Technics SA-560, Computer Drive and You

I have a Technics SA-560 receiver in amongst my collection of various Technics goodies. It's a nice sounding set and plenty powerful. (I only wish for two things--that its TV tuner covered the whole of the TV broadcast band and that I could still use it...)

As with others of its type, the front panel boasts "Computer Drive New Class A" as one of the features. I've been inside it, making repairs to a burnt out dial lamp and bad protection relay and just generally looking at things. But what I've never seen is any evidence of its actually having Computer Drive. There's no microcontroller and no front panel indicator lamps for it.

Perhaps more tellingly, the service manual for the set doesn't even talk about Computer Drive. (The manuals for my SA-310 and SA-1010 both talk about Computer Drive by discussing how it works.) In fact, the only related circuitry it shows is what would appear to be the "preheat" circuit.

So my questions are: does this set actually have Computer Drive or has marketing struck again? If it does, where's the microcontroller and related circuitry...built into the SVI2004 power amplifier module?

Its pretty much all marketing bulls**t.
JVC did the same thing with their "Super A" amps.
They are basically just a class AB amp pretending to be something
else through a different type of biasing circuit.
As far as the computer drive is concerned, they are
using the microprocessor to control the bias based
on signal level and temp.

I'm actually looking for the Computer Drive parts...

glen65 said:

As far as the computer drive is concerned, they are
using the microprocessor to control the bias based
on signal level and temp.

Click to expand...

I'm pretty familiar with that. The service manuals explain what's going on pretty well and some other reading here has filled in the gap. I was curious as to where the circuit (if any) is hiding in the SA-560 receiver.

The power module used in this unit is an SVI2004 if that would help anyone.

I have one of these.

the computer drive is awol... wonder why it got the decal?....

SVI2004A is a brilliant power IC it IS new class A having inbuilt synchro bias)

it is run in resistor strapped pull down constant current (whereas computer drive runs 2 transistors as current stabilizer) (this same circuit appears in SU-Z600 Z610 and SU-X90)

Sound of this reciever is very good, (only issue with mine is i need to clean the tape 3 input selector switch)

if you dont like it... send it to me

Sa-560

SVI2004A said:

I have one of these.

the computer drive is awol... wonder why it got the decal?....

SVI2004A is a brilliant power IC it IS new class A having inbuilt synchro bias)

it is run in resistor strapped pull down constant current (whereas computer drive runs 2 transistors as current stabilizer) (this same circuit appears in SU-Z600 Z610 and SU-X90)

Sound of this reciever is very good, (only issue with mine is i need to clean the tape 3 input selector switch)

if you dont like it... send it to me

Click to expand...

That's exactly what I wanted to know! I'd seen your posts before and knew that part number quite well! (I think I'm correct in stating that the SA-560 is driven by an SVI2004 module.) It was my hope that you were still around.

Anyway...I love the set. It would take a lot of convincing and probably a hefty amount of cash to make me give it up! It sounds great, looks great and generally IS great. I'd only wish that the TV tuner were a bit more capable (given that it's a PLL synthesized tuner, could it have been that hard to add the full TV band to it?) but it doesn't matter now with most analog TV off the air.



Here is a big picture. (Picture is copyrighted, but I don't mind most forms of non-commercial and personal use. Just don't pass it off as being yours or use it in anything demeaning/demoralizing/illegal/etc. Do, of course, feel free to tell your significant other that this is something you're thinking of buying or adding to your collection.)

I bought it from an electronic scrap dealer on eBay, tested to power on but with no display in the tuner. Upon receiving it, the case was a bit dinged up. It wasn't as hard as I thought to repair it. If you look really closely, you could tell that something happened, but that's about it.

