Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: etneccas on March 09, 2019, 02:57:49 pm

Title: Mesa Rocket44 Redplating
Post by: etneccas on March 09, 2019, 02:57:49 pm

The power tubes burning up I have the following DC voltages  Pin 2 -11vdc     pin7 483vdc   and pin 9 452vdc I could use some help to solve this ....Thanks

Title: Re: Mesa Rocket44 Redplating
Post by: sluckey on March 09, 2019, 03:29:41 pm

Plate voltage is 100V higher than it should be. Why?

Title: Re: Mesa Rocket44 Redplating
Post by: Colas LeGrippa on March 09, 2019, 10:14:22 pm

Check the bias resistors or grid leaks if cathode bias

Title: Re: Mesa Rocket44 Redplating
Post by: etneccas on March 10, 2019, 07:50:30 am

Reading were with the power tubes out  :BangHead:  The amp plays fine but after an hour or so cranking the volume drops why off and goes completely down these suckers sound unbelievable but generate alot of heat any ideas what might be causing the drop out? I've had the master cranked this morning and the preamp way down for about 2hrs this morning and holding up so far

Title: Re: Mesa Rocket44 Redplating
Post by: etneccas on March 12, 2019, 02:48:18 pm

I am still getting some crackly distortion on the contour channel that goes away when I chopstick the 4 contour filters or the 6 electrolytic in the 15 vdc area
The other channel is not having this problem
It seems like a grounding issue there doesn’t appear to be any grounds other the pre section grounded to the input jack and the 120v ground to the chassis the power transformer grounds are on the ribbon cable and molex to the circuitboard

Title: Re: Mesa Rocket44 Redplating
Post by: shooter on March 12, 2019, 03:48:11 pm

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crackly distortion

Quote

goes away when I chopstick

typically points to anything loose like solder pad,

Quote

ribbon cable and molex

pins, or solder pads for pins, or foil cracks.

usually just takes time and patience, good solder skills and maybe luck  :icon_biggrin: