- clamping circuit help - 1 Update
- RCA main board - 2 Updates
| Hem Jung <hemjA@netco.net>: Mar 15 12:38PM -0400 Been using a little square wave generator for experiments, has input values from 3-29 VDC. However, at 24 VDC input, it burned out. I have a replacement on the way, but vender suggested using a clamping circuit to limit voltage to 25 VDC if my power supply is prone to spikes and I suspect it is. Can someone suggest a suitable circuit with component values needed? Thank you. |
| Stu jaxon <stankowalski02@gmail.com>: Mar 14 10:40AM -0700 > The only way is to try it. There are two potential problems of high probability: the keyboard switches may not work as assigned, and you may have no picture, a badly pixelated picture, or an upside down picture because these boards don't drive the same screen. If the board is close enough, swapping the eeprom from the original board will usually fix the picture issues and likely the keyboard issues, but that's assuming the original eeprom is good. Since the eeprom is the most likely cause of any non-lightning failures of these boards, you may be moving a bad eeprom into a good board. > I've done that type of swap when I had a board in stock as it only takes a few minutes to try it, but wouldn't order a board for the attempt. > Did you confirm the power supply is OK? Getting standby 5V is not enough. You can jump the stby pin to the ps on pin and see if the 12V comes up. If it doesn't, the power supply is bad. If it does, it's the main. I'm reading a short across both sides of the fuse 3a/125v to ground, on the tcon board, there's short somewhere.??? |
| "ohg...@gmail.com" <ohger1s@gmail.com>: Mar 14 11:51AM -0700 On Sunday, March 14, 2021 at 1:41:01 PM UTC-4, Stu jaxon wrote: > > I've done that type of swap when I had a board in stock as it only takes a few minutes to try it, but wouldn't order a board for the attempt. > > Did you confirm the power supply is OK? Getting standby 5V is not enough. You can jump the stby pin to the ps on pin and see if the 12V comes up. If it doesn't, the power supply is bad. If it does, it's the main. > I'm reading a short across both sides of the fuse 3a/125v to ground, on the tcon board, there's short somewhere.??? With the LVDS cable disconnected, you should not be getting any low resistance to the ground screws of the TCON. If so, there's a short. The most common reason for a dead short on a TCON are one of the multi layer chip capacitors (they're surface mounted and have no markings). While any dead short is easy to find with an ohm meter, these caps are usually found in groups of two to ten or more all paralleled, so one shorted cap makes them all look bad. Other than a Huntron, the easiest way to find this is to feed a limited current (2 amps tops) into the short with a variable supply and spray the board with freeze spray until the board frosts over. The first cap to thaw is the shorted one. |
| You received this digest because you're subscribed to updates for this group. You can change your settings on the group membership page. To unsubscribe from this group and stop receiving emails from it send an email to sci.electronics.repair+unsubscribe@googlegroups.com. |
No Response to "Digest for sci.electronics.repair@googlegroups.com - 3 updates in 2 topics"
Post a Comment