Suddenly, no output from Copland CTA-501

[Kevster]

Hi guys, and I am happy to have found and joined your forum.
Initially I was wanting to find out about biasing the valves, which I have since found threads on.

However, I was dismayed to fire up my Copland CDA-288 CD player going into the CTA-501 and I heard nothing, nada, zilch.

The amp seems to power up OK, and all the valves are still well lit but there is no sound whatsoever coming through to the speakers.

Any ideas what might be wrong here?

I am new to valve amps, and am totally lost about where to begin the diagnostic process.

Any help would be gratefully appreciated

Regards
Kevin

[anatech]

Hi & welcome Kevin,
Unplug an RCA plug from the CD and touch the end lightly. Sound?

If not. Turn the amp off and let it sit for 1/2 hour. Check all connections. Then check for blown fuses.

Also, did you adjust the bias? If so, turn it back down or back where it was. Do you leave it running all the time (my opinion - don't)?

Do you have a meter, if so what type? How much experience do you have with electronics?

Have you read this ?

Do not do anything until you have.

-Chris

[Kevster]

Hi Chris

I was just about to consider looking at the bias when the whol eamp went down, although to be fair, I was slightly reluctat to, given my very modest electronics experience, and the fact that one has to do it with the amp powered up !

I've got a modest multimeter and haven't dismantled the amp to look at fuses yet.

Anyway, to answer your first question: yes, when I touch the positive pin of both L+R RCAs (from CD player side) I get a humming noise. Is this 'good' ?

Thoughts ?

Cheers
Kevin

[anatech]

Hi Kevin,
Your amplifier is okay. Time to start looking at the source and / or preamp.

Please click on the link and read the safety notes first.

-Chris

[Kevster]

Chris

I've tried the CD player elsewhere and its fine.
I don't have a pre-amp as such, I use the CD-Direct input on the CTA-501. That's all I use: CD, amp, speakers.

I can't see how its not the amp that is malfunctioning. Any other ideas for what could be up with the amp ?

Kevin

[anatech]

Hi Kevin,
The fact you got a hum by touching the end of the RCA would seem to indicate the amplifier is working. Short of hooking up a signal generator, load, 'scope and meter to measure the gain, it's a quicke test.

Turn everything off, redo the connections one by one and try it again. If it still doesn't work, try another CD player. The setup is so simple it has to be something simple.

-Chris

[Kevster]

Half curiosity, half desperation, I took your advice, stripped everything down and re-connected. And guess what...it's working again !?

That is the spookiest experience I have had in 20 years of hi-fi !!

I'm gonna leave it on for a few hours and see what happens, fingers crossed, and crack open a beer and toast you !

I wonder what caused that total shutdown ?

Kevin

[anatech]

Hi Kevin,
Confusion?

Just kidding, some times these things happen. It's called "no fault found" in the repair industry.

I'm glad it's working for you, and hope it continues to do so.

-Chris

[DigitalJunkie]

I was about to suspect the cables,but your "finger hum" signal traveled through them okay,so they're good.. Maybe the (RCA) connectors are loose somewhere?

[cogsncogs]

In some case's it was the operator! Not the original poster tho!
As DigitalJunkie posted, I'd say the next time it happens wiggle/change/use a different pair of interconnects from the CD Player to the amp.
A few nights ago I was listening to my muzac and all of a sudden the left channel slowly faded into silence! I RAN to my toob amp to look for a frying output tube, toobs OK. Wiggled volume control, selector switch, noop! Interconnects wiggled, found it! I've learned a lot of times in the repair business it the simplest of things and the cause of major headaches, time and money!
Glad you REPAIRED IT all by yourself! crossfingers

Wayne