400x’s would likely work, but there would be no margin. Turned to reasonable volume I’m sure they’d survive. They would certainly work to tell you if that was the remaining problem. 1.5A diodes would be better, but not “common as dirt”. At that low a voltage, I might be tempted to put in TO-220 dual schottkys. Those will fit the holes, but you might have to play games with the lead spacing. I probably can even find some common anode pulls out of old computer power supplies. Common cathode are common as dirt… at least around my shop.
Looks like R750 is being used as a fuse. Just be sure to use a carbon film resistor. If someone replaced it with metal film or metal oxide (thinking it was burnt so put in a BIGGER one), get it out of there and put in the right one. I’m sure 4.7 ohms is fine, but you want to be sure it “blows” before what’s downstream of it creates a bigger fire. Carbon films create a nice little localized fire and self extinguish when severely overloaded. It’s funny as hell doing it with 10 ohm 1/4 watt resistors and a battery or wall wart. College roommate would burn incense, and we’d do 1/4W resistors in protest.
Ok, I ordered those with 2 filter caps, I'm suspecting those are bad too, There's some residues of leakage on the board, probably they're gone..
Another question, It's ok turn the receiver on without the speakers connected?
I read somewhere that may ruin the receiver(asking myself if that shorted the receiver) cause I tested without them attached, but I'm afraid to damage those speakers too..
Another question, It's ok turn the receiver on without the speakers connected?
I read somewhere that may ruin the receiver(asking myself if that shorted the receiver) cause I tested without them attached, but I'm afraid to damage those speakers too..
Turn on the receiver through a dim bulb first. Then try the same with speakers, then speakers with music. Then turn the bias (VR703) all the way down. When you are satisfied nothing is going to blow, disconnect the dim bulb, leave the speakers unconnected, and adjust the bias till you get about 6mV across R735. With the way the 68 ohm emitter-base resistors are arranged, that will put about 8 mA in the driver and about 10 mA in the output device. The “optimum” is higher, but they are almost never run that high.
It’s not necessarily good to go blasting music through it (ie, clipping heavily) with no speakers connected. With tubes even music at normal volume with no speaker can be disastrous, but that won’t hurt transistors. You need them disconnected to set the bias, as just a couple mA of DC due to offset will taint the measurement.
“Residue” around caps is sometimes just glue to keep stress off the seals. If it is GOOEY, it’s bad cap. If it’s hard and crispy it may be dried/cured glue. Not too much different from construction adhesive.
It’s not necessarily good to go blasting music through it (ie, clipping heavily) with no speakers connected. With tubes even music at normal volume with no speaker can be disastrous, but that won’t hurt transistors. You need them disconnected to set the bias, as just a couple mA of DC due to offset will taint the measurement.
“Residue” around caps is sometimes just glue to keep stress off the seals. If it is GOOEY, it’s bad cap. If it’s hard and crispy it may be dried/cured glue. Not too much different from construction adhesive.
Thanks a lot again, you're being a life saver !
What impedance I should expect on the secondary windings?(orange + orange wires), cause I checked with the DMM, and its reading just 1.14 ohms
What impedance I should expect on the secondary windings?(orange + orange wires), cause I checked with the DMM, and its reading just 1.14 ohms
Sorry, I uploaded the transformer windings image on the original post, I tried to upload the entire thing, but it seems too heavy