Amp Repair???Any one

[morbe]

I have a
yorkville 100k amp that just crapped out on me. I get power but no sound. I know a littel about electronics and would like to fix it myself if I could.
Here are the facts.
Amp was taken care of very well,
all of a sudden the amp just stopped working,
I get power via the power light illuminates,
Get no sound at all, not even buzz,
The speaker does work, tested another speaker in the amp still no sound,
I didnt wanted to go further for fear of messing things up further.

Any suggestions???Thanks in advance.

[sumgai]

morbe,

If this is a Yorkville Sound amplifier, then we'll need a better model number than 100K. Their website, which has a large database of service manuals, shows no model by than name/number.




sumgai

[D2o]

Sumgai - Is either this or this it?

D2o

P.S. Harmony Central has no review of a Bloc 100K either (not that HC is the be-all end-all, but both Yorkville and HC do have mention of both the 100K and a Bloc 100G.

Morbe?

[morbe]

its actually that first one! That is what the support rep from yorkville.com sent me. but I would'nt know where to start. Though. Im hoping its a fuse but I was told that if it powers on chances are it's not a fuse.

[sumgai]

Go to www.yorkville.com, and search for "100K" - you get bupkis....

In fact, if you search for some of the items in the drop-down box on the "Obsolete" page, you find that nothing from the Obsolete category gives you a positive result. Interesting how they value their site enough to put in a search engine, then "blinder" it to a large part of their documentation.....

[sumgai]

morbe,

Look at the schematic.... see those two little gizmos in the upper right hand corner? Those are the effects Send and Return jacks. (Though you'd never know it from a can of Shinola - who taught those #%^@& how to draw a schematic? ) It so happens that all manufacturers (who don't use Switchcraft jacks) end up using crap jacks. In your case, the Return jack carries the signal from the preamp to the power amp. If the jack has a plug inserted, then the preamp signal no longer goes to the power amp.

Sometimes this jack goes bad for the helluvit, but often it happens when you plug in a cable, then unplug it, over and over again (over a period of time, not necessarily all at once). Testing this to see if it's the culprit is easy - simply plug a guitar cable into the Send and Return jacks.... if the sound is restored, then you know the Return jack is bad. Even if it works this time, when you unplug, it isn't guaranteed to work every time in the future. Time to replace it, muy pronto.

Now, take a look at the parts layout, page 4 of the "manual". The two jacks in question are shown as mounted on the PC board, so you'll have to remove said board in order to de-solder and replace the Return jack. Where to get a new one, and preferably one that lasts a little longer? Good question. As I said, absolutely all such designed jacks are crap, guaranteed to fail at some point. Which leaves you with two options:

1) Replace it with a like kind, and wait until the next failure;

or

2) Replace it with a Switchcraft jack that does not mount to the board. Instead, you mount it solidly to the chassis, then solder wires from the PC board to the jack. I've done this many times, particularly for pro musicians. They buy good-sounding stuff, but even Marshall, yes, and even Fender, will sometimes cut a corner where they think they can get away with it, and you, the poor user, gets a crappy jack (or two, or more...).

BTW, the reason these things fail is that their contacts can't carry the signal current reliably - ask ChrisK about wetting currents, and things like that. A jack that has never had to do this job (carry the signal from Point A to Point B) tends to not wear out the contact points. Point being, when you're in a rush, and/or need to keep the costs down, you can easily swap the Send and Return jacks - they're the same!! That's because the manufacturer needs stock only one part instead of two, which makes life easier for him, which translates to cheaper. All the jacks in your amp are exactly the same, but I wouldn't do this with any of the other ones, they're all doing about the same job - only the Send jack is free and clear for swapping like this. IMHO, of course.

HTH




sumgai

[morbe]

Well it wasnt that . I checked the connection, by passed the reverb all thather and still no sound. The amp is still picking up the signal because when the volume and gain are turned on I get the Clip light. Just No Sound!!! I know it has to be something simple, but the Phones jack doesnt even give sound.

