Bill M "Clean Boost" mod: how to install?

[Leo_Gnardo]

Has anyone here successfully installed a Bill M "Clean Boost" circuit card? It's intended for Fender's Blues Junior.

I know, call Bill M. Well I tried that, no dice. Over the last couple days Andrew isn't answering the phone and does not call back. It would only take a minute. I'm sure he's up to much more important things.

The Blues Jr I'm working on has the "cream circuit board."

Photo on the website shows the coax lead going somewhere near R17, the EQ drive triode cathode resistor. It looks like the core goes to the + end of that resistor, and shield to the ground jumper next to it. The blue and yellow leads head somewhere tantalizingly out of view - the picture is cleverly cropped to leave their destinations a mystery. Apparently the blue lead controls switching - it goes to the pole of the pull switch, as seen in photos found thru Google. But the card does boost the signal anyway, even with blue and yellow leads not connected to anything else. The trimpot and cap on the circuit board apparently work as an adjustable bypass to R17. Nothing new about that kind of circuit, I was modding old Marshalls with it over 30 years ago. I can find no text on the website detailing the correct implementation, and none was sent with the circuit card.

The amp does have a Presence control installed and working properly. There is a pull switch as part of the pot assembly, intended to switch in the boost when pulled.

Thanks in advance for any guidance!

[nosaj]

Has anyone here successfully installed a Bill M "Clean Boost" circuit card? It's intended for Fender's Blues Junior.

I know, call Bill M. Well I tried that, no dice. Over the last couple days Andrew isn't answering the phone and does not call back. It would only take a minute. I'm sure he's up to much more important things.

The Blues Jr I'm working on has the "cream circuit board."

Photo on the website shows the coax lead going somewhere near R17, the EQ drive triode cathode resistor. It looks like the core goes to the + end of that resistor, and shield to the ground jumper next to it. The blue and yellow leads head somewhere tantalizingly out of view - the picture is cleverly cropped to leave their destinations a mystery. Apparently the blue lead controls switching - it goes to the pole of the pull switch, as seen in photos found thru Google. But the card does boost the signal anyway, even with blue and yellow leads not connected to anything else. The trimpot and cap on the circuit board apparently work as an adjustable bypass to R17. Nothing new about that kind of circuit, I was modding old Marshalls with it over 30 years ago. I can find no text on the website detailing the correct implementation, and none was sent with the circuit card.

The amp does have a Presence control installed and working properly. There is a pull switch as part of the pot assembly, intended to switch in the boost when pulled.

Thanks in advance for any guidance!

Maybe the comments will help? Blue and yellow are control and power
The active connection uses Mogami low-noise coaxial. This is mixing board/studio-grade cable. The control and power connections are stranded, Teflon-coated wire for ruggedness
nosaj
http://billmaudio.com/wp/?page_id=105
Bill, if the audio taper gain and master volume controls are both installed, is there anything to keep from installing the clean boost and hardwiring it so it’s on all the time?

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bill says:
November 16, 2009 at 5:50 pm
Sure, you can just ground the blue wire and it’ll be on all the time. Or just leave the presence control pullswitch in the up position.

[Leo_Gnardo]

Maybe the comments will help? Blue and yellow are control and power

Yep, I had read all that and concluded blue goes to the pull switch on the presence control (another Bill M mod.) I'm guessing the transistor on the circus board is some sort of MOSFET to act as an electronic switch between the trimpot & bypass cap, and yellow goes to perhaps +15, or is it -15V picked off a point near the reverb chip. A mis guess could wreck the MOSFET so I await clear directions.

An email to info@billmaudio.com got me a canned response "we're busy" as of July 2. No fooling. Well so am I, and the crustomer wants his amp working 8/31 so I'm in a bit of a time squeeze. All for want of clear directions which should accompany the kit... phooey! Well he might get his much Bill M modded amp, less one mod, until this is sorted.

[nosaj]

Yep, I had read all that and concluded blue goes to the pull switch on the presence control (another Bill M mod.) I'm guessing the transistor on the circus board is some sort of MOSFET to act as an electronic switch between the trimpot & bypass cap, and yellow goes to perhaps +15, or is it -15V picked off a point near the reverb chip. A mis guess could wreck the MOSFET so I await clear directions.

An email to info@billmaudio.com got me a canned response "we're busy" as of July 2. No fooling. Well so am I, and the crustomer wants his amp working 8/31 so I'm in a bit of a time squeeze. All for want of clear directions which should accompany the kit... phooey! Well he might get his much Bill M modded amp, less one mod, until this is sorted.

Do you have a current limited dc supply? Would that help you determine something while waiting?

nosaj

[Leo_Gnardo]

Do you have a current limited dc supply? Would that help you determine something while waiting?

nosaj

Yes but MOSFETS give me the heebiejeebies. Wrong polarity, I'll be buying this guy a new Bill M circus board, plus be way beyond the deadline. And STILL won't have correct instructions.

[Pedro Vecino]

I imagine that it must be a copy of the FAT circuit to activate it at the same time with the option to select or not in combination with the original.
Check that it is a FET J111 or similar. If it has a diode 4148 in series with the gate, the other end of the diode should be connected to one of the wires. This wire should be connected to the same point as the 4148 diode of the FAT. The second wire would be ground. Practically identical to the "more drive" of an HRD (handling two steps at a time).
They are conjectures because I do not know the circuit, but everything seems to indicate that it must be like that.

[Leo_Gnardo]

Thanks Pedro.

Folks, I'm suspending the search for now. No need to reply unless I start it up again. Another source directed my attention to a photo that reveals the proper location for the yellow wire. I'm going to try it, and if it works, I'll see if I can copy the photo here. Failing that I'll show its URL in case anyone needs this information in the future.

[Leo_Gnardo]

OK, here 'tis. Yellow connects to the lower end of R57, a source for -15V. Who knows what might have happened if I punted and went for +15, that would be a big whoops! Thanks again to those who read and double that to those who posted.



Credit to ws6zep89 who posted this photo on picturepush, taken with a Fuji Finepix. Those are good cameras imho, with better than average lenses. He had his in the right place at the right time, nice crisp focus. Wish I'd found it days earlier but that's how the cookie bounces.

The Blues Junior I'm working on, now with presence control, plus "sparkle" control plus a couple other Bill M mods, is so bright you could split diamonds. And that's with the original Jensen C12N speaker. With a strat or tele, zingggg! careful you could hurt people. Use with care! I expect its owner will be well satisfied.

For good measure, here's the scene from a different angle:



Finally, a successful "mission accomplished" now on to the next victim, ummmm, I mean repair.

[mozz]

BillM himself has passed away. I don't know who is running things now. As was said, often you have to read all the comments to have a better idea on the mods.

[Leo_Gnardo]

BillM himself has passed away. I don't know who is running things now. As was said, often you have to read all the comments to have a better idea on the mods.

Son Andrew carries on the biz. FWIW from what I've seen, most folks who get BillM mods seem to like them.