Bottlehead Forum

Bottlehead Kits => Crack => Topic started by: polarpigs on October 10, 2016, 06:32:20 PM

Title: Voltage check error
Post by: polarpigs on October 10, 2016, 06:32:20 PM: My crack speedball had been picking up a buzz and been crackling in the right channel for a week so I decided to reflow the solder. In the process I'm pretty sure I messed something up but I have no idea what it is now.
There is no sound coming through to the headphones and the 2 red LEDs on the octal socket aren't lit.
The 12AU7 and 6080 are lit properly in both halves and the rest of the LEDs on the speedball are properly lit.
These are the wrong voltages:
Ground to:
T1: 0V
T5: 170V
T7: 53.7V
T9: 170V
Title: Re: Voltage check error
Post by: Paul Birkeland on October 13, 2016, 11:34:44 AM: Can you unplug the 6080, then recheck terminals 1-5.

Having 0V at terminal 1 on a Speedball can mean that the center leg of the MJE350 transistor needs to be reheated. Having 170V at T5 generally means that the R1 resistor on that half of the small Speedball board (or that small Speedball board for older kits) has the wrong value.

Having both of these creep up after reflowing joints would also make you want to check for any shorts both on and off the boards.

-PB
Title: Re: Voltage check error
Post by: polarpigs on October 13, 2016, 03:06:30 PM: Unplugged 6080

T1: 0V
T2: 222V
T3: 0V
T4: 222V
T5: 220V

The only lit LEDs are the 2 on the Speedball A board.
Title: Re: Voltage check error
Post by: Paul Birkeland on October 17, 2016, 02:58:28 PM: Do you have the new Speedball with the single small board up front?

Were your voltages ever in spec after the initial installation of the Speedball?
Title: Re: Voltage check error
Post by: polarpigs on October 17, 2016, 07:44:04 PM: Regarding initial voltages, I'm pretty sure that they were in spec. It's been 2 years since I've built this so I'm not 100% sure.

I'm not sure about the board, here's an image of the underside of the crack.

(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fi.imgur.com%2FujXpvTZ.jpg&hash=4104a48eb49835f9c214f3526fff0d19e1b7b5e5)
Title: Re: Voltage check error
Post by: Paul Birkeland on October 19, 2016, 11:11:58 AM: How about unscrewing the small boards and taking pictures of the bottoms, as well as what's underneath the boards.

-PB
Title: Re: Voltage check error
Post by: Doc B. on October 19, 2016, 11:18:24 AM: Yup, good call. If you were reflowing pads on the boards you may have created a solder bridge that is shorting something out. A pic of the bottom might help spot a bridge.
Title: Re: Voltage check error
Post by: polarpigs on October 19, 2016, 03:30:30 PM: SB Board A underside:
(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fi.imgur.com%2FNe7avi5.jpg&hash=e3322695a70033b057c9305eb9b56d129e10d80c)

Board B:
(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fi.imgur.com%2FfkMJTTr.jpg&hash=b2c3d1bde2eeded95c050306accc84922011378c)
Title: Re: Voltage check error
Post by: Paul Birkeland on October 20, 2016, 05:30:28 AM: Can you measure the DC resistance of the R1 resistors on each small board and let me know what you see?
Title: Re: Voltage check error
Post by: polarpigs on October 20, 2016, 02:32:40 PM: Jumps around a little but settles on 235Î© for both the R1 resistors.
Title: Re: Voltage check error
Post by: Paul Birkeland on October 20, 2016, 04:33:43 PM: Can I see the build under the boards?

It's very unusual that both the small boards wouldn't work of they were functioning before.
Title: Re: Voltage check error
Post by: polarpigs on October 20, 2016, 08:17:08 PM: I hope these are clear enough

(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fi.imgur.com%2FC1HaHFQ.jpg&hash=27f442e9551215cf8f05ea61933b9ce088398470)
(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fi.imgur.com%2FWCni5Ee.jpg&hash=673af9e937e4788540cfe584c2caf9db19ef4cb3)
Title: Re: Voltage check error
Post by: Paul Birkeland on October 21, 2016, 06:43:19 AM: The only advice I can offer is to reflow the joints on the PC boards. It actually looks like a little tiny bit more solder wouldn't hurt, and that the center legs of the MJE350 transistors could use quite a bit of extra heat.