Recommended HiFi / AV Repairers

[aussievintage 3,791]

6 minutes ago, JoelG said:

Hi all, just after a good technician to repair one of my vintage marantz mono blocks. One amp is running way hotter than the other... Not sure if it's the hot one or cool one that's the problem though, as both sound fine and they always ran hot.

Anyway any recommendations for a amp guru in Melbourne would be much appreciated.

 

Joel

 

Hopefully just a bias adjustment.  I had an stereo amp that had one channel running hotter than the other.  Yes, still sounded fine in both channels.    That's all it was, just needed the bias reset.

[JoelG 1]

1 minute ago, aussievintage said:

 

Hopefully just a bias adjustment.  I had an stereo amp that had one channel running hotter than the other.  Yes, still sounded fine in both channels.    That's all it was, just needed the bias reset.

Ok, I'm not very tech savvy but I kinda thought class A was just full on all the time so bias doesn't come into it?  Happy to be wrong about this and if it's just a simple adjustment I will be stoked 👍

[aussievintage 3,791]

14 minutes ago, JoelG said:

Ok, I'm not very tech savvy but I kinda thought class A was just full on all the time so bias doesn't come into it?  Happy to be wrong about this and if it's just a simple adjustment I will be stoked 👍

 

No, class A still has  a bias setting.  It's just set a lot higher than for class A/B to ensure all output devices never turn off - hence the "full on all the time" thing.  The only difference in design is the ability to have that much adjustment on the bias, and to have much bigger heatsinks and cooling    Also, some amps that call them selves class A, are only class A up to a certain output power, then behave as class A/B at the top end of their capabilities.

[andyr 5,867]

11 minutes ago, JoelG said:

 

Ok, I'm not very tech savvy but I kinda thought class A was just full on all the time so bias doesn't come into it? 

👍

 

AIUI, yes, Class A is "on" all the time - but, if it's a tube amp then 'bias' is involved.

 

And I believe that while the Class A circuit draws a constant current from the PS ... the amount being wasted in heating the heatsinks reduces, as the signal level goes up.  So driving the spkrs hard actually results in the amp getting less hot than when the volume is low.

 

Andy

[JoelG 1]

2 minutes ago, aussievintage said:

 

No, class A still has  a bias setting.  It's just set a lot higher than for class A/B to ensure all output devices never turn off - hence the "full on all the time" thing.  The only difference in design is the ability to have that much adjustment on the bias, and to have much bigger heatsinks and cooling    Also, some amps that call them selves class A, are only class A up to a certain output power, then behave as class A/B at the top end of their capabilities.

Ok, that's good to know... Hopefully it's an easy fix then. 🤞

Thanks,

 

Joel

[aussievintage 3,791]

1 minute ago, andyr said:

And I believe that while the Class A circuit draws a constant current from the PS ... the amount being wasted in heating the heatsinks reduces, as the signal level goes up.  So driving the spkrs hard actually results in the amp getting less hot than when the volume is low.

 

What really is happening is that the output devices spend more time away from the max power rating curve.  See below.  The loadline (purple-bluish) is the sloping straight line.  The curved line shows 25 watts  dissipation, in this instance.  As the amplifier outputs a sinewave, it 'travels' up and down the loadine.  You can see in this example, it even exceeds 25 watts for a short time.   At small, or zero signal, it sits in the middle at the biased operating point and will get hottest.   As the magnitude of the signal increase, it spends more and more time towards either end of the load line, and so power dissipated, on average, is less.

 

 

 

Another example for triodes with a couple of loadlines

 

[JoelG 1]

16 minutes ago, aussievintage said:

 

What really is happening is that the output devices spend more time away from the max power rating curve.  See below.  The loadline (purple-bluish) is the sloping straight line.  The curved line shows 25 watts  dissipation, in this instance.  As the amplifier outputs a sinewave, it 'travels' up and down the loadine.  You can see in this example, it even exceeds 25 watts for a short time.   At small, or zero signal, it sits in the middle at the biased operating point and will get hottest.   As the magnitude of the signal increase, it spends more and more time towards either end of the load line, and so power dissipated, on average, is less.

 

 

 

Another example for triodes with a couple of loadlines

 

Ok,  I actually unplugged everything from the amp and ran them to eliminate any variables and one was hot one cold so not sure, does your diagrams depend on having a load , being the speakers or is that the amps internal bias ?

Anyway I can see how it can be a variable load. 

