SOLVED Total Recall help needed please!

[Phil Hodson]

Morning all.

It pains me to post this here as I took my time on this one as I knew it's a complex built. I was hoping to beat @MichaelW to a build report but we both hit problems at the same time. He got a new board and got it working. I'm persevering with mine thought as I want to know what I have done or not done!

So before I loose my patience and or my mind and start ripping things off the board I thought I would ask around on here. I know there are some very accomplished builders and some total recall experts here!

Firstly I have checked values. Cleaned the board. And started an audio probe.

Going from the main audio schematic it's all good. I get a squeal on pin 3 of IC3 not sure if that's an issue.

Audio stopped at C14 so I replaced that and it's fine now. All the way to D in. After that nothing.

I her audio on pin 3 and 4 of IC6 but no delay at all.

Looking at my voltages everything looks good apart from IC4. I get nothing at all ok the right hand side.

I also get no voltage at pin 7 of IC7. Could this be related to the issue at IC4?

My thoughts is a bridge or issue in the socket for IC4. Before I take it off does this sound like it might be the issue?

Any thoughts and suggestions very very very welcome!

I cant seem to attach pictures. Please tel me how!!

Phil

[Phil Hodson]

Please see the attached pics for more details..

[madbean]

Seems like several issues happening at once. The squeal on pin3 of IC3 is the starting point. I'd look carefully at R9 - R15 and make doubly sure all the resistor values there are correct. Even if you think they are one more thorough check for those particular ones won't hurt. The audio should be pretty loud, but there's no reason for squeal (also, make sure your feedback pot is turned all the way down when checking the audio).

If you are hearing audio on pin3 and 4 of IC6, what you are hearing is delay so you are good there. From there, IC4 might be an issue due to the lack of proper voltage readings, which itself would effect the delay input and output of IC7. So, you may need a swap on that IC, or go deeper and figure out why you are getting no voltage readings on the second half of that IC.

[Phil Hodson]

Thanks Brian. I will go check those resistors again. Always helps to double and triple check. Will get back to you once I have checked those.

I don't know why but the issue with IC4 makes me feel something strange is going on there. I will keep investigating but am running out of ideas!

Watch this space....

[Phil Hodson]

Morning Brian

So I did what you suggested and checked all the resistors, from R9-R15 and all are good. I managed to check R15 and R14 in place and read 33K and 16K respectively

I wasn't getting correct readings from R9-R13 as im assuming, being in the circuit makes some difference to these. So I used a new one of each value and measured it correctly and then checked the code against the resistors and got 68K 24K and 51K for each of those.

I doubt replacing them would make a difference, but can do that if you think it would help.

The Values of all the resistors in the delay line and they are all fine too.

The "Squeel" is actually on pin 2 of IC3. Pin 1 and Pin 3 are fine. Adjusting the feedback makes no difference to the squeal. The audio on pin 3 is quieter than pin 3 but im guessing thats ok. I changed the JRC4558 out for several different ones and still the same.

I have audio on pin 3 and 4 of IC6 and also on pin 5 and 6 of IC 4. I still have absolutely no voltages on pin 5 to pin 8 on IC4!

I have NO audio at all on pin 3 or 4 of IC7.

I have swapped the MN3005 around and get the same issues.

I have continuity between IC4 pin 7 and IC7 pin 7 and R46 and Gain 1 etc. And from IC4 pin 4 and bias 2.

I have swapped out IC4 to several different JRC4558 and still the same issues.

Any thoughts from here about what else I could do? Got me totally stumped.

Thanks in advance.

[Maharg]

I can't offer any troubleshooting advice (my knowledge is not that advanced) but I did successfully build three of these simultaneously (kept one and gave two away to friends) - amazing delay that sounds just like my DMM.

If I can support at all by cracking mine open to provide pics or readings, let me know. Will subscribe to thread.

[Phil Hodson]

Thanks for reaching out. I literally just solved it with some help from some fine fellows!

I think it turned out to be a faulty voltage reg. I changed the, R57 and also the trim pot for Bias 2 and its working like a dream now.

Thanks to all those involved.

[jimilee]

Thanks for reaching out. I literally just solved it with some help from some fine fellows!

I think it turned out to be a faulty voltage reg. I changed the, R57 and also the trim pot for Bias 2 and its working like a dream now.

Thanks to all those involved.

That's the second time I've seen that in this build in the last week.


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[harryklippton]

Thanks for reaching out. I literally just solved it with some help from some fine fellows!

I think it turned out to be a faulty voltage reg. I changed the, R57 and also the trim pot for Bias 2 and its working like a dream now.

Thanks to all those involved.

That's the second time I've seen that in this build in the last week.


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That's cuz it's the same guy 🤣

[jimilee]

Thanks for reaching out. I literally just solved it with some help from some fine fellows!

I think it turned out to be a faulty voltage reg. I changed the, R57 and also the trim pot for Bias 2 and its working like a dream now.

Thanks to all those involved.

That's the second time I've seen that in this build in the last week.


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That's cuz it's the same guy [emoji1787]

Welll there you go. Glad you got them both sorted.


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[Phil Hodson]

Same guy, different forums 🤣
But thanks to everyone who helped out.
Don't know why it would have had an issue. I did use a gigrig electroman power supply to start with but then on advice got a proper EHX one.