Yamaha EM Series Reverb Not Working

[blackemmons]

Been searching for hours on a solution to a Yamaha EM300B issue and came across this site. So here is my first post.

I have a number of mixers which include a Yamaha EM100II and an EM300B. I like the simplicity and the warm sound of these units so I hate to take either to the curb.

The EM100II is fine but the EM300B has just developed a reverb problem. The issue is, I have no reverb on signal, although reverb crashes when the chassis is bumped. I have tried an external unit through the "Echo In and Out" on the rear but with the same results.

Any help would really be appreciated.

Also, does anyone know how to get the top off of this unit?? I would like to check the wiring at the "Reverb/Echo" control.

Thanks in advance.

JimE

[Jazz P Bass]

Here is the service manual.http://89.228.128.119/RemoteDownload...nual++-+EN.pdf
If crashing the enclosure makes the reverb tank emit sound, then the return side is good.
You need to track down why the signal is not reaching the tank.
Check the tank cables & inspect the tank itself.

[blackemmons]

Thanks Jazz P Bass.

If I can get the the thing apart, I will try to do some wire tracing this afternoon. If it's more than a wire I'm probably up a creek.

Thanks for the link also.

Jim

[nickb]

Since you get a noise out of the reverb we know the downstream circuit is probably ok so it's the the reverb tank or something upstream. It quite common for the drive coil in the reverb to break so if you have no diagnostic tools you could simply try replacing the tank. Better, would be to check if you have a drive signal into it. The connections are easy RCA jacks. You could connect the drive side to a speaker via a 100 ohm resistor (to protect the drive circuit) and see if you get a signal.

[Jazz P Bass]

If I can get the the thing apart

Jim

Look at Page 15 of the SM.
Screw # 18 holds the bottom on.
It looks like there are ten of them.
The top is hinged at the rear.
Remove the screws, flip the unit upright & the top should lift up & back.
The reverb pan is shown on the left side of the chassis.

[blackemmons]

Jazz,

You are so right.

Opens like a book and nothing falls on the floor. Great design.

Not much to look at(for me) when I got it open. Didn't remove any thing but checked all of the wires I could find. Nothing seem to be out of place or loose.

I'll give it another shot later.

Thanks for the continued help.

JimE

[Jazz P Bass]

The input & output jacks of the reverb pan are connected internally to a coil.
There is one at the input & one at the output jack.
Use your ohmeter & verify that each coil does have continuity.
You can measure right at the jack.
Look at the jacks themselves.
The coil wires run right to it.
Sometimes one (or both ) wires will be unattached.(overexscursion of the spring tray will break the wires)

[g1]

You said an external FX unit connected to the "echo in & out" did not work either. In that case it is probably not the reverb tank itself.
From the block diagram, the reverb/echo signal comes from monitor 1. Check whether mon.1 is working or not, it should help further isolate the problem area.

[blackemmons]

Jazz/g-one,

Thanks for the continued support.

I will try those suggestions tomorrow. Don't have time right now. But......

Here's another piece to the puzzle.

I plug my Boss RV-3 pedal into the external "send" and "return" jacks on the back panel and nothing happens. But, if I unplug the plug from the "send" jack of the mixer, leave it still pugged into the "in" jack on the RV-3 and touch the "tip" of the cord, the electronic noise(Hum or whatever you want to call it") can be heard in the speaker. I can change the amount of delay or the tempo of the delay/reverb pedal and it will be heard in the speakers.


RV-3 OUT............ TO ................. Mixer Echo Return

RV-3 IN ............. TO ................... Unplug from Echo Send and touch cord tip.

I hope that explains it.

I appreciate your help.

JimE

[J M Fahey]

From the block diagram, the reverb/echo signal comes from monitor 1.

This is a clue.
Maybe everything works fine, simply the OP is not sending signal to the reverb tank.
Just sayin'

[blackemmons]

This is a clue.
Maybe everything works fine, simply the OP is not sending signal to the reverb tank.
Just sayin'

Sorry J M, This isn't the first time I've turned it on.
Just sayin'

[g1]

Ok, so you know that when using the external loop the mon1 master has to be up, but with the internal reverb mon1 master can be down (just sayin' ).
The boss pedal thing confirms no reverb signal is getting to the send jack. Should you find the mon1 is not working, and assuming the reverb problem is for all channels, then your problem is probably in the IC15 circuit, it looks to be the only thing common to mon1, the internal reverb send, and external FX send.

[blackemmons]

JAZZ,

Checked the two little coils, in and out, and there is continuity.

???

[Jazz P Bass]

In that case you will need to trace the signal through the circuit to see where it is failing.

[52 Bill]

And did you check the drive cable as Jazz suggested earlier?