Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Travis8 on March 15, 2022, 06:10:46 pm

Title: Marshall Haze 40 Intermittent Volume Drop
Post by: Travis8 on March 15, 2022, 06:10:46 pm

Hi!

My Haze 40 have an intermittent volume drop, I check tubes and they work fine.

Some recommendation?

Thanks!!

Title: Re: Marshall Haze 40 Intermittent Volume Drop
Post by: uki on March 15, 2022, 06:41:19 pm

Some more info about the amp is helpful, like: schematic, voltage readings, some high resolution pics too.

Title: Re: Marshall Haze 40 Intermittent Volume Drop
Post by: Latole on March 16, 2022, 04:42:34 am

Bad solder or bad contact in power supply. Check all connectors
Input jack broken solder; shake the guitar cable and what happen with sound .
Bad contacts on Send / return 1/4 jack ;  Plug patch cable, it will bypass contacts it they are bad

Tubes can't be an issue; they always work or never work, never on and off

Schematic :
https://www.thetubestore.com/lib/thetubestore/schematics/Marshall/Marshall-Haze-MHZ40C-Schematic.pdf


Owner manual :
https://www.fullcompass.com/common/files/12328-MarshallHazeSeriesManual.pdf

Title: Re: Marshall Haze 40 Intermittent Volume Drop
Post by: Latole on March 16, 2022, 04:49:22 am

It is a amp for "pro".

More picture;  https://www.marshallforum.com/threads/marshall-haze-40-combo.7859/page-3

Title: Re: Marshall Haze 40 Intermittent Volume Drop
Post by: Latole on March 16, 2022, 04:54:36 am

Marshall Haze 40 Guitar Amp repair

Attempting to fix the Marshall Haze 40 Guitar amp
Has sound distortion issues. It plays fine for 10 minutes, but then gets really quiet and sounds horrible

Title: Re: Marshall Haze 40 Intermittent Volume Drop
Post by: Travis8 on March 16, 2022, 05:23:43 am

Quote from: Latole on March 16, 2022, 04:42:34 am

Bad solder or bad contact in power supply. Check all connectors
Input jack broken solder; shake the guitar cable and what happen with sound .
Bad contacts on Send / return 1/4 jack ;  Plug patch cable, it will bypass contacts it they are bad

Tubes can't be an issue; they always work or never work, never on and off

Schematic :
https://www.thetubestore.com/lib/thetubestore/schematics/Marshall/Marshall-Haze-MHZ40C-Schematic.pdf


Owner manual :
https://www.fullcompass.com/common/files/12328-MarshallHazeSeriesManual.pdf

I know hot rods have same issues, maybe R14 or/and R15 are bad? I will check all the power supply components

Title: Re: Marshall Haze 40 Intermittent Volume Drop
Post by: Latole on March 16, 2022, 05:30:11 am

A similar sound problem does not mean that it comes from the same parts. That would be too easy.

Different causes can cause the same problems; the sound on and off.

There are dozens of possibilities.

Start by checking the easiest part ; Input jack, Send and Return

Title: Re: Marshall Haze 40 Intermittent Volume Drop
Post by: Latole on March 16, 2022, 05:35:17 am

Quote from: RCZ on March 16, 2022, 05:23:43 am

I know hot rods have same issues, maybe R14 or/and R15 are bad? I will check all the power supply components

R14, R15 in the HR or in the Marshall ?

It can't be those on the Marshall, these are center tap heater resistors

Title: Re: Marshall Haze 40 Intermittent Volume Drop
Post by: Travis8 on March 16, 2022, 09:34:23 am

Maybe this cap is bad?

Its like its work fine but sometimes volumes drop.

Title: Re: Marshall Haze 40 Intermittent Volume Drop
Post by: Travis8 on March 16, 2022, 09:45:01 am

C17, C67, C31, C49, C15, C69 looks like the photo

Title: Re: Marshall Haze 40 Intermittent Volume Drop
Post by: Latole on March 16, 2022, 10:03:52 am

Bring amp to a qualified amp tech