• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

I have power but no sound???

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Hi,
I have a little hybrid valve amp I picked up in taiwan, for the price the sound it produces is (was) surprisingly good. Unfortunatley it's now not working and I want to get it going again.
I think the cause may of been a power surge in a storm... but it may not be... the main reason I think this is my DVD player broke at the same time, I have a really cheap multiplug adapter that claimed to have surge protection.... I live and bought it in thailand so this may not be true and we have big electrical storms here.
Anyway,
The amp will power up, lights come on, the digital input display comes on but no sound comes out... I know it's not the speakers or cables at fault. What are the most likely problems?
Thanks
 
This is very difficult to answer without more detailed information.

Can you provide a schematic for the amp? Pictures (especially with the cover taken off) may be helpful too...

Do the valve heaters come on when you apply power?

Andreas

PS. Your thread title is a common problem of many bands - they have power, but no sound :D
 
yes the valve heaters come on, until you actually try to play music it seems like everything works and comes on as normal....

I have no schematic and the manufacturer wont send one, I think so people can't copy the design... although it's nothing extra special. I'll take some picture and post them once I'm done.
 
One photo of the outside so you have an idea of the style of amp, then the inside. I've pulled the usb circuit out the way... so you can see more, but I think you'd have to be a genius to figure out the problem from the photo.... I have a multi meter if you can in very simple language describe for me where to poke the spikes and what values I would expect.
 

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Hi,
From the picture that showed the board I can see the pins for the tubes. Check to see if you have high voltages. You have to get the tube pins so you can check the voltage for the plate and grids. Also try to see if you can locate a fuses around the power supply. I know it is hard to troubleshoot without a schematic but you need to see if you can figure out where it is everything.
 
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This thing has a micro-controller in it, when you select other sources does it indicate that it switched to them?
Do the relays click when you select a (different source?) I can see the volume control is a pot.

Can you ship it back to the manufacturer for repair?

Since you are inexperienced please be aware that there may be moderately high voltages internally in addition to your hazardous 220V mains. Please read the safety thread here before poking around inside.
 
look for a b+ voltage fuse. Also, get someone to check your bias. sometimes you can have lit filiments but if the bias does not show current you could have a blown b+ fuse, or blown resisters, worse case....a blown transfomer. the filments are on different windings from the B+.
 
the main fuse (actually only one i can find) was blown but I replaced it and now when I turn it on it doesn't blow again.

The Inputs change as normal as I flick through them with a healthy 'click', so that all working.

The Valves are 6N2's... I think but may be wrong are similar to 12AX7.

Sending it to the manufacturer will be my last option as I'm likely to get stung by import duty as it come back Taiwan to Thailand.

What's a b+ voltage fuse and where do I find it.... I'm keen to learn, at the moment all I know is I don't like electric shocks and will be very careful to ensure I don't get one.
 
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Joined 2010
Hi,

I would forget the tubes, It looks like the power amp section could be a Chip amp (is this two IC's one for each channel on the large heat sink?)
Could be voltage regs?

If you have a multi-meter and use some cheap (car speakers) see if you get a hum (BUZZ) from the output if you connect a meter lead to the volume control connections. If the amp is in two stages tube preamp and chip output. You need to see if the chip output is working. If it has two chips one each for left and right
If they both don't work it could be a common PSU fault. If its a common stereo amp then this is a starting point<<<check to see if you have power rails and can you get a BUZZ if you connect a meter lead to the input..Can you hear a hiss from the speakers?

Its hard to give advise without a schematic..and be careful of high voltages!

Work from the output section to the input..ie if the power amp is faulty you can forget the rest!

So the trick is to find out where or what is the power amp..get this working first!

Regards
M. Gregg
 
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Ok I've made some progress.. I've had a reply from the manufacturer:

"First test headphone, if only 1 channel have sound, this problem is one TDA2030 breakdown.
other problem please see the attachment delay circuit diagram."

I tested the headphone socket, which to be honest I hadn't thought to do... and I have just the right headphone playing music, whilst the left just hums. So this must narrow down the problem to TDA2030.... but whats this and what does it mean?

They also sent me a circuit diagram of the delay circuit if it helps at all.
 

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Disabled Account
Joined 2010
The TDA 2030,

Is a chip amp see this link for an idea:

http://www.itisff.it/dip_eln/tda2030.pdf

So you need to do a test to see if you can get a hum from a test lead when connected to the volume control.

If you connect a meter lead to the center tap of the volume control for the left and right channel you should get a hum this would tell you if the power section is faulty. if you dont get a hum then the fault could be one of the TDA2030 chips. Or the power supply to the chip amp for that channel.

So first does the chip amp work for the faulty channel.
If not is there a power supply to that amp? if yes then test to see if you get a hum if you connect a meter lead to the input of that channel amp.
If no hum from that channel then it could be the chip amp.
If you get a hum its in the pre section and the TDA2030 is OK.

You need to do these tests first..

Watch out for the B+ high voltage for the tube section..if you don't know what I'm talking about get an engineer to test it!

Regards
M. Gregg
 
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