Ping Trevor Wilson

[Phil Allison]

Hi TW,


I have a Marantz SR2000 on the bench with both STK080G modules blown
and signs of attempted repair. I know the PSUs and tuners are OK.

WES does not stock the 080G but has the uprated 083G which appears to be pin compatible.

Can it be a drop in replacement?

Any mods needed ?



.... Phil

[Trevor Wilson]

**Puke. Worst. Marantz. Products. Ever. Cheap shit. Lemme check for any
080s I may have in stock.

I have one STK-080-II in stock. It will almost certainly be a drop-in
replacement. Not sure about the 083G.

Looking at the .pdf on this page, suggests that it will be a drop-in
replacement:

http://www.datasheetspdf.com/datasheet/STK083G.html

I don't think you'll have a problem. Piece of shit SR2000. All the SR
range was crap, along with the tuners and integrated amps at the time.
That was built at a time when Marantz was in deep shit. The Pianocorder™
almost sent them to the wall and the quality of their audio products
went downhill real fast. Then Philips bailed them out and the quality
returned. One product they released almost did make me puke - Imperial,
by Marantz (no, not the speaker systems). A return to those 1960s,
single unit stereo systems. Plastic moulding, made to look like wood.
Spectacular example of bad taste. I measured one. 1.75 Watts/channel. Yikes!

I just checked the web. I can't find any reference to the atrocities
anywhere.

Fuck I hate Sanken shit and I wish manufacturers would stop using their
semis. Bastards delete items forever, making it impossible to service
old products.


--
Trevor Wilson
www.rageaudio.com.au

[Phil Allison]

Trevor Wilson wrote:

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

> > I have a Marantz SR2000 on the bench with both STK080G modules blown
> > and signs of attempted repair. I know the PSUs and tuners are OK.
> >
> > WES does not stock the 080G but has the uprated 083G which appears to be pin compatible.
> >
> > Can it be a drop in replacement?
> >
> > Any mods needed ?
> >
> >
> >
>
> **Puke. Worst. Marantz. Products. Ever. Cheap shit. Lemme check for any
> 080s I may have in stock.
>
> I have one STK-080-II in stock. It will almost certainly be a drop-in
> replacement. Not sure about the 083G.
>
> Looking at the .pdf on this page, suggests that it will be a drop-in
> replacement:
>
> http://www.datasheetspdf.com/datasheet/STK083G.html
>
> I don't think you'll have a problem.

** Yep - I found that data sheet earlier today.

>
> Fuck I hate Sanken shit and I wish manufacturers would stop using their
> semis. Bastards delete items forever, making it impossible to service
> old products.
>

** The STK series is made by Sanyo.

Sanken modules, with numbers like SI1050 disappeared decades ago.

Both typically suffered from lack of short circuit protection.



.... Phil

[jurb...@gmail.com]

>"Fuck I hate Sanken shit and I wish manufacturers would stop using their
semis."

I had a Mitsubishi X-11 system the guy's olady was in love with. Had a bad SI series output chip. I ended up wiring in a pair of LM3886s which use almost no external components. Worked fine.

I would have considered just runing pre-outs from it so he could connect an external amp but they put the tone controls in the global feedback loop.

I agree that Marantz went to shit. I've actually seen a few with the tone controls in the global feedback loop. Marantz ? In my book that is no Marantz. Now a 2325, things of that vintage, now that's Marantz.

[Trevor Wilson]

**Well, in some ways. Big, heavy, big power transformer, nice to
service, but not a great sounding amp and with some serious issues with
the VI limiting system (I measured around 20 Watts, at limiting, when
driving a pair of AR 10pi speakers). For me, the last, really good
integrated amp from Marantz was the 1200b. Built in Chatsworth Cal.
Stunning sounding amp. It was my first Marantz amp, when I started work
at Marantz. The last receiver built in Chatsworth was the Model 18 (I
think). I still have mine. Very interesting model. Sounds pretty good
too. I also still have the mightiest Marantz of all - the Model 500
power amp. A big, beautiful, all hand built beast with phenomenal
unreliability. When it works, it sounds fabulous.

