....problems with dr q....

[-mick-]

Hi guys, some days ago I bought a Doctor Quack (E.H.) but it doesen't work well...  I tried to change the op amp but it doesn't work well yet :-( .... What can I do? Any ideas?

[Mark Hammer]

There should be a trimpot inside that adjusts what gets sent to the transistor governing the filter frequency.  Plug your guitar in and twiddle the trimpot.  In principle, that *should* change the filter frequency, regardless of how hard you are picking or where the sensitivity is set.  If it does not do so, then you have a problem with the filter itself.  If it does change the filter frequency, then you know that at least that portion of the pedal is working correctlyand the problem lies somewhere else - chiefly the inability of the guitar+envelope-follower to drive that transistor (what I like to call undersignalitis).  This latter problem is most likely to occur if you:

a) have a guitar with modest output levels (or you like to keep your guitar volume rolled back a bit)
b) you are a relatively gentle picker
c) you have no boost of any kind preceding the DQ

It is reasonably hard (though not impossible) to design an envelope-controlled pedal that will respond well over the potentially huge range of signal levels that might come its way.  Occasionally it happens that the design of that pedal is insufficient to meet the needs of player X using guitar Y.

[jimbob]

I had similar problems with mine a while back. As I learned from Puretube- Its probably something mechanical .Maybe a bad jack, loose wiring, switch ect..I have learned most my past EH repair experiences that the board is ussually the LAST place the problem exists.

Good luck.

[-mick-]

I had similar problems with mine a while back. As I learned from Puretube- Its probably something mechanical .Maybe a bad jack, loose wiring, switch ect..I have learned most my past EH repair experiences that the board is ussually the LAST place the problem exists.

Good luck.

The effect is new!!!  :cry:
I'll try to solve the problem... Thank you guys...

[Mark Hammer]

it doesn't work well...  I tried to change the op amp but it doesn't work well yet

Still not clear what that means.  The suggestions from others about mechanical problems would involve things like there being sound in bypass mode but not in effect mode, or something like that.

Let me ask you, do you have sound in effect mode?  If so, is it "dull-sounding" and bassy?  If so then your signal is just not strong enough. and/or the envelope follower is just not sensitive enough.  The "classic" circuit uses a 2.2Meg feedback resistor in the envelope follower.  You may find that a 2.7meg resistor improves things.

But still, you need to try adjusting the trimpot first.

[jimbob]

Question- If its new why dont you either take it back or for that matter contact EH or New Sensor and have them repair ir. I bought a new 16sec digital delay not too long ago that had 2 broken switches and I sent it to EH in New York - 15 $ and it was fed ex back working and looking great! Now there's a company thatll stand by its products.

BTW- Even though its new doesnt mean that the possiblity that something mechanical cant be  working. Most of all my collection of EH stuff had something wrong even though it was new and in the box. Thats because I bought it that wat from a clearance center-Musicians Friend ( when thier broken prices were reasonable. Now there insane. But thats another story.