[morbe]

You know I actually found the original schematics of that amp taped inside the amp it self and that schematics from the website are wrong. What worries me is that bother traynor and yorkville carry no information about the amp the model number according to my scheatics is the
Cube 100k. I know that it's a keyboard amp at 100 watts and solid state. I know that the speakers bothe work Woofer and tweeter. I took the entire things apart.
has three fuses all work fine. all the capacitors and resisters look fine (didnt test) but nothing looks like it over heated or is blown. the rca cables that connect to the reverb are soldered on to the circut board, then attach to reverb. I tried to connect the two cables together, bypassing the reverb completely. Still no sound. No sound through speakers and no sound through head phone jack. I spoke with an amp repair tech who said it had to be a connection somewhere or a bad component. but every thing looks fine. Its all in all a pretty simple design. I didnt test the jacks though it has quite a few. read that a faulty jack can cause some issues. but then again it recieves a signal just fine. it even clips out when all gains are on high. I know it's got to be a simple fix! and im going to get so mad taking it to a tech and having him fix in within an hours time.

[D2o]

Aug 18, 2009 6:43:01 GMT -5 morbe said:

You know I actually found the original schematics of that amp taped inside the amp it self and that schematics from the website are wrong.

Good. Suppose you can find a way to scan them and post them Photobucket?

What worries me is that bother traynor and yorkville carry no information about the amp the model number according to my scheatics is the
Cube 100k.

I know that it's a keyboard amp at 100 watts and solid state. I know that the speakers bothe work Woofer and tweeter. I took the entire things apart.
has three fuses all work fine. all the capacitors and resisters look fine (didnt test)

test

but nothing looks like it over heated or is blown. the rca cables that connect to the reverb are soldered on to the circut board, then attach to reverb. I tried to connect the two cables together, bypassing the reverb completely. Still no sound. No sound through speakers and no sound through head phone jack.

Good stuff, especially the less than obvious headphone jack

I spoke with an amp repair tech who said it had to be a connection somewhere or a bad component. but every thing looks fine. Its all in all a pretty simple design. I didnt test the jacks though it has quite a few. read that a faulty jack can cause some issues. but then again it recieves a signal just fine. it even clips out when all gains are on high.

test

I know it's got to be a simple fix! and im going to get so mad taking it to a tech and having him fix in within an hours time.

test, test, test ... there is no way to find that easy fix without finding that simple issue.

Good luck,
D2o

P.S. Just to be safe, this is not a Roland Cube 100 keyboard amp, is it?

Is it anything from this page? ... maybe this or this?

[morbe]

When I get hom I can attempt to scan the schematics. I'm really a beginner at all this so silly me that I didnt test the Jacks, resistors, copacitors, etc. Becuase I simply dont know how. I have a volt meter but I just know how to check if there is a contenuity.

[D2o]

Hey, I'm new to a lot of this stuff too (and you wouldn't believe some of the silly mistakes I've made!). So don't sell yourself short ...

... but don't short anything out, either. FIRST, UNPLUG THE AMP (I know this should be obvious, but ... )

Set you multimeter to 200 ohms and test the meter by touching the probes together - you should get a reading of 0 ohms (is it a multimeter that you have or does it measure Volts only?)

Start with the jacks - touch one probe to the tip and one probe to the sleeve (you are just looking for 0 ohms).

Then set your meter to 20K ohms (I think - don't worry, someone will be along to straighten the both of us out on the steps involved ) and continue on, checking potentiometers, capacitors and resistors where each component begins and ends - generally you are just looking for some sign of continuity, and if you find a component that is not continuous, that could be your culprit ... or not. But you won't know until you try.

Cheers,
D2o

[newey]

Morbe:

If you are indeed a newbie at this sort of thing, please read the warning I posted at the top of the amps page. And read ChrisK's warning on shock hazards.

guitarnuts2.proboards.com/index.cgi?board=Amps&action=display&thread=3595

There are capacitors in there that store a charge even when the amp is unplugged. They can give you a severe shock WHICH MAY KILL YOU!.

Checking a jack or 2 is probably OK, but once you get into checking the circuit board, you must be very careful not to touch the caps, or any other part of the circuit which would cause the cap to discharge.

It is necessary to discharge the caps before working on a circuit of this sort. Don't try this if you don't know how to do so. The caps will also discharge over time to a point where you might still get a shock but not at a high level. I think you would be OK if you unplugged it and waited several days- but maybe not, don't quote me on that one.

