Adapting a Homebuild Fulldrive 2 to 18V.... Fixed!!!!!

[Bernardduur]

OK. I read on the Fulltone website that their Fulldrive 2 and Bassdrive (my clone) can run on 18V. So I tried it at 18V (Dunlop brick). Result: total quietness..... no signal at all. I guess that the homebuild version I have is not capable of running on 18V???

Any guesses how to alter this? I've build the unit from the GGG website (http://www.generalguitargadgets.com/diagrams/ts_fulldive_2_sc.gif).

[cd]

As long as all the parts in your pedal are rated for 18V or more (all the capacitors mainly) there should be no trouble at all.

[Bernardduur]

I've checked all the caps and they are all above 25V.......
I've also checked the used IC and the transistors.... also for 18V.....

[WildMountain]

Silly question, but: No problems at 9V?

[Samuel]

Polarity the same on that adapter? Adapter size the same?

[petemoore]

Measure the adaptor voltage output.
 Compare that to all component ratings [caps mainly].
 If the #'s jibe you should be set to go to 18v.

[Bernardduur]

My other 18V pedal, my homebuild Bartolini NTMB works fine, so no problem with the polarity or the 18V (I use a Dunlop Brick)...

And no, no problems at 9V.

All my components are valued for 25V or more......

[Bernardduur]

OK, I found a problem: when I measure the voltage between the + and the ground I only read 1.9 to 5.3V with 18V supply and 9V with 9V supply.... I guess my "power section" is wrong.

Have checked it by removing my "other power consuming leads (as in LED's, mods, etc) and it is the power section that is messing with my signal giving me approx. 1.9 to 5V instead of 18V. Caps in the power section are rated 50V.

[Bernardduur]

OK. I will alter my power section than....


but how? Do I need to alter the caps or the resistors. Or is something "broken" right now....

The only other power section uses different caps (22 µf) and different resistors (30K) and this one works, but I know nothing about this topic.

[johngreene]

What's the current rating on your 18V supply? By doubling the voltage you are doubling the current draw on all the connections to ground. So you may want to change the 10K resistors in the Vr section and the emitters of the transistors to at least 20K. These 3 parts are drawing 3 mA @ 18V all by themselves with 10Ks. The LED is drawing over 5mA all by itself. I'd change the resistor there to as large as possible that still provides enough illumination to see it. That will also more than double your battery life @ 9V.

--johng

[Bernardduur]

Thanks....

I already did the last part. I'll add new resistors tomorrow.

[Bernardduur]

NOPE.... It does not work.

I've changed the power section to 2x 22 µf and the resistors to 2x 30K.... Still I only measure 1.87V with 18V.....

And with 8.97V with 9V


I AM GOING INSANE!

Oh, I measured the power section without any leads to Vr or other V+ on my board.

[Bernardduur]

Found it.

It was my DC brick that is acting up.....


3 18V portals, only 1 is doing it. :oops:



Still the pedal is not working on 18V........ Changed all

[Bernardduur]

Come on...... nobody else? I am desperate.

Oh, I've changed the layout to the Fullclone 2 version (wanted to try). Now I only get static at 18V with some signal through it (very quiet)...... I thought this to be easy!

Oh, I found this one (http://forum.musikding.de/attachements/fulldrive_2_2004.jpg). Will try it out!

[johngreene]

What would help is if you could measure the DC voltages around the opamp and transistors. Another easy way of narrowing down where the problem is would be to touch the signal path starting at the output, while plugged into the amp of course, and work your way forward until you find where you no longer hear the additional hum your finger is causing.

--john

[Bernardduur]

OK, I resolved it.

In my first attempts I used 2N5088 transistors; I checked and rechecked the voltage tolerance of these units and they are granted for 30V.

With the new schematic I found, as seen above, I changed the transistors used to 2SC828 (all I could find were BC5465B's; my book agreed on them) so I swapped them and now my unit works on 18V.....

So don't use the suggested 2N5088 transistors when you want to power a Fulltone pedal with 18V.

(and use a decent PSU; warrenty must resolve my problem with my Dunlop DC brick).

Thanks again for the good help with my problem.... I can be kind of a bugger when I am sure I am overlooking something simple......  :oops:

[Arno van der Heijden]

2N5088's should work fine as well!!!
Probably a wiring error or you assumed the wrong pinnout.

EDIT: maybe something to do with biasing?

[Bernardduur]

Nope. Checked and tripple checked as well..... Maybe a dead transistor although they were new.