Sound cutting in and out

Get a RCA cable and connect from your amp where it said Sub Woofer in the Pre Out box in the back of the amplifier top left hand side and take it to the "Sub In" located in the back of your Sub woofer bottom right hand (White round connector).
Good Luck!

Are they defined? How do they sound with test tones?

http://www.retrevo.com/support/Onkyo-TX-DS838-Receivers-manual/id/365ag203/t/2/

We can't assume that all has been followed in the manual.

Does it have a cooling fan? if it does, then check its actually working. Protecton circuit maybe cutting in.

Not worth repairing until the root cause of the failure is proven.
The reason being is that you can have it happen again if caused by any of the devices attached to it, such as inefficient speakers.

Hello sir, there are several factors that might cause this:

1. Low voltage. check for filter leaking capactor. defective regulator, or a burnt resistor.
2. High voltage peak, check for the voltage output VCC.
3. the main amplifier is defective. if it is an IC amp. replace it. if transistorized check for the pushpull driver/transistor.

Hope this helps. let me know your progress. thanks

Go to http://www.retrevo.com/, regsiter for free and search for Onkyo TX-DS838. It will prompt you to download the manual (3.3MB).

Sight unseen my money says the new problem is a direct result of the 'repair' to the channels that are giving you problems now. You didn't elaborate on what it was you were trying to fix in the first place. Backtrack your steps and undo what you can to see if the bug changes.

The speaker impedance is not the problem.

sounds like the tape monitor may be turned on. First place to check anyways. If it is not the problem, I am happy to talk more about it with you and do some more diagnoses.

regards
Graeme

The problem here is that the output amplifier section has a problem. This is detected internally and the system shuts down in a "protect" mode. The output section really only kicks in when you attempt to bring up the volume. Another possibility is a problem in the "front end" where DC current is being passed to the amp section. Without takeing measurements, it is difficult to determine the exact cause. This should be a relatively stright-forward repair for a service shop and should cost about $20-$40 in parts plus the local labor charge.
Dan