Building a Black Eye : tubes daughter boards mistake, is it really bad ?

[eh là bas ma]

Are these 2 highlited 10k?

Yes they are.



First, i guess i have to restore the right voltage at UF4007. I need to investigate why i only have 170V.

I wonder if it's safe to read voltages everywhere in the power supply aera ?

 

[Anton K]

No, it isnt. Read the post from vigilante earlyer in this thread. Than google about how to handle high-voltage circuits. Don't be hurry. Be careful. No PCB is worth the cost of your life!

 

[Anton K]

@eh là bas ma possibly found it: your "stacked" resistors - think again!

 

[eh là bas ma]

@eh là bas ma possibly found it: your "stacked" resistors - think again!

I don't get it.

What would be the issue with these stacked resistors at R22 ?

 

[Anton K]

think: how resistores are summed up?

 

[eh là bas ma]

think: how resistores are summed up?

I have no idea, i am not sure i even understand the question.

I'll salvage a 330k from another build, replace the stacked resistors and report.

 

[music6000]

think: how resistores are summed up?

I don't like the way it has been done but they are in series, Are you talking about them being stacked together???

 

[music6000]

It could be a case that is further down the line where the Right angle adapters were removed & replaced with bent pieces of individual leads!???

 

[Anton K]

I don't like the way it has been done but they are in series, Are you talking about them being stacked together???

bummer! to me its looks like, they are parallel. sure there is no unwanted contact?

 

[music6000]

bummer! to me its looks like, they are parallel. sure there is no unwanted contact?

Take the Guess work out of the PCB & put the correct value in, We are talking 200+ Volts!!!

 

[vigilante398]

I have no idea, i am not sure i even understand the question.

I'll salvage a 330k from another build, replace the stacked resistors and report.

Try removing your stacked resistors and just use a 220k by itself in that place. Shouldn't affect the build much.

In high voltage circuits tidiness is more important than in low voltage circuits. I would recommend going over the whole build and cleaning things up where possible. Snug your capacitors down to the PCB, shorten wire lengths, go over your solder joints and make sure there are no shorts.

This project was designed to be as easy as possible to assemble, but it is still not a simple project. Take your time, don't rush anything.

 

[eh là bas ma]

I shortened the electro caps legs when it was possible (100uF is above a pot, so i can't).

Replaced the stacked resistors by a 330k, 1/4W.
It was a musikding kit, so i had the exact amount of resistors (except one 330k), and i measured them before populating the board, as usual.

Still 172V at UF4007 instead of 240V, and it still sounds dark, unfortunately.

Is UF4007's negative side the only point where i can safely measure voltage ?

I guess there are at least 30V disappearing somewhere in my power section... How should i proceed to find the issue ?
Continuity tests following schematics i guess, but i couldn't find anything so far...

Here are a few pics, in case you can help me spot something wrong or suspicious on this build :

 

[eh là bas ma]

The issue seems to have changed :

I tested the effect after reflowing a few pads, now it doesn't sound dark anymore, it's perfect.

Only remaining problem is a very low volume, even when it's set fully CW.

The effect is barely audible on its own, i had to use a volume boost after it, but the tone was much brighter, with a beautiful distortion sound.

Some progress at least !

I guess audioprobing the signal path is absolutely unsafe ?

 

[eh là bas ma]

I looked for instructions about "stompbox high voltage circuits troubleshooting" and such on google, but i can't easily find something useful.

Any suggestions ?

For exemple, i'd like to know wich connections in the signal path are safe to audio probe, in order to find where my volume is dropping.

I guess the pots are safe ?

 

[vigilante398]

I looked for instructions about "stompbox high voltage circuits troubleshooting" and such on google, but i can't easily find something useful.

Any suggestions ?

For exemple, i'd like to know wich connections in the signal path are safe to audio probe, in order to find where my volume is dropping.

I guess the pots are safe ?

View attachment 62654

I recommend probing these three spots. The first two should be pretty damn loud, third should be quieter but not super quiet. If all else fails and you just need more output volume, remove R21 and/or jumper R18. That will give you a lot of volume back.

 

[eh là bas ma]

Thank you very much for your help !

Volume at 12'. Tone fully CW. Gain at 12'.

At R20/R13 the signal is very very loud and distorted as expected.

