Mission amp schematics ...

[Arfa Daily]

Anyone by any chance got a set of schematics for a Mission Cyrus amp to hand
? It has a small DC offset on one channel. Not large, but enough for the
protect circuitry to see it as a problem. Unfortunately, I am seeing lots of
tantalum bead caps in it ... :-(

Arfa

 

[Fleetie]

Arfa Daily wrote:

Anyone by any chance got a set of schematics for a Mission Cyrus amp to
hand ? It has a small DC offset on one channel. Not large, but enough
for the protect circuitry to see it as a problem. Unfortunately, I am
seeing lots of tantalum bead caps in it ... :-(

Arfa

No, but I did have an alarming offset incident with my Cyrus 2 about 5 years ago.
I was about to sell it to this girl I knew, so I got out a damp cloth, and
gave the top and sides a good rubbing to remove the dust, before she came round.

I'd had the thing for years by this time, with no problems.

She came round, I let it rip, and it nearly blew the cones out of the
speakers I was also selling her, with HUGE static DC offset out of both channels.

As soon as I'd shat myself, I yanked the power and plugged another amp into
the speakers. Luckily they were fine, but I measured the DC out of the
Cyrus 2 at about 20V each side.

So I sold her the speakers, which were fine ever since, but had to apologise for
the unbelievably Sod's-law-esque failure of the amp, and she bought one
elsewhere.

Days or weeks later, I decided to give it another go with a multimeter on
the outputs. No offset. Plugged in speakers - fine again.

Obviously my "damp" cleaning cloth had been a bit more than damp, and dripped
water into the amp, causing the offset temporarily.

I'm still using the same amp now!


Martin

 

[Arfa Daily]

"Fleetie" <fleetie@fleetie.demon.co.uk> wrote in message
news:nsKdnS_06OSzvz_RnZ2dnUVZ8qSdnZ2d@bt.com...

Arfa Daily wrote:
Anyone by any chance got a set of schematics for a Mission Cyrus amp to
hand ? It has a small DC offset on one channel. Not large, but enough
for the protect circuitry to see it as a problem. Unfortunately, I am
seeing lots of tantalum bead caps in it ... :-(

Arfa

No, but I did have an alarming offset incident with my Cyrus 2 about 5
years ago.
I was about to sell it to this girl I knew, so I got out a damp cloth, and
gave the top and sides a good rubbing to remove the dust, before she came
round.

I'd had the thing for years by this time, with no problems.

She came round, I let it rip, and it nearly blew the cones out of the
speakers I was also selling her, with HUGE static DC offset out of both
channels.

As soon as I'd shat myself, I yanked the power and plugged another amp
into
the speakers. Luckily they were fine, but I measured the DC out of the
Cyrus 2 at about 20V each side.

So I sold her the speakers, which were fine ever since, but had to
apologise for
the unbelievably Sod's-law-esque failure of the amp, and she bought one
elsewhere.

Days or weeks later, I decided to give it another go with a multimeter on
the outputs. No offset. Plugged in speakers - fine again.

Obviously my "damp" cleaning cloth had been a bit more than damp, and
dripped
water into the amp, causing the offset temporarily.

I'm still using the same amp now!


Martin

Hey Fleetie - long time no hear ! Trust you are well ? Would that this
bloody amp was a simple as that ... The guy owns two of 'em. I had the other
one in a few months back. It was making nasty howly farty noises due to a
bunch of 'afterthought' electros glued across the rail reg ICs on the back
of the board, all of which were bulging ready to burst. New caps fixed that,
and it was fine for a couple of months, then it came back with an
intermittent rustly crackle. That turned out to be o/p tr's on that channel.
Now I have his other one failing to fully power with the status LED flashing
forlornly. There is an offset of about -3v max on one channel. You can
follow it back at least as far as the pre-driver stages by eye, but after
that ... ?? Hence the need for a schematic. Ah well, I guess that one
goes to the back of the bench for now

Arfa