[D2o]

Aug 18, 2009 10:04:13 GMT -5 newey said:

Morbe:

If you are indeed a newbie at this sort of thing, please read the warning I posted at the top of the amps page. And read ChrisK's warning on shock hazards.

guitarnuts2.proboards.com/index.cgi?board=Amps&action=display&thread=3595

There are capacitors in there that store a charge even when the amp is unplugged. They can give you a severe shock WHICH MAY KILL YOU!.

Checking a jack or 2 is probably OK, but once you get into checking the circuit board, you must be very careful not to touch the caps, or any other part of the circuit which would cause the cap to discharge.

It is necessary to discharge the caps before working on a circuit of this sort. Don't try this if you don't know how to do so. The caps will also discharge over time to a point where you might still get a shock but not at a high level. I think you would be OK if you unplugged it and waited several days- but maybe not, don't quote me on that one.

Thanks, newey - no point in morbe changing to morgue.

D2o

[morbe]

I actually broke down and took it to a reapir shop and really good cheap and reputable one. $30 an hour compared to the $60+ an hour that this town averages. This is from hs ad.

" there is NEVER a charge to just open your amp and look at it. If I do repair your amp, I only charge $30 per hour (1-hr minimum) and most jobs take less than an hour (or at least that's all I count anyway). Only major jobs like re-capping or complete board rebuilds take longer than an hour. I will always let you know what it will cost before I repair your amp. "

I think that a board rebuild is self explanitory, but what is " re-capping" ?

BTW I know that I ask alot of question, but thats only because my mind is built like a sponge LOL. I'm a knowledge buff. My wife is even impressed that I know atleast 50-70% of all jeopardy, triva, 5th grader, cash cab, millionare etc game show answers.

Really though you guys are awesome!!! Never have i ever run inot a more knowledgable group of musician eager to lend a helping hand. all other are too arrogant for me.

[D2o]

Aug 18, 2009 13:46:15 GMT -5 morbe said:

I think that a board rebuild is self explanitory, but what is "re-capping"?

Hey Morbe,

It is simply replacing the capacitors.

I wiped out "simply" because, as newey has mentioned, this can be some serious business.

Cheers,
D2o

P.S. $30 an hour is a bargain if he's good.

[morbe]

Yeah it is especially here in San Antonio. I like that they are a cool laid back home buisness out to give back to the music industry and not trying to give too much into thier wallets.

the guy os good from whay I have been told, and he's somewhat sponsered by a guy that garantees every. from service to equipment to give free classes on how to set up and use the equipment he sells.

[ashcatlt]

Aug 18, 2009 9:46:50 GMT -5 D2o said:

Start with the jacks - touch one probe to the tip and one probe to the sleeve (you are just looking for 0 ohms).

Not sure what you're looking for here. Seems to me like 0 Ω between tip and sleeve would be a bad sign. There should be some impedance between the signal hot and the return. More likely, there's a AC coupling capacitor in there which will make it read open. (see below)

Then set your meter to 20K ohms (I think - don't worry, someone will be along to straighten the both of us out on the steps involved ) and continue on, checking potentiometers, capacitors and resistors where each component begins and ends - generally you are just looking for some sign of continuity, and if you find a component that is not continuous, that could be your culprit ... or not. But you won't know until you try.

Capacitors block DC current flow, and will always read as an open circuit when you measure across them like this. Well, big caps will show as an increasing resistance until they end up fully charged and go to infinite, which can take a little while. The smaller caps tend to "fill up" in the blink of an eye.

Also, I'm not sure that you'd get much continuity through certain junctions in transistors, opamps, etc. Even diodes can read as open when they work, particularly if you've connected the probes backwards.

On top of all this, your meter doesn't know that you just want to test this one thing. All it does is test the DC resitance between its probes. There are occasionally spots in a circuit where there will be a parallel path around a particular component, which could give you a "false positive" when checking continuity.

I think what would work better for this type of diagnostics would be a very careful use of an audio probe. First, look at the schematic and trace the actual audio signal flow through the circuit. Now open up the amp and identify this same path in the circuit. Be sure to identify the begining of the power amp section.

