MARK III Red Reverb Issue

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mgbanach
Bottle Rocket
Posts: 2
Joined: Thu Feb 25, 2016 12:26 pm

MARK III Red Reverb Issue

Post by mgbanach » Thu Feb 25, 2016 12:33 pm

Howdy yall. This is my first time on, as I have recently acquired a mk iii red stripe combo amp. Such a rad amp. Currently I am having issues when I turn my reverb up. When I turn it up, there is lou crackling and volume boosts, but when I turn it to 0 everything is fine. I figured it was a pre amp tube. Cant seem to find which is the preamp tube for the reverb though. My amp has two 6L6 power tube ports and 5 pre amp ones. I went through all of the pre amp tubes, with my one replacement pre amp tube, and couldnt find the port. I interchanged all of them but the port 1, silver encased one. Do I need to replace all of the pre amps and power tubs? Is it a circuitry issue?
Thanks so much for the help.

stokes
Single Recto
Posts: 1459
Joined: Sun Feb 19, 2006 11:43 am
Location: NYC

Re: MARK III Red Reverb Issue

Post by stokes » Fri Feb 26, 2016 12:10 am

"When I turn it up, there is loud crackling and volume boosts, but when I turn it to 0 everything is fine".Do you get any reverb effect at all?

tommyhawk13
Mark III
Posts: 227
Joined: Fri Jun 09, 2006 11:31 am
Location: Jacksonville, FL

Re: MARK III Red Reverb Issue

Post by tommyhawk13 » Fri Feb 26, 2016 12:12 pm

[quote= I interchanged all of them but the port 1, silver encased one.
[/quote]

This might be the tube for reverb. I think the metal casing is for noise suppression. The old Boogie catalogs advertised a shielded tube for reverb. You can use a regular 12AX7, or even a 12AT7 like they did in the old days.
1987 .50 Caliber, no eq
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stokes
Single Recto
Posts: 1459
Joined: Sun Feb 19, 2006 11:43 am
Location: NYC

Re: MARK III Red Reverb Issue

Post by stokes » Fri Feb 26, 2016 6:07 pm

The reverb tube is V4.

Promethean
Mark II
Posts: 81
Joined: Wed Nov 13, 2013 7:53 am

Re: MARK III Red Reverb Issue

Post by Promethean » Sat Feb 27, 2016 1:54 am

v4 should be the one furthest from the input jack. The preamp valve set behind is the phase invertor.

I always had a hissing, buzzy noise problem with my MK3 whenever I used reverb. I cleaned all the connectors from the amp to the reverb unit. They could be rusty. What finally sorted it was a mail to Boogie. They directed me to make an additional connection to earth from a transformer wire and that eliminated all the noise problems completely..

"120k resistor on the red lead from the smaller reverb transformer to ground."

I am not sure if that was resolved by the red stripe - mine is the purple one before. It was called the 'reverb glitch mod' so seemed common to the amps. I have a copy of the Mark 3 mod sheet from Boogie themselves.

I also added a 10k 1/2 watt resistor in series to the black wire going to the fx return jack. That significantly boosts the amount of reverb available. 3.3k or 5k would work too

mgbanach
Bottle Rocket
Posts: 2
Joined: Thu Feb 25, 2016 12:26 pm

Re: MARK III Red Reverb Issue

Post by mgbanach » Sat Mar 05, 2016 11:13 am

replaced the reverb pre amp tube. still happens. called boogie, and they recommended I take it to a tech.

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