Speedball upgrade - Voltage wrong (Resolved)

[Lolovitch]

Hi all,

I have been enjoying my Crack since Feb 2014 and finally found some quiet time today to do the speedball upgrade.

Build went smoothly, however when checking voltages, I had all correct readings excepts for 7 and B3 reading 55V instead of 100V.

I am attaching three pictures below if this helps.

I am missing my crack already  , if you can help that would be very appreciated.

[Paul Birkeland]

If your voltages at 1-5 are indeed correct, but you have 50V at terminal 7, then I would reheat all the solder joints on the large PC board, focusing especially on the center leg of the TIP50C.

-PB

[Doc B.]

This is not a suggestion for the issue at hand as much as it is thinking out loud. One possibility (not the most likely) could be that a tube is actually declining and pulling the voltage down. And that made me think if a person measured the voltages before they did the upgrade, that might give them a point of reference with respect to the measurements made after the upgrade is installed. We've never really emphasized that, but particularly in the case where an upgrade is installed a fairly long time after the initial build it might be good to check the general health of the amp before scheduling surgery.

[Lolovitch]

If your voltages at 1-5 are indeed correct, but you have 50V at terminal 7, then I would reheat all the solder joints on the large PC board, focusing especially on the center leg of the TIP50C.

-PB

Hi Paul, Thanks for your input. I will do that and report back.

[Lolovitch]

This is not a suggestion for the issue at hand as much as it is thinking out loud. One possibility (not the most likely) could be that a tube is actually declining and pulling the voltage down. And that made me think if a person measured the voltages before they did the upgrade, that might give them a point of reference with respect to the measurements made after the upgrade is installed. We've never really emphasized that, but particularly in the case where an upgrade is installed a fairly long time after the initial build it might be good to check the general health of the amp before scheduling surgery.

Hi Doc, interesting that you mention that because it is exactly what I did. Before the upgrade I had 102.5V on terminal 7.

[Lolovitch]

Hi Paul, Thanks for your input. I will do that and report back.

Hi again, so I just did reheat all solder joints of the large board and re-checked. Unfortunately terminal 7 still reads 55V. 

When comparing again my build with the manual I noticed that the gap between the board and the 2N2222A transistor is larger on the picture than on my build (see picture in 1st post). May this be an issue?

[Paul Birkeland]

What are your voltages at 1 and 5?

[Lolovitch]

Hi Paul and others, appreciate your time and effort. I have re-assemble the amp and took complete readings of the voltages, they now look as follows:

1 76.6
2 174.8
3 0
4 174.5
5 75.5
6 0
7 53.5 instead of 100
8 0
9 104.5
10 0
11 0
12 0
13 173
14 0
15 193
16 0
17 0
18 84.6
19 85.2
20 0
21 212.6
22 0

A1 75.3
A2 0
A3 1.6
A4 0
A5 0
A6 43.7 instead of 75
A7 0
A8 0.1 instead of 1.56, further the LED is not lighting up!
A9 0

B1 1.9 instead of 75
B2 172.8
B3 54.3 instead of 100
B4 75
B5 173
B6 104.7
B7 0
B8 0

Hope this will help you to identify the issue.

[Paul Birkeland]

1 76.6
A6 43.7 instead of 75

A6 wires to terminal 1.  Since A6 and terminal 1 show a 30V difference, they are not wired together in your amplifier.

If the voltage at A6 was indeed 43V, that would cause the low voltage at terminal 7, so you can ignore the voltage at terminal 7 for now and fix the issue up at the front of the chassis. 

Also, please do not attempt to repair the LED on the 9 pin socket, as it is only an indicator of the general issue you are having, the LED is almost certainly working properly.

[Lolovitch]

Hi Paul, thanks for your input. I have re-checked A6 and now the issue can be summarised as follows:
A6 - 1 - B1 show 44V instead of 75V
B3 - 7 show 82V instead of 100V (I am a little puzzled as to why this went up from 55V my first post in this thread)
A8 still at 0V with the LED not lighting.

[Lolovitch]

One more thought and experiment: If I have 174V at terminal 2 but only 44V at terminal 1, wouldn't that indicate that there is an issue with the small left-hand side PC board?

Anyway I thought so and double checked that board and reheated all joints. Unfortunately no improvement. Would swapping both small PC boards be a recommended course of action to isolate the issue?

[Paul Birkeland]

One more thought and experiment: If I have 174V at terminal 2 but only 44V at terminal 1, wouldn't that indicate that there is an issue with the small left-hand side PC board?

No.

Anyway I thought so and double checked that board and reheated all joints. Unfortunately no improvement. Would swapping both small PC boards be a recommended course of action to isolate the issue?

No.

Your 43V is consistent with the C4S board working perfectly but having 0V of bias, which you have measured.  Either there is something touching the socket pin where the non-glowing LED is mounted (is it touching an adjacent pin? Is there a little wire finger poking into it?), or you have the first shorted LED on the socket that I believe we have ever seen (they usually fail open).

Your C4S boards are working properly, they do not need to be debugged.  The variation of voltages during your measuring suggests that perhaps there is a loose connection on the socket or some kind of short as mentioned earlier.

-PB

[Lolovitch]

Gentlemen, we are making progress!
Are we there yet? Not sure but I am finding out as I am writing this.

But first things first, let me give you an update on what happened so far.

Paul, I have taken your recommendation to heart and checked for anything shorting one of my A-terminals but after double and triple checking I was still not further. It then happened that in an effort to make sure A7 and A8 were distant enough, I snapped the lead of the LED (which "luckily" was the one not lighting). By coincidence I had a replacement remaining from the initial build, therefore this was quickly mounted. Checked, powered up and all voltages were fine and all LED shining! 
Honestly I could not be categoric whether all my checking there is no shorts in the A-terminal or the replacement of the LED (which did not look damaged) made the trick; but hey, I am not complaining.

What next then? Now that all voltages were fine, I plugged in my HD650, powered up again and. ... that horrible noise!

No source attached, Crack plugged in directly into the wall on its own, volume to zero, I had rather loud (too loud to comfortably put the headphone on) noise, which suspiciously sounded like 50 Hz! 

I then tried:
> Reheated the joints of the 220uF/250V capacitors (didn't find that by myself but a little googling can bring you a long way  ) => No success
> Re-checked the group wires => No success
> Plugging a source in => No success
> Playing Mozart, turn the volume delicately up to see if we have some music in addition to the noise => Surprise: noise gone & music here!

This is where I currently am: listening to music (smiling as Speedball definitely makes a difference). 1st CD is nearly over and no trace of noise. Turning the volume back to zero but no noise. No sure what did make it go away but I like what I hear, what more to ask?

Unless you have any other recommendation at this point in time, I will now put the Crack back into my office and again use it regularly. Let's say the patient is moved to rehab under careful observation.

I hope that was it but would not like to end my post without thanking you Paul for your support and guidance. This is real customer support and value added to your product.

PS: Speedball rocks! 

[Paul Birkeland]

You're very welcome.

If you turn the amplifier on with no sources plugged in and the volume pot all the way up (or close to it), you will indeed pick up spurious noise.