Two questions:
1) what's the benefit of the buffered rate LED circuit in the 2015 Harbinger compared to the old version? Is it to prevent ticking?
2) I subbed a BC560C for the 2N5087 in the rate LED circuit and the LED doesn't flash now. It does sometimes, but usually is just permanently on. Maybe I see a very faint flickering. Could this be due to the substitution? I looks to me like the 1uF cap may be charging up to quickly and the potential not going down anymore. Maybe subbing a smaller cap will fix it, but maybe there's other ideas?
Other than this, the build is working fine by the way :)
Don't know what was wrong, but I replaced the 1uF electrolytic with a similar one and now it works fine.
I read somewhere on here on some old thread that someone replaced the 1 uF with a 10uF and that solved it, from memory...
Quote from: cooder on December 23, 2018, 05:04:36 PM
I read somewhere on here on some old thread that someone replaced the 1 uF with a 10uF and that solved it, from memory...
Which 1Uf did you replace?
Quote from: cooder on December 23, 2018, 05:04:36 PM
I read somewhere on here on some old thread that someone replaced the 1 uF with a 10uF and that solved it, from memory...
Which 1Uf did you replace?
Quote from: Axeman on January 05, 2019, 09:37:40 PM
Quote from: cooder on December 23, 2018, 05:04:36 PM
I read somewhere on here on some old thread that someone replaced the 1 uF with a 10uF and that solved it, from memory...
Which 1Uf did you replace?
I assume he's talking about C22, the cap in the Rate LED portion of the circuit. Its the one controlling the tickle on the base of the transistor lighting the LED. Bigger cap would mean more juice needed to trigger a flash.
Ok I'll change C22 and R55 with no positive results. My light does not pulsate.
I used this circuit to replace the original mainly because putting an LED in line with R45 does work for flashing but it also does have some effect on the LFO overall. I wanted to have something that operated without influencing the depth of the LFO in any way.
Not sure why one 1uF would work over another. Looking at it again, I think I could have done something better with that flasher circuit.
Like Q13 and Q15?
Quote from: Axeman on January 07, 2019, 01:56:44 PM
Like Q13 and Q15?
Try a 10uF for C22 as suggested. But, you can test it first! Simply touch the leads of a 10uF cap to the soldered leads of the 1uF in C22 and see if the LED starts pulsing. This is just to see if greater capacitance on C22 has an effect on the end result.
I can look at the circuit again but probably not for a couple of days. I seem to remember having trouble getting it to work with an NPN which is why I used a 5087. But, it's been a few years :)
Well if I get it work I'l buy 2 more and 2 of the Harbinger 2. I build Plexi amps and 800, so I have a general knowledge of this stuff.
Thanks
Well, I replaced Q15 with a new 2n5087 I tested it as well and now the red led doesn't turn on. I also used a 10uf to jump/bridge c22 and the red led will flash once and dim off. I'm starting to wonder of the thin copper circuit is to thin and dissolves after heat of a soldering pin is applied.
Ok, really embarrassing question is the 100KC dual log pot or dual Anti-Log?
It's a dual Anti-Log.
Also called 'reverse audio' http://smallbear-electronics.mybigcommerce.com/alpha-dual-gang-16mm-solder-terminals-100k-rev-audio/ (http://smallbear-electronics.mybigcommerce.com/alpha-dual-gang-16mm-solder-terminals-100k-rev-audio/)
Got it, I have the right one installed and still will not work.
Quote from: Axeman on January 10, 2019, 10:48:42 PM
Got it, I have the right one installed and still will not work.
The actual pot value would also not be a cause for this problem, it would just have a different feel to how the speed increases or decreases. The spread of range would be not so even with a normal log pot. It shouldn't have any effect on the LED flashing.
I replaced Q11 and 12 and used a MPSA13 for Q13 and the light became brighter only, no pulsating.
OK I replaced R46 and R47 to check if correct value and they are, replaced with checked new ones. Replaced Q13 from 2n5088 MPSA13 and now my head hurts from the laud buzzing sound. When I short out the C22 1uf cap the LED turns on, if I rapidly adjust the gain the LED pulsates only one time.