It's much quieter and a bit less distorted at R17/R22, but still perfectly audible, and well above bypass level.

R21/R18, i probed the middle pad of the tone pot, which is connected to these resistors. Signal disappears because it's a very faint signal. I have to set the volume fully CW and turn up the amp volume to finally hear it.

If i understood correctly, there should be the same very loud volume level at the first two points you mentioned ?

Surely there's an issue between R20/R13 and R17/R22. I'll focus on this aera and see what i can do.
If the volume was loud enough at the second location (R17/R22), i guess it wouldn't be so faint at the Tone pot...

Edit : i wonder, if it's not too much trouble, if you would be so kind to post a picture of the pcb with the numbers designations (R1, R2, etc.), please ?
I am having a hard time figuring wich 100k is R11, which 1n is C6... I know it's not a big circuit but it would be really useful, probably also for other builders in the future ?

 

[vigilante398]

Thank you very much for your help !

Volume at 12'. Tone fully CW. Gain at 12'.

At R20/R13 the signal is very very loud and distorted as expected.

It's much quieter and a bit less distorted at R17/R22, but still perfectly audible, and well above bypass level.

R21/R18, i probed the middle pad of the tone pot, which is connected to these resistors. Signal disappears because it's a very faint signal. I have to set the volume fully CW and turn up the amp volume to finally hear it.

If i understood correctly, there should be the same very loud volume level at the first two points you mentioned ?

Surely there's an issue between R20/R13 and R17/R22. I'll focus on this aera and see what i can do.
If the volume was loud enough at the second location (R17/R22), i guess it wouldn't be so faint at the Tone pot...

Edit : i wonder, if it's not too much trouble, if you would be so kind to post a picture of the pcb with the numbers designations (R1, R2, etc.), please ?
I am having a hard time figuring wich 100k is R11, which 1n is C6... I know it's not a big circuit but it would be really useful, probably also for other builders in the future ?

Try probing before that last divider, like right at pin 3 of the Output pot. This should be as loud as the others if not louder.

I was planning to do this when it was time to re-order Black Eye boards as purple C2C boards to match the rest, so may as well get it out of the way now. Hope this helps.

 

[eh là bas ma]

Thank you so much, this will be most useful !

Continuity tests on various points between R20/R13 and R17/R22 are all right, couldn't find anything suspicious there so far.

I probed Volume pot's pin 3 (considering pin 1 as the square pad), the signal is audible, louder than on the output jack's tip (where it's very faint, almost gone).

It's quieter than the other two locations though, so i'll focus on this aera now. Thanks to your picture, this should go much faster.

 

[eh là bas ma]

I couldn't find anything neither between R20/R13 and R17/R22 nor in the volume pot aera.

I tried to swap the tubes, i tried another 2N3904, i spent at least half an hour on each and every solder joints, i traced the circuit entirely with continuity tests, couldn't find anything suspicious and nothing have changed.

There is still 170V at UF4007 negative side, signal is still very faint at the output.

I removed R21, jumpered R18 as suggested. Output signal level has increased significantly, but it's still slightly below bypass level, and i don't think it sounds as good as it should. It's kind of thin and weak, as if some frequencies have been removed.

I can't use this circuit as it is now. It's not good enough, and i'm not sure it's even safe.

Looks like i've hit a wall, for the first time in 5 years and more than 200 builds. Even Aion's Xenotron was much easier to build...

It's probably some tube daughter board damaged pad or trace, if only i didn't mess with their orientation in the first place, it would probably work. I had to heat lots of pads for a long time to be able to remove them.

I am tired of being scared for my life every time i use the audio probe, or plugg in the DC power on a faulty device running at 240V, so i am thinking about giving up.

Next step is ordering a new pcb from musikding with new tube sockets, i'll salvage the parts from this build and try again.

Be that as it may, thank you very much for your help !

 

[vigilante398]

These are unfortunately difficult builds, not because the circuit is wildly complex, but because they're so different. The tube daughter boards are definitely the big hurdle and they are the most common thing I see people mess up, but they are the best way I've found to keep the tube inside the enclosure and not sticking out the top.

I hope you're able to figure something out, either on this build or on a fresh board, because this really is a great circuit. Just take your time, read the directions carefully, and try to keep it as neat as possible. You'll get it!