Speedball Flucuating Voltage

[Perrin]

Hi

I installed the speedball upgrade during Christmas, after having running the Crack(240V version) without any issues for 2 years.
When I measured the voltages (1-21) the first time after installing speedball all looked ok so I continued to the TRS voltage check.  The TRS voltage was high, T= 28V peak  and R= 23V pea, both returning to zero quickly.

Next time I measured the voltages started fluctuating.
A1: 0V
B1 90V dropping very quicly to zero
B2 165V dropping very quicly to zero
B3 110V dropping very quicly to zero
B4 90V dropping very quicly to zero
B5 170V dropping very quicly to zero
B6 100V dropping very quicly to zero

All 6 leds very alight and went black when the voltage dropped. Tubes alight all the time.

Small board A O: 0,05V, I:1,5V
Small board BO: 0,03V, I:1,4V
Big board
A O: 1,5V, A B+: 1,6V
B O: 1,5V, B B+:1,5V

Other  terminals were nomal.

Checked again today, The voltage on 2,4,13,B2,B5,Big Board B+ and Small Board A&B were fluctuating together (identical voltage) from 0 to 163V until they suddenly dropped to zero and stayed there. Tubes are still alight.
While the voltage fluctuated I tried the chopstick test on almost all connections but I could not identify any pattern.

Checked T20 and T21:
20: minus 224V
21: 0V.

Anyone have an idea of whats happening? faulty tubes maybe?

Grateful for tips

Regards
Andy(http://)

[Doc B.]

Looking at it logically, the description indicates that you have a bad solder joint. Try reflowing all of the new connections.

[Perrin]

Hi again

After refloving all joints touched when installing speedball I found no difference, deceided to remove the kit and installing the regular Crack resistors again. When measuring the resistance according to the Crack Manual (whilst moving components with chopstick) I found the bad joint, the solder on T20U was poor, resoldered and it worked, checked measurements, dimantled the resistors and installed Speedball again. All leds lights up, voltage measurements inside +-10% toleranse. When starting up I measured a peak on T to 28V and R to 25V, before quicly returning to zero.
Any actions I can take to fix this or should I just wait a minute before connecting my headphones?

I'm currently enjoying music on my HD650's and typing this post, nice end of the weekend here in Norway
Thanks for the support!

[Paul Birkeland]

Any actions I can take to fix this or should I just wait a minute before connecting my headphones?

With headphones plugged in, this spike is severely damped, so it's not an issue.  There's also a modification that will keep the voltage spike at 0V whenever no headphones are plugged in.  The headphone jack has two unused lugs, just wire those to the ground lug below them.

-PB

[Deluk]

I've seen this extra ground mod mentioned before. Mine doesn't have it but I have considered doing it although I don't have issues. There can't be an easier mod but wonder why it isn't part of the original build. Any comments?

[Paul Birkeland]

When we updated the power transformer to the new universal primary model, we also included this modification in the manual.

[Deluk]

Thanks PB, I will do it when I add my Speedball.

[Perrin]

With headphones plugged in, this spike is severely damped, so it's not an issue.  There's also a modification that will keep the voltage spike at 0V whenever no headphones are plugged in.  The headphone jack has two unused lugs, just wire those to the ground lug below them.

-PB

Thanks PB.

This afternoon I grounded the headphone jacks T and R lugs to S (ground), and in addition to that I mounted the resistor mod (75K resistor between the wires from RCA jack and where its connected on the pot and  33K resistors between each outer pair of lugs on each level of the volume pot.

When I powered on the Crack afterward I could hear a very small hiss in the left channel. The sound level is the same regardless of pot position and if a source is input or not. waited an hour and the sound was the same. The Crack have been dead silent before today, no hiss what so ever.

Is it again a bad solder joint, with remedy to reflow the joints?
Or shall I remove the grounding og the TRS jack?

[Paul Birkeland]

Is it again a bad solder joint, with remedy to reflow the joints?
Or shall I remove the grounding og the TRS jack?

It could be an iffy solder joint, or the amp may need to run for a while.  The grounding the extra lugs of the TRS jack is switched out when you plug headphones in.