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 Post subject: Crown Jewel Problem
PostPosted: Fri Jan 05, 2018 9:35 pm 
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Okay, so I assembled the pedal... Thought I had a Rev 1.1 but turned out to be a Rev 1.0. I used the MOSFET boost.

So here's how it went:
I plugged in, boost and drive both lit leds. Boost would work alone, presumably properly. Drive would light the led but cut the signal, this didn't matter if boost was on or not, signal would cut. I also noticed that if the hard clipping switch was in the neutral position I would get some signal in and out but nothing desireable. I looked through the manual and my board again, traced the schematic as best as I could. I eventually found out I missed the edit in the Rev 1 regarding the reverse orientation of the 10 microfarad aluminum electroyltic capacitor.... I reversed it and still have the same issue.

So my questions are:
1) Any idea on what my issue could be?
2) The capacitor doesn't look puffed or anything but could it be bad and causing this?

I have attached photos (note this is before I swapped the polarity of the capacitor) ** Trying to downsize them as they are too large**


Attachments:
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IMG_8099.JPG
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 Post subject: Re: Crown Jewel Problem
PostPosted: Mon Jan 08, 2018 11:49 am 
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The capacitor should be fine.

What voltages are you getting on the pins of the 4558 chip?

I understand that the volume drops significantly, but does the drive volume knob do anything? Does the drive knob do anything? Are you certain you have the A500k pot in the correct spot?

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 Post subject: Re: Crown Jewel Problem
PostPosted: Mon Jan 08, 2018 12:59 pm 
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I will check the voltages tonight.

The volume doesn't drop, it cuts completely out. The knobs don't seem to do anything.


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 Post subject: Re: Crown Jewel Problem
PostPosted: Mon Jan 08, 2018 5:03 pm 
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RiffnHook wrote:
I will check the voltages tonight.

The volume doesn't drop, it cuts completely out. The knobs don't seem to do anything.


Oh. I see. That makes a big difference. I was under the impression that it still passed some signal, but it was just very anemic. Do you have a signal tester? That's going to be the best tool for this job. I would suggest reflowing all of your solder joints on the PCB again. Let us know those voltage readings as well. You need to take readings on the 4558 and TL072 as well. Take two sets of readings. One in 9v mode, the other in 18v mode.

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 Post subject: Re: Crown Jewel Problem
PostPosted: Mon Jan 08, 2018 5:19 pm 
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byoc wrote:
....I would suggest reflowing all of your solder joints on the PCB again.

viewtopic.php?f=9&t=52188

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 Post subject: Re: Crown Jewel Problem
PostPosted: Wed Feb 28, 2018 10:45 pm 
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And life got in the way.... Finally back to troubleshooting this again.

Reflowed twice. Drive still does not work - very quiet with no clipping, with any sort of clipping it doesn't make sound unless you make an aggressive attack on the strings. The sound is then quickly and sharply in and back out.

I have taken voltages for both the 4558 and the TL072
    9 Volts
    4558 TL072
    1 1.4 1.4
    2 1.4 1.4
    3 1.2 1.0
    4 0.0 0.0
    5 4.4 1.4
    6 4.4 1.5
    7 4.4 1.5
    8 9.0 8.9

    18 Volts
    4558 TL072
    1 1.4 1.4
    2 1.3 1.4
    3 1.2 1.0
    4 0.0 0.0
    5 8.0 1.4
    6 8.0 1.4
    7 8.2 1.4
    8 16.0 16.0

Any Ideas? Thanks in advance.


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 Post subject: Re: Crown Jewel Problem
PostPosted: Thu Mar 01, 2018 10:55 am 
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Based on your voltages, it looks to me that your 1/2V tap has a problem. The 1/2V tap is comprised of R21, R22, and C22. Carefully check those out and resolder them. You should have full voltage on one side of R21 and 1/2 that voltage on the other side of R21.

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 Post subject: Re: Crown Jewel Problem
PostPosted: Thu Mar 01, 2018 2:01 pm 
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Morgan wrote:
Based on your voltages, it looks to me that your 1/2V tap has a problem. The 1/2V tap is comprised of R21, R22, and C22. Carefully check those out and resolder them. You should have full voltage on one side of R21 and 1/2 that voltage on the other side of R21.

EDIT: I've deleted my previous comments here, as they weren't accurate. I agree with Morgan's comment that the problem appears to be somewhere around the R21/R22/C22 voltage divider. While there's a second 1/2V voltage divider at R13/R14/C10, it only biases the B half of IC4, and the measured voltages there are correct.

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 Post subject: Re: Crown Jewel Problem
PostPosted: Thu Mar 01, 2018 2:26 pm 
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Thanks for the responses.

I believe the 1/2V tap is fine - I checked that V+ and the 1/2V portion of R21 and R22. The 1/2 V for the 4558 also tested as I would have expect. (iirc on 9 volts it was around 4.4V). However the 1/2V at R19 and R26 were different readings. (I believe this would also make sense given the voltages at the ICs). This is also by memory so I may be missing pieces/miscommunicating this, I 100% remember the 1/2V reading at the R21,R22 branch being 4.5 V though.

The strange part that I saw were the voltages of the Q5 and Q6 were strange (forgive me I wrote it down but now forget). Could an issue with q6 (or the feeds) affect the tl072 in the manner that you found confusing duhvoodooman....?