As for your tone control thing, ALL Baxandall type tone controls (which
is most of them) operate within a feedback loop. However, I suspect you
mean within the power amp stage? If so, then you are thinking of 1980s
vintage Luxman amps. ALL Marantz amps employed separate tone control
circuits, with their own amplification and feedback systems.



--
Trevor Wilson
www.rageaudio.com.au

[jurb...@gmail.com]

>"As for your tone control thing, ALL Baxandall type tone controls (which
is most of them) operate within a feedback loop. However, I suspect you
mean within the power amp stage? If so, then you are thinking of 1980s
vintage Luxman amps. ALL Marantz amps employed separate tone control
circuits, with their own amplification and feedback systems. "

Yes I meant in the power amp stage. And I swear I saw a Marantz that was like that, in fact I probably got the print on the PC but I have alot of Marantz prints. I was actually surprised to see it, and it was the only one. I remember it was a lower end model but it still had the Marantz look.

[Trevor Wilson]

**I could be wrong, but I doubt it. Luxman, absolutely. Quite a few of
theirs employed such a system. If you figure out which Marantz, let me
know. I have pretty much every service manual for every model.



--
Trevor Wilson
www.rageaudio.com.au

[jurb...@gmail.com]

>"**I could be wrong, but I doubt it. Luxman, absolutely. Quite a few of
theirs employed such a system. If you figure out which Marantz, let me
know. I have pretty much every service manual for every model."

I took a quick look around and the answers were not forthcoming. I did not imagine this, I remember it because it was unusual, for them at least.

Luxman I don't really know about, but I have seen them with pre out/main in jacks, I would assume then that though the volume worked for the pre out, the tone controls did not ?

Not unfathomable.

My buddy in Florida had a decent system, Luxman receiver with a pair of ADS with blown tweeters, slaved to it was another amp running a Bose Acoustimass system with the sub way back in the corner and the satellites on top of the ADSes. Damn did that sound good. And you couldn't get it to distort, even at cop calling levels.

[Trevor Wilson]

On 19/05/2017 10:32 PM, jurb...@gmail.com wrote:
>> "**I could be wrong, but I doubt it. Luxman, absolutely. Quite a
>> few of
> theirs employed such a system. If you figure out which Marantz, let
> me know. I have pretty much every service manual for every model."
>
> I took a quick look around and the answers were not forthcoming. I
> did not imagine this, I remember it because it was unusual, for them
> at least.
>
> Luxman I don't really know about, but I have seen them with pre
> out/main in jacks, I would assume then that though the volume worked
> for the pre out, the tone controls did not ?

**I did not say that ALL Luxman integrated amps used such a system. Just
their low end ones. I know of no amplifier that employs pre/main
connectors that does not disable the the tone controls when it is used
as a power amp only.

>
> Not unfathomable.
>
> My buddy in Florida had a decent system, Luxman receiver with a pair
> of ADS with blown tweeters, slaved to it was another amp running a
> Bose Acoustimass system with the sub way back in the corner and the
> satellites on top of the ADSes. Damn did that sound good. And you
> couldn't get it to distort, even at cop calling levels.
>

**If you think an Acoustimess™ system can EVER sound good, then you need
to get out a lot more. Bose Acoustimess™ are absolute crap. There is a
huge, deep and wide hole in the frequency response of the system,
centred around 200Hz, the woofer module (it cannot, EVER, be called a
subwoofer) doesn't deliver anything of consequence below 40Hz (I have a
pair of NEAR 10M-II bookshelf speakers that can go lower and louder than
the Bose woofer). Distortion is horrible and the ability of the system
to deliver a credible image is non-existent.

But women love them. They are small and cute. They just sound like shit.


