*** 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
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
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-
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
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...(-;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-
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