Hi I have a meridian 557 that's burning up resistor r230, it wouldn't come out of protection at all when I bought it as a faulty unit so I've replaced the 1000uf 16v caps and all the 10uf 50v caps, all measured poorly when tested. Ive checked all diodes and transistors with the meter and can't find any obvious shorts, can anyone help ?
Build a "dim bulb tester", it's a incandescent lamp in series with the load/amp, it acts as a current limiting device so as to limit further damage. Also allow you to do some voltage measurements with unit partly powered up, some of the tested transistors may need a few "volts/amps" before they fail. Can you post a schematic? Look downstream of R230. When powered up on DBT certainly check output and driver transistors...
Meridian 557 issue (see description/schematic)
found link to schematic in above thread, couldn't locate R230...
found link to schematic in above thread, couldn't locate R230...
Thanks for help guys and nice to meet u all, ill have to see if I can source an incandescent bulb from somewhere. R230 is connected between ground on the power supply section and the chassis ground, its connected via the black wires to the right hand rca where a few ground connections terminate.
Yes that's the fellow, I was thinking maybe I had a bad ground somewhere ? Output trannys look ok and emmitter resistors are all in one piece, the current resistor for the front led has taken a battering at some point also. I have a sansui au919 that I rebuilt a few years ago that needs looking at I was hoping to put the meridian in its place for a good while ! I found the sui easier tbh n it's a monster !
Using a dim bulb tester this amp powers up and comes out of protection and stays on still burning up r230 anyone got any ideas ?
1) make sure the Bridge Mode switch is in OFF position and no speaker connected.
2) unplug and measure the joint of R230 and black wire continuity to ground, then disconnect all the inputs cables and measure again.
3) there should be a R230 on both amp boards, see if both were burnt.
4) switch on and see if in 2-5 seconds a relay will click. ( no input connected )
5) after relay clicked, measure the voltage from R230 to ground. ( and both ends of R230 )
measure voltages from chassis to the ( cd/dac )signal input rca connectors see if voltage present.
6) measure the +/- 15 voltage rails.
the above are for basic checking
2) unplug and measure the joint of R230 and black wire continuity to ground, then disconnect all the inputs cables and measure again.
3) there should be a R230 on both amp boards, see if both were burnt.
4) switch on and see if in 2-5 seconds a relay will click. ( no input connected )
5) after relay clicked, measure the voltage from R230 to ground. ( and both ends of R230 )
measure voltages from chassis to the ( cd/dac )signal input rca connectors see if voltage present.
6) measure the +/- 15 voltage rails.
the above are for basic checking