onkyo 919 Receiver... hum problem but...

[budwich]

I have an onyko 919. It has a hum problem at cold start which eventually dies / goes quiet. I have been "chasing" it for a while. Tightening ground screws and checking a few places. Basically, the problem is in the "back half" of the unit.... that is, if I take the sound out of the "pre-out" and feed it to a stand alone amp, it is good. If I feed in a signal at the external decoder input and play thru the back end of the onkyo, it has the hum.

Anyway, along the way (the chase), a number of components (resistors, capacitors, etc) on the main board and the DSP board are loose and appear to have "cold solder joints" or equivalent (ie. poor solder connections). These may be contributing the problem... maybe. Some are addressable with the boards in place BUT the DSP board is at the back of the front panel and the board itself needs to be removed. :-(

To get the board out, I have been fighting with "damn onkyo ribbon connectors". The individual wires of the "ribbon" are "ribbed" and each appear to push into the body of the connector. I have ruined on connector that I have included a picture of. It has 5 wires / pins. As you can see the wires are somewhat "ribbed" making it very hard to pull them out of the holder. As you can see, the entire body of the connector pulled away from the board... :-( I think I have figured out how to remove the wires "normally" by pushing down on the "top holder cover" of the connector. My question is: Does anyone know what the name of the connector is referred to as and can they be found anywhere for sale?

To get at the board, I need to release about 5 others and am hoping not to "crunch" any others.

Thanks for any help / direction.

[budwich]

Re: onkyo 919 Receiver... hum problem but...

closer look at the dsp board with the "wiggling" components. The pads of those components have come "dislodged" from the board substrate. The component, itself, is still soldered / connected electrically thru to the subtending track. Perhaps a bit of crazy glue to give some "solidness" to the area to prevent possible fracture of the track????

[redwire]

Re: onkyo 919 Receiver... hum problem but...

The ribbon cable connectors have a release latch. If you don't undo the latch- you will trash the connector. I thought it's a bar that you poke with a small screwdriver that pushes back the spring on all pins.
edit: I think you pop up the top plate

[budwich]

Re: onkyo 919 Receiver... hum problem but...

thanks... yep... one tab on one side of the "cover" broke off and then continual pulling caused the whole connector to become detached. Yes, pushing on the top helps release the grip but it still seems very difficult to pull up on the ribbon wire as it appears that the "release tab" in the underside doesn't have enough "drive" in to the fingers to spread them to release the wire. I have not found any such connectors in my search so far so it is unlikely I will find a replacement. I hope I can make do with the existing connector "remains".

On a side note, I found an electrolytic cap (vertical mount, thru the hole) that has its outside "can" able to rotate / turn. Strange, never come across that before. The "legs" are still soldered / attached properly to the boards. Its a likely candidate for replacement and potentially the "root cause" of the noise... I am hoping.

edit: out of circuit test on the cap indicates 368uf as opposed to the 100uf value. fingers crossed.

[budwich]

Re: onkyo 919 Receiver... hum problem but...

well, the replacement of the cap didn't resolve the hum problem at cold startup. It seems a bit better as it dissipates more rapidly. Perhaps more than one cap is an issue or some cold / broken solder joint exits. Might try heating areas with a hot air station to see if I can pinpoint anything better. Could be a long process as cool down takes a bit to bring back the problem. :-(

The damaged connector for the ribbon cable is posing somewhat of a problem as its connections are not stable. One finger in the 5 spring tabs is not making good connection at all times resulting in the loss of source selection on the sources on the far right of the panel source buttons. I haven't found any replacements for this type of ribbon connector. It appears to be some form of IDC type connector.

[budwich]

Re: onkyo 919 Receiver... hum problem but...

Using a hot air soldering station with directed heat, found another cap (parallel to the other bad cap) also bad. The system starts up quiet with the cap heated. Hopefully, that's it and I can get the problem connector to hold the ribbon well.

[budwich]

Re: onkyo 919 Receiver... hum problem but...

Upon trying to re-assemble the front panel to the body, the ribbon cable going to the dsp board lost its "backing". There was some sort of plastic "backing" that held the alignment of the very flat thin wires to allow them to slide into the connector. Now it seems impossible to slide them back into connector. looking for ideas on how to get this connected again. :-( maybe they fold over and are taped down with something??? The cable has the following labelling... sumitomo-y awm 2898 vw-1.

thanks for any help.

[budwich]

Re: onkyo 919 Receiver... hum problem but...

does not look good. I tried to fold over the contacts on to the existing cable structure... not good, one broke off so I need some way to salvage the existing cable or find a replacement. The "good end" (on the left) has some sort of "tape backing" to reinforce the area so it can be pushed into the socket receiver. That's what was missing on the "bad end" (on the right).

Any ideas or leads on these types of cables?

[budwich]

Re: onkyo 919 Receiver... hum problem but...

I giving the "old dremel will fix anything" trick a try. Used a fine wheel to remove some of the insulation on the "bad end". I hope that I can get good connection with what is there and it holds in the connector.
As it turns out, it worked well and the unit has been buttoned up.