EHX - Q-Tron+

The Rotagilla · Post by **The Rotagilla** » 01 Jan 2009, 00:26

I know the IP Police are hot on anyone posting current EH schematics but if someone has it and could PM me I'd be most appreciative.

The Rotagilla · Post by **The Rotagilla** » 01 Jan 2009, 00:44

Thanks guys for the PM's but the Q-Tron+ is a different animal than what we have schematics for. It has an effects loop plus a Response switch. From the manual -

Response Switch — Changes the sweep response between two optimized settings. “Slow” response creates a smooth vowel-like response. “Fast” response creates a snappy response identical to the original Q-Tron.

So still looking.

Dr. Molly · Post by **Dr. Molly** » 08 Jan 2009, 21:12

The Rotagilla · Post by **The Rotagilla** » 08 Jan 2009, 21:41

Thanks!

brianeharmonjr · Post by **brianeharmonjr** » 25 Jan 2009, 04:41

Hello to everyone. I recently got a pretty sweet deal on a big box Q-Tron+, but it's got some problems. First of all, the LED status light in the upper left corner never turns off. Second, I have to have the boost on, the gain cranked, and the drive switch up to get near unity gain. Even then, the sound I get is very shrill and the envelope barely opens. Also, the Overload LED is on nearly all the time. I assume this is because I have to crank everything, but I am not sure. I've tried every possible knob and switch configuration, checked that I'm using the correct power supply, and looked inside to make sure that nothing is blown or disconnected, but I've found nothing. Right now, the only way it is at all useful is if I run a jumper cable from the effects loop send to the effects return. If anyone has any advice, please help me. I REALLY want to get this thing going because I know what it is capable of. Below are links to a couple of pictures I took of the guts. I don't know if this will help, but I figured it would be worth the try. If anyone has a working Q-Tron+ that they could open up and compare, that would also help. Thanks.

fuzzfan · Post by **fuzzfan** » 01 Mar 2011, 22:54

Hi,

I just got an old big boxed 24v eh Q-tron plus that has a volume drop issue, and was wondering if the schematic is essentially the same as the regular q-tron or if the effects loop plays a significant role. If anyone has the schem I'd really appreciate it; I already have all the other q-tron schematics, just no info on the loop.

Here's whats wrong and what I've done so far; it drops to well below unity gain in any setting when engaged but passes the bypassed signal fine. Also the signal coming from the effects send jack is fine and the boost knob works normally when plugging in there. This leads me to believe I can rule out the pre-amp as the source of my problem. However, everything post effects loop suffers from this huge volume drop, including signals straight into effects return, as well as both nothing in the effects loop and a patch cable across it. You can hear the filter working quietly when its on and the overload light is functioning as normal.

Any one have any ideas?

borislavgajic · Post by **borislavgajic** » 02 Mar 2011, 21:41

fuzzfan wrote:Hi,

I just got an old big boxed 24v eh Q-tron plus that has a volume drop issue, and was wondering if the schematic is essentially the same as the regular q-tron or if the effects loop plays a significant role. If anyone has the schem I'd really appreciate it; I already have all the other q-tron schematics, just no info on the loop.

Here's whats wrong and what I've done so far; it drops to well below unity gain in any setting when engaged but passes the bypassed signal fine. Also the signal coming from the effects send jack is fine and the boost knob works normally when plugging in there. This leads me to believe I can rule out the pre-amp as the source of my problem. However, everything post effects loop suffers from this huge volume drop, including signals straight into effects return, as well as both nothing in the effects loop and a patch cable across it. You can hear the filter working quietly when its on and the overload light is functioning as normal.

Any one have any ideas?

I have one idea....!

please post some nice pictures of PCB......traces and component side.....then we will be able to see something you do not see....or draw schem

thanks

Boris

fuzzfan · Post by **fuzzfan** » 03 Mar 2011, 22:13

For the purpose of drawing a schematic this thread viewtopic.php?f=1&t=3955 has better gut shots than I can make, and this one has a regular q-tron schematic viewtopic.php?f=1&t=6849

As for pictures from my unit, all I have is the camera on my phone so the picture's are bad but here's the trace side and I'll post the component side when I get home today.

Any help would be great, also worth mentioning is that in mix mode, which mixes the clean signal with band pass, it still suffers the volume drop. I just got it so I don't know if the loop affects the clean signal in mix mode but if so could a buffer on the way back into the loop be at fault? I make this assumption because looking at the regular q-tron schematic there doesn't appear to be anything following the filter stage and the filter effect can still be hear albeit very quietly. Also as the overload light seems to be part of the envelope detection circuit and is functioning normally I take it as a sign to look somewhere else first.

seedseed · Post by **seedseed** » 27 May 2011, 12:54

Any pictures of the component side of the board so this can be traced. Would also be a nice unit

airfrankenstein · Post by **airfrankenstein** » 23 Nov 2012, 08:50

Hi all,

I want to add a response switch to my old big box q-tron. Does anyone know where that would go ? Or can anyone pm me a schematic of the Q-tron + that i can compare to the q-tron?
Have scoured various forums for an answer on the question without luck.
Thanks,

airfrankenstein · Post by **airfrankenstein** » 25 Nov 2012, 09:49

if someone has a q-tron + schematic could they kindly pm it ?

thanks

Post by **modman** » 26 Nov 2012, 09:53

The guts linked to above are still online -- I removed al troubleshooting demands from this thread.
People who own unit (faulty or not) can contribute in this folder to establish a schematic. If they come complaining that they don't find a schematic -- they have the unit... they could establish the schemo or work towards it.

Please keep debugging and troubleshooting questions in the proper sections.

Bernardduur · Post by **Bernardduur** » 10 Apr 2013, 11:38

Got one in with a faulty 'return-jack' switch and a floppy boost switch

Quite similar to the Qtron with some additional mods. The response switch just alters two resistors (by putting another one in parallel with the first). The FX loop is quite nice. After this the input stage is repeated before the signal goes into the filter. Great way to use OD / fuzz without changing the filters responseness

Dr.Detroit · Post by **Dr.Detroit** » 11 Apr 2013, 18:43

Magical pre-thank you for Bernardduur's schematic!

EHX - Q-Tron+ [schematic]