Hi all.My A77 has dropped a channel,record and playback.Was recording great etc,put it in its box,brought it upstairs,unpacked it and there it was gone.Cleaned heads just in case,but,as always,cant find my head demagnitiser(been in the same place for years,until i need it in an emergency!!)
Any ideas,anyone??
Sick as ............... :tears:
Peace and pie
W :hdphones:

If it worked downstairs, and suddenly stopped upstairs, then I would look at your connections. Perhaps you have a bum cable, or the switching on your amp is problematic.

Thought that too,so plugged in my B77 and PR99..........................worked perfect.Bugger..........maybe a loose board,but that wouldnt explain why rec and playback bad,if it was one or the other........well,at least ive something to do today when i get up(4am sunday here,need sleep!!)
Thanks for the suggestion Goldenear!!
Peace and pie
W

Next I would try re-seating the cards inside your A77. I don't remeber how the boards are layed-out inside of the a77 off the top of my head, but perhaps the entire record, and playback electronics are on one board, and it has lost power due to a loose connection? Just a guess...

If it's like the original A77, each channel's record and reproduce cards are on separate boards (two record cards, and two reproduce cards). If you have a tape known to have sound on both channels that now plays back on one, swap the two repro cards. If you now have sound on the opposite channel, you have a problem on one of the repro cards. If the same channel is dead, there's a problem with the repro head. If, when monitoring source (i.e. input), you still have sound only on the one channel that is now working, the problem is likely in the line output circuitry.

YIPPIEE!!!
Loaned a signal generator,and whacked a 1khz tone thru it,recorded it an played back,just to start at the begining and go from there.Swapped board at a time,no difference.so..........................having a scratchy head thinky session staring at the heads when i noticed a line of crap,stuck to the heads for about 20 year by the looks of it and the amount of rubbing with isopro and q-tips it took to shift it,dont know how it was working briefly but its all calibrated now and working great.Thanks for all the hints/advice. :D

Man, I feel sorry for you. You own a B77, a PR99 and a A77.
I wonder if the rest of your set up is just as humble. :D
Jorge

:D Thanks,i think!!!
Seeing as you asked,here it is:
Bedroom:Quad 303/33/FM3
Castle Harlech speakers
Revox a77/b77/pr99,all of which with its own dbx224 n.r unit
Thorens TD125mkII/sme3009/shurev15 mkIII
Meridian 206 cd
Pioneer rt 707 reel to reel
Technics rsb 965 cassette
Marantz DR6000 cd recorder
Sony dtc-ze700 dat
Technics EL7500 elcaset
AMC av81 audio/video control unit(glorified tape loop switch)
Yamaha KX690 cassette
Leak sandwich speakers(idle at the minute)
TV/Video/dvd/betamax also,but its only a tv/video...you get the idea where the priorities lie
Downstairs:
Pioneer HPM100/sg9500/sa8500II/tx9500II/ctf1000/rt707/pl570
Lots more stuff sitting gathering dust(linn sondek/SME3009/Shure v15III,Quad fm4,naim cdi)
Whats your system anyone/everyone????
Peace and pie
W
:music: Tom Waits-Nighthawks at the diner

Jesus All Mighty.

That´s awesome stuff. :thmbsp:

You came to the right place. Plenty of other looneys, just like you, here. :D

Compared to some of them, though, you´re just an average looney. You wouldn´t believe what some of the guys here own. :yes:

I´m attaching a pic of my listening room system. I love it.


Jorge

Very nice Jorge!!
My camera is out on load at the moment,but will send some pictures when i get it back!!!
Enjoy the music!!
Was listening to "in the wake of poseidon"earlier,just as a tie in to the King Crimson reference:)

I have a problem with my beloved Revox A77mkIII HS. The right channel will go out within a few minutes of playing a reel--sometimes it does and sometimes it doesn't. I have switched the 2 repro cards, as suggested here, and the problem still happens on the same right channel--so I take it the cards are OK. The heads are clean and demagged. If I switch the deck off and on then it will usually work on both channels--for a few seconds. I popped the front lower panel off and noticed several wires/connectors going into the VU Meter/input board. I unplugged each of these wires, cleaned the terminals and the problem went away--for a couple of days. Any ideas on what I should do to fix this irritating issue? Listening to my 2 track stereo tapes in mono mode is not the best way to enjoy my A77. Thanks.

