Total Recall (2024) - No delay

[Bumfluff101]

Hi all,
Put this together and although a signal passess through there is no delay.

1) All ICs have the approx -15v on pin 4 but there are some low voltages on some of the pins (see pics)

2) TP1 has signal

3) Level control works

4) Blend control 'works' in that you can hear a difference in the level of the output but no other control impacts the signal

6) TP2 there is signal but not delayed and BIAS1 trimmer takes away some of the static noise

7) TP3 there is signal but GAIN1 trimmer doesn't really do anything

I am not really sure of the next steps as the signal does seem to hit everything, I am assuming its not MN3005 as I got them from a reputable dealer but could be.

Any ideas as to where to start?

[madbean]

That actually sounds like a clock problem. If you are getting some signal at TP2 then something is working, but not correctly.

Do you have a frequency measurement setting on your multimeter? I'd use it to check both pin2 and pin6 of IC8. First with the delay pot CCW, then CW. Write those down and post them here.

[Bumfluff101]

Hi,

Readings are

Pin 2
CCW - 49hz
CW - oscillates between 586-637hz

Pin 8
CCW - 49hz
CW - 57hz

[madbean]

Hi,

Readings are

Pin 2
CCW - 49hz
CW - oscillates between 586-637hz

Pin 8
CCW - 49hz
CW - 57hz

Did you mean pin6, not 8?

You do appear to have something wonky with the clock. It looks like all your resistor values around the clock are correct. What value is printed on your MICA cap (C40)?

Also, I just noticed a lot of wrong voltages on you NE570. It's getting power and ground fine but something else is wrong there.

[Bumfluff101]

Yes, pin 6 sorry

240 on the mica cap

I've swapped out the ne570 but still get the funky voltage readings

[madbean]

I'm looking more at your resistor values and I'm seeing what could be a number of incorrect values. However, sometimes image compression plays tricks with the light.

Here's what I'm seeing:

Around IC1, there are several 100ks that appear to be 1M on your build (yellow stripe instead of orange stripe). R7 and R8 seems like they are 1M or 2M, not 200k. R5 appears to be 1k5, not 150R. R57/58 again appear to be 1M not 100k. There may be others. Can you please take another look and see if I'm wrong? Did you pull the resistors out of a pre-labeled bag. Could they be labeled incorrectly?

[Bumfluff101]

Thanks, I have checked the ones identified with a MM and they are all the right values except R57/R58 which have the right code for 100k but are only measuring about 50k on the MM. I will replace those and check all the others again and report back

[Bumfluff101]

Checked everything and replaced a couple of resistors but still no change.
I've ordered another PCB and will give it another shot.
One query I had was that for C8 the cap reads -15.3v on the negative leg and -1.34 on the positive leg which then feeds pin one of ic2. Does this mean the cap is the issue? This is one I hadn't changed but not sure whether it's worth it now?

[thomasha]

It seems more like a bad joint somewhere. You have a lot of pins with voltages as low(high, because its negative, but you get the point) as -1.3v. The bias of the gain stages will be way off and as a result signal will not pass or only barely, distort, and so on.

Before we blame the BBDs I would remove them from the board and check that the signal chain to their input is working.

My suggestion is, check where the voltages are way off and look for those points in the schematic. Any part could be missing a connection, and, as a result the voltage is way lower(higher).

I would definitely try changing the capacitor, if you think that might be the problem.
As Brian said, check around the NE570, its bias is way off, and that might affect everything that comes afterwards, like IC3A and IC5B.
I know this might be annoying, but check continuity with a multimeter between the surrounding parts and some of you solder joints. Some of them look very suspicious, with large blobs of solder.

R38 is also difficult to check, its small and I can only see 3 bands, and one is green?
Isn't the bias of the NE570 set by that resistor? 11k to inverting input?

[Bumfluff101]

So... I started again and this is the outcome. The signal does delay now which is progress but I cant get it cleaned up. Before I post more voltages etc is there any obvious diagnosis from the sound in the video as to what the problem might be?