80's Technics Integrated Amps

*** be sure that a V4X is not fitted with SVI2004C - it never sounds right.


If in USA check out Z600 Z610 -------- MCS 2270 and Curtis Mathes KA270 (cheap bracket but fun) amps.... awesome power for little cost

Hi SVI2004A, I'm new here and wanted to thank you SOO much for all the great info.I bought a V4X after reading your entries and it is indeed a magnificent sounding amp. Driving 2 Infinity Crescendo-3008s. Huge sound stage, crystal clear and great instrument separation.
I am trying to buy spares for this unit for the future and can no longer find new SVI2004A chips. I can buy the SVI2004Bs, are these also good?
Thanks again for all your great info. Best Regards
 
Awesome:)

This it what it’s all about...
SVI2004B is Synchro bias... a few Z600 amps I have have this IC - I desoldered one and shone a torch on RHS pin cover - it was the original format SUP2869 substrate - not a white etched Z869Z substrate -

Glad to see you enjoying the sweet music:music::music::music:
 
I've had my new setup for a couple of weeks now and I'm very happy with it so far. I was pleasantly surprised that the SU-Z1 looks and works immaculate. It's in absolutely beautiful condition. Visually not even wear and tear on the switches, knobs, case, all the overprint is immaculate. If it wasn't for the smell of a 40 year old amp I'd be convinced it's a brand new unit. Pairing it with the Tannoy Eclipse 1 was a good choice. I was worried that the little £69 (£119) bookshelf speakers won't have the punch, that they would be inferior to my active KRK's but maaan was I wrong. This whole setup packs a punch despite the 2x25W power output and has a really nice sound. I did not dare crank it all the way up yet (mostly because of my 1 year old baby :) ) but interesting things start happening as soon as I reach the 2 - 3 region on the volume knob. This is definitely enough power for our flat. I still do have some work to do on the turntable, I think I need to work on the stylus pressure AFAIK because I'm having some issues with the "TZ", "TS" sounds here and there. So far so good. Take a look at some pictures I took earlier on. I'll try to take some more detailed pics in better light soon.

PS: The TV is not crooked, it just wasn't retracted back to it's position. ;p
 

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I had an SU-Z2 a while back and l thought it was a nice sounding little unit. Your Z1 certainly does look in excellent condition.
 
Hi SVI2004A,
I have to echo what Guillaume57 said...thanks to you, we've both leapt into the SU-xxx world and can't be more impressed with how great these amps perform! We're currently trying to revive a sick SU-V8, that seems to be getting DC from one channel in the preamp board. Is it safe to unplug the board and briefly power up the rest of the amp (with variac of course)?
 
Awesome:)

This it what it’s all about...
SVI2004B is Synchro bias... a few Z600 amps I have have this IC - I desoldered one and shone a torch on RHS pin cover - it was the original format SUP2869 substrate - not a white etched Z869Z substrate -

Glad to see you enjoying the sweet music:music::music::music:

Thanks for your fast reply. I will try to upload a pic, maybe you could weigh in on whether it looks genuine.
Not sure what you mean by RHS pin cover and SUP2869? is it better than Z869Z? I do not know the difference. Sorry for my ignorance here...)-:

My friend "stereo71" is helping to restore a sick and abused SU-V8, thanks for any light you can shed on that problem!

Thanks again and best regards to you.

IMG_3281.JPG IMG_3282.JPG
 
Last edited:
Hi Stereo71...

Awesome... it’s good to hear you’re enjoying the good sounds...

You can unplug J2 on centre of the drive board up the top - this will disconnect the tone board

Having said that, is there DC voltage at R301 or R302...

If unplugging power amp from drive board, do hook up lead H & N to ground via 5.6K resistor... this will stop output drifting.



Guillaume57

That would be a genuine SVI2004B.. still has its batch number on rear - if you look at lower right on the C version you can see the white etch Z869Z
The A version has the green coated copper which is SUP2869 - pic is not the best... will get more detailed shots of this later for future reference


F06D25C8-C145-4F73-9BB6-923F5543BAF5.jpeg

I usually check simply with a torch- through the unused pin holes you can quickly see the imprint-
 
SVI2004A,

Thanks for the info! Will check for DC at the two resistors. We were concerned about lifting the ground; that's generally a risky thing. At this point we still haven't found the cause, checking the tone board as well. Feedback loop is connected through it, if we're not mistaken. This amp has been hacked on before, so all bets are off as to correctness. Will report back!

I see what you mean about the construction of the BC module. Very different, glad we have a good spare...and hope not to need it!
--stereo71
 
Hi Stereo71...

Awesome... it’s good to hear you’re enjoying the good sounds...

You can unplug J2 on centre of the drive board up the top - this will disconnect the tone board

Having said that, is there DC voltage at R301 or R302...

If unplugging power amp from drive board, do hook up lead H & N to ground via 5.6K resistor... this will stop output drifting.



Guillaume57

That would be a genuine SVI2004B.. still has its batch number on rear - if you look at lower right on the C version you can see the white etch Z869Z
The A version has the green coated copper which is SUP2869 - pic is not the best... will get more detailed shots of this later for future reference


View attachment 1188305

I usually check simply with a torch- through the unused pin holes you can quickly see the imprint-

SVI2004A,
Thanks much for the very helpful info. I have ordered two more, they are pulls but new is unobtanium here. The one in the V4X I have was used a lot according to the previous owner.
Amazing that after 35 +/- years of use this stock unit still produces stellar sound!
We're eager to get this SU-V8 running, thanks for the help with that! We are also replacing the outputs with Sanken 2SA1494/2SC3858s as per a previous post of yours.
Best Regards
 
J2 that goes to the tone pcb can be safely pulled, as it’s input is grounded with 100K resistors R303 R304

Near on all of my V4X amps have never had power ic touched... - when I get one I check joints on Q501-4 then run it to make sure there’s no noise/pop from them...
If I replace them I use 2SA1124/2SC2632⚠️ Be careful as there seems to be counterfeit versions of these which can wreak havoc. But I haven’t had any issues with these original ones for some time now... and I’ve been getting a few more (in one month I got 4 from the UK - not an issue.

