Evening people....after a recent post by MentalDental on my behalf regarding problems with my rare Technics SE-A1 power amp I thought I'd post an update.
Thankfully I perservered and didn't hand it over to someone else to repair, I've learnt so much more about its construction by delving in and going through it methodically to find the issue but thanks to those that suggested people that could possibly help with the repair, I was so worried about it leaving my sight given its possible worth: http://www.audioscope.net/the-ultimate-century-stereo-p-1786.html
Anyway for those not knowing of the amp it was designed in the 70's to be the absolute best, the japanese parent company Matsushita threw millions in development money at creating their few statement pieces. Its patented (three engineers at Matsushita) topology is class A+ which used a clever sliding bias design to get the musical quality of class A but be 5 x the efficiency so it didn't double as your heating system for the room it was in....some may argue whats wrong with that!
The result is an incredibly complex amplifier the like of which I've not come across before...and hence its £4000.00 asking price in 1977! The equally huge preamp was £6000.00 then!!! :shock: So what's that in todays money!?
When I originally bought it I was skepital, surely things have improved massively since then? It would appear not, as soon as you start listening you are in no doubt it's still something very special. http://www.thevintageknob.org/TECHNICS/SUA2/SUA2.html
So the fault, I'd noticed a slight whiff of electrical burning at initial switch on which then quickly disappeared, so the usual I should get around to looking at that quickly turned into music fading out to a crackle and 4 blown 10 amp fuses on one channel!! After much digging and I mean removal of parts (this thing is clad in metal before you get anywhere near the circuits), once at the circuit for this channel you then have to remove no less than 17 connectors (all 2,3 and 4 way), then the PCB, then a sub chassis before you find 8 fuses per channel!
The problem was the normal 7 amps of bias current had shot up to 15 amps per rail which caused the transistors (16 on the low 5 volt rail, theres also a further 8 larger TO3 package ones on the 100 volt rails) to go into saturation after 5-10 mins and take 4 x 10 amp fuses out! After days of stripping down and measuring every transistor etc I finally found the problem as it then became intermittent, a little dry joint on a signal diode! Thank god, a few seconds with a soldering iron and we were back in business!!!!
At the same time I recapped what hadn't been done fairly recently, one of the caps looked fit to burst and was doing virtually nothing.
So I'm still on the look out for the preamp, it took me 15 years to find the power amp....sadly I think even if I did find one the money wanted would be 10's of thousands, another person I know has one and turned down an offer of 80,000 for the pair! :shock:
Thankfully I perservered and didn't hand it over to someone else to repair, I've learnt so much more about its construction by delving in and going through it methodically to find the issue but thanks to those that suggested people that could possibly help with the repair, I was so worried about it leaving my sight given its possible worth: http://www.audioscope.net/the-ultimate-century-stereo-p-1786.html
Anyway for those not knowing of the amp it was designed in the 70's to be the absolute best, the japanese parent company Matsushita threw millions in development money at creating their few statement pieces. Its patented (three engineers at Matsushita) topology is class A+ which used a clever sliding bias design to get the musical quality of class A but be 5 x the efficiency so it didn't double as your heating system for the room it was in....some may argue whats wrong with that!
The result is an incredibly complex amplifier the like of which I've not come across before...and hence its £4000.00 asking price in 1977! The equally huge preamp was £6000.00 then!!! :shock: So what's that in todays money!?
When I originally bought it I was skepital, surely things have improved massively since then? It would appear not, as soon as you start listening you are in no doubt it's still something very special. http://www.thevintageknob.org/TECHNICS/SUA2/SUA2.html
So the fault, I'd noticed a slight whiff of electrical burning at initial switch on which then quickly disappeared, so the usual I should get around to looking at that quickly turned into music fading out to a crackle and 4 blown 10 amp fuses on one channel!! After much digging and I mean removal of parts (this thing is clad in metal before you get anywhere near the circuits), once at the circuit for this channel you then have to remove no less than 17 connectors (all 2,3 and 4 way), then the PCB, then a sub chassis before you find 8 fuses per channel!
The problem was the normal 7 amps of bias current had shot up to 15 amps per rail which caused the transistors (16 on the low 5 volt rail, theres also a further 8 larger TO3 package ones on the 100 volt rails) to go into saturation after 5-10 mins and take 4 x 10 amp fuses out! After days of stripping down and measuring every transistor etc I finally found the problem as it then became intermittent, a little dry joint on a signal diode! Thank god, a few seconds with a soldering iron and we were back in business!!!!
At the same time I recapped what hadn't been done fairly recently, one of the caps looked fit to burst and was doing virtually nothing.
So I'm still on the look out for the preamp, it took me 15 years to find the power amp....sadly I think even if I did find one the money wanted would be 10's of thousands, another person I know has one and turned down an offer of 80,000 for the pair! :shock:
