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New 2203 build, no power at speakers??

JDW3

Member
Messages
3,637
I just finished a Metro 2203 kit I had sitting for awhile. It's my second build and I took my time. I checked all the voltages and bias twice. Everything looks good; biased at around 35.5mA.

There's not even a hiss coming through the speakers. I checked the cab and cable with another amp, all good.

It's not the 470ohm resistor in the PI, either!

Is there a way to check for power at the impedance switch? I was trying to check for 13/15 ohms at the cliff jack and I couldn't get a reading. The speaker cable reads 13.4 ohms from the speaker load.

I accidentally used input jacks on the output; I don't think this is the problem.

Anybody have an idea?
 

gldtp99

Member
Messages
3,880
Do you have the signal shunted to ground at the speaker jacks ? check your wiring---- many types of jacks can be used for speaker jacks, if they're wired up correctly............................gldtp99

PS--- I also have two leftover Metro 100 watt MV kits sitting in boxes---- I'll get around to them one of these days
 

JDW3

Member
Messages
3,637
Do you have the signal shunted to ground at the speaker jacks ? check your wiring---- many types of jacks can be used for speaker jacks, if they're wired up correctly............................gldtp99

PS--- I also have two leftover Metro 100 watt MV kits sitting in boxes---- I'll get around to them one of these days

These look exactly the same. I've seen other builders use them for outputs, it appears. I hate to rip them out if it's not the problem.
 

Jerry

Gold Supporting Member
Messages
667
Do you have a sine wave generator? You need to send a signal into the amp and follow it through the different amplification stages to find out where it stops. Set your meter for AC volts to read the signal passing to the output stage. If you don't a have signal generator you can find freeware programs on the internet that will work. Here's one:

http://www.nch.com.au/tonegen/index.html
 

JDW3

Member
Messages
3,637
Do you have a sine wave generator? You need to send a signal into the amp and follow it through the different amplification stages to find out where it stops. Set your meter for AC volts to read the signal passing to the output stage. If you don't a have signal generator you can find freeware programs on the internet that will work. Here's one:

http://www.nch.com.au/tonegen/index.html
Send it into the amp through an Apogee duet or something? Never used one.

Neat device to have.
 

Jerry

Gold Supporting Member
Messages
667
You can send the signal out of your computer headphone jack. IIRC, you could possibly get 100mv of AC signal out of the headphone jack.
I just tried it with my MacBook Pro and got 1.0? V at the headphone out. I used a 3.5mm TRS to 1/4" cable that Hosa sells. The 1/4" plug is a mono plug. You can download a free version for trial.
 

Prairie Dawg

Member
Messages
1,928
I think it's time to get back to fundamentals. Troubleshooting 101 says that you did something wrong or overlooked something.

Do all that is necessary to localize the problem, by using temporary bypasses and such.

If you have B+ at the output transformer center tap and vP on the plates and your screens are hooked up right and your connection between the PI section, the two coupling caps and grid stoppers and all is correct, then you should see some output. You can ring out your transformer primaries and secondaries while you're working in that area.
That'll limit it to a few things like jacks or impedance selectors.

On the other hand, you can always really go back to fundamentals and get a schematic and a highlighter and validate your build connections and component values from one end to the other.
 

JDW3

Member
Messages
3,637
I got it running!

One of the output cliff jacks is bad. Can't believe it. So, I'll replace it.

Ears are ringing! Way too bright, haha. Can't wait to make some adjustments.

I think the standby switch is also suspect. Making some thumps, too.

They do not make them like they used to.

Thanks guys, for the tips!
 




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