Another handy thing to have for V4X amps is gold caps (for memory) some of mine got amnesia (forgets where input select was - defaults to tuner) they’re 3.3 Farad.

Yep... 1494/3858 have been bulletproof for me - and I’ve put them through some testing times... remember to turn bias/clamp V down and re set - this is all described in service manual...

The worst thing about output stage failure in these amps is the loss of unobtanium parts... top notch output transistors and well set bias, and no sneaky dry joints will stop this from happening.
 
Ah thanks! Great info...we'll proceed with caution. Will be into the weekend before more work can be done on the V8. Danged day job gets in the way! But the audio adventure must go on!
--stereo71
 
1978-1987

The SU-V series was Technics full sized HiFi line that introduced new class A circuitry in 1978. Their other offering was the SU-Z series (Z1 and Z2) which were not quite as wide. The Later Z series also become full width (43cm). The first lineup of the V series consisted of V2 V4 V6 and the flagship V8. The V4 also was known as V4A and V4K. The V2 and V4 were both based on STK80*0 output ICs, the V6 and V8 on transistor outputs. All featured the synchro bias outpit stages. In 79/80 the lineup was the V3 V5 V7 and the flagship V9. All these amplifiers were discrete output, with the V9 using high current outputs. All were new class A with synchro bias. In 82/83 Technics developed computer drive in their amplifiers where a microprocessor could alter ICQ levels in the output stage calculated by signal and thermal sensing, also doubled as a protect circuit for overtemp overcurrent and some cases overinput. These were released as V303 V505 V707 and the flagship V909 again all were discrete output with the V909 having the same high current outputs. In 84/85 Technics had simplified the computer drive circuit with the MN1421STA being retired with a MN1404STE appearing in the new lineup except the SE-A3MK2. Also Heatpipe heatsinks were introduced. The new lineup being V1X V2X V4X V8X. In this lineup the V1X introduced Technics 1st own developed hybrid IC, the SVI2003 which was a 50 watt per channel ic that had synchro bias. The V1X didnt feature computer drive. The V2X featured computer drive, earlier V2X amps were fitted with STK2038IV and others recieved the SVI2003. The V4X was computer drive and all were synchro bias with the SVI2004A power IC, this amp I consider to have the best sound. The V6X and V8X were discrete outputs with synchro bias. In 1986 the V7X and V10X were late additions to the series, both having computer drive discrete outputs with synchro bias. Also in 86 the V40 V50 and V60 were produced. This phased in class AA amps which have a very different setup with a voltage control amp and current drive amp with a wheatstone coupling to the speakers. These amps are not featuring synchro bias. V40/50/60 have discrete voltage control amps with SVI400* current drive IC that has the wheatstone resistor bridge inbuilt. In 1987 the V85A was added class AA discrete output with no synchro bias. The amps from 86 were still in production

All these amps were very well made, all had metal faces. The BPC had not entered the SU-V series. Though it surfaced in the 1986 with the SU-500 and the SA series recievers

Hi
Dont mean to hijack this tread, but recently got a SU-V45A which I happen to like a lot, then I had another offer of buying a 'defective' Technics SU-V4A (80-81)
My question is are these repairable and is it possible to get parts for them? all I know its not powering up at all.
Best regards
KO
 
No power up... could be a fuse / bridge rectifier

As for parts OA90 diodes (Synchro bias) are gettin tricky to find..... STK8050 are unobtanium with counterfeits running rampant... there is a lessse known STK8070 - which are very hard to find - as far as I know there’s no counterfeit version of that.
 
Hi Stereo71...

Awesome... it’s good to hear you’re enjoying the good sounds...

You can unplug J2 on centre of the drive board up the top - this will disconnect the tone board

Having said that, is there DC voltage at R301 or R302...

If unplugging power amp from drive board, do hook up lead H & N to ground via 5.6K resistor... this will stop output drifting.



Guillaume57

That would be a genuine SVI2004B.. still has its batch number on rear - if you look at lower right on the C version you can see the white etch Z869Z
The A version has the green coated copper which is SUP2869 - pic is not the best... will get more detailed shots of this later for future reference


View attachment 1188305

I usually check simply with a torch- through the unused pin holes you can quickly see the imprint-
Thanks for that. I got it now. They are genuine, good news, I ordered 2 more. At these low prices it makes sense to get them while one can, but at 35 year lifespan and still going strong they will outlive me...(-;
 
1978-1987

In 82/83 Technics developed computer drive in their amplifiers where a microprocessor could alter ICQ levels in the output stage calculated by signal and thermal sensing, also doubled as a protect circuit for overtemp overcurrent and some cases overinput. These were released as V303 V505 V707 and the flagship V909 again all were discrete output with the V909 having the same high current output

I bought the 505 with a pair of Cerwin Vega D-7. The sound was flat, and anytime the volume was higher than 5 the unit would go into thermal protection and shut down. If I tried to increase the bass the unit would shutdown at 4. Tried upgrading speaker wires, no change. Lackluster to the least. My 15 Watt Onkyo TX1500 sounded better with the D-7s.
 
My SU-V45A
Never repaired, Thousands of hours since -89. Midrange clarity is outstanding. I have run it with all kinds of speakers.

32508767_10155401168732551_7436386434484797440_n_zpskgh4emlf.jpg
 
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