Crack & Speedball -Wrong resistance and Voltage readings

[Paul Birkeland]

This is usually an issue with the solder joint on the center leg of the MJE-350 (assuming there are no other problems).  If the LED's on the 9 pin socket aren't lit up (permanently), this further suggests that current isn't passing through the small PC boards, and this is generally a mistake of either:

1.  Solder joints, especially on the MJE-350, as mentioned above.
2.  2N2222 transistors installed in place of the 2N2907.
3.  A missed or improper connection into the amp when installing the boards.
4.  A Crack that wasn't working prior to putting in the Speedball.
5.  Backwards MJE-350's (yours look OK).

-PB

[alesi]

Thanks, I'll go through the steps again.
When I removed the 6080, then both LED on the 9pin socket were lit up and also stayed until I switched it off again. But then the 2 LED on the bigger board were rather dimmed.
Not sure whether this matters.

[Paul Birkeland]

Thanks, I'll go through the steps again.
When I removed the 6080, then both LED on the 9pin socket were lit up and also stayed until I switched it off again.

Please recheck your voltages at terminals 1, 2, 4, and 5 under these conditions.

But then the 2 LED on the bigger board were rather dimmed.
Not sure whether this matters.

This isn't super important right now.  The focus is on getting the 12AU7 and the small C4S boards loading it operating properly. 

[alesi]

I went through each solder joint again, not only on the boards. I get the same readings, 1,2,4,5 -> ~195
What should be the correct reading without 6080?

Coming weekend I plan to remove the speedball addon again, detach all components and start from scratch.
However I would like to replace some components, as I want be sure that it is not a broken part that is causing the issue.
Are there any components on the Speedball addon you think might be worth replacing. Just to be sure.

Thanks.

[Paul Birkeland]

The voltages should be between 60 and 100V on terminals 1 and 2 with no 6080 present.  You have a separate issue on the large PC board feeding the 6080 that needs to be dealt with separately but can't be properly dealt with until the front half of the amp is working properly.

If you go to remove all the components on the PC board, you will likely destroy the board.  Can you post top and bottom photos of the PC boards as they are now?  By chance, would it be possible to get a DC voltage reading on A3 and/or A8?

-PB

[alesi]

I have gone through the solder joints on the large pc board again. No luck.
The voltage readings for A3 and A8 are 1 (one). T1, 2, 4, 5 - ~195.


Appreciate any help.

[Paul Birkeland]

Bottoms of the boards was meant to be bottoms of the small PC boards.  We'll deal with the large board later.

Do you get 1.5V at A3 and A8?  (You may need to turn your meter range down to see what the exact voltage is.

-PB

[alesi]

I just realised that I mixed two different solders for the boards. Unfortunately one was nearly 20 year old which was till in my toolbox, might explain the excessive flux.
I spent some time with desoldering  braid and alcohol to clean as much as possible and apply the correct solder again on all boards.

Unfortunately the voltage readings have not really changed Now it is about T1,2,4,5 ~ 199
A3/A8 ~1,6

[Paul Birkeland]

Tell me about the 20-year-old solder, what does it say on the roll?

[alesi]

Well, once I realised it I binned it straight away. So I can't tell what the specifications were.
I remember using it partly for the speedball addon only. The rest was 60/40.

Used this for Crack and it did work
https://www.amazon.co.uk/gp/product/B000LFVHK6/ref=oh_aui_search_detailpage?ie=UTF8&psc=1

And this for the speedball (with the ancient one)
https://www.amazon.co.uk/gp/product/B002L5Y8R8/ref=oh_aui_search_detailpage?ie=UTF8&psc=1
 
Are there more ways to test the components?

[Paul Birkeland]

I think the ancient solder you used might have been solder for plumbing.  The flux in this solder is mildly conductive, and would explain some of the issues you're having.  Unfortunately, since you threw out the roll, it will be very difficult to tell, but I would start by cleaning all of the flux off the PC boards.

[alesi]

Thanks for your help.
In case you have few other ideas to debug the issue I'll call it quits then.
I have spent a few hours this morning to remove the old solder, clean up all the flux and re-solder it again.

[Paul Birkeland]

Yeah, that plumbing flux really likes to stick around in FRP (PC board and terminal strip material).  If I had your Crack on my bench, I would be putting in a new Speedball.

[Doc B.]

We had another kit on the bench last month that had an excess flux problem. I thought I could getaway with replacing just the board that had a short on it from the flux. When the customer got it back a noise started up, from another board. We took it back and replaced that one too. So it might be necessary to replace your boards.

If that is the case you might have nothing to lose by pulling the boards off, running them through a dishwasher cycle and reinstalling. Might help, might not.