I have things written down at home and can provide more insight with that later. Thanks again for the responses.


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 Post subject: Re: Crown Jewel Problem
PostPosted: Thu Mar 01, 2018 3:00 pm 
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RiffnHook wrote:
....However the 1/2V at R19 and R26 were different readings. (I believe this would also make sense given the voltages at the ICs). This is also by memory so I may be missing pieces/miscommunicating this, I 100% remember the 1/2V reading at the R21,R22 branch being 4.5 V though.

The strange part that I saw were the voltages of the Q5 and Q6 were strange (forgive me I wrote it down but now forget). Could an issue with q6 (or the feeds) affect the tl072 in the manner that you found confusing duhvoodooman....?

Hmmm, that's interesting because R19, R26 and R34 are all connected to the same 1/2V rail. The latter two provide 1/2V to the low voltage half of the 4558 and both sides (if I'm interpreting the schemo correctly) of the TL072. So it seems to make sense that something amiss at Q6 could potentially cause this low voltage issue. But you should also recheck the voltage at the R21/R22/C22 divider. Seems like that would have to show the low voltage, too. Maybe a partial short to ground across C22 is a possibility, as well.

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 Post subject: Re: Crown Jewel Problem
PostPosted: Thu Mar 01, 2018 3:22 pm 
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I will verify/test further and reply back when I have definites. I was also feeling the same way as I was testing it last night. I assume all the labeled nodes share common feeds.

Also, side-note: I'm not sure if it's me or the schematic, but to me the Drive and Boost switches are open, yet the relays show them sending signal to the drive and boost circuits as opposed to bypassing to the out. Just thought I would make comment on that!

Again thank you!!


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 Post subject: Re: Crown Jewel Problem
PostPosted: Fri Mar 02, 2018 9:36 am 
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Appears there is an issue there (my memory is failing!)

R21 8.96 and 0.194 volts - Reflowed and pulled out of circuit to ensure resistance was correct value with ohm meter
R22 is 0.194 and 0.00 volts - Apparent that it has ground and is connected to R21
C22 is 0.194 and 0.00 volts - Same as last resistor

Ruled out R21 being the wrong resistance - connection appears good and has been reflowed a few times now.

My next steps after work today:
Ensure R22 is the right resistance - I believe that may be my issue.

Update: Did some math and I'm willing to bet I confused a red stripe for a brown - given that portion of the circuit with some simple calculations, the R22 can be expected to be a 220 ohm resistor by theory. I will be inspecting the 220 locations near the momentaries and am willing to bet I mixed them up.

Thanks everyone for the help. I will post back (if and) when it's solved!!


Last edited by RiffnHook on Fri Mar 02, 2018 1:33 pm, edited 1 time in total.

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 Post subject: Re: Crown Jewel Problem
PostPosted: Fri Mar 02, 2018 3:37 pm 
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RiffnHook wrote:
Update: Did some math and I'm willing to bet I confused a red stripe for a brown - given that portion of the circuit with some simple calculations, the R22 can be expected to be a 220 ohm resistor by theory. I will be inspecting the 220 locations near the momentaries and am willing to bet I mixed them up.

I think you're onto the problem. Good job calculating the value that R22 would need to be to give 0.19V out of the divider.

Though you can't really trust visual differentiation of the resistor color bands from a photo, looking at R22 and R5 in your large photos, it surely appears that the former has two red bands at the bottom and the latter has a brown (not a red) band at the top. See blowup shots below. Obviously, you need to confirm this with a multimeter, but I think you've nailed it.

R22:

Attachment:
R22_blowup.jpg
R22_blowup.jpg [ 26.19 KiB | Viewed 6769 times ]


R5 (right side):

Attachment:
R5_R7_blowup.jpg
R5_R7_blowup.jpg [ 37.85 KiB | Viewed 6769 times ]

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 Post subject: Re: Crown Jewel Problem
PostPosted: Fri Mar 02, 2018 9:50 pm 
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That was indeed the problem. I had mistaken a brown ring for a red.

Lesson learnt:
A third hand with a magnifier will help in the future with these tiny 1/8 watt resistors, and many other aspects.

You zoomed right in on the problem spots duhvoodooman.

Thanks for the help everyone! Another Crown Jewel is plugged in and doing it's thing!


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 Post subject: Re: Crown Jewel Problem
PostPosted: Fri Mar 02, 2018 9:52 pm 
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A magnifier helps for sure. However measuring these on the meter will be the source of truth!


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 Post subject: Re: Crown Jewel Problem
PostPosted: Fri Mar 02, 2018 10:06 pm 
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mmarsh wrote:
A magnifier helps for sure. However measuring these on the meter will be the source of truth!

^ This. I've had good luck sorting these 1/8W resistors with a magnifying glass under a high intensity lamp and then cross-checking the counts of each size vs. the parts list in the instructions. But there's no doubt that the best way is to measure them all with a multimeter, especially if you don't have a lot of build experience and familiarity with the color band coding.

RiffnHook: Good job running this beast to ground!

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 Post subject: Re: Crown Jewel Problem
PostPosted: Mon Mar 05, 2018 12:00 pm 
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Very good point on measuring - the irony is I used this during troubleshooting.... but apparently lacked the humility to take the time during the build to do this for each.

Many lessons learnt - now onto the next project!

Thanks again everyone!!


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