EVALUATION: Vintage Marshall small box JMP 1987 50 w from 1971

[denrrou]

Hi guys! Some advice is needed from the marshall guys here

Bought this marshall some years ago and it looks pretty much original, the transformers and filter caps (says daly) seems to never been replaced and the circuit seems mostly untouched.

The only changes the guy who serviced it some years ago did was the resistors on the power tubes and a single wire he changed place... he told me it had something to do with an error regarding the standby voltage or something like that...

I have not been using the amp since my attenuator was gone and the other day i powered the amp and its volume appears lower and there ares some pop noises randomly occurring.... i guess i need new tubes and i am decided to change the filter caps for security purpose.

Other than that, what else do you suggest for me to service in this amp to give it new life again?

Also, what would you guys say based on the pic of its circuit? Its serial is 54866C, In the back it says lead, but inside on the paper it also says bass, also it it lacks the bright cap on the volume knobs. I felt it never distorted the way i like (hard rock style) and i was told it would have to do with the lack of this bright cap, specially on lower volumes

thanks in advance!

Hi guys! Some advice is needed from the marshall guys here

Bought this marshall some years ago and it looks pretty much original, the transformers and filter caps (says daly) seems to never been replaced and the circuit seems mostly untouched.

The only changes the guy who serviced it some years ago did was the resistors on the power tubes and a single wire he changed place... he told me it had something to do with an error regarding the standby voltage or something like that...

I have not been using the amp since my attenuator was gone and the other day i powered the amp and its volume appears lower and there ares some pop noises randomly occurring.... i guess i need new tubes and i am decided to change the filter caps for security purpose.

Other than that, what else do you suggest for me to service in this amp to give it new life again?

Also, what would you guys say based on the pic of its circuit? Its serial is 54866C, In the back it says lead, but inside on the paper it also says bass, also it it lacks the bright cap on the volume knobs. I felt it never distorted the way i like (hard rock style) and i was told it would have to do with the lack of this bright cap, specially on lower volumes

thanks in advance!

pics: https://postimg.cc/gallery/HdqbDkV