Thanks,

 

Joel

[aussievintage 3,791]

1 minute ago, JoelG said:

Ok,  I actually unplugged everything from the amp and ran them to eliminate any variables and one was hot one cold so not sure, does your diagrams depend on having a load , being the speakers or is that the amps internal bias ?

Anyway I can see how it can be a variable load. 

Thanks,

 

Joel

 

Yes, there must be a load.  In a valve amp, you can damage them without one.   The curves happen to be for a valve amp, but the principle is the same.

 

The load is represented by the straight line.  Changing bias will just shift that line up and down, while remaining parallel to itself.  Without signal, the amp sits at one point on that line, usually about in the middle.  This is known as the operating point, and is what one sets when the bias is adjusted.

[aussievintage 3,791]

5 minutes ago, JoelG said:

having a load , being the speakers or is that the amps internal bias ?

oh yes, meant to say.  Yes the load is the speakers, or their reflected impedance via an output transformer for valves, mostly.

[JoelG 1]

4 minutes ago, aussievintage said:

oh yes, meant to say.  Yes the load is the speakers, or their reflected impedance via an output transformer for valves, mostly.

I see, so without a load the operating point might be out. A load will just relatively change the relationship based on the starting point... And adjusting this bias will do the trick 👌

[aussievintage 3,791]

2 minutes ago, JoelG said:

I see, so without a load the operating point might be out. A load will just relatively change the relationship based on the starting point... And adjusting this bias will do the trick 👌

 

Bottom line, if the amps sound good, even with the temperature difference, I don't think you'll find much wrong.   Hopefully just a tune-up. 👍

[rt3m 2]

Hi there, i have Monitor Audio subwoofer which is not powering on, looking for recommended repairer in Sydney area, thanks!

[rockeater 731]

On 22/10/2020 at 7:34 AM, JoelG said:

kinda thought class A was just full on all the time so bias doesn't come into it? 

All active devices (like transistors and valves) are non-linear.

They have their most non-linear area closest to the 0 (crossover point into the negative part of signal curve) and become more linear as the voltage and current increases.

To offer better performance, in Class A, these active devices are biased high, so that they are always in their most linear area. Another words, they are driven hard even when there is no signal.

Hence increased power consumption and heat.

They use the same power whether the music is playing or not.

[ozmatchbox 5]

Hi all,

am  a newbie with hi-fi gear and recently bought the following used Sansui gear (to start off with my hi-fi journey) 😁 and needs servicing

• AU-417 - volume knob is loose
• TU-417 - working so far during demo test
• SC-1330 - doesn't play, rwd or fwd

Would anyone here be able to recommend an electronics/vintage hifi repair/service shop in Sydney?

Preferably near the lower north shore area?

Would be great if you've used their services before to work on your Sansui gear.

 

Appreciate your help on this. 😊

 

Thanks.

[SONDEKNZ 12]

Hi guys!

I have a friend who needs his STEREO REMOTE CONTROL repaired.

It's a pretty simple device, but is absolutely essential to the entire operation of his beloved (and rare) CLASSIC amplifier - so he can't afford any screw-ups.

So I'm looking for a trusted repairer that won't disappoint.

Preferably in EAST AUCKLAND.

Can anyone make a recommendation please?  Appreciated.

 

JINGLE BELLS!

[muon* 2,979]

@SONDEKNZ Might help to mention the amplifier model and make.

[SGS 111]

NAD M25 fault, fans, possibly channel failure.

 

Would you use a local repairer who seems quite good or take to a NAD specialist 2 hours away or arrange for NAD Australia to repair and ship it?

 

NAD Au want $99 includes pickup but I don't have box.

Local want $55 upfront to inspect.

Don't know about other option.

 

Chatting to a guy from NAD Au, he seemed strongly recommending authorised due to being Masters series.

[ag47 1]

EAD Powermaster 2000 which recently has some buzzing coming through. Any suggestions for someone that will know how to handle it perfectly (Sydney, Au)? The sound out of this amp is amazing and I would like it to stay that way...

[MattyW 2,208]

Brisbane Electronics did wonderful work recapping my Victor TT-Y5 as well as installing quality RCA sockets + a banana plug for the earth wire. It should now last another 40 years and will work with any interconnects I should want to run. 

 

https://www.briselec.com.au/

Edited January 6 by MattyW

[vagrahb 11]

Hi Guys,

 

Happy New year!.   I'm looking to get my Parasound A51 amplifier serviced and could any Brisbane folk recommend a good technician locally. 

