Build Report and small problem

[jimmy]

hi all

finished my mxr dist+ and my pulsar trem. for the mxr i swapped some diodes around for a while and eventually settled on 2 1N914s and some weird germanium one. i hooked them up for assymetrical clipping and it sounds great! its a little frustrating that the drive pot is useless 3/4s of the way but nothing i cant live with. if i ever order from small bear (which i intend to do at some point) ill get a reverse log.

the pulsar trem. i know you all advised me against it, and it IS quite noisy, but i quite like it. its got some weird sounds coming out of it. the problem i have is this: with the 'Chop' switch on, i can get nice choppy sounds, and it works fine, but with the chop off, i get an unmodulated signal. i was poking around in there and when my finger hits something and i get radio, the guys on the radio ARE modulating in a smooth tremolo.
whats the go?

Cheers

[jimmy]

anyone?

[gez]

"3 Australians die each year from testing 9 volt batteries on their tongues. I guess what im trying to say is dont lick batteries"

I thought that was from licking toads???

[Paul Perry (Frostwave)]

As an Australian, I can tell you it isn't the guys testing the batteries that die, it's their friends who die laughing at them!
And putting your finger inside the trem, is probably modifying the bias on the fet. The different results people get wiht modulation depth on fet trems, is due to fet variability, whihc can (usually) be fixed by varying the bias.

[jimmy]

... theres no FETs in a pulsar

[Chawk]

I'm having this same issue with my tonepad built Pulsar. The chop side of the switch works fine but the smooth gives me an unmodulated signal. However I'm not getting a radio signal only guitar tone. The only changes I made to the schem were swapping a couple resistor values but they were only within a 10k range. Nothing major. Any thoughts on this?

*Edit: After poking around a little more I do get the same problem. When I touch the legs of the Q1 tranny with an Exacto I get a smooth modulated radio signal.

[oskar]

You might want to add a link to the project...

I'm having this same issue with my tonepad built Pulsar. The chop side of the switch works fine but the smooth gives me an unmodulated signal. The only changes I made to the schem were swapping a couple resistor values but they were only within a 10k range. Nothing major.

The mode switch change between two caps. The bigger of them C6 is taking care of the smooth modulation. It could be too big so the LFO signal gets filtered to close to DC or, which is more likely I think, it could be shorted to ground. Then no signal will reach Q1.

Edit: After poking around a little more I do get the same problem. When I touch the legs of the Q1 tranny with an Exacto I get a smooth modulated radio signal.

Strange and mysterious things happen when you poke around...   

[Chawk]

I'm not sure if I'm allowed to link to the tonepad site. Is that within the rules?

[oskar]

http://www.tonepad.com/getFile.asp?id=29

As long as you don't repost the project file. I also use to copy a part of the schemo with notes and pointers
when hunting down buggs. I don't think Señor Peña will disagree.   
Otherwise it becomes very difficult to help someone building any of the Tonepad projects.

[gez]

The only changes I made to the schem were swapping a couple resistor values but they were only within a 10k range. Nothing major. Any thoughts on this?

Which resistors and what values?

Oskar has pretty much covered this.  With power off, check for continuity between the junction of R12/R13 and ground.  Or measure resistance.  If there's no ramp up and little/no resistance (with the latter) or you get a beep when checking for continuity, there's a short to ground.  Could also be the wrong value cap (it's too large).

[petemoore]

  The DIST+ Gainpot has 'fixes' that are easy, not so sure about the tremolo.
  The gain pot of the D+ is a wierd taper to work 'right'.
  When it's like the original the gain pot is well past half way up 99.99% of the time, because the only time the gain is turned down is to find out that lower gain settings aren't what the box does well and sound muddy.
  Then you simply put a 50k or 100k linear gain pot [which eliminates the low gain settings], and have the gain range settings you do use spread across the pots full rotation, 100k giving a lower lowest gain setting than 50k.
  Additional tapering resistors for pottaper didn't seem necessary to me.