Problems: A little less than unity gain at full volume. Compression pot and H/L switch have no/very minimal effect. The effect sounds like it is compressing a little but it could be that it is just the volume issue.
Only sub is 100k at R10. Everything else is per build doc.
Q3 Source resistance to ground is ~15 Ohms with no change during playing with comp at max.
Reflowed all joints although none looked suspect.
Thanks in advance for the help!
Is Q2 socketted? If so, pull it out and see if the boost side works. If it doesn't, we'll have to debug that, first.
Q3 (drain) is the place you'll see a resistance to ground shift during playing -- but we need to make sure Q1 is working, first.
Post your voltages, and pics if you have them.
And just to be sure ... BS170 in Q1, right?
Thanks Jon.
I have to hit the road but will be back this evening and will start with your suggestions and report back
OK,
1: Q1 is a BS170
2: With Q2 removed, it makes no difference. The effect still works the same
3. Measurements:
Q1: D 7.1v, G .39v, S 2.0v
Q2: E .47v, B .65v, C 7.6v
Q3: D 0v, S 0v, G 0v
Obviously I am getting nothing at Q3. tried a few different 2n5457's with no luck.
Thoughts?
Same problem here with mine, just volume but no compression.
Will follow this thread closely when I get home from work tonight.
Quote from: Tremster on February 12, 2013, 10:04:43 AM
Same problem here with mine, just volume but no compression.
Will follow this thread closely when I get home from work tonight.
This is the opposite problem. Pryde has no boost. Please start a new troubleshooting thread.
Quote from: pryde on February 12, 2013, 04:01:07 AM
OK,
1: Q1 is a BS170
2: With Q2 removed, it makes no difference. The effect still works the same
3. Measurements:
Q1: D 7.1v, G .39v, S 2.0v
Q2: E .47v, B .65v, C 7.6v
Q3: D 0v, S 0v, G 0v
Obviously I am getting nothing at Q3. tried a few different 2n5457's with no luck.
Thoughts?
Your Q1 voltages are wrong. I don't have voltages for Q1 handy here at work, but I'm pretty sure you should have at closer to 5v on the gate. Try swapping out the MOSFET -- you can try any number of things, including a regular bipolar transistor, to see if there's something wrong elsewhere in the circuit. If it doesn't boost with something else in Q1, post pictures, and check the following parts carefully again:
R1, R2, R4-R7, C2, C4, C6, D2, and the volume pot. Fortunately Q1 is a very, very tiny portion of the circuit.
Quote from: midwayfair on February 12, 2013, 01:41:19 PM
This is the opposite problem. Pryde has no boost. Please start a new troubleshooting thread.
Oh. Derp. People who can read clearly have an advantage.
Quote from: Tremster on February 12, 2013, 02:19:08 PM
Quote from: midwayfair on February 12, 2013, 01:41:19 PM
This is the opposite problem. Pryde has no boost. Please start a new troubleshooting thread.
Oh. Derp. People who can read clearly have an advantage.
(http://farm1.staticflickr.com/230/474003082_f9ae8e3927_z.jpg)
;)
Damn, wife has the camera. I cant get pics til later.
I swapped Q1 with other BS170 with no luck. re-checked ALL components and reflowed your suggested components and also changed D2 with another 9.1v zener. No changes, the circuit still behaves the same and getting same voltages.
consider myself stumped :-\
Quote from: pryde on February 12, 2013, 04:11:15 PM
I swapped Q1 with other BS170 with no luck.
same deal with a regular transistor?
Sorry, forgot to mention that. Same deal with a 2n2222 and a 2n5088
Quote from: pryde on February 12, 2013, 04:37:53 PM
Sorry, forgot to mention that. Same deal with a 2n2222 and a 2n5088
Do you have your audio probe handy? Check the signal on both sides of C2 and at the drain. I'm curious if you're somehow losing signal to ground at the input.
You can also pull Q3 (if you used a socket) and jumper the drain and source holes. It should become insanely loud.
OK.
Signal passes fine on both sides of C2 and Q1 Drain. Also jumped Q3 D and S, as you predicted the circuit became very loud.
Again, thanks for the ongoing help.
Quote from: pryde on February 12, 2013, 04:58:37 PM
OK.
Signal passes fine on both sides of C2 and Q1 Drain. Also jumped Q3 D and S, as you predicted the circuit became very loud.
Again, thanks for the ongoing help.
What is your gate voltage now?
Something's weird with your Q3. Measure the resistance across the FET. It should be ~300R.
The thing that's really bothering me, though, is that even if Q3 were buggered, it would simply be taking the bypass cap out of the circuit, and so you should be at or above unity volume because of the 2.7K setting the minimum gain at ~2x.
Put Q2 back in. Keep Q3 out for the moment, since that appears to be part of the issue. You can audio probe up to D3/D4 at least -- it should continue to be extremely loud at that point, even louder than it is at the drain of Q1. Check the voltage on the anode of D3 and play a loud chord (turn the comp up). Does it change?