--
Trevor Wilson
www.rageaudio.com.au

[jurb...@gmail.com]

>"**I did not say that ALL Luxman integrated amps used such a system. Just
their low end ones. I know of no amplifier that employs pre/main
connectors that does not disable the the tone controls when it is used
as a power amp only. "

Seems to be a misunderstanding here. If the tone controls are in the power amp feedback loop then they would not affect the pre out of course. Whether this is desirable or not is up in the air. By disabled when used as a power amp I assume you mean bypassed, because regular pre outs are after the tone controls.

>"**If you think an Acoustimess™ system can EVER sound good, then you need
to get out a lot more. Bose Acoustimess™ are absolute crap. There is a
huge, deep and wide hole in the frequency response of the system,
centred around 200Hz, the woofer module (it cannot, EVER, be called a
subwoofer) "

No disagreement here, but this was in conjunction with another system. Together they sounded good. It was a corner situated system. The Bose sats were on top of the big speakers and the bass module was way back in the corner.

Best thing Bose made was the wave radio, they don't sound all that great but for their size the do pretty well. Convenient, the customer doesn't have to hook anything up. The sound is adequate for quite a few people.

But when you get like 901s, who the fuck brainiac got the idea to use nine speakers and face eight of them away from the listener ? We strive to have clear sound, to have loudspeakers that sound almost like the best of headphones but on a larger scale. Some people like Bose but I think he was a snake oil salesman.

All this "ambiance", that is your room, you DON'T WANT THAT. You want the ambiance in the recording. Not your room.

Another good thing Bose made were my Mother's speakers. Smaller than a toaster but shake the floor. I can't even get a model number, they were some kind of special order I bought from where I worked at the time.

Other than that I don't have much use for Bose. In my buddy's system they served well as tweeters.

[Trevor Wilson]

On 20/05/2017 10:09 AM, jurb...@gmail.com wrote:
>> "**I did not say that ALL Luxman integrated amps used such a
>> system. Just
> their low end ones. I know of no amplifier that employs pre/main
> connectors that does not disable the the tone controls when it is
> used as a power amp only. "
>
> Seems to be a misunderstanding here. If the tone controls are in the
> power amp feedback loop then they would not affect the pre out of
> course. Whether this is desirable or not is up in the air. By
> disabled when used as a power amp I assume you mean bypassed, because
> regular pre outs are after the tone controls.

**There is no misunderstanding on my part. Any amplifier that uses tone
controls as part of the power amp section (and Luxman is the only
manufacturer IME to do so - And I have serviced pretty much every
Marantz product made since the late 1960s - I was Marantz service
manager in Australia for several years) will not have pre/main
connections fitted.

>
>> "**If you think an Acoustimess™ system can EVER sound good, then
>> you need
> to get out a lot more. Bose Acoustimess™ are absolute crap. There is
> a huge, deep and wide hole in the frequency response of the system,
> centred around 200Hz, the woofer module (it cannot, EVER, be called
> a subwoofer) "
>
> No disagreement here, but this was in conjunction with another
> system. Together they sounded good. It was a corner situated system.
> The Bose sats were on top of the big speakers and the bass module was
> way back in the corner.

**Not a snowball's chance in Hell that such a system would provide a
credible high fidelity result. Certainly, someone with a poorly educated
ear might think it sounds impressive. But good (ie: HI FI), not a chance.

>
> Best thing Bose made was the wave radio, they don't sound all that
> great but for their size the do pretty well. Convenient, the customer
> doesn't have to hook anything up. The sound is adequate for quite a
> few people.

**WAY too expensive. Sound was OK. Just. The best two products Bose ever
did was their 'sound bar' and their desk top computer sound system. Both
were easy to use, sounded good and were reasonably well built and
presented. Everything else is shit.

>
> But when you get like 901s, who the fuck brainiac got the idea to use
> nine speakers and face eight of them away from the listener ? We
> strive to have clear sound, to have loudspeakers that sound almost
> like the best of headphones but on a larger scale. Some people like
> Bose but I think he was a snake oil salesman.

**Of course. The entire premise was faulty to any sane thinking human
(ie: Non-Trump voters).

>
> All this "ambiance", that is your room, you DON'T WANT THAT. You want
> the ambiance in the recording. Not your room.
>
> Another good thing Bose made were my Mother's speakers. Smaller than
> a toaster but shake the floor. I can't even get a model number, they
> were some kind of special order I bought from where I worked at the
> time.
>
> Other than that I don't have much use for Bose. In my buddy's system
> they served well as tweeters.

**They don't even do a good job at that. The cone area is far too large
to enable decent sound quality without beaming.

People forget that Amar Bose was the wealthiest person in the audio
business. By a very considerable margin. He got that way, by building
stuff as cheap as possible and selling it for as much as possible and
ploughing huge amounts into promotion. People forget that when Bose
first introduced surround sound systems, Bose was too cheap to pay Dolby
Labs to use their ubiquitous systems and, instead, developed their own,
incompatible, shitty sounding one.

We must NEVER make excuses for Bose. Shitty products, shitty company.



--
Trevor Wilson
www.rageaudio.com.au

[Phil Allison]

Trevor Wilson wrote:

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

>
>
> **I did not say that ALL Luxman integrated amps used such a system. Just
> their low end ones.
>

** Luxman were always a prestige brand that did not make low end models.

Simple models like the SQ606 from the late 60s ( single supply, cap coupled) still had Baxandall feedback tone controls.

http://www.hifido.co.jp/photo/10/608/60845/h.jpg

Lux had another brand called L&G aimed at the mass market:

https://i.ebayimg.com/00/s/NzY4WDEwMjQ=/z/VVQAAOSwWTRW1b5q/$_86.JPG

They were kinda colourful, like Sonab.


.... Phil

[Trevor Wilson]

On 20/05/2017 3:36 PM, Phil Allison wrote:
> Trevor Wilson wrote:
>
> ---------------------
>>
>>
>> **I did not say that ALL Luxman integrated amps used such a system.
>> Just their low end ones.
>>
>
>
> ** Luxman were always a prestige brand that did not make low end
> models.

**I can assure you that they most certainly did. Perhaps not quite as
low end as those Sansui atrocities, but models that were significantly
less costly to make than their good models. As an authorised service
agent for the importer, since 1980, I've seen them all, though Interdyn
no longer import Luxman.

>
> Simple models like the SQ606 from the late 60s ( single supply, cap
> coupled) still had Baxandall feedback tone controls.

**Here's one of their budget models that employed tone controls as part
of the power amp stage feedback line:

https://www.hifiengine.com/manual_library/luxman/l-205.shtml

Cheap. Lots of failures with this model and others in the same range.
Usually simple stuff, like failed zeners. Using 0.5 Watt zeners at their
limits is asking for trouble. The engineer should have been sacked.

Of course, not as bad as this rubbish:

https://www.hifiengine.com/manual_library/sansui/a-40.shtml

Check out the output stage. You'll note two things:

* No current limiters
* Mild steel plates that hold the output devices onto the heat sink
(badly).

There's much more with this range. They were horrible things.

>
> http://www.hifido.co.jp/photo/10/608/60845/h.jpg
>
> Lux had another brand called L&G aimed at the mass market:
>
> https://i.ebayimg.com/00/s/NzY4WDEwMjQ=/z/VVQAAOSwWTRW1b5q/$_86.JPG
>
> They were kinda colourful, like Sonab.
>

**Yep. Make no mistake: Luxman, like every other Jap brand has built
cheap stuff, to capitalise on the reputation of their good stuff. Except
Accuphase. I can't recall ever seeing anything cheap and nasty from them.



