TP1 voltage too low

[macross]

I got stuck on this step:

Power up the
circuitry again, and measure the supply
voltages on IC5 (pin 1 = -5v), IC11 (pin
8 = -5v), and IC12 (pin 8 = -5v). The
output of IC5 (TestPoint 1) should measure
slightly negative, and vary with the
Frequency and Pulse Width adjustments.
It should fall between -0.25 and
-1.25 volts, and be roughly -0.5v with
both adjustments centered.

IC5, IC11, IC12 are all ok -5v. But with TP1 i get at minimum of 0.04v to maximum 0.71v when i adjust the pots... (SW1 shorted)

Here is my circuit:
https://imageshack.us/a/img823/539/20130504210044.jpg

Any ideas what could be wrong? Or maybe it's just my DMM really inaccurate?

[Carl-NC]

Not sure why you have -5v on the supply and a positive voltage on TP1. But you need to install D8 to get the right pulse.

[macross]

Not sure why you have -5v on the supply and a positive voltage on TP1. But you need to install D8 to get the right pulse.

Sorry my mistake it's -0.04v and -0.71v... Going to install D8 and will report back if there are still any problems.

Thanks Carl!

Edit: Just installed D8 still i get -0.04v to -0.78v

[Carl-NC]

I assume you installed the diode in the correct direction... do you have an oscope, or does your DMM measure frequency?

[macross]

I assume you installed the diode in the correct direction... do you have an oscope, or does your DMM measure frequency?

Yes diode is installed correctly! I have triple checked everything from the beginning and i can't find any mistakes... Unfortunately i do not have an oscilloscope and my DMM can't measure frequency so i guess i'm stuck at this point.

[macross]

I have ignored the first problem until i can find a way to fix it and so i just continued with the build, but as i noticed this kit (from silverdog.co.uk) did not include R34 1M pot and R23 100ohm pot, according to the HH1 documentation (Opt1) it should have 1Meg pot and 100ohm pot... So did anyone manage successfully build HH1 from the latest kit batch? I'm getting pretty frustrated at this point...

[macross]

I encountered a problem once again. Now i'm stuck on page 9 where you have to adjust R23 to zero out IC8 pin 2/3... When i try to adjust R23 nothing happens i'm still getting 1.1v on the pin 2 and 3, however adjustment with R18 is working on TP4. (SW1 and SW2 shorted, IC8 pin 1 shorted to IC9 pin 4)

Here is a picture of the board:
https://imageshack.us/a/img35/2474/20130507113054.jpg

[Carl-NC]

If the pulse generator isn't working right (ignored problem #1) then the demod switches won't fire (IC7a/b) and the adjustment won't work. You can temporarily get around this by pulling IC7 out and shorting pins 1&2 and pins 3&4. At some point you need to revisit the pulse gen. Make sure R2 and R3 didn't get swapped. Your other components look OK. Also check for a bad solder joint. The pulse gen circuit is fairly bombproof so the problem shouldn't be too hard to find.

If you are going to use a mono coil, there is a jumper next to TP2 and R14 you will need to short.

- Carl

[macross]

Alright i have now solved TP1 issue! Now i get 1.2v pots maxed out! The TLC555CP chip was the issue... I have replaced it with NE555N and problem solved, however IC8 adjustment via R23 still doesn't work... I haven't changed anything on the board since the last picture. Any ideas what could be wrong? (Solder joints all look good)

[macross]

Sorry for double post but i just tried shorting IC7 pins 1&2 3&4 and still R23 is not adjusting anything... Also if i short jumper near TP2 for mono coil i get 4.2v at TP4 and it breaks R18 adjustment.

[macross]

Can someone please help me diagnose why r23 doesn't adjust ic8 pin 2 and 3? I finally got my hands on oscilloscope so maybe now some will be willing to help...

Output of TP1:
http://imageshack.us/photo/my-images/211/newfile0.jpg/

Also is there any more jumpers i should short out? The guide says nothing about which to short out.

[Qiaozhi]

Can someone please help me diagnose why r23 doesn't adjust ic8 pin 2 and 3? I finally got my hands on oscilloscope so maybe now some will be willing to help...

Output of TP1:
http://imageshack.us/photo/my-images/211/newfile0.jpg/

Also is there any more jumpers i should short out? The guide says nothing about which to short out.

From the Hammerhead article:

Short pad 1 of IC8 to a convenient
ground (simple to do when using IC
sockets — IC9 pin 4 is ground). This
should never be done with IC8
installed. R24-R26 is now a simple
voltage divider, the same as R25-R27.
A DC voltage can be applied to R23,
and if there is a mismatch in the two
dividers, R23 can be adjusted to null it
out. This should be done with the ana-
log gates turned on, which will be the
case as long as Q8 & Q9 are not
installed.

[macross]

From the Hammerhead article:

Short pad 1 of IC8 to a convenient
ground (simple to do when using IC
sockets — IC9 pin 4 is ground). This
should never be done with IC8
installed. R24-R26 is now a simple
voltage divider, the same as R25-R27.
A DC voltage can be applied to R23,
and if there is a mismatch in the two
dividers, R23 can be adjusted to null it
out. This should be done with the ana-
log gates turned on, which will be the
case as long as Q8 & Q9 are not
installed.

Yeah i did that and still R23 doesn't adjust anything...

[Qiaozhi]

Yeah i did that and still R23 doesn't adjust anything...

With IC8, Q8 and Q9 removed, you are effectively left a simple voltage divider network. i.e. just a few resistors connected together.
Have you checked that the analog gates (IC7a and IC7b) are turned on?

[macross]

With IC8, Q8 and Q9 removed, you are effectively left a simple voltage divider network. i.e. just a few resistors connected together.
Have you checked that the analog gates (IC7a and IC7b) are turned on?

Sorry i'm pretty new to electronics which pins are analog gates of the IC7a/b? Also i have noticed that by adjusting R18 i can only go to -1.1v and up to +1.9v, according to the guide it should be +1.6v to -1.6v....