Not sure when you say measure resistance "across" Q3 but with probes on G and S (or S and D), I am getting about ~16k resistance.
With Q3 out and D/S jumped, I trace loud signal up to D3 anode. At D3 anode the volume drops pretty significantly and there is clipping as well.
Also, voltage jumps from 0 to ~2.5v at D3 anode when striking heavy chord.
D3 bad?
Quote from: pryde on February 12, 2013, 06:09:36 PM
Not sure when you say measure resistance "across" Q3 but with probes on G and S (or S and D), I am getting about ~16k resistance.
With Q3 out and D/S jumped, I trace loud signal up to D3 anode. At D3 anode the volume drops pretty significantly and there is clipping as well.
Also, voltage jumps from 0 to ~2.5v at D3 anode when striking heavy chord.
D3 bad?
The voltage change should be negative. I just want to confirm that.
So far everything's working fine except for some reason your FET has too much resistance between the drain and the source. In-circuit, it should only be ~300 ohms. When you create the voltage at D3 (which is right but does seem a little low), it applies voltage at the gate of the FET and increases the resistance between the gate and source (so you ought to measure ~300 ohms from ground to the drain when Q3 is plugged in, then play a chord and see it jump up to 1-2K).
But at this point, I might have to wait until you can get photos, and wait till I can get home to give you precise voltages off a working model, because electronically I'm fairly stumped. Your FETs just don't seem to be linearizing. I'll give it some more thought and pull out mine when I get home, unless someone else has theirs handy that they can test.
Yes Q3 is wonky concerning voltages. I will get some good pics posted this evening and we can go from there. It might help if I knew anything about compressor circuits but not so much :-[
Quote from: pryde on February 12, 2013, 08:31:34 PM
Yes Q3 is wonky concerning voltages. I will get some good pics posted this evening and we can go from there. It might help if I knew anything about compressor circuits but not so much :-[
Check the original project thread -- I explain the inner workings of the Bearhug. I don't know if it'll help with your build, but it might.
But you've confirmed that resistance to ground at the drain of Q3 does not change with a guitar signal? edit: Resistance at Q3, not voltages!
OK for clarification: vol on full, compression on full...
Q3 drain settles at 8.8k resistance, then jumps up to ~14k with hard strumming. So yes the resistance does change.
thoughts?
Quote from: pryde on February 12, 2013, 08:54:00 PM
OK for clarification: vol on full, compression on full...
Q3 drain settles at 8.8k resistance, then jumps up to ~14k with hard strumming. So yes the resistance does change.
thoughts?
Man, that is *crazy* out of spec. Flip it around, and try another FET (if you have a 2N5952, that will work, too). Same-ish readings?
Just out of curiosity, did you get the 2N5457 from Tayda? I had a batch recently that didn't work in the Blue Warbler and I'm not certain they didn't get a bunch of bad trannies.
DING DING DING ;D
Bad 2N5457's it was!
I never ordered from tayda but I have a mixed bag between mammoth and mouser. I tried 4 more with the same result then pulled one out of an old orange squeezer vero I have in the pile and bingo, it works!
The drain resistance is 430R then jumps to about 1k with hard strumming. I assume this is within a reasonable spec?
Man it is kinda hard to trouble-shoot when you have a batch of bad transistors >:(
Thanks for all your help Jon
Quote from: pryde on February 12, 2013, 09:25:40 PM
DING DING DING ;D
Bad 2N5457's it was!
I never ordered from tayda but I have a mixed bag between mammoth and mouser. I tried 4 more with the same result then pulled one out of an old orange squeezer vero I have in the pile and bingo, it works!
The drain resistance is 430R then jumps to about 1k with hard strumming. I assume this is within a reasonable spec?
Man it is kinda hard to trouble-shoot when you have a batch of bad transistors >:(
Thanks for all your help Jon
sounds like that's a good FET!
I hear ya, it SUCKS troubleshooting around a bad part ... my favorite was some mis-marked resistors I got recently. Big difference between 8.2R and 8.2K ... ::)
Glad it's working, and thanks for sticking with the troubleshooting through to the end. Jumping to 1K sounds about right for single coils. My DQ caster hits 1.3K in my test unit, well within several tolerances of Q1 and Q2.
thank you again for everything. Kudos to a really nice compressor. It gets that subtle-sweet OS compression and then can really clamp down from there if you need it to.
As a bonus, it has a great clean boost with the comp turned all the way down.
Looks like I got a small batch of 2n5457's to sort through to see if any are usable ::)
Quote from: pryde on February 12, 2013, 10:28:33 PM
thank you again for everything. Kudos to a really nice compressor. It gets that subtle-sweet OS compression and then can really clamp down from there if you need it to.
As a bonus, it has a great clean boost with the comp turned all the way down.
Looks like I got a small batch of 2n5457's to sort through to see if any are usable ::)
Even if they aren't usable in a linearized FET application, they will still make good amplifiers and/or buffers. You could test them in a Fatpants for that. :)
There are few parts that are useless just for failing on some weird spec.