Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Latole on February 27, 2021, 03:19:58 pm

Title: Marshall Vintage Modern 2466 amp ; looking for Middle pot
Post by: Latole on February 27, 2021, 03:19:58 pm
Hi ,
I have a Marshall Vintage Modern 2466 amp with intermittent Middle pot.
Clean it with Deoxit with no success. There are some hole from the front of the pot

It is a B25 K like the pictures It is a green pot , the blue one is to show more the flat shaft.
I can't find one anywhere. Can you help me ?
Thank's

Title: Re: Marshall Vintage Modern 2466 amp ; looking for Middle pot
Post by: acheld on February 27, 2021, 09:08:56 pm
Is this close enough?

https://www.tubesandmore.com/products/potentiometers_0?filters=2341a2403
Title: Re: Marshall Vintage Modern 2466 amp ; looking for Middle pot
Post by: Latole on February 28, 2021, 03:14:37 am
Quote from: acheld on February 27, 2021, 09:08:56 pm
Is this close enough?

https://www.tubesandmore.com/products/potentiometers_0?filters=2341a2403


Thank you.
I look there before, there is only a 20 K pots, not 25k.
Same value everywhere.

I don't know how a 20K will work for middle tone circuit ? It could be not too bad ? Or I'll loose some middle ?

 
Title: Re: Marshall Vintage Modern 2466 amp ; looking for Middle pot
Post by: Latole on February 28, 2021, 04:31:22 am
I look at more 30 stores with Google selling Marshall parts.
The only pot available is the 20k .

I live close to the Quebec province Marshall Products distributor, West Coast Music. I'll go there next open day
Title: Re: Marshall Vintage Modern 2466 amp ; looking for Middle pot
Post by: Bieworm on February 28, 2021, 09:35:59 am
Maybe put a 5k resistor in series to get the 25k. Who sets his knob to zero anyway?
Title: Re: Marshall Vintage Modern 2466 amp ; looking for Middle pot
Post by: Latole on February 28, 2021, 09:43:30 am
Quote from: Bieworm on February 28, 2021, 09:35:59 am
Maybe put a 5k resistor in series to get the 25k. Who sets his knob to zero anyway?

Yes, why not, thank's.
Title: Re: Marshall Vintage Modern 2466 amp ; looking for Middle pot
Post by: thetragichero on February 28, 2021, 10:17:40 am
or if you can get a larger value pot the appropriate value resistor in parallel to the outer lugs to get 25k
Title: Re: Marshall Vintage Modern 2466 amp ; looking for Middle pot
Post by: Latole on February 28, 2021, 10:33:28 am
Quote from: thetragichero on February 28, 2021, 10:17:40 am
or if you can get a larger value pot the appropriate value resistor in parallel to the outer lugs to get 25k


You are 100 % right
A 100 K is available .

Thank you

https://www.tubesandmore.com/products/potentiometer-marshall-linear-11mm-pc-mount-square
Title: Re: Marshall Vintage Modern 2466 amp ; looking for Middle pot
Post by: thetragichero on February 28, 2021, 11:05:08 am
33k resistor puts you closer to 25k than probably the original
Title: Re: Marshall Vintage Modern 2466 amp ; looking for Middle pot
Post by: Latole on February 28, 2021, 11:22:45 am
Quote from: thetragichero on February 28, 2021, 11:05:08 am
33k resistor puts you closer to 25k than probably the original

I will try, I have many 100K pots and resistors.
Thank's
Title: Re: Marshall Vintage Modern 2466 amp ; looking for Middle pot
Post by: Bieworm on March 01, 2021, 12:10:37 pm
I prefer 50k for mid pot. It does all a 25k can do, and beyond...
It's a common mod on 18W TMB amps.. part of the jalapeņo tone stack
Title: Re: Marshall Vintage Modern 2466 amp ; looking for Middle pot
Post by: Latole on March 01, 2021, 03:31:25 pm
Quote from: Bieworm on March 01, 2021, 12:10:37 pm
I prefer 50k for mid pot. It does all a 25k can do, and beyond...
It's a common mod on 18W TMB amps.. part of the jalapeņo tone stack

Good to know. Thank's
Title: Re: Marshall Vintage Modern 2466 amp ; looking for Middle pot
Post by: Latole on March 01, 2021, 03:40:52 pm
I think I fix the pot, work fine since yesterday.
 
1- I spray Deoxit on two holes ( picture ) . These holes make Deoxit go inside the pot.  Feeling change when turning pots . I do all pots

2- I close the 4 pressure tabs, two where loose ( picture)

Title: Re: Marshall Vintage Modern 2466 amp ; looking for Middle pot
Post by: Latole on March 02, 2021, 04:06:00 am
I have noticed that these potentiometers are fragile and can age prematurely.

Mainly with play in the shaft if you push the button, the potentiometer could become intermittent.

To prevent this play, I installed nylon spacers found at Home Depot in bulk in locker # 3580 in Canada. To see the photo.
This same type of pots would also be found on the models
CM2000 series TSL100, TSL122, DSL100, DSL50, DSL401 and VS65R well as some of the late 90's ValveState models.

These spacer do not change the appearance or operation of the knob at all.

Title: Re: Marshall Vintage Modern 2466 amp ; looking for Middle pot
Post by: Latole on March 04, 2021, 03:08:47 am
My answer to a e-mail ( see screen picture)

Thanks for your feedback. In the meantime, I managed to repair the potentiometer.
If the repair does not last over time, I will order from you. I keep your reference.