Pop from speakers when using dolby digital mode, works fine when not using any processing mode

What I suggest is that you reset the receiver as you mentioned. If you look in your owner's, there will be a procedure that says, "Return to factory default, or Reset" I believe you have it set wrong, or are not providing it with Dolby Digial signal. Dolby Digital, is not processed by the DSP board(Digital Sound Processor), which handles the THX, Neo, and every other format. Dolby Digital, is one of the earliest form of Home Theater. It has to be processed through the 2 RCA jacks(left and right). It is really not used anymore, in light of Dolby Pro Logic, THX and others.

Popped power supply hi sorry if you can't get it on trying to do a diagnostic won't matter if you can open the back check where the power is going into you will c a power supply board a cap has carrots on it check if any of them is popped up

Hissing or high-level digital hash noise? Undecoded DTS or data bitstreams produce very loud 'rush' sound when treated as analog sources. Is it all sources or just some?

http://www.retrevo.com/support/Yamaha-DSP-Z9-Amps-manual/id/1071dj786/t/2/

As far as service manuals go, web search it "Yamaha DSP-Z9 service manual" - many for sale.

http://www.ebay.com/itm/Service-Manual-YAMAHA-HTR-5740-DSP-Z9-YST-SW1500-/130526188617

http://srvman.com/9131h1-d2pz9-rmrvicm-28u58l-p-1010.html

Are all the speakers turned off (set to None) in the speaker menu.(except the sub)?

2 channel direct analog stereo may still work, but any surround modes will use the speaker settings and the full DSP digital section.

Check also the input mode isn't incorrect - although if the sub is wired correctly and gives sound this can't be whats wrong.

In the manual it says switch off leave for 30 seconds and switch back on .

The P.BASS function is only available with 2 channel LPCM sources such as mp3,Divx,cd
and wma. Press P.BASS button and "POWER BASS ON" will be displayed on the screen.
The P.bass does not work with DSP/EQ or DOLBY PRO LOGIC ll modes.
If you press P.BASS in the DSP/EQ mode, the DSP/EQ mode is automatically shut off and the P. BASS function comes on.
The DSP/EQ function is only available in STEREO mode.
Press the PL ii mode button to show STEREO on the display.
This feature works with CDs, MP3-CDs, 2 channel DVD-Audio, DivX and Dolby Digital discs.
When playing a DVD disc encoded with two or more channels, multi-channel mode will be selected automatically and DSP/EQ function does not work.

The A1 has an internal self diagnostic program which you can go through to find the fault. You can access the diagnostic program by simultaneously pushing some buttons on the front panel. The Yamaha service manual for the A1 tells how to do it and what the diagnostic codes mean. You can get a copy of the service manual on the web from several suppliers for a small fee.

The A1 has an internal self diagnostic program which you can go through to find the fault. You can access the diagnostic program by simultaneously pushing some buttons on the front panel. The Yamaha service manual for the A1 tells how to do it and what the diagnostic codes mean. You can get a copy of the service manual on the web from several suppliers for a small fee.

If it is a new DVD that may be a problem, as signal changes may be frustrating this old machine... but it is likely the cabling from the DVD player to the reciever. Are you on the right channels/settings? is the optical cable and digital cable recieving digital output from your DVD player? Try changing those settings and you should be in good shape Thanks! good luck!

i am no expert but i had simmilar problems and it turned out that some capacitors needed replacing