Onkyo TX-SV70 Pro Amp-Tuner - Display But No Sound

Onkyo TX-SV70 Pro Amp-Tuner - Display But No Sound

The owner states that "all the buttons do something" on the front display when she presses them, but she hears no sound out of the speakers attached to it.

I asked her to make sure she had selected the correct speaker group(A or B). Still no sound. She was tuned to a known good local radio station.

Any other suggestions?

Reply to
Chris K-Man
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Chris K-Man wrote: =================

** Speaker relay not closing is likely. Blown internal fuses another.

....... Phil

Reply to
Phil Allison

So, she's tried the 'tape monitor' button, and that didn't fix the problem?

Reply to
whit3rd

______

I'll check all that when I visit the customer

Reply to
Chris K-Man

lem?

The easiest thing to have the customer check is the sound of the protection relay releasing/engaging. Turn on the unit and listen for a click. If non e, then there is a problem with the output section and the protection circu it is engaged preventing the speakers from connecting. This can be caused by many things in the output section.

When you get this for repair, look at the driver ICs (uPC1298V) for poor co nnections. This is a common failure point. Check any voltage regulators fo r poor connections as well.

Dan

Reply to
abrsvc

:

oblem?

on relay releasing/engaging. Turn on the unit and listen for a click. If no ne, then there is a problem with the output section and the protection circ uit is engaged preventing the speakers from connecting. This can be caused by many things in the output section.

connections. This is a common failure point. Check any voltage regulators f or poor connections as well.

____

On my personal JVC receiver, there's a click almost concurrent with pressing the power button, then about two seconds later, a second click, after which I can hear sound. Is that the click I should listen for o n hers?

Reply to
Chris K-Man

Chris K-Man wrote: ===============

** The first click is the power relay - it turns on the main PSU. The second is the muting/ protect relay.

BTW brand names are not models and models all differ.

...... Phil

Reply to
Phil Allison

Probably, yes. The first "click" would be a relay closing in the primary AC-power circuit, turning in the main power supply to the tuner and preamp and the amplifier. The second "click" would be the output (speaker-protection) relay closing, connecting the amplifier output to the speakers. This approach protects the speakers, and eliminates any bothersome "POP" when the DC power comes on.

In most such designs, the second "click" won't happen if there's been a failure in the amplifier or power supply circuit which would allow damaging DC voltage to be sent to the speakers. It can also happen as a result of a problem in the circuit which detects such failures.

A few years ago I diagnosed a huge Heathkit amplifier which wouldn't make music... the output relay never operated and the red "FAULT" light stayed on. It turned out to be a simple matter... a tiny (1/8-ampere) fuse providing power to one channel's input circuitry had opened up due to old age, and this created a DC-voltage fault that was caught by the protection circuitry. Simply replacing the fuse fixed the problem.

Another possible problem can be the relay itself - sometimes the contacts get dirty or arc-damaged, and won't make a proper circuit. This _usually_ seems to happen on only one channel, not on both at the same time... replacing the relay is the best solution in these cases.

Reply to
Dave Platt

Sorry for jumping into a continuing thread, but I 've had trouble with Onkyo an receiver, but I found a very interesting thing: they can heal themselves. The tuner on my first Onkyo failed. Since everything else worked I put the receiver aside and bought a new Onkyo. After a couple of weeks I decided I wanted to swap it out for a Denon. So I packed up the new Onkyo, and before I could return it I went back to the old Onkyo and the tuner was working, as was everything else. The tuner healed itself by sitting idle for a couple of weeks. Sometime later the sound went out, and this time I just unplugged the unit for a couple of days and, again the unit worked fine.

I still have the Onkyo, but I did switch to a Denon because I got a 4K display.

Reply to
root

root wrote: =========

------------------------------------------------------------------

** That is called an " intermittent fault " in the repair business.

When the unit works fine most of the time, they are often near impossible to track down.

..... Phil

Reply to
Phil Allison

Indeed!

