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Bottlehead Kits => Crack => Topic started by: barbz on December 07, 2020, 01:07:03 AM

Title: Buzzing in both channels after speedball (resolved)
Post by: barbz on December 07, 2020, 01:07:03 AM

Hi all,

Ive had a working crack amp for the past fortnight and decided to add speedball - everything checked out however once powering it up im getting loud static that is present when the volume is at 0% the buzzing after 10 seconds from power on is too loud to attempt to listen to any music with.

All Leds are alight (4 + 4 + 2)
Both tubes are alight
Resistance checks for speedball large board were OL on my unit

Large Voltage readings

oa 108.8v
ob 102.6v
g   0v
b+ 171v

Small Voltage Readings

oa 68.1v
ia 171.2v
b-a/b 0v
ib 171.1v
ob 79.4

Tubes are the supplied tubes

Any suggestions on where to start troubleshooting? I have reflowed the U1/2/3/4/5 and U7/9 along with the oa/ob/ib/ia's

Thankyou

Title: Re: Buzzing in both channels after speedball
Post by: barbz on December 07, 2020, 01:10:00 AM

Some photos

Title: Re: Buzzing in both channels after speedball
Post by: oguinn on December 07, 2020, 05:15:03 AM

You need more solder on the big board. I can see a couple spots on resistors and LEDs where the solder hasn't covered the pad.

Also, if you're not passing your resistance checks, don't plug headphones into your amp.

Title: Re: Buzzing in both channels after speedball
Post by: Paul Birkeland on December 07, 2020, 05:38:30 AM

Buzzing would be something other than the Speedball that's loose.  You can plug in an inexpensive set of headphones and poke at the amp while it's powered up with a wooden chopstick to see if you can change the behavior of the amp by poking it in a specific place, then that can focus your efforts.