Technics SU-V8 Amp - ICQ problem - dead trim pot?
- Thread starter Flapper
- Start date
teal'c
Nuclear Cardiac Parent
Capacitors dry out. Life expectancy for electrolytic caps is 25ish years. That amp is 36 years old.
Just because someone else is incompetent, why would you let that stop you from performing preventative maintenance?
If your friend forgets to refill his engine oil when doing an oil change, do you stop changing your oil?
Just because someone else is incompetent, why would you let that stop you from performing preventative maintenance?
If your friend forgets to refill his engine oil when doing an oil change, do you stop changing your oil?
Flapper
Member
Anyone know if KSC3503 is a suitable replacement for 2SC2632:
https://www.mouser.com/datasheet/2/149/KSC3503-90028.pdf
https://www.mouser.com/datasheet/2/149/KSC3503-90028.pdf
Flapper
Member
Hi all.
Brief update. I'm waiting for the transistors to arrive. I've bought from two different UK places on ebay with good feedback and no suggestion that they're selling fakes but of course I can't be sure. I've also got a dim bulb tester coming. It costed only slightly more than the components used to make it and I'm very reluctant to mess with mains power myself.
I've had a look at the caps on the power board and I'm considering whether to replace them as preventative medicine, as advocated by teal'c above. I wouldn't change any of them until the transistor issue was resolved.
The Caps
It looks like there are four large filter caps in the middle:
4 x 10,000uf 71V caps. It looks like they're polar. Is there any benefit / danger in upping the values or should I stick to like for like? I'm guessing the newer ones may be smaller and also mounted differently. [EDIT: Do these need to be 'audio grade'? Maybe these: https://www.mouser.co.uk/ProductDet...iMZZMsh%2B1woXyUXj%2BATRo13k2ktvnbJxk%2BLVJQ=]
Apart from that there are:
C610 & C609 which are 100V caps but it's very hard to tell the capacitance - it may be 10uf. I guess I'd have to pull them to be sure, unless anyone knows the value (maybe SVI2004A?)
1 x 220uf 16v bipolar
3.3uf 50v caps C552 and one other.
Any advice or comment - particularly on the replacement of the filter caps - gratefully received.
Brief update. I'm waiting for the transistors to arrive. I've bought from two different UK places on ebay with good feedback and no suggestion that they're selling fakes but of course I can't be sure. I've also got a dim bulb tester coming. It costed only slightly more than the components used to make it and I'm very reluctant to mess with mains power myself.
I've had a look at the caps on the power board and I'm considering whether to replace them as preventative medicine, as advocated by teal'c above. I wouldn't change any of them until the transistor issue was resolved.
The Caps
It looks like there are four large filter caps in the middle:
4 x 10,000uf 71V caps. It looks like they're polar. Is there any benefit / danger in upping the values or should I stick to like for like? I'm guessing the newer ones may be smaller and also mounted differently. [EDIT: Do these need to be 'audio grade'? Maybe these: https://www.mouser.co.uk/ProductDet...iMZZMsh%2B1woXyUXj%2BATRo13k2ktvnbJxk%2BLVJQ=]
Apart from that there are:
C610 & C609 which are 100V caps but it's very hard to tell the capacitance - it may be 10uf. I guess I'd have to pull them to be sure, unless anyone knows the value (maybe SVI2004A?)
1 x 220uf 16v bipolar
3.3uf 50v caps C552 and one other.
Any advice or comment - particularly on the replacement of the filter caps - gratefully received.
Last edited:
Flapper
Member
Thanks.
Am I in the right ballpark for replacing the 2SC2632 ? (see below).
https://photos.app.goo.gl/VRVegJLChTuGhNbw9
Otherwise I guess I'm stuck with the Ebay buys as online research hasn't thrown up a direct modern replacement for the 2SC2632
Am I in the right ballpark for replacing the 2SC2632 ? (see below).
https://photos.app.goo.gl/VRVegJLChTuGhNbw9
Otherwise I guess I'm stuck with the Ebay buys as online research hasn't thrown up a direct modern replacement for the 2SC2632
Attachments
Last edited:
Flapper
Member
We have a complete success! Swapped out the faulty 2SC2632 for a direct replacement and I'm now able to set the bias/IQC on both sides to 40mV and the amp is sounding lovely again.
I'm not going to recap the power board immediately. I'll live with it for a while - not least because it will cost £50 - but it's on my to-do list, so I'll probably do it in a few months.
Thanks all so much for your help.
I'm not going to recap the power board immediately. I'll live with it for a while - not least because it will cost £50 - but it's on my to-do list, so I'll probably do it in a few months.
Thanks all so much for your help.
eizner23
Super Member
Glad you got it up and functioning properly. Did you go with KSC3503, spec-wise it looks like a good replacement. Otherwise original 2SC2632 can be found here.
Flapper
Member
@eizner23 I got hold of two 2SC2632s on ebay from a guy who seemed to be selling off stuff he'd bought for a project (rather than a big components dealer). They looked legit and have been working fine so far.
I was certainly considering the KSC3503 but I don't have the expertise to know which attributes can be approximate and which have to be bang-on on the original spec.
I was certainly considering the KSC3503 but I don't have the expertise to know which attributes can be approximate and which have to be bang-on on the original spec.
I experienced it when I did this on the technics SU-V1X. The luck was that I mounted a capacitor with the reverse polarity in a place where it didn't damage anything else.
SVI2004A
Synchro Bias
It can happen lol… at least the Technics amps in this line aren’t riddled with caps…I experienced it when I did this on the technics SU-V1X. The luck was that I mounted a capacitor with the reverse polarity in a place where it didn't damage anything else.