--
Trevor Wilson
www.rageaudio.com.au

[Phil Allison]

Trevor Wilson wrote:

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

> >
> >
> > ** Luxman were always a prestige brand that did not make low end
> > models.
>
> **I can assure you that they most certainly did. Perhaps not quite as
> low end as those Sansui atrocities, but models that were significantly
> less costly to make than their good models. As an authorised service
> agent for the importer, since 1980, I've seen them all, though Interdyn
> no longer import Luxman.
>
> >
> > Simple models like the SQ606 from the late 60s ( single supply, cap
> > coupled) still had Baxandall feedback tone controls.
>
> **Here's one of their budget models that employed tone controls as part
> of the power amp stage feedback line:
>
> https://www.hifiengine.com/manual_library/luxman/l-205.shtml
>
> Cheap. Lots of failures with this model and others in the same range.
> Usually simple stuff, like failed zeners. Using 0.5 Watt zeners at their
> limits is asking for trouble. The engineer should have been sacked.
>

** I've seen an L-205 on my bench, a couple of years back.

Not a bad little amp, I felt.

The oddball tone control thing is not important, specially if you set them flat .

> Of course, not as bad as this rubbish:
>
> https://www.hifiengine.com/manual_library/sansui/a-40.shtml
>
> Check out the output stage. You'll note two things:
>
> * No current limiters
> * Mild steel plates that hold the output devices onto the heat sink
> (badly).
>

** Seen one of them too, a budget model for sure.

Still, used with ordinary care they work fine long enough to outlast the sort of peripherals generally found.



..... Phil

[Trevor Wilson]

**Back when I had my retail store, I sold Sansui, NAD, Marantz and a few
other brands. NAD walked out the door, being the flavour of the month.
Whilst a decent performer, particularly with difficult speakers, I felt
the mid range Sansui was a superior product. Better built, using better
quality components (the trimmer pots didn't fall apart and the knobs
didn't fly off the switches with the Sansui), the Sansui sounded better
with most speakers. The rep asked if I wanted to sell their cheaper
stuff (similar to the A-40). I asked for a sample for a week. I stripped
it down and checked out carefully. There were a number of potentially
problematical areas and I declined the offer to sell the range.

Sometime later, an acquaintance popped in to buy a stereo. I
demonstrated several system, including the Sansui (not the cheap stuff)
and he went away to think on it. I met up with him a few months later
and asked how his search was going. He ended up buying the cheap Sansui
from DME. I told him that there were no hard feelings and wished him
well. Another year passed and I ran across him again. I expressed my
condolences on the loss of his house. I asked him if they fire
authorities had tracked down the source of the fire that burned his
house down. "Yep." He said. "It was that bloody Sansui stereo. It caught
fire."

See, one of the issues that I identified with the Sansui, is that there
are combustible materials on each end (plastic end pieces) and a pressed
fibre board base-plate. That, combined with a power transformer, where
the thermal fuse connections are easily accessible from the outside of
the transformer, means that lazy techs simply short the thermal fuse
when it fails (which it did in 90% of that range of Sansui amps). I
suspect my old friend had picked up a repacked amp, that had failed. You
can work out the rest. Horrible quality products.


--
Trevor Wilson
www.rageaudio.com.au

[Phil Allison]

Trevor Wilson wrote:

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

> "Yep." He said. "It was that bloody Sansui stereo. It caught
> fire."
>
> See, one of the issues that I identified with the Sansui, is that there
> are combustible materials on each end (plastic end pieces) and a pressed
> fibre board base-plate. That, combined with a power transformer, where
> the thermal fuse connections are easily accessible from the outside of
> the transformer, means that lazy techs simply short the thermal fuse
> when it fails (which it did in 90% of that range of Sansui amps). I
> suspect my old friend had picked up a repacked amp, that had failed. You
> can work out the rest. Horrible quality products.
>

** The purpose of the thermal fuse inside the power tranny is to preserve the integrity of the Class 2 insulation. If that were bypassed and the tranny ever got hot enough to catch fire, there is a glass fuse that blows very quickly soon as turns begin to short out.

For the tranny to get seriously hot, the amp must be in use playing music loudly. This is not gonna be the case when no-one is home or all are asleep.

