"Phil Allison" wrote in message
...

"Gareth Magennis"
"Phil Allison"

** Techs often get a sinking feeling when they discover a burnt AC power
transformer in a device. The unit simply blows fuses at switch on and
cannot be seen to work at all - so maybe it has other serious faults.
Also, exact replacement transformers are often not available or else
involve a long wait and high cost.

Had one this week, a baby size 6VA tranny in the PSU for a new looking "
Mojave" valve microphone. The PSU has an IEC inlet and a switch for
115V and 230V AC power - some goose had tried to use it with 240VAC
and the switch set to 115V !!!

The burnt tranny had two secondaries, 9V at about 300mA and 120V at
about 25mA - so nothing off the shelf would do. The local importer was
blaze and any replacement would involve a long wait. The PSU case is
very compact, so it was simply impossible to fit two transformers to get
the required voltages.

The tranny looks similar to the one in this pic:

http://www.chinatransformers.cn/User...5004507496.jpg


Was this the PSU?

http://i47.tinypic.com/144ch4.jpg


** No, this mic is an MA-200.

http://www.swee****er.com/images/clo...A200_inbox.jpg

The AC tranny is smaller and mounted off the PCB.


Just wondering if all these cheapo tube mics are all made in the same
factory.


** Not so cheapo here in Aussie - the RRP is $1300.

I expect that most like it are coming from the same Chinese maker.

BTW:

The MA-200 uses a type 5840W sub-miniature pentode with wire leads.

http://www.radiomuseum.org/tubes/tube_5840w.html

Connected as a cathode follower and with a DC heater supply - it's as
QUIET as a mouse.



.... Phil





OK, cheers.

Both mine use ECC83. The HST had a cheap chinese one that sounded like a
mouse caught in a sandstorm.



Gareth.