to put another in again the way the silk= > screen says and assume I somehow put it in backwards, but I would rather= > not keep blowing parts and possibly doing other damage till I figure out= > what the issue is. > > Much thanks to anyone that can help out here. > > > Don Cohen > DC Electronics > Shinglehouse, PA=20 > > **************************************************************************** * > CHECK OUT THE NEW CHATROOM! Just login and click on chat! > http://www.tech-assist.org/secure/tip/main.htm > The Tech Address Book: > http://www.tech-assist.org/secure/tip/contact.htm > Add a Repair Tip Here, or Change/Remove your Email Address: > http://www.tech-assist.org/secure/tip/main.htm > Lost Password: > http://www.tech-assist.org and select "Lost your Login Info?". > Email Archives: > //www.freelists.org/archives/techassist/ > ***************************************************************************** CHECK OUT THE NEW CHATROOM! Just login and click on chat! http://www.tech-assist.org/secure/tip/main.htm The Tech Address Book: http://www.tech-assist.org/secure/tip/contact.htm Add a Repair Tip Here, or Change/Remove your Email Address: http://www.tech-assist.org/secure/tip/main.htm Lost Password: http://www.tech-assist.org and select "Lost your Login Info?". Email Archives: //www.freelists.org/archives/techassist/