There were some other problems. Once I'd put a new 194 bulb in the tuner display, I noticed that some of the front panel LEDs weren't working properly and that occasionally one speaker wouldn't start playing at power on. That should be easy--my SA-929 did that as well. Bad relay contacts! Of course, I broke the relay in this one while opening the case. Oops. It now has a bit of a "flying repair" in place with an electrically equivalent relay. I ran wires up from the circuit board mounts, soldered them to a relay and zip-tied it down. I did that because getting a relay of the right physical dimensions looked like it was going to cost almost as much as the receiver did.

For the front panel LEDs, it was nothing a little resoldering couldn't cure. What little solder was there seemed to kind of evaporate.

Do you have any information on the SVI-2004 module, like a datasheet or interesting facts? I'd love to know more about it and how it compares to the Sanyo STK series, as well as how robust they are. I blew the STK-2038 II in an SA-310 by winding it up. The left channel just kind of crumpled. The SVI2004 seems a lot more robust so far, although I have never seen anyone selling replacements and I do not want to break it.

I don't operate the receiver in its current location, and I'd never have equipment on top of it. The CD player on top is something I just picked up, bought it from an old man who took phenomenal care of it. Every last bit of documentation is there with it (down to the sales receipt), and it's flawless.

In fact, right now I'm waiting for finances to allow me to get some speakers to use with this receiver. I may buy a speaker kit and put it together.

I had to fight myself not to pick up an SA-360 that probably had a lot of the same problems. It did find a home, though. I'm trying to keep my vintage Technics habit in check.

SVI2004A is a 2X 80W Power IC
Darlington Power Pack config
Inbuilt Overload Detection
Symmetrical build
Synchro~Bias
WAY better than the STKs

Attached are some pics

Internal


Schematic


And the Disappointing SVI2004C (NOT new class A)

The STK 20*8 series did not use SMD resistors etc and the power transistors are nowhere near the size of the SVI - unfortuantely there is no other IC that comes close to it :S

SVI2004A said:

The STK 20*8 series did not use SMD resistors etc and the power transistors are nowhere near the size of the SVI - unfortunately there is no other IC that comes close to it :S

Click to expand...

Thanks for the info! That is really great stuff to see. Were those SVI2004 modules dead?

After getting a replacement module for my SA-310 (an STK-2048 II, found by a kindly person from Youtube and still in its "Genuine Panasonic Replacement Part" packet), I decided to take the old module apart. This ended up involving some violence, but I wasn't too worried about that.

Interestingly, the STK-2038 II module doesn't look a whole lot different. Its transistor dies are very similar, and it also has those surface mounted components. They do look more like what you showed in the SVI2004 "C" example though. I've never had one apart, as I have not lost one, but I have seen pictures of the "series 1" STK modules and they don't look very good inside at all!

I thought the dies inside the STK-2038II were kind of pretty. They were all covered in a clear sealant that was still compliant after 27 years. I could even see where the old module had gone bad. One of the dies had a small burn mark on it.

I'm in the process of modifying the SA-310 by adding some cooling fans. Call me nuts, but I don't like the fact that it idles at a whopping 130 degrees F.

The SVI was alot more reliable, (one would have to usually do something bad to kill one) though in the SU-V4X if the current stabiliser and pre driver went short, it turns the SVI short over supply) my mate had the SU-8 (STK2048II) it died when he ras having a shootout against my SU-X90 (SVI2004A) i have here STK2068II to replace smaller 20*8IIs with...

the SVIs you see in the pics arent dead, both are fine - i used them to display how well they were made - STK resistors are film based and all transistors are in die form - SVI uses SMD resistors and pre drive transistors / diode packs...

interesting on the side - these ICs can be installed in reverse and still function correctly (though heatsink would need to be moved too)

i have seen the SVIs survive some fairly radical conditions and not faulter, though considering theyre no longer available, recommend looking after them

Sorry I'm so long in getting back to this...here's what I found when I cracked open the dead STK-2038 II from the SA-310 receiver. I really meant to take this picture ages ago and just kept pushing it to the bottom of a long list of things to do!



