Aquaboy Deluxe - Intermittent Delay

[twin1965]

Symptoms:

Dry signal passes through but there is no delay. When power is toggled on and off the delay kicks in. Effect works as it should. When switched off and on after a few minutes, effect still works. When left for longer there is no delay.

Over the last couple of days the toggling of the power no longer makes the delay work (the dry signal still passes through). In order for it to work again I have to go through the calibration process again. i.e removing IC4, turning Bias 1 trimmer etc

The same issue happens with two different  power supplies and batteries. Both inside and outside of the enclosure.

I'm running this at 9V and using: v3205, SA571, MN3102.

Audio probe works up to pin 7 of IC3. No output from pins 3 and 4. Dry signal passes through IC1.

Here are some IC voltages:

            IC3                        IC4                        IC5                       IC2

   1  0.00   8  7.60      1  0.00   8  7.60      1  8.14   8  3.87      1  1.10   16  0.84 
   2  4.05   7  4.10      2  4.05   7  4.11      2  4.05   7  4.25      2  1.82   15  1.82
   3  3.56   6  4.05      3  3.62   6  4.05      3  0.00   6  4.09      3  1.82   14  1.82
   4  3.58   5  8.14      4  3.67   5  8.14      4  4.05   5  7.60      4  0.00   13  9.00
                                                                                        5  1.82   12  1.82
                                                                                        6  1.81   11  4.81
                                                                                        7  3.05   10  4.81
                                                                                        8  1.82   09  1.82

Haven't had the time to take transistor voltages yet. Will be busy this week so it might take a few days.

I'll carry on trouble shooting this one as soon as I can because I really do like this delay!

[Scruffie]

Check your electrolytic orientations and for any cold joints... being an intermittent issue sounds like the circuit itself is okay.

[twin1965]

I normally go through the circuit after I've soldered everything but its true you can miss certain things! I will check all the components and all solder joints. I just have to find some time to do this.

Could well be an electrolytic problem. Its unusual that I can get this to work and then when its switched off for a long period of time and then powered-up, it doesn't work.

A soon as I get more testing done I'll post any results and hopefully a solution   

[twin1965]

All electrolytics were spot-on. Both values and orientation.

Tested voltages around the circuit board and also some continuity tests. Checked component values around the BBD's, power supply filtering and clock. All ok.

Audio signal flows from input through to the compandor, into Q2 and to pin 7 of IC3. That's as far as it goes. Nothing comes out of pins 3 and 4 of IC3.

When I go through the calibration process I get delay and everything is fine. I can switch power on and off and it still works. The problem is when power is off for a long period of time. I haven't timed this (don't know if it would help the troubleshooting).

At one point it was enough to switch the power on and off a few times and the effect would 'kick-in'. Now it has to be re-calibrated every time.

The fact that I get delay when calibrated means that all the components are ok - including the BBD's. I can't figure out - yet - why it 'looses' its settings. I thought it could be bad trimmers but the bias voltages always stay the same.

I'm using the MN3102 clock with these v3205's. Could there be an 'incomparability' issue?

[twin1965]

Could there be an 'incomparability' issue?

That should be incompatibility!

Had a play around with it tonight and re-calibrated. Swapped the BBD's around set all trimmers to mid positions. Got delay. Switched it off for around 18 minutes and then nothing. Just the dry signal.

I think this one's going to be tricky to troubleshoot 

[twin1965]

I've had no luck troubleshooting this one 

Re-flowed all the ic holder joints and any others that didn't look shiny. Even changed capacitor C33 for a new one in case it was causing an issue with the clock.

It still exhibits the same symptoms.

All the voltages seem to be correct and getting to the correct places!

The fact that there is no output from IC3 makes me think that maybe the clock is not supplying the correct signal or is not compatible with the Cool Audio chips. Or the BBD themselves are not working correctly. But its not likely that two BBD's have gone bad at the same time.

I might have to get the v3102 clock and try that. (I'm using the MN3102 at the moment).

Any other tips on what I can try next?

[Scruffie]

where did you get the MN3102 from? I recall a thread about fakes that seemed to only work when one of the pins was lifted...

Does sound like a cap to me though still... just can't see why it would keep working and then failing, maybe C19 & 36... or the zener.

[twin1965]

I got it from http://www.uk-electronic.de/. I'll do a search for the pin lift issue just in case!

I have a suspicion that its a cap issue too. Just trying to find the offending one! Will change all if I have to.

The zener is producing the correct voltage so I assume that its ok.

I just tried something else. I took out IC3 out and jumpered R55 (IC3 pin 7 side) (effectively running on one BBD) to the input of IC4 (pin 7) and I got delay!

I've been looking at the area around the trimmers and BBD's but I can't see anything wrong.

I've switched the power off and will try to see if I can reproduce this again.

[twin1965]

I just tried something else. I took out IC3 out and jumpered R55 (IC3 pin 7 side) (effectively running on one BBD) to the input of IC4 (pin 7) and I got delay!

I re-produced this again with both BBD's. Popped IC3 back in and got full delay. So its not the chips.

I might try the MN3101 that I have in my Pork Barrel and socket D3 to see if the MN3102 is the problem.

I'll do this before I start removing components. I hate doing this on double sided boards! Otherwise I'm going to replace some caps (one by one). Will start with C19 and C36.

[twin1965]

I think I have managed to sort this out. I swapped the MN3102 with a MN3101 and used D3. Calibrated and delay was passing. Switched the power off for 30 minutes. Powered it back up and there was delay. Effect working as it should

When using the MN3102 this was not possible.

I also tried the MN3102 with D3 and it didn't work.

I will try again tomorrow after the effect has been off all night to see if it fires-up. I think it will.

Looks like the MN3102 doesn't want to play nicely with this circuit!

What is happening to cause this issue? Is there a problem with the MN3102 not outputting the correct VGG voltage for the Cool Audio chip?

Any way I'm going to toggle the power on and off several times tonight and tomorrow to make sure that this is fixed!

[jimilee]

Nice job!!!

[twin1965]

Thanks Jimi. Hopefully anyone having problems can look at what clock/bbd combinations they are using.

I can safely say that this is powering-up correctly now and effect is passing delay as it should 

Couldn't wait until tomorrow!

[Scruffie]

Hmm... I wonder if putting in D3 and cutting the trace between it and the MN3102 would do the trick, and adding a 1uF electrolytic from the 3102 VGG to gnd. So the 3205 gets its own Vgg and the MN3102 generates its own.

I also notice on the DM-3 schematic (3205 DM-2) there is a diode between pin 3 and gnd, K to gnd.

[Kivjah]

  Nice job ! I'll try change soon the clock IC, thanks.

Edit : I change mn3202 with 3201 and recalibrate and full work thank's all !