VOX AC15 repair

[Phil Allison]

** Hi,

not some relic from the 1960s, but a near new looking combo called an "AC15HW1X". The HW indicates the deluxe "hand wired'" version - see pic.

http://www.planetz.com/wp-content/uploads/2011/03/2010-11-05-Vox-AC15HW1-003.jpg

Features a bright blue, 12 inch Alnico magnet speaker, 2 x EL84s, 3 x ECC83s and a 6CA4 rectifier - but no tremolo circuit and no pentodes in the preamp so not a clone of the original AC15.

Usual assortment of faults including intermittent sound, cracking noises and completely shot EL84s.

AC30 & AC15 amps of all ages run the EL84s deep into class A and way too hot - so I normally change the wire wound cathode resistor to one of double the value and bypass it with a pair of 7.5V, 5W zeners in series. This changes it to class AB, similar to using grid bias. The 84s now run much cooler and put out a tad more power too.

As you can see from the pic, the tag board is wired with mainly carbon comp resistors - for a "vintage sound" no doubt. Should be no surprise that some of them had gone high in value, one 220kohms reading 457kohms.

So, a fake vintage amp with real vintage faults !!

BTW, on the back in small print it says:

" Made in Vietnam ".

Tom Jennings must be rotating in his grave....


.... Phil

 

[Arfa Daily]

"Phil Allison" <pallison49@gmail.com> wrote in message
news:0ff17f1c-6573-4433-aa63-c72515eeb6a7@googlegroups.com...

** Hi,

not some relic from the 1960s, but a near new looking combo called an
"AC15HW1X". The HW indicates the deluxe "hand wired'" version - see pic.

http://www.planetz.com/wp-content/uploads/2011/03/2010-11-05-Vox-AC15HW1-003.jpg

Features a bright blue, 12 inch Alnico magnet speaker, 2 x EL84s, 3 x
ECC83s and a 6CA4 rectifier - but no tremolo circuit and no pentodes in
the preamp so not a clone of the original AC15.

Usual assortment of faults including intermittent sound, cracking noises
and completely shot EL84s.

AC30 & AC15 amps of all ages run the EL84s deep into class A and way too
hot - so I normally change the wire wound cathode resistor to one of
double the value and bypass it with a pair of 7.5V, 5W zeners in series.
This changes it to class AB, similar to using grid bias. The 84s now run
much cooler and put out a tad more power too.

As you can see from the pic, the tag board is wired with mainly carbon
comp resistors - for a "vintage sound" no doubt. Should be no surprise
that some of them had gone high in value, one 220kohms reading 457kohms.

So, a fake vintage amp with real vintage faults !!

BTW, on the back in small print it says:

" Made in Vietnam ".

Tom Jennings must be rotating in his grave....


... Phil

Yebbut ya gotta say it is actually quite nicely made in terms of the
soldering quality and how nicely regimented the components are on those
strips, Phil ...

At least it is readily fixable, which is more than can be said for some
'modern' offerings !

Arfa

 

[Phil Allison]

Arfa Daily wrote:

Yebbut ya gotta say it is actually quite nicely made in terms of the
soldering quality and how nicely regimented the components are on those
strips, Phil ...

** Interestingly, the coloured wires used appear to be silicone coated - which makes tidy soldering easy and ought to remain flexible indefinitely.

However, when I replaced any component on that strip using regular 60/40 solder, the previously shiny joint became very dull looking. Must be some odd brew Pb free solder they have over in Vietnam.


.... Phil