Thanks Naresh,
you mean a simple 1/4 watt resistor across the main caps ?? Yes I tried the caps in series with the speakers. No result. I have not found the right MOV yet. Must have them lying around somwhere ;-)
I also tried a second new power switch, next tot orginal one. No result.
you mean a simple 1/4 watt resistor across the main caps ?? Yes I tried the caps in series with the speakers. No result. I have not found the right MOV yet. Must have them lying around somwhere ;-)
I also tried a second new power switch, next tot orginal one. No result.
This an old post, but just in case anyone is interested. I solved the problem (with help of a friend).
Three things to do!
1: open and clean the power switch, preferably with a ultrasonic cleaner. You will find the contacts are totally blackened.
2: solder a 0,1uf 275AC capacitor on the power switch connections
3 add a 220uf 25/35V capacitor on the power supply board on the empty position of C410. There are holes and solder pads on this position, but the capacitor is only mentioned on in the service manual of the former US layout of the PCB. (see pic). It mentions 100uf but increase this to 220uf.
These solutions solved the problem on several TA-4650's. And of course this should be part of a restoration. There are many more things to do on this beautiful amp.
1: open and clean the power switch, preferably with a ultrasonic cleaner. You will find the contacts are totally blackened.
2: solder a 0,1uf 275AC capacitor on the power switch connections
3 add a 220uf 25/35V capacitor on the power supply board on the empty position of C410. There are holes and solder pads on this position, but the capacitor is only mentioned on in the service manual of the former US layout of the PCB. (see pic). It mentions 100uf but increase this to 220uf.
These solutions solved the problem on several TA-4650's. And of course this should be part of a restoration. There are many more things to do on this beautiful amp.
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Interesting. I have similar problem when both are connected on the bigger brother. The units work OK when used separately but trigger (probably) oscillation when connected together....I used 3 o 4 100Watt light bulbs in series with the AC power and this prevented speaker damage while showing troubles...
Thanks for the useful tip.
Thanks for the useful tip.
Interesting!
I recently had a 4650 on the bench that needed repair. I did all the required modifications to power supply and powe amp boards and the amp performs great. However the owner contacted me about the popping speaker problem. I did not noticed this otherwise I would not have shipped the uinit back to the owner. The unit will arrive back at my workshop later this week and will implement your suggestions and will let you know about the results. Thanks!
I have not yet the energy nor the will to open the switch but the tinny cap trick delayed the oscillation until the relay kicks-in....
you have to take your time with the switch. Be sure nothing can fall on the floor... never to be found again. I clear my desk and use a white sheet. The switch is not hard to open. putting it back.... replace the two copper contact after cleaning. Put some Vaseline to hold the tiny plastic part in the tiny springs so you can turn over this part of the switch and put it together.
Think of putting MOV and / or NTC in the power supply area, as a spark quencher (MOV) and inrush current limiter (NTC).
That might help.
That might help.
Completely. I am just sharing my experiences. Cleaning the power switches made the difference several times.
Fair enough, just as a side remark - it has never ever had any effect in my gear. Power either passes or does not (usually some smoke applies).