Now get your audio probe (it's a guitar cable with one end cut off, and a capactior attached to the "hot" conductor, plugged into something that will allow you to hear the signal). Carefully attach the shield wire to the ground of the amp circuit. Turn the amp on and feed it some input that is relatively steady and identifiable. I usually use a synthesizer set to Hold and Arpegiate, but even a CD player or iPod would work given the proper cabling.

Very carefully use the free end of the audio probe capacitor (or an alligator clip attached thereto) to touch the leads of each component in the previously identified signal path up to the power amp section. Do not probe anything in the power amp section itself. Be careful to only probe in places where you expect to hear a signal. Don't touch any power supply components. Through the signal path there will likely be differences in volume and tone at different points. That's okay. When you find a spot where you think you should hear something but don't, you've likely identified the problem component.

Did I mention to be careful? There's not much to worry about when you're poking around inside pedals and other battery or wall-wart powered contraptions. These amps - and other things connected to the AC mains - can and do have enough juice to mess you up pretty good.

[D2o]

Aug 18, 2009 9:46:50 GMT -5 D2o said:

..... (don't worry, someone will be along to straighten the both of us out on the steps involved ) .....

See? Told ya.

Ash, now that I read the post above, I don't remember where I was going with it.

D2o

[morbe]

So I was doing some research on my amp and of the issue that it was having and came across this.
www.musictechnologiesgroup.com/repairs.htm
If you do a search for the bloc 100K you will see in this data base that one Bloc 100K (BTW its listed as a yorkvill Sounds) had my exact same issue "NO SOUND PERIOD"
It says the the repair was "REP'D Preamp and Supply" I'm assuming that "REP'D" here means replaced? Can you repair a Preamp and supply is that possible or does it have to be replaced. Because all I was when I took it apart was ONE MAIN Circut Board and only 3 separate circut boards for all the jacks. So IMO to replace the preamp one would have to replace the enitre circut board?? Right? But then again the circut boards where not complex just a few Caps here and there as well as resistors. very simple looking if you ask me. back in 190 when this was done it was only bucks so I wonder what he purchased?? Any how I got this amp for real cheap ($30) and was wondering what the amp was worth these days. One Tech told me the speaker alone was worth about 50 in its current condition. from what I gathered mine was made from yorkville but has the Traynor brand on the Speaker grill. It's 100 watts loud enough to place an effects loaded mixer into the input and make it a decent PA for garage and backyard practice sessions. I don wonder what its worth when its in working condition to other100 watt models catch a rather nice price considering what I paid for it.

[sumgai]

morbe,

If the Clip lights are working, then the Pre-amp stages are all fine - no need to contemplate replacing this part of the amp.

Sometimes it's nothing more than a solder joint gone completely bad. I hit those once in a great while, and the only solution is to take the iron to every joint in the area. (I mean 'area of the schematic', not the physical area of the PC board, though they do often coincide. But it's connection points between the various circuits we're talking about, and they aren't necessarily located all together on the PC board.)

Oh, and Traynor metamorphosed into Yorkville Sound way back when.

HTH


sumgai

[morbe]

Well I hope the amp can easily be saved. This is getting me nervous that he's going to call bacl with this huge work order or worse that the amp cant be repaired. Well guess I wont know for a few days. I hope that it's not bad I would hate to drop major bills on a real PA this thing does a great job as a vocal amp.

[thisistgh]

Aug 19, 2009 13:51:42 GMT -5 morbe said:

Well I hope the amp can easily be saved. This is getting me nervous that he's going to call bacl with this huge work order or worse that the amp cant be repaired. Well guess I wont know for a few days. I hope that it's not bad I would hate to drop major bills on a real PA this thing does a great job as a vocal amp.

Morbe - did you ever figure out the issue? I’m dealing with the same thing.

[thetragichero]

hello welcome to the nut house!
this thread was last posted in over a decade ago, but i see morbe logged in about a month ago
if they are unable to respond, we'd be glad to help in any capacity that we can

[thetragichero]

so just to clarify: you're getting indications that the orange is working but zero sounds from the power amp? tried different cords, sources, etc?
using some contact cleaner on the effects loop jacks might solve the issue, but the more information you give us the better