What else
Ok. I did a voltage reading on every transistor and they check within perimeters. I also checked continuity, when I checked Q12 B and C the light appeared as if it wants to pulsate, the 2 transistors Q12 and 13 were replaced with new ones 2 weeks a go with some Fairchilds .
HELP
The LED1 not flashing is not going to be helped by changing Q11/Q12 or R46/R47. I've double checked the flashing circuit and it can indeed crap out at the slowest speeds, but this is fixed by using a 10uF in place of 1uF for C22. And, that's really the only change needed - leave all the parts stock as listed. You can brighten the LED up by reducing R54 to 470R or 330R.
So, we might need some pics of the top and bottom of your board specifically in that area of the circuit to see if there's something weird going on. Keep in mind that the flasher is basically a hack for a cool flashing light (and it's pretty much on/off and not ramp up and down in brightness) but not intrinsic to the operation of the vibe.
Ok while I was taking some photos I shorted out something on the board and the led turned on.
Does Diode 4 and 5 have anything to do with the light pulsating?
"The two diodes across the center capacitor limit the size of the LFO output waveform. An oddity of this particular way of building a Univibe is that the LFO amplitude goes up with increasing speed, even with the diodes there. " This explanation is from the RG Keen article about the Univibe (http://www.geofex.com/Article_Folders/univibe/uvfrindx.htm ).
Thanks, but I have very slight understanding what the literature you refereed me to meant. :-[
I know what you mean, but it is not often you can find a good article explaining what is happening in each part of an effect you are building, and it is an opportunity to put some time into understanding it since that will pay off in other projects where all you might have will be a circuit diagram. The short answer to your question is yes those diodes are part of the flashing circuit. They limit the range of the voltage that drives the flashing circuit to make the bulb glow brighter and dimmer.
Roger that. I figured they did based the schem. I removed them and tested them they are good. Installed some new one they also got tested. So where I'm now is, signal goes through and when I apply an external flash light that blinks the pedal works. I'm going to remove and test R41 through 46.
I know from other forums posts on these builds that it can be tricky getting the flashing circuit to work. at least you know that the filters and LDRs are working since your flashlight gets a reaction when you turn it on and off.
what voltage reading are you getting with a DMM at the bulb? Also try turning your trim pot to each extreme and see if you get any kind of variation in the voltage at the bulb then.
I hope the numbers and the arrows of the trim pots make sense
I see the range of voltages you measured. Now, if you put the trim pot for the flashing circuit minimum/middle/maximum and just measure the voltage at the bulb while the rate control is set to the slower part of its rotation, are you getting a fluctuating voltage for each setting? (and my apologies if that is what is on your chart and I did not understand it). Since it is an LED you only need something that falls below and then goes above the LED turn on point. It may be that you have a fluctuating voltage going to the LED but it is either above or below that threshold.
The arrows on the image are the trim pots and the directions they are turned and with the corresponding voltage. I hope that makes sense
Are you getting those volt ranges when testing at the bulb? I would think that those diodes in the circuit would cap the volts at the bulb from going that high. And are you using the bulb for the light and not an LED? (I mistakenly referred to an LED in my earlier post)
Yeah I'm using a bulb in combination with LDR. LED for indicators on top of the pedal.
I read somewhere stating if the speed pot is faulty, it will fry transistors
Does your bulb light up when the effect is on? Or does it remain off?
Setting your rate control at the slowest setting (fully counter-clockwise), the intensity control at mid-point, with the gain and offset trim pots set in the middle of their rotations, using your DMM, what voltage do you get at the bulb when the effect is plugged in? Does the voltage change or is it constant? If it changes, what is the range of the volts? Does your reading change if you set the intensity control all the way clockwise? If it changes, what readings are you getting then?
https://www.youtube.com/watch?v=auhPHlOekxk
https://www.youtube.com/watch?v=takED599vxs
Thanks for posting the two videos. Pondering what to suggest.
I'm going to inject a signal and trace it with my scope. I had to jump C22 to R56 because the negative part of c33 broke off, I had fixed it prior to the video.
I don't recall, have you tried swapping out the transistors in the LFO? The transistors are reportedly working under stress when the circuit is working correctly, so maybe one of them failed while getting the other parts of the power to the transistors sorted out.
Q11 and 12 are new 2n5088 and Q13 is a MPSA13. I'm going to replace the Darlington transistors again.