Changing input voltage on multi-tap transformer - Bad Cat

[scinoz]

I've got a Bad Cat BlackCat-30 that I brought to Australia from the States. It has a multi-tap transformer and I want to change it from 120 to 240 so I can lose the stepdown box I'm using.

Is this simple and safe for me to do myself? I'm good with a soldering iron etc on guitars -- but never been inside an amp before.

Thanks!

[Structo]

Well you need to be aware of the possibility of the power supply filter capacitors holding a charge, even when unplugged.

I'm not familiar with that amp. Some amps have bleeder resistors that bleed the voltage off the caps when it is turned off.
Some don't have these so you have to manually discharge the caps.

Do a google search on discharging filter caps and you should be able to find a plethora of information.

[scinoz]

Thanks Tom -- I am aware of the need to bleed the caps.

I'mwondering about how to figure out which input leads to change.

The transformer is marked TDS 1161 if that helps.

[iknowjohnny]

Are you sure it is multitapped? Theres a schematic of that amp at schematicheaven and it doesn't show that. Maybe they just left it out of the drawing, i dunno. But if you haven't opened it up, do so and look for the extra wires. It should be pretty obvious, plus there may a label or something noting the 240v tap. Especially if it's a lay down PT where there could easily be a label on the part of the PT thats inside the chassis. Might be a good idea to post a pic. Or call bad cat. You paid for thier product so they should be willing to tell you. Tell them you have a friend who is a tech that said he'd do it for you once you get the required info. That way they are relieved of any responsibility in giving you this info in case you electrocute yourself and they'll be more likely to part with the info. Might wanna open it up so you can look at it while they are telling you.

[Structo]

Yep the schematic shows that transformer but as Johnny says, it doesn't show any other primary taps.

http://www.schematicheaven.com/newamps/ ... cat_30.pdf

[rfgordon]

If the PT has extra taps, it should be pretty straightforward change. Assuming you find the right tap on the first try (some international PTs have more than two choices), it's basically two solder joints: remove one of the primary leads and replace it with the other one.

You may find that the alternate leads have been clipped down somewhat. Hopefully you have enough wire left on it to work with.

You need to be sure, though, that the lead you replace is the other end of the primary from the one you don't change. That is to say that all of voltage choosing leads are going to be at the same end of the primary (unless this PT uses dual primaries, where they are wired in series for use with 220 or 240 volt power).

If it were me, I'd first look carefully at the chassis. If it's not terribly obvious which lead to choose, I'd call Bad Cat.

[scinoz]

Thanks very much!

The Hotcat is different from the BlackCat. Havent found a scematic for it

I spoke to James at BadCat -- which is how I found out that it was multi-tapped. I didn't ask him about the leads as I had an amp tech in mind -- unfortunately he has moved.

I may take a look myself and hope they are labeled -- and call James again.

Thanks!

[Wayne]

This may fall under the category of "experimental house wiring", but with the appropriate grain of salt, here goes...

While plugged into your stepdown box, the appropriate leads on the primary should measure the right voltage, i. e. if you've got it configured for 120V, one of the unused primary taps should measure 240V when you're plugged in. I don't know what your level of experience is, so I highly recommend the following:

- unplug the amp
- connect your meter to the suspected taps using clip leads
- plug in and observer meter reading without touching anything
- unplug

rinse & repeat until you get the desired result.

Also, once you change the wiring, I would recommend a "bulb limiter" or some other means of limiting current for your initial power-up. At 240V (or even 120) that which goes wrong can go wrong in a hurry

W

[scinoz]

Thanks! Sounds good.