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A new project arrives - JVC A-X30 'Super A' amplifier.

Markoneswift

Markoneswift

Quartz locked n ready to rock
Well, I did another run to the town dump at the weekend and I just happened to wander into their 'recycle shop' whilst I was there. This place has provided some interesting pieces before and on Saturday, it gave up a nice little JVC A-X30 amp. The chord is cut, it's marked as '$10 for parts' and inside is as filthy as anything !!

Cosmetically, despite being filthy, it's in decent shape. The volume control is loose which is weird. Inside is all discreet circuits - I expected to find a chip amp but no, it's all transistors on a decent size heatsink. Rated power is 40 WPC / 8 ohm.

I'm going to make myself a DBT and use this little guy as my first patient - I'm moving into repair amps now after messing with tape decks, turntables, boomboxes etc so hopefully this will be a good starting point.
 
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Looks like a nice amp / project. Maybe the loose volume control had it's lube flushed out and needs renewed. Look up damping grease. I'm guessing this amp is very similar to my R-X40 receiver. Sounds very good and had good reviews when new.
 
redk9258 said:
Looks like a nice amp / project. Maybe the loose volume control had it's lube flushed out and needs renewed. Look up damping grease. I'm guessing this amp is very similar to my R-X40 receiver. Sounds very good and had good reviews when new.
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The volume control is physically loose, as in wobbles around. I checked inside and the small PCB that the volume pot mounts on is also loose. I'm unsure if there's a mounting that's broken off or whether the PCB relies on perhaps a nut behind the volume knob to hold it tight against the fascia. I'll do a bit more digging around soon.
 
Well good news, the amp works ! I put a temporary chord into it and powered up on my DBT. Headphone output sounds great, the main issue being scratchy balance slider.

Looks like this will be a pretty quick turn around :-)
 
slimecity said:
What city? I'm in Welly. I used to find heaps of vintage gear at the dump shops in Dunedin when I lived there, but things are a tad more competitive up here....!
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I'm in the Tron mate. Really my only source of stuff is the Salvation Army, the Waikato Hospice, the dump shop, or Trademe. I keep meaning to check out Cambridge cos there's lots of oldies live there so you never know :-)
 
slimecity said:
The best source I've ever found is auction houses - that's where all the deceased estates go to die.....theres bound to be one in Hamilton aye!
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Well, I'm not sure to be honest. I suppose there will be - there's a Turners for sure but whether there are others, I'll have to check.
 
OK - re: your other post (which I should really post there, but I wont). I agree with using MJ21194 or MJ21196 for the outputs -these are available from RS Online (do you use this supplier? Free shipping in NZ). I have used MJ's tons of times for good output replacements.

Yes the 2SA527 is tricky to replace as others note. One suggestion is to use a 2SA940 instead -these aren't available at RS.

It looks like you may be able to sub 2SA940 with MJE15031. The latter is available at RS Online and I get these often. To verify this however I'd recommend downloading the datasheets from both of these trannies and comparing them side by side to ensure this sub will work - especially pinout! Another problem is that the frequency of the MJE15031 is much faster than the 2SA940 so oscillation at the outputs may be an issue and this can only really be verified with a scope. on the other hand, the position of the 2SA940 in the circuit may not make this an issue. Overall however - to reduce this risk - I'd recommend getting a proper replacement for the 940.

See the list of equivalents here - search for each of these for availability in NZ - you may need to suck it up and order from element 14 if RS doesn't have them ($25 delivery charge to NZ):

http://alltransistors.com/crsearch....5&ic=1.5&tj=125&ft=4&cc=110&hfe=40&caps=TO220

Cheers
 
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slimecity said:
OK - re: your other post (which I should really post there, but I wont). I agree with using MJ21194 or MJ21196 for the outputs -these are available from RS Online (do you use this supplier? Free shipping in NZ). I have used MJ's tons of times for good output replacements.

Yes the 2SA527 is tricky to replace as others note. One suggestion is to use a 2SA940 instead -these aren't available at RS.

It looks like you may be able to sub 2SA940 with MJE15031. The latter is available at RS Online and I get these often. To verify this however I'd recommend downloading the datasheets from both of these trannies and comparing them side by side to ensure this sub will work - especially pinout! Another problem is that the frequency of the MJE15031 is much faster than the 2SA940 so oscillation at the outputs may be an issue and this can only really be verified with a scope. on the other hand, the position of the 2SA940 in the circuit may not make this an issue. Overall however - to reduce this risk - I'd recommend getting a proper replacement for the 940.

See the list of equivalents here - search for each of these for availability in NZ - you may need to suck it up and order from element 14 if RS doesn't have them ($25 delivery charge to NZ):

http://alltransistors.com/crsearch....5&ic=1.5&tj=125&ft=4&cc=110&hfe=40&caps=TO220

Cheers
Click to expand...

Have sent you a PM mate, to avoid confusing this thread :-)
 
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