Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Oddvar on July 07, 2016, 01:29:27 pm

Title: Help with locating 240 v
Post by: Oddvar on July 07, 2016, 01:29:27 pm

Does anyone know the 240v and nutral to the Blues Junior transformer?  I use the Hoffman turret build, no reverb.

Title: Re: Help with locating 240 v
Post by: Ritchie200 on July 07, 2016, 02:45:19 pm

There is more to the schematic you are showing.  This may be more helpful.

Jim

http://support.fender.com/schematics/guitar_amplifiers/Blues_Junior_schematic.pdf (http://support.fender.com/schematics/guitar_amplifiers/Blues_Junior_schematic.pdf)

Title: Re: Help with locating 240 v
Post by: HotBluePlates on July 07, 2016, 03:02:45 pm

I'll label the power cord wires as "Mains-Brown" & "Mains-Blue" and label the PT wires as "PT-Violet", etc.

For 240v (from page 2 of the file Ritchie200 linked), the wiring is:
Mains-Brown  ->  PT-Violet  ->  PT-Black/Green  ->  PT-Black/Yellow  ->  PT-Black/White  ->  Mains-Blue.

In other words, connect the PT-Black/Green & PT-Black/Yellow wires. Use the PT-Violet and PT-Black/White wires to connects to your mains (with the power switch in between, on the hot wire if you're not using the standard double-pole double-throw switch). Place a fuse between switch and the PT (and if you're only using 1 fuse, put on the line which is hot).

Title: Re: Help with locating 240 v
Post by: Oddvar on July 07, 2016, 03:20:28 pm

That's great, thanks again.  I am thinking about using two pin on/off?

Title: Re: Help with locating 240 v
Post by: HotBluePlates on July 07, 2016, 03:43:19 pm

Do you mean a single-pole/single-throw (SPST) switch like this?

(http://www.mojotone.com/Fender-Style-Carling-110-63-Toggle-SPST-Power-Stand-Switch-image.jpg)

You can, between the Mains-Brown and PT-Violet, while adding a fuse between Mains-Brown and one side of the switch. But the standard European use of a double-pole switch to control both sides of the mains line is "better".

Title: Re: Help with locating 240 v
Post by: Oddvar on July 07, 2016, 03:47:03 pm

Ok, I'll stick to that then.  And the fuse goes between the hot mains and switch?

Title: Re: Help with locating 240 v
Post by: HotBluePlates on July 07, 2016, 03:52:05 pm

Yes. If there is a fault which would cause a fuse to blow, you really want to break the circuit as soon as electricity enters the chassis. That means placing the fuse right after the switch.

Of course if you use some IEC power inlets, the fuse holder is built into the assembly...

Title: Re: Help with locating 240 v
Post by: Oddvar on July 07, 2016, 03:59:14 pm

I stick to the Hoffman build....

Title: Re: Help with locating 240 v
Post by: Oddvar on July 07, 2016, 04:09:51 pm

One last thing, in the heater circuit there are two 47 ohms resistor going to ground, but says they are on the bj board,  is it?

Title: Re: Help with locating 240 v
Post by: HotBluePlates on July 07, 2016, 04:38:09 pm

Quote from: Oddvar on July 07, 2016, 04:09:51 pm

One last thing, in the heater circuit there are two 47 ohms resistor going to ground, but says they are on the bj board,  is it?

Yes, they are on the board, but are in different places on the board epending on which revision you're looking at.