Issue with Speedball Install (Low Voltage Readings and 3 LEDs out)

[Eddy_Z]

Hi,

I built the crack about a month ago and it was working great. So I decided to install the speedball the other day and ran into a problem on the last step.

I powered the crack on for the final voltage check of the big board and everything appeared normal (all the LEDs light up and both tubes were working). All terminals were within the guidelines expect for OA, which was reading around 170V. I unplugged the crack for a bit then plugged it back in to recheck voltages.

(Note that I was only checking the voltages on the big board at this time as I thought I passed the voltage check on the small board and resistance check in the previous steps)

During the second test everything looked normal again but I was still getting a very high reading for terminal OA. Then the 2 LEDs on the right side of the little board and the LED on A3 went out. This is when I tested everything in the speedball again and here are my current voltage readings :

Small Board

OA  84V
IA  188V
B-A/B  0V
IB  188V
OB  30V

Big Board
OA  69V
OB  115V
G    0V
B+  189V

I looked around for a solution but couldn't find this exact problem. Some troubleshooting I tried already with no luck:

- resoldered the MJE350 and PN2907A on the OB side two different times
- resoldered some joints on the 9 pin socket and terminal lugs that looked questionalbe
- flipped the little board 180°. The voltage readings were the same as above except the OA & OB big board switched. The LED on A3 light up but the LED on A8 went out. 2 LEDs on OB side of the little board still did not light up.

Thank you for any help.

 

[Paul Birkeland]

When the small PC board and 12AU7 aren't working properly, all bets are off for the 6080/big board.

My suspicion is that your LED isn't lighting up because the tube pin that it's connected to has shorted to an adjacent pin and is grounding out.  Can you post photos of the build around the 9 pin socket?

 

[Eddy_Z]

Below are some photos of my build.

I've been trying some things to fix it but still no luck. Everything is the same from my first post expect for the voltage reading on OB little board is bouncing all over the place.

 

[Paul Birkeland]

Can you unscrew the small PC board, bend it up a bit, and take a photo of the 9 pin socket underneath?

 

[Eddy_Z]

Here's what the 9 pin looks like

 

[Paul Birkeland]

Can you carefully measure the DC voltage at pins A2 and A3?

 

[Eddy_Z]

A2 = 0.5 mV
A3 = .670 V

The LED at A8 just went out on me now too

 

[Paul Birkeland]

What DC voltage do you have at A8?

When these LEDs get damaged and/or go bad, they tend to open up.  This will result in high voltage where the LED connects (12V or so in a Crack).  If one of the wires coming from the pot to the 9 pin socket isn't well connected, that will throw off tube operation as well, but this will be accompanied by a weird voltage at A7 or A2.

You appear to have a dead short across at least that LED, which is generally from an external source. Can you also tell me about the solder you used?

 

[Eddy_Z]

I'm not with my crack right now so I'll post the voltage readings for you later. I've been looking for bad soldier joints and when I try to fix them things seem to only get worse.

Here is the exact solder I've been using: https://www.amazon.com/dp/B00030AP48/ref=asc_df_B00030AP485326256/?tag=hyprod-20&creative=394997&creativeASIN=B00030AP48&linkCode=df0&hvadid=198093934741&hvpos=1o2&hvnetw=g&hvrand=10615134916449796722&hvpone=&hvptwo=&hvqmt=&hvdev=m&hvdvcmdl=&hvlocint=&hvlocphy=9021551&hvtargid=pla-381576167660

 

[Eddy_Z]

A8 = 2.4 V

 

[Paul Birkeland]

Woah, that's odd.  What voltage do you get at A7?  With 2.4V at A8, the LED should be very brightly illuminated, or one end may be loose (or the black wire that lands at the center lug on the 9 pin socket may be loose on one end).

 

[Eddy_Z]

A7 = 0.5 mV

I did resoloder the center pin a couple times so maybe I didn't connect every good enough last time. I'll try to fix that to see if it helps.

I also noticed the voltage at A1 is just looping. Is that normal?

 

[Paul Birkeland]

What does looping mean?

 

[Eddy_Z]

Looping probably isn't the right term, I'm a total novice when it comes to this stuff.

The multimeter is giving me readings at A1 like of 0V->60V->90V->150V->0V...repeat

The lead broke off on one of the LEDs so I have to wait for the replacement parts before I can get back to working on the crack.

I am still kind of curious as to what went wrong in the first place. When everything appeared to be working but the voltage reading was too high on the big board. Then all of the sudden the 3 LEDs went out and the voltages dropped. Did a part fail somewhere or was it a result a bad connection?  Do you have any idea?

 

[Paul Birkeland]

That sounds like a broken wire or a bad connection.