I wasn't too worried about breaking an already dead module, so I used a bench vise to open this one.

Maybe you've already seen that, but if not, there is a larger image available by clicking on that one. I guess I was remembering things "better than they really were". Compared to your SVI2004 shots, it doesn't look anywhere near as impressive. Then again, it's not capable of that kind of power output, either.

If you look really closely (the flash almost knocked it out) you can kind of see where one of the transistor dies has a burn on it. It's the one on the lower right.

I would be interested in some STK-2068 II modules to have around as spares, but I'm in the US. Still, if you'd be willing to sell me a few, I would be interested. Feel free to send me a private message.

Yeah the STK darlington packs are usually very good... Some of them though tend to die out for no reason though (STK8050 was one that does this) was like the silicon in some batches were not as refined as others... On the other hand SVIs made after 91/92 were cheapened up drastically (BC power module) I really think these were made in a different factory to the original SVI ics

Hello,
I´ve one question, which coresponds with this thread, but this question is probably for SVI2004A:
I´ve got amp Technics SU-8 (it was mentioned here) where I replaced dead IC STK2048II and now need setting bias current for new STK. There are the test points at "computer drive" PCB, but because I don´t have service manual (have schematics only), don´t know, how bias value needs this STK...I was set the voltage at the testpoints "by eye" at 1,5mV (minimal heating of the heatsink), but how exactly does have to be?

Many thanks for the replies and sorry for my bad english..
Tibor.

Ahh yes.... The 2048II

This is the adjustment for SU-8

Thank you very much for your help, it´s exactly, what I need.
Now I´m sure, the amp works in the correct area :thmbsp:

PS. Now is temperature of the heatsink about 38-40°C (no load), is that right?

I do remember these did run quite warm. Small heatsink. Iirc The regulators also knock out a bit of heat.

My X90 amps also run at a similar temp.

Hey, very timely thread for me... I obtained a SA-560 in a trade.. it's a nice sounding unit in my opinion. I'm selling it though as I have no use for this.
Interesting pics of the IC innards...never took apart one of those chips before!

Thanks for the photos

And the Disappointing SVI2004C (NOT new class A)
[/QUOTE]


I wasn't the first in my ebay amp here but thanks for the photos...

An impostor:

uxwbill said:

I'm pretty familiar with that. The service manuals explain what's going on pretty well and some other reading here has filled in the gap. I was curious as to where the circuit (if any) is hiding in the SA-560 receiver.

The power module used in this unit is an SVI2004 if that would help anyone.

Click to expand...

I have a sa550 70wpc just. like your 560

my 550 has slightly better specs



the 4 bit processor is on the amp board

my. 550 uses output transistors - no stk type output module

Electrolyte said:

And the Disappointing SVI2004C (NOT new class A)

Click to expand...

I wasn't the first in my ebay amp here but thanks for the photos...

An impostor:

[/QUOTE]

Interesting.... Blockslide on both channels.... What amp was that in?... Was it in a cabinet with other things on top being run loud? I usually see that on SVI32XX series after the cooling fan quits.

It's possible that it was fitted after manufacture, it seems that MEIC must have had a heap of spare A covers they found then released the C type with A covers.

Yet SVI2004B was synchro bias. (A small run of these were made often found in Z600 amps) then the C type with the grey patterned Cover was released.

Interesting looking more at your IC is the fact it has the shallow holes next to the screw holes (a trait seen from SVI32XX ON) wonder why they went on to re print A suffix after B was run and finished and C had started... One has to wonder

Hi.

The amp is a SU-V4X that I got from a local ebay seller - she had around 30 or so pieces of untested HIFI separates.

As I mentioned, I wasn't the first one inside the amp & the chip had at least had its pins touched up with someone's soldering iron.

Apart from not working it's otherwise in pretty good condition and those power transistors all test OK with the usual 2 diode test. I'm glad you find it interesting.