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-   -   Transformer needed or "solid state guy needs help from tube guys" (http://www.diyaudio.com/forums/tubes-valves/158646-transformer-needed-solid-state-guy-needs-help-tube-guys.html)

quasi 14th January 2010 10:20 PM

Transformer needed or "solid state guy needs help from tube guys"
 
Greetings to the other side.

Quasi here,

http://www.diyaudio.com/forums/solid...ry-design.html

http://www.diyaudio.com/forums/solid...velopment.html

http://www.diyaudio.com/forums/solid...her-quasi.html

Anyway enough background.

A friend of mine has asked me to fix a faulty Guitar stomp box called a Bad Cat 2-Tone. The unit is based around 2 x 12AX7's. Anyway the transformer is cooked. The transfomer measures 50mm x 50mm x 40mm (W x D x H) with mounting holes 60mm apart and it looks like a 6va to 7va unit. The unit is labelled PACIFIC 0303 1227 A.

Secondary voltages are: 177v and 6v
Primary voltage needs to be 240v. The old one was 110v but it would be great to get one for 240v so he can get rid of the step down.

Does anyone know where I could find one or very similar.

Greatly appreciated guys.

Cheers
Quasi

quasi 14th January 2010 10:27 PM

Photo of faulty unit
 
1 Attachment(s)
Cheers
Quasi

llwhtt 14th January 2010 10:41 PM

Have you talked to or emailed Bad Cat themselves to see if they have an international PT?

Craig

aardvarkash10 14th January 2010 10:44 PM

hiya quasi - you may be better off getting that one rewound. Its waaaaaay small! The secondary voltages are likely 180/6.3 loaded. I haven't seen a PTX that small before as a stock item.

Good luck!

dsavitsk 14th January 2010 11:21 PM

If you can rewire the filaments to be 12V instead of 6V, or put them in series, and assuming that the 2x 12ax7's are the only draw on the HT supply, the Edcor XPWR080 looks pretty good

EDCOR - XPWR080

srh 14th January 2010 11:23 PM

Hi Quasi, is the primary open circuit? If so, alot of xformers have a thermal fuse in the primary winding which sometimes fails due to prolonged slow cooking. If you cut the winding insulation over the top of the primary terminations you may be able to access the ends of it or the device itself.
HTH
Cheers,
Steve.

quasi 15th January 2010 12:40 AM

Quote:

Originally Posted by llwhtt (Post 2048038)
Have you talked to or emailed Bad Cat themselves to see if they have an international PT?

Craig

Thanks Craig, I have emailed an Australian distributer and I'm waiting for a reply, hopefully it will be a reasonable price.

Quote:

Originally Posted by aardvarkash10 (Post 2048042)
hiya quasi - you may be better off getting that one rewound. Its waaaaaay small! The secondary voltages are likely 180/6.3 loaded. I haven't seen a PTX that small before as a stock item.

Good luck!

Rewinding is definately an option. Might try it myself but there's lots of turns of thin wire. I'm thinking of a small torroid also.

Quote:

Originally Posted by dsavitsk (Post 2048079)
If you can rewire the filaments to be 12V instead of 6V, or put them in series, and assuming that the 2x 12ax7's are the only draw on the HT supply, the Edcor XPWR080 looks pretty good

EDCOR - XPWR080

The 12AX7's are the only draw on the HT but this one's a little large especially in height.

Quote:

Originally Posted by srh (Post 2048082)
Hi Quasi, is the primary open circuit? If so, alot of xformers have a thermal fuse in the primary winding which sometimes fails due to prolonged slow cooking. If you cut the winding insulation over the top of the primary terminations you may be able to access the ends of it or the device itself.
HTH
Cheers,
Steve.

The unit's main fuse blows so either the primary or secondarys have gone low impedance.

Thanks for the quick responses guys, I'll feed back to the dark side how helpful the tube guys are.

Cheers
Quasi

thevoice 15th January 2010 01:07 AM

Look up Southern Electronic Services in Melbourne. They should be able to do a rewind, I've used them to get large industrial chokes rewound and they were very good. I believe they do all sizes of work.

Arnulf 15th January 2010 08:57 AM

Is space a serious concern here ? If not, grab one 230V/12V (or 2x 6V secondary) and one 230V/9V transformer of lower rating than the first one and wire them back to back. Heaters draw the most current, 12AX7 can work with either 6.3V or 12.6V (and 6V/12V is close enough and will keep tubes alive longer) and current draw for high voltage rail is minimal with 12AX7. You can find such transformers in junked wall adapters, chargers, etc.

FWIW, custom wound toroid shouldn't cost much more than 20 Euros.

pointy 15th January 2010 11:56 AM

if you put an ohms meter at each end of the shorted winding.
then drive a thin wooden wedge in to the coil sometime you can find and split the short which will show on the meter.
and then put hot lacquer in to stop the short.


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