I have a problem with my beloved Revox A77mkIII HS. The right channel will go out within a few minutes of playing a reel--sometimes it does and sometimes it doesn't. I have switched the 2 repro cards, as suggested here, and the problem still happens on the same right channel--so I take it the cards are OK. The heads are clean and demagged. If I switch the deck off and on then it will usually work on both channels--for a few seconds. I popped the front lower panel off and noticed several wires/connectors going into the VU Meter/input board. I unplugged each of these wires, cleaned the terminals and the problem went away--for a couple of days. Any ideas on what I should do to fix this irritating issue? Listening to my 2 track stereo tapes in mono mode is not the best way to enjoy my A77. Thanks.
Please clarify: Does it go out a few minute after pressing the play button, or a few minutes after powering up? If it is a few minute after pressing play, then does pressing stop and then play again give you another few minutes of sound, or do you have to wait until the deck cools?

I'm guessing that this problem has to do with the unit warming-up and that something has become intermittent with temperature.

While I think that this is a long shot, have you attemtped to check the continuity of the playback head after the channel has gone-out? You may need to demag your heads after doing this test, but I think that it would be worthwhile, and would represent a starting-point to trace the problem.

The following suggestions are separate from your complaint.

There are some .47uF/250v capacitors in rectangular packages near the relay farm at the left rear of the machine. These leak air and often you can see bluish oxidation inside. Eventually they will undergo dialectric failure and will short. These should be replaced before they short and burn.

Look closely at the pinch roller tension adjustment, and in any case clean the pinch roller and treat with rubber restorer.

Fred

Please clarify: Does it go out a few minute after pressing the play button, or a few minutes after powering up? If it is a few minute after pressing play, then does pressing stop and then play again give you another few minutes of sound, or do you have to wait until the deck cools?

I'm guessing that this problem has to do with the unit warming-up and that something has become intermittent with temperature.

While I think that this is a long shot, have you attemtped to check the continuity of the playback head after the channel has gone-out? You may need to demag your heads after doing this test, but I think that it would be worthwhile, and would represent a starting-point to trace the problem.

Thanks for the response. This may sound strange but the sound could go out anywhere from 5-6 seconds to 2-3 hours (if I play with 1 or 2 those 7? slide on connectors going into the board that houses the VU meter. It reminds me of a soldering joint acting up. Pressing stop and play does not return the sound. I haven't tried putting the ohm meter on the head connections (I always thought that could ruin the heads) But at this point I will try it and demag if necessary. Thanks again Goldear.

The following suggestions are separate from your complaint.

There are some .47uF/250v capacitors in rectangular packages near the relay farm at the left rear of the machine. These leak air and often you can see bluish oxidation inside. Eventually they will undergo dialectric failure and will short. These should be replaced before they short and burn.

Look closely at the pinch roller tension adjustment, and in any case clean the pinch roller and treat with rubber restorer.

Fred

I remember reading posts about this. Since my machine was idle for so long before being put back into service, I really need to look into those caps. Should I still replace them for safety even if I don't see the bluish oxidation? I had to replace the pinch roller and checked the adjustment. Thanks.

Thanks for the response. This may sound strange but the sound could go out anywhere from 5-6 seconds to 2-3 hours (if I play with 1 or 2 those 7? slide on connectors going into the board that houses the VU meter. It reminds me of a soldering joint acting up. Pressing stop and play does not return the sound. I haven't tried putting the ohm meter on the head connections (I always thought that could ruin the heads) But at this point I will try it and demag if necessary. Thanks again Goldear.
Honestly, I'm not completely certain tht this is 100% safe either, so please proceed with extreme caution. But I do know that when I ordered some replacement notronics heads once (for a different machine), that I was asked for resitance and inductance measurments on the heads. So it seems like with a high-impedance meter that this can be done safely.

Frankly, that is a very long shot anyway. But is does sound like a connection either before your playback card, or after you amp card has become thermally intermittent. A solder joint could be at fault here, but so could a flakey connector, or switch.