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Problem with my revox B710 no record or playback

Simon smith

Simon smith

New Member
Hello everyone..I have a revox B710 cassette..it was in a poor state...broken switches dirty and damaged..I'm completely refurbishing it..I've replaced switches by sourcing the toggles in Germany...replaced all the electrolysis.. esp psu..checked voltages..the problem is there's no audio out except a sniff of noise on left channels.im monitoring at mic out line out and right channel is totally dead...the heads are fine..they have resistance..even with line input signals and on standby no monitoring signal and in record nothing...mechanism is fine all buttons work...off.rw..play etc...xp and Dolby lights come on ok.as well as record...I now have ordered all the ics. For record and playback boards..which I'm awaiting...I've checked connectors are ok..and for solder flashes etc after I replaced capacitors throughout...I do hope a blitz on the boards will do the trick..by the way ac and DC bots out from pcb fine...so what else could be my problem..as I said when all the ics arrive I will keep you posted...anyway it's a nice deck to work on..all modular...except for the tissue paper tracks....keep the temp down on the soldering iron helps...anyway thanks for reading.any advice would be appreciated regards simon
 
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You don’t mention if both channels are live when in source mode. That alone eliminates a ton of things. There are like 9 4066 quad cmos switches in the B710, and they are always a weak point. Also, good resistance does not guarantee a head channel works. Usually, but not always. Open (infinite resistance) does always mean a head channel is dead.
 
Thankyou for your message ..well in course mode there is a sniff of signal on left channel..nothing on right...I dont suspect the heads as in source mode right channel is dead.. yes I'm replacing cmos ics as soon as I get them. Also on the bottom left hand board with the large processor and piggyback arrangement is that just board for motor logic or does it control audio as well anyways I keep you posted simon
 
perryinva said:
You don’t mention if both channels are live when in source mode. That alone eliminates a ton of things. There are like 9 4066 quad cmos switches in the B710, and they are always a weak point. Also, good resistance does not guarantee a head channel works. Usually, but not always. Open (infinite resistance) does always mean a head channel is dead.
Click to expand...
 
Any progress? The large processor board has no audio processing directly, but some signals travel through it. I always reflow the connectors. They are also a weak spot.
 
Thankyou for your message...ive checked connectors ok...i replaced cmos switches on all modular boards ie pb record etc..and transistors...all frako caps and phillips...what happens now...on standby there was smoke comming from ic2 cmos on audio board...even.just on standby...i think 5 volts has to be present for standby and remote...tx live...so i replaced cmos again....same thing....i heard from a guy said my micropressor had it first time when it had poor caps on psu which caused a surge before blowing a fuse that burnt out part microprossors..on main bottom.motherboard...then now ...sends dc volts to boards...what do you think of his theory..he thinks the deck is inrepairable unless i get a replacement motherboard..he think cmos blown there due to current surge...i said i wait till a motherboard comes on ebay...i might change the cmos.s on moyherboard...what do you think...the logic for tape functions though are fine...ie mechsnical pb fast foward etc when buttons pressed.. no bar graph displays of corse except sniff noise on left channel ...2 bars anyway back to the drawing board as they say...i also have a problem with my revox cd player..it wont load cd automatically when you press load..if pushedhin manally it loads and plays..and ejects..what could this be?it did work a while ago...again replaced fracos...after fault occured..i noticed sensors on tray at back and front leading again to logic boards etc...simon
 
Next step is to remove IC2, find which pins are power and ground, and measure voltage. It was hard for me to follow your thread. Are you saying you think the main processor on that motherboard is cried and therefore passing high voltages to other components? It is very possible the processor is fried. The Frako PS caps are do often fail badly, and can easily destroy a large processor, and if all audio signals go through it, then that is easy to determine. But if everything else works, and only IC2 fails, its failure is not likely to be caused by the processor chip. It is more likely a PS, maybe diode or bridge issue, since all caps are replaced. You need to measure all PS voltages (with IC2 removed) and compare to the expected values in the manual.
 
Yes its vintage alright 1983 approx...yes there very little souce mode either...just couple bars on left.nothing on right...i changed all cmos switches on all boards .triple check everything was as it should tracks etc .ics round right way he he etc etc..when i plugged in again on standby there was smoke coming from ic2 on audio pb board..ic2 is a cmos switch..so i presume mother boards sending volts there..someone said..initially before i bought it it had maybe cap problems with surges blowing devices on mother microprocessor components..is he right..simon in dispair..thanks for your patience with me..
perryinva said:
You don’t mention if both channels are live when in source mode. That alone eliminates a ton of things. There are like 9 4066 quad cmos switches in the B710, and they are always a weak point. Also, good resistance does not guarantee a head channel works. Usually, but not always. Open (infinite resistance) does always mean a head channel is dead.
Click to expand...
 
Simon smith said:
Yes its vintage alright 1983 approx...yes there very little souce mode either...just couple bars on left.nothing on right...i changed all cmos switches on all boards .triple check everything was as it should tracks etc .ics round right way he he etc etc..when i plugged in again on standby there was smoke coming from ic2 on audio pb board..ic2 is a cmos switch..so i presume mother boards sending volts there..someone said..initially before i bought it it had maybe cap problems with surges blowing devices on mother microprocessor components..is he right..simon in dispair..thanks for your patience with me..
Click to expand...
also i think heads ok as source is dead on output to bar graph and audio out..
 
Simon smith said:
Yes its vintage alright 1983 approx...yes there very little souce mode either...just couple bars on left.nothing on right...i changed all cmos switches on all boards .triple check everything was as it should tracks etc .ics round right way he he etc etc..when i plugged in again on standby there was smoke coming from ic2 on audio pb board..ic2 is a cmos switch..so i presume mother boards sending volts there..someone said..initially before i bought it it had maybe cap problems with surges blowing devices on mother microprocessor components..is he right..simon in dispair..thanks for your patience with me..
Click to expand...
Simon smith said:
Yes its vintage alright 1983 approx...yes there very little souce mode either...just couple bars on left.nothing on right...i changed all cmos switches on all boards .triple check everything was as it should tracks etc .ics round right way he he etc etc..when i plugged in again on standby there was smoke coming from ic2 on audio pb board..ic2 is a cmos switch..so i presume mother boards sending volts there..someone said..initially before i bought it it had maybe cap problems with surges blowing devices on mother microprocessor components..is he right..simon in dispair..thanks for your patience with me..
Click to expand...
Simon smith said:
also i think heads ok as source is dead on output to bar graph and audio out..
Click to expand...
 
Update of my revox b710..on plugging in when on standby smoke came from ic 2 of amp module..ic2 is a cmos device..im back to square one...no output or souce audio..it does have mechanical play rw.ff functions smoothly
 
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