Crack, with small Speedball board

[sfojws]

I've resumed the effort to revive a Crack amplifier that I built three years ago. It worked well in the standard configuration, and after installing the small Speedball board. After I built and installed the large board, the amplifier just wouldn't work, even after a number of posts on this forum, and actions to follow up on the advice given. Recently, I removed the large board, and reinstalled 3K wirewound resistors. The results of the resistance test were as specified in the Crack manual. I then checked voltages, as specified in the Speedball manual, with the following results: 0A, 57.2V; 1A, 192V; B-A/B, 0.3 mV; 1B, 179V, 0B, 192mV, with fluctuations. I reflowed the adjacent solder joints, and replaced the red solid-core wire between terminals A1 and 5U. Voltage reading were essentially the same. It appears that no power is reaching terminal 0B. Is there some other action that is advised? Thank you.   

[Paul Birkeland]

Can you post some build photos?  57.2V on the OA terminal usually means the PN2907 is in backwards.  Having 0V at OB means there's likely something wrong with the stock build that's shorting out that half of the small C4S board (these issues can go undetected until you dig back into the amp to install the upgrade).

[sfojws]

Thanks for the suggestions. I'm going to perform another check of the wiring, with a different meter, to try to uncover a broken wire somewhere. It appears that I have the transistors on the board oriented as shown in the assembly manual, but I'm open to any other advice that you can offer. I need to figure out a way to convert the photos to a format other than jpeg, as the forum utility does not seem to allow that format to be used. If there is a way to send them in the jpeg format, please let me know.

Many thanks.

JS

[Paul Joppa]

From the attachments utility:

Allowed file types: doc, gif, jpg, mpg, pdf, png, txt, 3gp
Restrictions: maximum total size 25000KB, maximum individual size 25000KB

[Doc B.]

.jpg files upload fine. If the filename suffix happens to be .jpeg try changing it to .jpg

[sfojws]

If this file conversion works, here's the first photo, with four more to come.

JS

[sfojws]

#2

[Paul Birkeland]

You need to get some kind of award for taking the clearest photos of any customer I can remember in the last 20 years. 

1.  All legs of Q2A need more heat and time for the solder to flow out.
2.  R1B appears to not have received adequate heat on both joints.
3.  Both R2 resistors need more heat and time on the joints.   

Your LEDs look well soldered and I would leave those alone. 

It could be very useful to unscrew the two screws holding the board on, flip it up 90 degrees, then shoot a picture of the bottom of the board and the 9 pin socket.

[sfojws]

Why, thank you, Paul. I'll take up your suggestions. In the meantime, would it be of any further help to send the next three photos? When I've tried sending more than one, it's beyond capacity of the utility. Perhaps that's a reason that they're as clear as they are?

JS

[Paul Birkeland]

Definitely check that the solder you're using has lead in it, and that your soldering iron is cranked all the way up.