If the primary of the tranny failed due to voltage spikes on the AC supply, the
glass fuse would still prevent fire.

Maybe the Sansui amp was involved in the fire, rather than the cause of it.

I've see people sit candles on top of their stereos.



.... Phil

[ohg...@gmail.com]

On Saturday, May 20, 2017 at 9:49:42 PM UTC-4, Phil Allison wrote:

>
> Maybe the Sansui amp was involved in the fire, rather than the cause of it.
>

That's what I was thinking, but who knows? Around here firefighters need college degrees plus a few more years of specific training to advance beyond a typical grunt riding on the back of a hook and ladder. Unless someone died in the fire it wouldn't surprise me if the investigator just blamed the stereo, called it a day and went for a pizza.

Anyway, I remember the Sansuis of the 80s that would blow outputs and burn all the way back to the speaker selector switch. I never saw one that exteriorized flame but if the owner left the stupid thing on to keep the cat from being bored, it might have shorted it's outputs. Still, it's hard to believe it made it outside the case.

[Phil Allison]

Trevor Wilson wrote:

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

>
> **I can assure you that they most certainly did. Perhaps not quite as
> low end as those Sansui atrocities, but models that were significantly
> less costly to make than their good models. As an authorised service
> agent for the importer, since 1980, I've seen them all, though Interdyn
> no longer import Luxman.
>
>

** Did you deal with Gordon Hoskins at any stage?

I met him in the late 70s while doing service work for a hi-fi and TV shop in Woollarah.

Despite the store stocking various Interdyn items, he refused to supply any spares or info on Luxman etc.



... Phil




... Phil

[Trevor Wilson]

On 21/05/2017 1:52 PM, Phil Allison wrote:
> Trevor Wilson wrote:
>
> --------------------
>
>>
>> **I can assure you that they most certainly did. Perhaps not quite as
>> low end as those Sansui atrocities, but models that were significantly
>> less costly to make than their good models. As an authorised service
>> agent for the importer, since 1980, I've seen them all, though Interdyn
>> no longer import Luxman.
>>
>>
>
> ** Did you deal with Gordon Hoskins at any stage?

**Of course. I even did work for him for a few years. To his credit,
bills were always paid by the due date. I mostly dealt with Dianne down
there at Arncliff, I never bought Luxman spares from him. I went
straight to the importer - International Dynamics. Excellent company to
deal with. Always pay their bills on time.

>
> I met him in the late 70s while doing service work for a hi-fi and TV shop in Woollarah.
>
> Despite the store stocking various Interdyn items, he refused to supply any spares or info on Luxman etc.

**That's because he is a massive dickhead. Certainly be 1980 (and
probably a long time prior) Interdyn were the importers for Luxman.
Hoskins was their Sydney agent and pretty much sole retailer for a long
time.


--
Trevor Wilson
www.rageaudio.com.au

[Phil Allison]

Trevor Wilson wrote:

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

> >
> >>
> >> **I can assure you that they most certainly did. Perhaps not quite as
> >> low end as those Sansui atrocities, but models that were significantly
> >> less costly to make than their good models. As an authorised service
> >> agent for the importer, since 1980, I've seen them all, though Interdyn
> >> no longer import Luxman.
> >>
> >>
> >
> > ** Did you deal with Gordon Hoskins at any stage?
>
>
> **Of course. I even did work for him for a few years. To his credit,
> bills were always paid by the due date. I mostly dealt with Dianne down
> there at Arncliff, I never bought Luxman spares from him.
>

** Think I dealt with her over the phone once, to get some Luxman amp BJTs.

She was polite, efficient and I got the *correct* parts in the mail the next day. So I rang her back to say how pleased I was.

I remember her being astonished that anyone bothered to do such a thing.

