No experience of the amp but if you have suspicions then the three definitive tests are to check the rails are correct and if that is OK then to confirm that the output stage bias is correct as per the service manual together with a confirmation of the DC offset (should be less than say 60 millivolts DC)
I am using A900s Technics amps and i can confirm that they always heat up even when not driven. The idle bias is set quite high by the design and increased as the signal amplitude increases. Do not worry, just make sure the power supply is filtered correctly. Measure the ripple because being an old design, it might be time to re-cap the amp.
thanks,
they eat power but sound is quite surprising!!! and it is vintage....
I am looking also for original rack, for now I have all components acc. to catalog from Technics 84/85
RSM 253X
SH 8044
SU V 4X
ST G5... not on pic...
very nice - fun staff to use them... it brings me back when I was a kid...
excluding the all CAP especially 10000 um should I change something else... everything is original in amp... never repaid...
they eat power but sound is quite surprising!!! and it is vintage....
I am looking also for original rack, for now I have all components acc. to catalog from Technics 84/85
RSM 253X
SH 8044
SU V 4X
ST G5... not on pic...
very nice - fun staff to use them... it brings me back when I was a kid...
excluding the all CAP especially 10000 um should I change something else... everything is original in amp... never repaid...
An externally hosted image should be here but it was not working when we last tested it.
I have modified a lot of Technics units and i recommend that you start by changing the op-amps to OPA1612 or similar. Also, there are a lot of 4,7uF Pansonic aluminium caps in the signal path. These are easily and directly replaced with Wima 4,7uF 50V film caps since they use 5mm pin spacing.
Technics su v4x is my favorite in terms of sound.My question is whether it really suits to apply one OPA1612 without changing anything before or after entering this OPA1612.
it fits?
I'm not referring to physical size but to certain values of components around.Thanks in advance.(as vrea sa pot discuta mai detaliat si pe romaneste cu tine rrrremus despre subiectul asta)
it fits?
I'm not referring to physical size but to certain values of components around.Thanks in advance.(as vrea sa pot discuta mai detaliat si pe romaneste cu tine rrrremus despre subiectul asta)
The SVI 2004 A Power ICs do run quite warm indeed... these out of the pack of SVI series always ran the warmest... a lot to do with its inbuilt Synchro Bias. with the computer drive adding to levels...
Usually amps running these packs run approx 7K ohm to -V for current stabiliser... the computer drive replaces the resistor pull down with a transistor controlled by the ICQ Controller
A look at the internal schematic of the SVI
- as for replacing op amps... I have not yet done that... only used in phono eq and tone circuitry
Voltage amp (diff/cascade) is all in AN7062 - beware of eBay fakes.
Usually amps running these packs run approx 7K ohm to -V for current stabiliser... the computer drive replaces the resistor pull down with a transistor controlled by the ICQ Controller
A look at the internal schematic of the SVI
- as for replacing op amps... I have not yet done that... only used in phono eq and tone circuitry
Voltage amp (diff/cascade) is all in AN7062 - beware of eBay fakes.
Attachments
Thanks SVI2004A!!!
I have listened to more or fewer amplifier models from the brands: Yamaha, Marantz, Denon, Pioneer, Sony, Philips, Onkyo, Grundig, Jvc,Sansui and Technics.
We all left behind for the dynamics offered by Technics (puncky bass) and because of your opinion on the HIFIENGINE website we also bought a su v4x model,
and this is really the most superb sounding amplifier I heard.
Soon they have a Sansui they have 317 that they did not want to start until after they had sucked their dust...
I tried it for a few minutes, since it was manufactured in 1978 and the electrolytic capacitors as well as 6 fuserezistors are very affected by the passage of time and I do not want to ruin it...in these few minutes of the test I was amazed at the sound quality,I think it is similar to su v4x
in terms of bass and clarity, detailed sound.Have you ever heard the sound of Sansui AU317?
I want to replace all electrolytic capacitors on su v4x and I wonder if it would be appropriate to replace the ceramic with wima polypropylene(???)
also change the problematic transistors and add extra radiators,and change wire conectors.
I have two v4x bought and will be mine forever(thanks to you SVI2004A)
I have listened to more or fewer amplifier models from the brands: Yamaha, Marantz, Denon, Pioneer, Sony, Philips, Onkyo, Grundig, Jvc,Sansui and Technics.
We all left behind for the dynamics offered by Technics (puncky bass) and because of your opinion on the HIFIENGINE website we also bought a su v4x model,
and this is really the most superb sounding amplifier I heard.
Soon they have a Sansui they have 317 that they did not want to start until after they had sucked their dust...
I tried it for a few minutes, since it was manufactured in 1978 and the electrolytic capacitors as well as 6 fuserezistors are very affected by the passage of time and I do not want to ruin it...in these few minutes of the test I was amazed at the sound quality,I think it is similar to su v4x
in terms of bass and clarity, detailed sound.Have you ever heard the sound of Sansui AU317?
I want to replace all electrolytic capacitors on su v4x and I wonder if it would be appropriate to replace the ceramic with wima polypropylene(???)
also change the problematic transistors and add extra radiators,and change wire conectors.
I have two v4x bought and will be mine forever(thanks to you SVI2004A)
It’s rather pointless changing capacitors as only 3-4 per channel in signal path..
1 on phono amp... 2 in tone Controller pcb and 1 in main amp
—— for the transistors beware of fakes. The original ones will last a lot longer if a little heatsink is attached to them (these can be found in better electronic wholesalers)
The memory capacitors usually need changing.. 2x 2.3v 3.3F ‘Gold caps’
Can’t remember a lot of the sansui... I have replaced output transistors on a few of them though.. (im sure it was this model)
Do enjoy your V4X amps
As far as cooling... make sure amp is level (this affects the fluid cooling system) and if using at volume make sure nothing is on top... it gets quite hot...
1 on phono amp... 2 in tone Controller pcb and 1 in main amp
—— for the transistors beware of fakes. The original ones will last a lot longer if a little heatsink is attached to them (these can be found in better electronic wholesalers)
The memory capacitors usually need changing.. 2x 2.3v 3.3F ‘Gold caps’
Can’t remember a lot of the sansui... I have replaced output transistors on a few of them though.. (im sure it was this model)
Do enjoy your V4X amps
As far as cooling... make sure amp is level (this affects the fluid cooling system) and if using at volume make sure nothing is on top... it gets quite hot...
Thanks and Thanks for the tips.
I'm sorry but I do not understand what you mean with:
*make sure amp is level *...?
I bought Panasonic GOLD CAP 10F 2.5v(do you think it would be a problem because they have a higher value?)
Previously, I bought a Kenwood ka990v which, due to inappropriate packing,has arrived broken,so I have the happy opportunity to use my original transistors in number of:4-2sc2631 and 4-2sa1123,even 4-2sc2632 und 3-2sa1124(all evil for good)
I'm sorry but I do not understand what you mean with:
*make sure amp is level *...?
I bought Panasonic GOLD CAP 10F 2.5v(do you think it would be a problem because they have a higher value?)
Previously, I bought a Kenwood ka990v which, due to inappropriate packing,has arrived broken,so I have the happy opportunity to use my original transistors in number of:4-2sc2631 and 4-2sa1123,even 4-2sc2632 und 3-2sa1124(all evil for good)