Another Yamaha EM 150 question...

[Drummer53]

ok, will do, my excitement of this "little gem" has definitely got the best of me! And to some degree, consumed me to the point of "I'm gonna make this thing work if it's the last thing I do!!" I am going to downshift and go slow and take it one problem at a time. It maybe a day or two or three before I post any results. Can't thank y'all enough for the continued advice and patience!

Like a kid on Christmas, opening up a RC toy, got the controller, pushing all the buttons and nothing! Hello?..it takes batteries!

[Enzo]

That can of Deoxit is not cheap, but it probably will last the rest of your life. It doesn't take a lot of the stuff, it ain;t like hosing down your driveway to clear the grass clippings.

[Drummer53]

thanks Enzo, I kinda figured the ol' "little dab will do ya" would come into to play, something that comes in that small of a container and cost that much tells me, it don't take much. See, I do have some common sense somewhere in this rusty ol' brain!

In my slowing down mode and checking things a bit more, I did come to find that one of the 0.47 k Ω 5 w resistors (white block ones) on each board has no continuity. One board has the two new ones, and the other has the two that were there when I bought it. If you hold the board up in front of you, both the bad ones are on the left side of each board.

And while I'm at it, I might as well ask, I read where an 8 ohm resistor soldered to speaker wire makes a quick and easy "dummy load", is this sound advice and does it work?

How to Make an 8-ohm Dummy Load | eHow.com

[Jazz P Bass]

The bad transistors probably took out the 0.47 cement resistors.
An 8 ohm resistor is fine for a dummy load as long as the wattage rating is high enough for the device under test.

[Drummer53]

Whooo Hooo! Success!!!!, both speakers crankin' and clear!!!! Replaced the bad 0.47 k Ω 5 w resistors, made the 8 ohm dummy load, read the manual, set the bias, and "boom chakalaka...laka...laka!!!". Tried calibrating the VU meters, didn't have much luck there, will try and calibrate them on another day along with the indiviual channels, had a pretty bad storm roll in, kinda put a damper on things! So does mean I graduate from "rusty ol' cob web head" to "rookie who now knows a little less than nothing"? Couldn't done it without y'all! And I'll probably have some VU meter and channel questions once I get to those, but y'all are the best! 10,000 thanks and more! Although my neighbors probably won't be thankin you! hahahaha!

[Jazz P Bass]

For the VU meter setting, I ran a 1K 100mv signal into a channel.
With the channel & master volume set to read 17.3Vac RMS at the 8 ohm output load. (37.5 watts)
The balance should be set either in the middle or you can go full over for whichever side (left/ right) you are setting.
Turning the pot until the output on the VU meter reads "0".

[Drummer53]

Still haven't got to the VU and individual channels calibration, but I just had to share this with y'all....so I go back to the thrift store where I bought the board, looking for other "gems" of course, and tell the guy what I did and how great the board is working. And I first and foremost let him know that it was "two guys on this forum I joined" that walked me thru it. Well, a little chit chat goes on and then he asks me, "hey, do you think you'd like to repair any old systems I get in?" (insert the double take..what did you say?) ....I'm like sure as long as you know up front that I am a novice, I know nothing about all the technical side of things, and it wouldn't be me alone as I would have to search and ask the experts for help! He seemed to be ok with it and explained to me that he throws a lot of repairable stuff out because he doesn't have the time to fix them or he sells it to another guy for double dirt cheap who then repairs them and then sells them himself at the local flea market, Craigslist, etc. At any rate, I just thought it was cool for him to offer, don't know if anything will ever come of it, but if by chance it does, and I end up asking y'all for advice, etc. and if you are up for it, I would and will definitely try and compensate you somehow. And trust me, I know my limits in this stuff and I'm not going around thinkin I can repair "all things". You guys deserve the credit and if you lived here, I'd tell the guy to call y'all!

[Jazz P Bass]

Just my 2 cents.
While it is always a good thing to repair ones own equipment, venturing out into the no-man's land of repairing other people's equipment should not be taken lightly.
#1: they are relying on you to repair the equipment in a professional manner.
Meaning the repair is to factory spec's & in will perform as such.
#2: there is the liability issue that will now be hung over your head.

[Enzo]

On the other hand it is a trial by fire learning experience. You are being honest with the guy to not misrepresent yourself. SO learn how to say "no". "This is beyond my skills," is a perfectly legitimate thing to say. But instead of working on the same five amps you own all the time, you will constantly face new things. Forces you to learn but also shows you how much various amps have in common.

Now an industry secret - a large percentage of repairs are utterly simple: broken jack, broken pot, bad tube, bad power amp IC, bad speaker, loose wire, that kind of stuff. Most repairs are simple. And a good portion of repairs that come in actually have nothing wrong. Guys complain about hum in the amp, but it really is coming from his guitar. A dead chanbnel on a power amp is really the stereo/bridge switch in the wrong position. That sort of stuff.

[Jazz P Bass]

Ahh.
"Trial By Fire"
That I like!

[Drummer53]

Thanks again Enzo and Jazz, and I definitely let him know up front that I am "super novice" but am willing to try if he wants to take the "risk". Most of the stuff he gets is "pennies on the dollar" stuff and he doesn't have a lot invested into them. He told me the other day he just got an Onkyo receiver in that as he put it "has to read the manual just to turn it on!", and I'm like, "I ain't touchin that one!". And thanks for the "industry secret" Enzo, in the back of my mind I kinda figured that, it reminded me of our small engine mechanic. I asked him one day, "so are all small engine problems in the carburator?" and he said about 90-95% of them. I then asked him if he could show me some small engine "industry secrets" and he did and it does not take any work away from him as I reassured him that we are still going to bring him our "problems", but if I can fix a 5 minute problem, I'm going to fix it myself. And not that I'm a small engine guru now, but I do know how to look, check, and fix things with more confidence. My biggest fear/obstacle with electronics is the "lingo" and all the levels, impedances, ohms, etc.. But since undertaking this mixing board adventure, I've been learning how to read schematics, learning about all the "lingo", etc. I really don't expect a lot of repairs from this guy, but it was just cool that he asked.

Now for another quick question and please point me to the proper forum if it needs to go there. I also got a Sherwood S-7100A receiver from this guy, which as you probably know, is a really cool vintage receiver and as you've probably guessed, I'd like to hook the Sherwood up to the Yamaha. What I'm trying to accomplish in the end is to have a decent "outdoor" live setup. We live on a small farm and I'm planning on having some "little jams/gigs" this summer. I'd like to be able to hook up the Sherwood, a Zoom H2, my laptop, and a projector (still treasure huntin on the projector item) to this mixing board. And as limited as the board is, I do believe it can be done, I'm just not confident enough in where all the "hook ups" go or what would be the "best" set up to do this. And as the old sayin' goes "a picture is worth a thousand words!" hahahahaha!

[lokeycmos]

Those are generic replacement series types for whatever used to be there. Let us look for real parts instead.


here is your service manual attached below

Good luck finding 2SC1079, but if it were mine, I;d probably just stick a couple MJ15003 in their place and move on with my life.

i know that this is an old thread, but im looking for the same service manual and the link doesnt seem to work. could someone please repost it or provide a download link? thank you!

[Jazz P Bass]

Yamaha EM 150 Service Manual

Here you go.