> >
> > Despite the store stocking various Interdyn items, he refused to supply any spares or info on Luxman etc.
>
>
> **That's because he is a massive dickhead.
>
>

** ROTFL !!

> Certainly be 1980 (and
> probably a long time prior) Interdyn were the importers for Luxman.
> Hoskins was their Sydney agent and pretty much sole retailer for a long
> time.
>

** After taking on Alpage and Celestion plus opening the "Quality Hi-Fi" store in York Street, he didn't get any better.

Gordon must have been a sleazy used-car salesman in a previous life....



..... Phil

[Trevor Wilson]

**Well, a new car salesman. But close enough.



--
Trevor Wilson
www.rageaudio.com.au

[Phil Allison]

Trevor Wilson wrote:

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

>
> >
> > Gordon must have been a sleazy used-car salesman in a previous
> > life....
> >
>
> **Well, a new car salesman. But close enough.
>
>

** Really ??

When I first came across the horrible man, I suggested to the owners of Woollahra Hi-Fi ( Roger and Sue Tonkin ) that he must be linked with the nearby " Larke Hoskins " car dealership.

When asked, Gordon strenuously denied any connection.

Are you saying he lied ?




.... Phil

[Trevor Wilson]

**Oh yeah. He was, indeed, the 'Hoskins' part of Larke-Hoskins.


--
Trevor Wilson
www.rageaudio.com.au

[Phil Allison]

Trevor Wilson wrote:

------------------
>
> >
> >>> Gordon must have been a sleazy used-car salesman in a previous
> >>> life....
> >>>
> >>
> >> **Well, a new car salesman. But close enough.
> >>
> >>
> >
> > ** Really ??
> >
> > When I first came across the horrible man, I suggested to the owners
> > of Woollahra Hi-Fi ( Roger and Sue Tonkin ) that he must be linked
> > with the nearby " Larke Hoskins " car dealership.
> >
> > When asked, Gordon strenuously denied any connection.
> >
> > Are you saying he lied ?
>
>
> **Oh yeah. He was, indeed, the 'Hoskins' part of Larke-Hoskins.
>
>

** I know the question was put directly to him by Roger Tonkin.

Wonder why he denied it??

Natural instinct to lie?



.... Phil

[Phil Allison]

Phil Allison wrote:

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

** New Sanyo STK083Gs are now installed and working fine.

The old, blown modules were an STK080G and an STK084G - the latter having its white markings obliterated. I cut them both open for a look revealing all the chips inside. The output devices in the 080G are puny, similar to TIP34s while the ones in the 084s are larger, more like 2N3055 ones.

But this is not the problem.

The problem is that there is simply NO current limiting at all - making the modules fail instantly if there is a short on the speaker line.

ALSO there is a thin, phenolic PCB *between* the thick copper headers used for the output devices and the alloy heatsink on the back of each module. The temperature drop across this would be many times that of the usual mica or silicone insulators.

PLUS there are no emitter ballast resistors employed at all - making the output stage prone to thermal runaway.

I intend to write a stern warning to the owner to be VERY careful with the speaker wiring from this unit and to NEVER use 4 ohm speakers.




.... Phil

[Trevor Wilson]

**All good reasons to avoid any products using those horrible output
stages. I never liked them. When Marantz began employing them, I was
very concerned. When I started at Marantz, even their 35 Watt amps
(Model 1070) used proper, TO3, output devices (matched sets). By the end
of the 1970s, the SR shit-boxes had appeared, with their unreliable
output modules and very unreliable tuner ICs. I liken it to someone who
works at Lexus, then being presented with the new model, which was as
sophisticated and quality built as a Chery. I recall the boss calling me
into the office, sometime around 1977-8 and explaining to me that
Marantz was engaged in an exciting new concept called
'value-engineering'. I soon learned what that term really meant. Even
after Philips took over, they persisted with using those driver modules.
They proved to be quite unreliable too.

FWIW: I have an ancient Pioneer here, which has a blown module. There is
no replacement available, but the client still wants the thing repaired
(God knows why). I've suggested that he look for another amplifier and I
can canabalise it to fix his.


--
Trevor Wilson
www.rageaudio.com.au