Author Topic: 24VDC on Sunn Beta Lead output  (Read 429 times)

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Offline groovtubin

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24VDC on Sunn Beta Lead output
« on: November 04, 2015, 11:13:18 am »
Hello Sunn Techs! i need HELP< i`m normally a tube junkie, but have repaired lotso SS gear, this one me pulling hair out on!  Replaced Q1 ( Tip 29) for humming issues, seemed to work fine, but customer brings back, still humming..

1. replaced a KNOW defective 2N4888 w/2N5400...( Q-16) weeded out several bad solder joints, with the outputs IN or OUT i`m getting the 24vdc on output.....i can pull the pre-drivers Q7 and Q-16 and it will go away, W/Q7 out i have the 24 volts coming from collector of Q5, cut that lead 24 volts goes away, it`s a GOOD transistor n installed correctly ( i have done point to point ID n traced leads to parts for correct installs) i`ve pulled every TO-92 out n read w/sencore T checker, inc outputs..i`ve replaced ALL electrolytics, both power nad small supply, i`ve cleaned in-between traces on entire board, and read out every resistor, what gives? I really appreciate input, i know i`ve got something either in wrong, or maybe  a leaky 1N458? They read good in circuit!

Most respectfully, jim@Omegaamps.com

Offline robschwett

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Re: 24VDC on Sunn Beta Lead output
« Reply #1 on: February 26, 2018, 10:45:56 am »
Ever find out the issue?

Offline groovtubin

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Re: 24VDC on Sunn Beta Lead output
« Reply #2 on: February 26, 2018, 11:13:31 am »
Ever find out the issue?
YES i did, n it didnt take long, the ONLY TIP 91/92 cant remember exactly which one... i DIDNT change was it!  I Blv it was prob a regulator.....Thanks for chiming in n asking!  Tel ya a quik story, HAD to have. A job, back in 99.....n SS wasnt my best area of expertise,( tubes, Navy trained w/Basic EnE repaired F-14 Tomcats) )  FIRST week at Action Music in Charlote NC, im LOSING the game, go home, get out some really old GRT how to books from 60s\70s on SS....Pray, go back n Anhilate the stuff.....blew their MINDS!  Lolol......Now i`m working on a EAW  power amp..n cant get a schematic, even from EAW.........arrggg..... Grt day, hope all your repairs go great!!  God bless.....jim