Meyer Sound 833 problem

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Trevor Wilson

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Sep 25, 2022, 4:03:07 PMSep 25
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I have a Meyer Sound 833 control unit on my bench. It has a weird fault
that appears to centre around a 15kHz oscillation that affects one
channel, directly, but is bleeding through to the other channel.

Meyer Sound refuses to supply a schematic. They will repair it for a set
charge of US$592.50 (nice round figure). That's a bitter pill to
swallow, but it gets worse. I (and my customer) are here in Australia
and I figure on the freight charges to blow that figure out to around
US$1,000.00 or so.

I am hopeful that someone has some experience with this product. Maybe
even schematics.

TIA

Trevor Wilson


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legg

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Sep 27, 2022, 9:08:18 AMSep 27
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On Mon, 26 Sep 2022 06:03:06 +1000, Trevor Wilson
<tre...@rageaudio.com.au> wrote:

>I have a Meyer Sound 833 control unit on my bench. It has a weird fault
>that appears to centre around a 15kHz oscillation that affects one
>channel, directly, but is bleeding through to the other channel.
>
>Meyer Sound refuses to supply a schematic. They will repair it for a set
>charge of US$592.50 (nice round figure). That's a bitter pill to
>swallow, but it gets worse. I (and my customer) are here in Australia
>and I figure on the freight charges to blow that figure out to around
>US$1,000.00 or so.
>
>I am hopeful that someone has some experience with this product. Maybe
>even schematics.
>
>TIA
>
>Trevor Wilson

You can start by trying to locate the source w/r to different
gain settings in the signal chain.

So how can you make it worse, first. Then you can concentrate on
smaller sections of the circuitry, without the schematic.

You seem to be happy running without that specific channel -
complainibg about feed-through only - so just killing
the section may be enough of a fix to satisfy your customer,
if you can't cure the actual local fault.

RL

ohg...@gmail.com

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Sep 27, 2022, 9:52:05 AMSep 27
to
Will they supply parts? Even buying the complete guts can't cost as much as their charge plus freight. I think I know the answer to that.

In Connecticut U.S., we had a law years ago that required any company that sold electronics in our state to supply schematics to a licensed repair facility and free of charge as well (I guess to cut off any attempt to sell schematics for $500 each). When I informed a company (can't recall which one) that they had to supply me a schematic by state law, they essentially told me to pound sand.

We definitely need "right to repair" laws with teeth in them.

Phil Allison

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Sep 27, 2022, 7:42:54 PMSep 27
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ohg...@gmail.com wrote:
=====================

> Trevor Wilson wrote:
.
> > I have a Meyer Sound 833 control unit on my bench. It has a weird fault
> > that appears to centre around a 15kHz oscillation that affects one
> > channel, directly, but is bleeding through to the other channel.
> >
> > Meyer Sound refuses to supply a schematic. They will repair it for a set
> > charge of US$592.50 (nice round figure). That's a bitter pill to
> > swallow, but it gets worse. I (and my customer) are here in Australia
> > and I figure on the freight charges to blow that figure out to around
> > US$1,000.00 or so.
> >
> > I am hopeful that someone has some experience with this product. Maybe
> > even schematics.

> >
> >
> > --
> > This email has been checked for viruses by Avast antivirus software.
> > www.avast.com

> Will they supply parts? Even buying the complete guts can't cost as much as their charge plus freight.

** The unit is nearly 40 years old.
Consists of one PCB in a box.

FYI TW is an agent for an audio product with the exact same policy.

Karma ??

..... Phil



ohg...@gmail.com

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Sep 28, 2022, 9:40:13 AMSep 28
to
Fair enough, but if they offered to "repair" the unit, they must either have parts or a substitute board I would imagine, unless the repair cost is actually an exchange cost with a later model.

JC

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Sep 30, 2022, 11:12:59 AMSep 30
to
Trevor Wilson wrote:
> I have a Meyer Sound 833 control unit on my bench. It has a weird fault
> that appears to centre around a 15kHz oscillation that affects one
> channel, directly, but is bleeding through to the other channel.
>
> Meyer Sound refuses to supply a schematic. They will repair it for a set
> charge of US$592.50 (nice round figure). That's a bitter pill to
> swallow, but it gets worse. I (and my customer) are here in Australia
> and I figure on the freight charges to blow that figure out to around
> US$1,000.00 or so.
>
> I am hopeful that someone has some experience with this product. Maybe
> even schematics.
>
> TIA
>
> Trevor Wilson
>
>

not familiar with the amp and not an audio guy but:
15Khz sounds like switching supply noise? Bad caps on power rails?
JC

ohg...@gmail.com

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Sep 30, 2022, 1:31:14 PMSep 30
to
I thought of and then dismissed that assuming both channels shared a common supply, but I guess there could indeed be a separate converter for each channel. One thing I've found consistent in consumer electronics is that that lazy electros generally respond to heat and cold. Warm it up with a heat gun. Noise gone? Good chance an electro bypass is the cause.

Trevor Wilson

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Oct 1, 2022, 1:11:22 AMOct 1
to
**Not power supply noise. The power supply is as clean as a whistle.

All electros have been replaced with high quality (Panasonic and
Nichicon) components.

The unit is pure analogue. NO digital stuff to be seen.

There are 25 dual OP amps (5532), a handful of bipolar transistors, 2 X
dual gate MOSFETs, four Vactrol opto-isolators and here's the big one:
27 preset pots. Every single one has been moved from factory settings by
a previous tech. Without access to factory service data, I have no
chance of restoring this thing to anything resembling normal operation.

I have been able to stabilise one channel (though I still have a low
level 2MHz oscillation to deal with). I was able to measure the
frequency response curve and fell confident that I can duplicate the
curve using a a 32 band, digital parametric EQ. I won't have the ability
to use the speaker feedback section, but that should be a concern, give
that the system is designed for sound reinforcement use, but will be
used in a domestic application. The speaker feedback system is designed
to protect the HF drivers under very high power operation. MY solution
should work well and will cost my client much less cash.

Trevor Wilson

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Oct 1, 2022, 4:29:30 AMOct 1
to
On 1/10/2022 3:11 pm, Trevor Wilson wrote:

"... but that should be a concern,...."

Should read: "...but that should NOT be a concern,...."

Phil Allison

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Oct 1, 2022, 5:24:17 AMOct 1
to
Trevor Wilson wrote:

===================
> I won't have the ability
> to use the speaker feedback section, but that should be a concern, give
> that the system is designed for sound reinforcement use,

** Errr - no it ain't.

https://www.manualslib.com/manual/915648/Meyer-Sound-833.html?page=6#manual

And this section is dead funny for all the wrong reasons.

https://www.manualslib.com/manual/915648/Meyer-Sound-833.html?page=9#manual

...... Phil


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