Mark IIB tone stack caps

[MK IIB]

Hi Folks
I would really appreciate if someone could take a quick look at some pics of my Mark IIB.
The treble cap(ceramic)on my Mark IIb looks really worn and I was wondering if this can have any detrimental effect on the tone at all?
I would also really appreciate if anyone could have a look at the pic of my preamp and the highlighted resistors at V1 and V2 and tell me if they are original and what their purpose is as I suspect they may have been changed?
Lastly a couple of resistors on the bias area look a little funky and would like a second opinion?

 

[lovetoboogie]

Treble cap looks a little chewed up on the leg but nothing to lose sleep over. There should be another one under the silicon that is the Treble shift cap as they become paralleled when you pull the Treble knob...

as for pic 2, that carbon film 56k is the part of the effects loop send/return matrix. Though it seems out of place because it is a different "type" of resistor, that is original. Boogie used whatever was lying around in those days and there is nothing wrong with carbon film resistors in low voltage/current apps...

the other resistor, the big 100k on the right is a plate load resistor for V1b. That is also original...it is a Piher brand which is high quality. Although you would usually see a 1/2w resistor there, that big honking 2w resistor is what they used. Leave it, if ain't broke don't fix it.

in pic 3, the bias matrix, that 10k on the right is original and fine. It's part of the voltage drop down/balance for the negative bias voltage...the other resistor in conjunction with the trimpot is what you would swap out to get your trimpot in range for the correct negative voltage. Does not look original for what Boogie was using for the IIB's. I assume this amp wasn't biasing properly with a given set of tubes so that resistor was replaced to get the trimpot to "cooperate". I like to use high quality 1% tolerance resistors when I modify or repair bias supplies. It's a extra .17!!!

*Upon second look at the 3rd pic, that bias trimpot does not look to be original either. Though a number of IIA's and IIB's did have adjustable fixed bias, that looks a little messy. The majority of the ones I have service have a round/circular 10k Bourns trimpot. I could be wrong of course because Boogie used alot of different types...

Hope this helps!

 

[MK IIB]

Treble cap looks a little chewed up on the leg but nothing to lose sleep over. There should be another one under the silicon that is the Treble shift cap as they become paralleled when you pull the Treble knob...

as for pic 2, that carbon film 56k is the part of the effects loop send/return matrix. Though it seems out of place because it is a different "type" of resistor, that is original. Boogie used whatever was lying around in those days and there is nothing wrong with carbon film resistors in low voltage/current apps...

the other resistor, the big 100k on the right is a plate load resistor for V1b. That is also original...it is a Piher brand which is high quality. Although you would usually see a 1/2w resistor there, that big honking 2w resistor is what they used. Leave it, if ain't broke don't fix it.

in pic 3, the bias matrix, that 10k on the right is original and fine. It's part of the voltage drop down/balance for the negative bias voltage...the other resistor in conjunction with the trimpot is what you would swap out to get your trimpot in range for the correct negative voltage. Does not look original for what Boogie was using for the IIB's. I assume this amp wasn't biasing properly with a given set of tubes so that resistor was replaced to get the trimpot to "cooperate". I like to use high quality 1% tolerance resistors when I modify or repair bias supplies. It's a extra .17!!!

*Upon second look at the 3rd pic, that bias trimpot does not look to be original either. Though a number of IIA's and IIB's did have adjustable fixed bias, that looks a little messy. The majority of the ones I have service have a round/circular 10k Bourns trimpot. I could be wrong of course because Boogie used alot of different types...

Hope this helps!

Thanks for your help.
Upon looking at other pics of mark IIB's I haven't seen any with these 2 resistors and was curious if it could impact on the tone/performance of the amp.
I was told there was a non stock resistor on V1 at pin 6?
Both the treble cap and treble shift caps are prety chewed up?This wouldn't affect the amount of treble?
Yes the bias pot was added by a tech and isn't original.I was more concernd with the appearance of those resistors as one looks to be covered in a substance it wasn't before and I thought one may have been a bit charred.
Thank you for your reassurance.