AquaboyDLX, another dry signal only thread

[Hangingmonkey]

Hi all.  Im stuck with the aquaboy DLX.  Actually, I built it several months ago but shelved it in the hope that looking at it with a fresh pair of eyes might help. 

Anyway, the problem Im getting is no delay but dry signal only.  Ive looked through the multiple other threads with the same problem but no luck. 

Anyway, Im running it on 15v via the road rage. Ive used an audio probe on pin 3 of IC3 but I'm getting a whine only which i presume is the clock noise, but no guitar signal.  Ive set the clock frequency to 6.5kHz on pins 2 and 4 of IC5. 

Im getting clean signal at pin 7 of IC3.  Turning the bias1 trim makes no difference to pin 3. Ive also swapped it out with a tested 3005 but no difference.  (also got one of the legs of the 3005 stuck under my fingernail in the process of lifting it, which I wouldn't recommend to anyone!)

Heres the voltages:

IC1 LF353
1 - 7.38
2 - 7.38
3 - 7.38
4 - 0
5 - 7.38
6 - 7.38
7 - 7.38
8 - 14.8

IC2 NE570
1 - 0.95
2 - 1.8
3 - 1.8
4 - 0
5 - 1.8
6 - 1.8
7 - 7.88
8 - 1.8
9 - 1.8
10 - 4.64
11 - 4.64
12 - 1.8
13 - 14.8
14 - 1.8
15 - 1.8
16 - 0.9

IC3 MN3008
1 - 14.32
2 - 7.16
3 - 10.21
4 - 10.21
5 - 0
6 - 7.16
7 - 14.19
8 - 0.95

IC4 MN3008
1 - 14.32
2 - 7.16
3 - 4.88
4 - 4.86
5 - 0
6 - 7.16
7 - 5.82
8 - 0.95

IC5 MN3101
1 - 14.32
2 - 7.16
3 - 0
4 - 7.16
5 - 6.14
6 - 7.82
7 - 6.85
8 - 0.95

IC6 TL062
1 - 0.6-14 variable
2 - 6-8 variable
3 - 6-8 variable
4 - 0
5 - 6-8 variable
6 - 6-8 variable
7 - 6-8 variable
8 - 14.8 variable

Q1
C - 14.8
B - 6.7
E - 6.38

Q2
C - 14.8
B - 7.83
E - 7.23

Q3
C - 14.8
B - 4.8
E - 4.2

Q4
C - 14.8
B - 4.24
E - 3.64

Heres a pic of the board.  Let me know if theres any other info/pics that might help.

Cheers

[madbean]

At 14.19v, your bias on pin7 of IC3 is way too high. Can you tell me what the min max range you get on pin7 when you set the BIAS1 to full left and full right?

This might be nothing but your clock chip looks a little off to me. Not the voltages, the actual chip looks different than most of the ones I have used. If you have any other MN3101 it would not hurt to pop it in there.

[Scruffie]

The 3101 is working fine

[Hangingmonkey]

Thanks for your replies guys. It's midnight here in England, I'll report back tomorrow evening.


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[Scruffie]

Turning trim 1 makes no difference? Did you get it from Tayda...? Just wondering if the trim its self is a dud.

As you're in England, if you can't get it sorted i'd happily take a look if you wanted.

[Hangingmonkey]

Turning trim 1 makes no difference? Did you get it from Tayda...? Just wondering if the trim its self is a dud.

As you're in England, if you can't get it sorted i'd happily take a look if you wanted.

Thanks Scruffie, much appreciated, it's good to know there's a plan b if all fails.

I've adjusted the bias resistors and the best I can get out of pin 7 is 7.1v with an input of 14.8-14.9 on the ne570. I used 39k for the resistors. Is that close enough?  Otherwise I'll have to order some odd values.

Your comment about the trimpots made me suspicious as they are indeed from tayda, so I pulled them and they are to spec. It's strange, it's not that turning the trim doesn't do anything, there's a very brief moment on turning the trim really slowly when I get some signal from the oscillator I've connected the circuit to but it's not delayed signal and all I get is a brief blip but can't get that signal to stay. Otherwise it's just clock noise.

I don't know if the above helps in anyway but I'd be interested to know if you make anything of it. I probably have a replacement 3101 so I could try changing that but haven't done so yet. The source was Steve from dr tweek in the UK and generally they are reputable.




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[madbean]

If you can get down to 7v on the bias that should be enough range. Usually 7-10v is about the range you would start hearing delay from the two output pins.

I'm a little stumped. Your voltages are good. You obviously did the jumpers right. You are getting clock signal. Going on the assumption that the clock and BBDs are in fact working parts, there are no bad solder joints or bridges anywhere then we are running out of options. I don;t like sending you on goose chases but one other thing to try is to remove C19 and jumper the + and - pins. This puts Vgg all the way to ground. In my experience this has never been imperative to make an MN3008/05 work but it's something at least.

If that doesn't do it, I will send you a for-sure working MN3101.

[teknoman2]

Something odd is going on here probably....
Before going to the BBD section I would probably have a closer look on your compandor,
the compression (pin7 of IC2) is looking a little high, choose values of the voltage divider (R13 & R14) so that pin7 is around 7v as Brian and Scruffie suggested.
Also from your readings voltages the expansion section is a little low (pin 10 & 11) should be around 7v also.

Swap the resistors of the voltage divider and post your new voltages of the compandor only and then we are gonna examine the BBD section.

[Scruffie]

If your bias trim is working, I think the issue might be at the output of your BBD, the outputs (Pins 3 & 4 ) should only be about 1V less than pin 7s as it is with the other BBD (although with it closer to a normal bias point they may have gotten closer in line) I would check the value and soldering on R21 & 22.