 

Thanks.

[candyflip 3,850]

The big problem I'm finding at the moment is the wait times to get in to see anyone... upwards of a month just to get something on the benches around Melbourne, because the queue of repair jobs they already have to do is so long. JLS are quoting a wait time of 5-6 weeks just to have something appraised, before the repair starts.

Of course given COVID, this is completely understandable.

 

Just frustrating is all.

 

 

 

Edited January 13 by candyflip

[mud_shark 24]

1 hour ago, candyflip said:

The big problem I'm finding at the moment is the wait times to get in to see anyone... upwards of a month just to get something on the benches around Melbourne.

Of course given COVID, this is completely understandable.

 

Just frustrating is all.

Am definitely feeling this. Given the wait to get in, and then for the actual service time... half makes me want to buy a second TT for such emergencies 😁

Edited January 13 by mud_shark
Typo

[MattyW 2,208]

3 minutes ago, mud_shark said:

Am definitely feeling this. Given the wait to get in, and then for the actual service time... half makes me want to but a second TT for such emergencies 😁

 

Yeah, not many people willing to work on them these days. Most places don't have the knowledge or skillset. That and because so few people actually get gear repaired there are not many repairers to start with. It's that whole throw away mentality 

 

I've 2x spare tables though the Victor TT-Y5 is the best of them in my mind. That said my Victor TT-71 based tables with Fidelity Research tonearms are not far behind.

Edited January 13 by MattyW

[static 49]

CVE Electronics in Pascoe Vale South have done good repair work on two old amps for me recently. Couple of weeks turnaround. I found them from other recommendations here. 

[Timoth 0]

Hi,

Can anyone recommend someone to service my Luxman SQ 505X Amp? I'm in Sydney. 

Thanks,

Tim

[dneco 24]

Given that the amount of backlog repair techs have right now might be a very long wait here in Melbourne.

 

I have a cd player where the disc won't spin so i'm assuming its a relatively straight forward fix with a replacement motor if anybody knows how to do that?

 

Located in Melbourne's North

 

Thanks

[ag47 1]

On 20/01/2021 at 5:00 PM, dneco said:

Given that the amount of backlog repair techs have right now might be a very long wait here in Melbourne.

 

I have a cd player where the disc won't spin so i'm assuming its a relatively straight forward fix with a replacement motor if anybody knows how to do that?

 

Located in Melbourne's North

 

Thanks

I don't know if you've opened it up already, but the motor usually runs a belt that looks like a rubber band. Check that it hasn't come off / isn't broken as your first check.

[rockeater 731]

4 hours ago, ag47 said:

On 20/01/2021 at 2:00 PM, dneco said:

its a relatively straight forward fix with a replacement motor if anybody knows how to do that?

I don't know if you've opened it up already, but the motor usually runs a belt that looks like a rubber band. Check that it hasn't come off / isn't broken as your first check.

Unless it is a belt driven C.E.C. this is never the case.

These belts that @ag47 talks about normally drive CD trays and clamps, not TT motors (C.E.C.s excepted).

The fact that CD does not spin is virtually never a motor fault.

The fact that the motor does not spin, means that one of the number of things that need to happen before you get to spinning CD, did not happen.

It could still be a belt which did not close the tray properly or CD is not fully clamped.

But most likely some limit switch is not activated and servo simply does not know that everything is already in place. 

Most likely it is a matter o finding it and cleaning it.

Hope it helps.

[Wilco 70]

On 13/01/2021 at 1:25 PM, candyflip said:

The big problem I'm finding at the moment is the wait times to get in to see anyone... upwards of a month just to get something on the benches around Melbourne, because the queue of repair jobs they already have to do is so long. JLS are quoting a wait time of 5-6 weeks just to have something appraised, before the repair starts.

Of course given COVID, this is completely understandable.

 

Just frustrating is all.

 

 

 

 

This.

I dropped stuff off start of 11th Jan, 3 speakers and 1 integrated amp, and still not done.

I had made one call 2 weeks later, and they were kinda onto it.

Not planning on calling until 1st March I guess.

 

Has anyone had any experience with Class A Audio and repairs (I know they are a seller here and they regularly list on other platforms), just curious if anyone has had experience with them regarding repairs:

https://www.classaaudio.com.au/content/7-hifi-repair-service