I use the "Thump Test" (patent pending) when dealing with intermittents

- it does turn up a fair percentage of bugs. Just today I spotted an electrolytic cap that wiggled slightly when the case was lightly thumped. Turned out one lead was not actually connected to the solder (the joys of single sided PCBs), and the cap was a loose connection causing other parts to fire (a strobe system) seemingly at random. This was easy to fix, as it failed periodically, but only when tapped/thumped.

Other times not so lucky.

John :-#)#

Reply to
John Robertson

John Robertson wrote: =====================

--------------------------------------------

** That technique is known as " percussive maintenance ".

Another technique is " tune for maximum smoke". This involves a source of high current connected to a DC rail shorted to ground. One increases the voltage gradually while looking for smoke signals.

.... Phil

Reply to
Phil Allison

We also use the "dim light test" where you put a light bulb in series with the line input to the item under test. The light should not glow brightly except for initial turn-on, where it would be brightish, then dim as the caps charge.

Regulated power supplies are the technicians friend - where you can dial up the current available...

John :-#)#

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Reply to
John Robertson

______

So long story short: this lady and her brother lived next door to each other on the same street. When he passed, she sold her property and moved into his house. Included was this Onkyo receiver and CD player, and about four pairs of speakers all over the house.

You can just about imagine what I thought when I went min back and looked at how all of this was hooked up. The main speaker bus(A) is to the pair in the dining room. Bus B is where it starts to get hairy: the left speaker output goes to one of the speakers out on her deck, and the right terminal, as well as the surrounds and center, all had at least TWO SPEAKERS EACH hooked up to them!

Now she states that her brother ran it this way for years, and she just continued using it when she inherited the house, and this mess. Neither of them over drove it, just for background music from the built in tuner or the CD changer.

So I explained to her that it was improper to havr more than one speaker per terminal, let alone THREE, and that over time this affected the impedance, and caused the Onkyo to eventually overheat and probably blow a fuse. She says her brother worked in the stereo buisness for years. Hmmmm.

Sure enough, only one click after I turned it on, no delayed second click.

She said she doesn't care about "surround sound" and just wants to be able to hear the radio or her CDs. So I said she could probably just find ankther 10-15 year old receiver, plus a separate speaker sleector, and wire up her whole house that way. Or, just runn speakers A in stereo in the living room, speaker B left in e dining room, and speaker B right outside on the deck.

Reply to
Chris K-Man

John Robertson wrote: ===================

** That crude idea has very limited application. The series resistance of the lamp plus the rather large voltage drop does not alloy many items to operate.

I use a Variac and a digital current meter when powering up anything on my bench.

..... Phil

Reply to
Phil Allison

Actually the dim bulb, say 100W, has a rather small cold resistance so it doesn't end up with a large voltage drop - yet limits the current. It works well for amplifiers, even tube amps, that don't draw more than perhaps 3A when running. In other words our jukebox amps. For anything higher powered I'd use a higher wattage bulb...

A variac (have a few of those) is a handy tool too, but the dim bulb can be left in circuit while you wander off to do other things and if that side of the room suddenly gets brighter you know something has happened that now needs attention.

Might you also have a High-Pot tester? Great for verifying insulation breakdown up to 2500VAC...(1200VAC for 120V requirements)

Comparing toys, what fun!

John :-#)#

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(Please post followups or tech inquiries to the USENET newsgroup) 
                      John's Jukes Ltd. 
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Reply to
John Robertson

John Robertson wrote: ===================

** Total nonsense. In a 240VAC country, the hot resistance is nearly 600 ohm. This causes a huge voltage drop with 90% of what I service.
** Indispensable in fact. Dial up as slowly as you like, avoiding all surges. Dial back to check regulation " drop out " conditions.
** Yeah, OK but the item on test is running way below normal voltage. IMO a worthless tests.
** And destroying it. Cannot be used on normal working equipment.

...... Phil

Reply to
Phil Allison

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