Hi i have a marshall jcm2000 tsl60,it turns on but when u flick the standby switch on r32 10k 1w started smoking then r64 1k 1w,both on the ht line.ive replaced these resistors plus the capacitors around it but still the same fault.any ideas?
To be passing enough current to burn the powerrail resistors there is clearly a short to earth from the HT line. Given the circuit of that amp, unless there is physical damage to internal wiring causing the problem, the most likely cause of the problem is one of the ECC83 preamp valves failing with an internal anode to cathode short. Have the valves tested or if there is nowhere local test them yourself with a resistance meter. Check pins 1 to 3 and 6 to 8. There should be no connection in a good valve. Its also worth checking there is no continuity between the heater filament and these pins (heater is pins 4,5 and 9). If you find a fault then discard the valve and buy a new one, repair the dead resistors and try the amp again.
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The thermal cycling of these receivers can result in a failure of the solder joints around the components that get hot. The large capacitors if failing usually show signs of bulging or electrolyte leaking.
When the unit boots up out of standby the unit does a self check to confirm all power supplies are within determined limits. components such as resistors operate near failure limits. These parts are designed to fail similar to a fuse if the circuit is over loaded/heated.
Common problem is the required ventilation is restricted by covering the top etc preventing required air flow, overheats and a safety resistor fails.
Replace resistor with same type to retain saftey features.
Look for a burnt resistor. They are usually raised off of the PC board.
To do the reset you need to turn the receiver on, then on the front panel of the receiver press and hold the "VCR/DVR" button while doing that press the "STANDBY/ON" button.You will see the word "Clear" in the display screen and the receiver will go into standby mode.PLEASE UNDERSTAND THAT YOU WILL LOSE ALL YOUR AUDIO & VIDEO ASSIGNMENTS ON THE RECEIVER PLUS YOU WILL LOSE ALL YOUR SPEAKER CONFIGURATIONS, SPEAKER DISTANCE AND ALL LEVEL CALIBRATION SETTINGS.YOU WILL ALSO LOSE ANY PROGRAMMED RADIO STATIONS IN MEMORY.Once the receiver goes into standby mode turn it back on and go thru the setup menu for all custom settings., Thanks, JT
Usually it is bad power supply problem or bad channel problem. Look for any burned parts, it helps you locate the problem. Burnt resistors in one channel- you need to replace output transistors (better to replace all transistors in that channel) and bunch other surrounding parts. If you do not see any burned parts, check all voltages coming from power supply +15 -15 +5 etc then check dc at every channel output (not at speaker terminals but at control pins on the amp/main pcb), should be +-10mV
Same problem. C901 on the vertically-mounted input board next to the power supply transformer was burned. Replaced with ceramic cap from RS with same specs. Still did not work. Talked to Jeb, great guy at HK tech support. He suggested that R901 would probably be blown and maybe 902 also. These are flame-proof resistors and do not show damage. Tested with multimeter and Jeb was spot on. Replaced 1w resistors with 5w (all RS had) at same resistance. Works great.
Most common cause of no sound is a blown fuse. Check both the fuses with a resistance checker if you have one, sometimes they may look good, but be faulty. If this is the case, you probably need to look for a reason why the fuse blew in the first place. Running a tube rig without a speaker connected is often the problem. the HT fuse will pop almost straight away. Another is using a signal lead instead of a speaker lead to connect your Speaker cab. Always use at least an 18 gauge speaker lead with decent connectors like Switchcraft or Neutrix. NOT a cheapo patch lead. A Failing tube will also commonly cause it to blow. If it happens again, then change the output tubes. If it is not the fuses, and you have experience with repairing valve amps, I suggest you take the head into a repair guy for a look.
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HOWDY, NOW YOU COULD TRY THIS ONE: POWER THE RECEIVER UP , THEN PUSH&HOLD !THE VIDEO 1 BUTTON, THEN TURN THE PIECE IN THE OFF (STANDBY MODE ) ,IT WILL SAY "CLEAR SO IT SHOULD BE BACK TO IT,S ORIGINAL FACTORY SPECIFICATION,S.
SUCCES ! AMSTERDAMCOWBOY-HOLLAND-NOW FLORIDA! 4-EVER
It is likely that the PA stage has developed an offset voltage in the output stage. The faulty amplifier channel can be found by progressively disconnecting the collectors of the of the power transistors until the protection fault disappears. Once the faulty channel is found the the cause of the offset has to be traced to the faulty transistor or resistor. Don't forget that if you can smell smoke or burning then there are likely to be components(esp transistors) that have been damaged by the fault. I had a Luxman unit that destroyed 5 transistors in the output stage that was due to an open .5W resistor in the driver stage. Good luck.