Yamaha MD8 CH2 problems

S

skybolt6

New member
My band has been using an MD8 for about two years now, and we keep running into the same problem - everything is fine, then one day you go to use CH2 and ... nothing. No input, no phantom pwr, nothing. We are now on our 3rd MD8, and now that it's out of warranty we're stuck with a lemon. Wasn't there a thread about this issue a while back? Anybody know where I can get the service bulletin from Yamaha that explains this problem?

Thanks

Matt Farrow

PS we've got a song recorded on an MD8 at http://www.mp3.com/skybolt6
 
preamp bug

I copied this from http://f16.parsimony.net/forum26295/messages/638.htm

"as you are probably finding out,the md8 has a notorious preamp bug. there are two reasons this happens.. 1 some
of the origional md8s were manufactured with pre amps that just plain fail on there own..yamaha has since
upgraded the preamps in the newer models..i had to send mine back to yamaha for the upgrade because of this
little problem..the other thing that happens is if you have the phantom power on and plug a 1/4 inch plug into a
input that has a phantom powered mic also pluged in ,this will also pop the preamps and unplugging the mic wile
the phantom power is still on will also. unfortunatly the manual doesnt warn of this,i found out from the yamaha
tech when i had to send it back.
mine was covered under warrenty so i only had to pay shipping,which by the way was 22 bucks to california from
michigan..so the only help i really can do is recomend you send it to yamaha for the fix,it will save you time and
money as opposed to doing it yourself."

Seems like maybe they should have said something about this...But I think on ALL equipment it's inportant not to go plugging things in with the phantom power on.
-Nilbog
 
Hmm... Yes, that's the same trouble we've had. Does anybody know which part(s) of the preamp get affected by that? Seems like maybe the front-end opamp for the preamp, maybe the phantom-power feed resistors? I have no trouble fixing it myself, but if anybody has any more info, that'd be great!

Matt
 
you could try tech support. I dont know if theyd give you a schematic of the preamp, but it's worth a shot.
 
Sent mine back a awhile ago as the preamps for 2 and 3 were pretty noisy (-30 dB on full gain). I didn't send it back to Yamaha themselves, but instead an authorized Yamaha fixer-upper, who also fixed other toys. (by the way, each of the inputs should read about -66 dB on full gain.)

He said the soldering was shit. A good number of cold solders on the entire shebang, which is fine with me as long as I can drop it and still use it. This particular fellow was cool enough to re-solder all the cold joints he found, and it was under warranty (always get a warranty from your dealer on used shit), so what did I care?

Throw in the underbody rust protection!

I love my MD8, by the way. Don't get me wrong. Sure do miss 19KHz and up, though.
 
OK, here's the scoop from Yamaha!

I spoke with a guy from Yamaha and we sat down with the schematic and the unit and here's what he told me.

The IC for the mic pre for CH1 and 2 is a NJM2068, labelled on the board as IC101. This is what actually blows when the phantom power is on and you insert or remove a 1/4" plug from CH1 or CH2. This needs to be replaced, and R106, R107, R206, and R207 need to bre changed from 10R to 100R. That's the good news. The bad news is that all that stuff is surface mount. No problem for me but if you can't solder surface mount devices I wouldn't practice on my MD8.

Anyway, once my op-amps come in, I'll let you all know how I made out.

Farrow
 
I discovered about a month ago that channel 3 on my MD8 wasn't working properly. It seemed to record OK (using the digital meters in the recorders window as a guide there was signal going in and signal present after recording) but no audio on playback although the meters suggested that there was definitely something happening on the track. Is this the same problem you guys are talking about even though the phantom power (presumably) doesn't affect Ch 3?

I don't recall ever having done anything on Ch's 1 or 2, like plugging or unplugging, with the phantom power 'on' as a result of extreme paranoia with electronic equipment but I have switched the phantom power on and off with the MD8 on in the past - never having seen anywhere in the manual where this could cause a problem.
 
DOH! Blackwood, you broke it. But don't worry--I'll take that MD-8 off your hands for free.

I think your microphones and your instruments are broken, too. I might have to charge you for taking those in, but we might be able to work something out.
 
back off Kelly! You already have one, and you can't link two of them together anyway :D

Blackwood - Are you positivly sure you can't get ANYTHING out of that track? Have you tried both through the stereo bus, and through the cue mix? I've had times when I couldnt hear a channel and it turned out some knob or button was pushed that was stopping the playback.
If you have already tried everything possible, and are sure it's an issue with faulty hardware, I would either a.)take it back if it's under warranty and get a new one b.)have it repaired by yamaha
Sorry I couldnt be of more help.
-Nil
 
Actually, I have five. And after four or so, they do start working together (but you must drink a beer for every MD-8 you have to make this possible).

Yep, five MD-8s. Two Rolls-Royces. Fifteen 300-year old Bonzai trees. And a partridge in a pear tree.

Of course, I couldn't afford any of these things. I just reply in BBSs to broken equipment and rack up. You wouldn't believe how many Yugos I've got!

NILBOG! YOU RUINED EVERYTHING!
 
skybolt6 said:
I spoke with a guy from Yamaha and we sat down with the schematic and the unit and here's what he told me.

The IC for the mic pre for CH1 and 2 is a NJM2068, labelled on the board as IC101. This is what actually blows when the phantom power is on and you insert or remove a 1/4" plug from CH1 or CH2. This needs to be replaced, and R106, R107, R206, and R207 need to bre changed from 10R to 100R. That's the good news. The bad news is that all that stuff is surface mount. No problem for me but if you can't solder surface mount devices I wouldn't practice on my MD8.

Anyway, once my op-amps come in, I'll let you all know how I made out.

Farrow
Click to expand...

Does this fix the problem?
i have the same problem just wanted to know if this works!!
Phil
 
philst said:
Does this fix the problem?
i have the same problem just wanted to know if this works!!
Phil
Click to expand...

This is one old thread... Half the people involved are probably drug addicts by now.

ha - just kidding, they were drug addicts before.
 
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