ABDX - no delay

[muehring]

Yeah, I probably cranked those trimmers too far and brought the voltage down when trying to find the middle position for biasing.
I'll report back when I have a chance to make the adjustments.

[DutchMF]

Thanks!  I'll try to get the voltage up on pin 7 and check those resistors.  Do you think that would effect the signal at pin 1 on the LF353?

For D3 it depends on the clock you're using.  Here is the info from the build docs:
NOTE: if you are using the MN3101 with the v3205, you must use D3 to approximate the correct Vgg voltage for pin8 of the clock (14/15 of Vdd). In all other cases (including when using an MN3102, BL3102 or v3102) you should omit D3. The 3102 variety clocks automatically generate the correct Vgg voltages needed in each case.

I was reading up on this yesterday.... The first line of this note is quite clear, but I'm still not sure if D3 needs to be in place when building an MN3005/MN3101 ABDX.... Anybody know this? Sorry for the hijack....

Paul

[Scruffie]

Thanks!  I'll try to get the voltage up on pin 7 and check those resistors.  Do you think that would effect the signal at pin 1 on the LF353?

For D3 it depends on the clock you're using.  Here is the info from the build docs:
NOTE: if you are using the MN3101 with the v3205, you must use D3 to approximate the correct Vgg voltage for pin8 of the clock (14/15 of Vdd). In all other cases (including when using an MN3102, BL3102 or v3102) you should omit D3. The 3102 variety clocks automatically generate the correct Vgg voltages needed in each case.

I was reading up on this yesterday.... The first line of this note is quite clear, but I'm still not sure if D3 needs to be in place when building an MN3005/MN3101 ABDX.... Anybody know this? Sorry for the hijack....

Paul

No, leave it out.

[DutchMF]

Thanks Scruffie!!

[muehring]

OK, I was able to get the voltage up on pin 7 on each BBD pretty quickly, but still no signal on pin 1 of LF353 or any of the pins on the compander or BBDs.  I took the bias voltage from 3.1 volts to around 6v when testing for a signal.
I was also able to get the voltage to 7.63 on pin 8 of the BBDs on the first board.  C19 wasn't connecting to pin 8 of the clock.  Not sure why, but I put a jumper between those.  Same problem with the signal on that board.
Any thoughts?  I think I'll order some new LF353s since I don't think it makes sense that the signal dies on pin 2 there.

[Scruffie]

OK, I was able to get the voltage up on pin 7 on each BBD pretty quickly, but still no signal on pin 1 of LF353 or any of the pins on the compander or BBDs.  I took the bias voltage from 3.1 volts to around 6v when testing for a signal.
I was also able to get the voltage to 7.63 on pin 8 of the BBDs on the first board.  C19 wasn't connecting to pin 8 of the clock.  Not sure why, but I put a jumper between those.  Same problem with the signal on that board.
Any thoughts?  I think I'll order some new LF353s since I don't think it makes sense that the signal dies on pin 2 there.

That is odd as your voltages look okay...

Got any other dual opamps you can try in there?

[muehring]

I just tried a OPA2132PA and a TL072.  Same problems.  I'm pretty stumped.  It looks like the inverting inputs of the lf353 are pins 2 and 6.  I get a signal on both of those.  In madbean's reply he mentions it's normal to not hear a signal at the inverting input.  Should I not have a signal at these pins?

[Scruffie]

Just seen you said you get dry output, your opamp is fine.

Taking V readings on all the transistors.

[muehring]

Here are the transistor readings:
first board          Second Board
Q1
C 9.44               C 9.44
B 4.34               B 4.33
E 3.93               E 3.90
Q2
C 9.44               C 9.44
B 3.07               B 2.99
E 2.50               E 2.42
Q3
C 9.44               C 9.44
B 4.24               B 7.02
E 3.67               E 6.43
Q4
C 9.44               C 9.31
B 3.66               B 6.41
E 3.08               E 5.81

Thanks Scruffie!

[jimilee]

Maybe I missed it, are you sure the bbd's are good?

[Scruffie]

Maybe I missed it, are you sure the bbd's are good?

They're new Cool Audio v3205 BBDs, no reason all 4 should be dead unless they were really badly mishandled.

This is odd, your voltages all look within limits, you have dry signal yet have 2 separate builds not firing up...

I'll have a think what to do next when my heads working.

[twin1965]

I'm following this thread very closely as my ABDX has developed a similar problem.

Dry signal gets through but no delay. The only difference is that if I toggle the power on and off a few times the delay kicks-in and it works as it should. It does this both in and out of the box and with different power supplies. It might be a different issue but it might help the troubleshooting process (haven't had the time to do this yet).

Also using v3205's.

I wonder if the Cool Audio chips are the issue? How many people have built this with these chips? Has anyone had any issues with powering the effect? Where did you source the chips?

This is odd, your voltages all look within limits, you have dry signal yet have 2 separate builds not firing up...

This is indeed odd.

[Scruffie]

I'm following this thread very closely as my ABDX has developed a similar problem.

Dry signal gets through but no delay. The only difference is that if I toggle the power on and off a few times the delay kicks-in and it works as it should. It does this both in and out of the box and with different power supplies. It might be a different issue but it might help the troubleshooting process (haven't had the time to do this yet).

Also using v3205's.

I wonder if the Cool Audio chips are the issue? How many people have built this with these chips? Has anyone had any issues with powering the effect? Where did you source the chips?

This is odd, your voltages all look within limits, you have dry signal yet have 2 separate builds not firing up...

This is indeed odd.

It is possible there is a bad batch, but there could also be a bad batch of companders or user error or lack of ESD handling, I wouldn't jump to the BBD being the issue (people seem to do this as it's the most expensive part).

And you say the delay does work some times so it's not the BBD.

Start a thread and post your voltages.

[jimilee]

Na, I just thought I'd ask cause it wasn't mentioned and it seems to be stumping you guys. Bad parts is the worst kind of trouble shooting for sure.

[twin1965]

Start a thread and post your voltages.

Will do. Have already started troubleshooting.