It is currently Mon Mar 16, 2020 8:09 pm

All times are UTC - 7 hours



Post new topic Reply to topic  [ 23 posts ]  Go to page 1, 2  Next
Go to page 1, 2  Next
Author Message
Post subject: Blues Jr replacement jack
Posted: Tue Sep 30, 2014 8:35 pm
Offline
Aspiring Musician
Aspiring Musician

Joined: Sun Jun 30, 2013 9:59 am
Posts: 420
Sooo... What type of jack do I need to buy to replace the cheap plastic on in this thing?

I just finish up the last of the BillM mods I bought for it and now the jack is going out. I think I reefed the amp around with the guitar cord still plugged in. Was probably the end of it.

I've switchcraft jacks laying around if that is a good idea.

Finally put the adjustable bias mod in. Dropped the voltage diff to 2.35v for some odd reason. Down from 2.66v or similar.


Top
Profile
Fender Play Winter Sale 2020
Post subject: Re: Blues Jr replacement jack
Posted: Tue Sep 30, 2014 9:55 pm
Offline
Rock Icon
Rock Icon
User avatar

Joined: Tue Jun 29, 2010 1:20 pm
Posts: 9640
Location: Indiana
DarkPenguin wrote:
...I've switchcraft jacks laying around if that is a good idea...


What are you waiting for? :wink:

You probably should isolate the jack from the chassis with a fiber shoulder washer and fiber flat washer.

Image

_________________
---> "The amp should be SWITCHED OFF AND UNPLUGGED before you do this!" <---

Por favor, disculpe mi español, no se llega a la práctica con mucha frecuencia.


Top
Profile
Post subject: Re: Blues Jr replacement jack
Posted: Wed Oct 01, 2014 1:06 am
Offline
Rock Icon
Rock Icon
User avatar

Joined: Fri Feb 05, 2010 4:31 am
Posts: 14049
Location: Province de Québec, Canada
shimmilou wrote:


You probably should isolate the jack from the chassis with a fiber shoulder washer and fiber flat washer.

[ ]



Are you sure of that ? I know original jack are plastic but is this mean it should be isolated to the amp chassis ?

If you need to put fiber shoulder , the chassis hole need some work , they are too small for fiber shoulder isn't ?


Top
Profile
Post subject: Re: Blues Jr replacement jack
Posted: Wed Oct 01, 2014 7:27 am
Offline
Aspiring Musician
Aspiring Musician

Joined: Sun Jun 30, 2013 9:59 am
Posts: 420
Fiber shoulder needs a 1/2" hole, I think. That pretty much matches what is there. Switchcraft is way narrower than the existing jack.

The existing one is way loose, too. Cheap.


Top
Profile
Post subject: Re: Blues Jr replacement jack
Posted: Wed Oct 01, 2014 8:05 am
Offline
Rock Icon
Rock Icon
User avatar

Joined: Fri Feb 05, 2010 4:31 am
Posts: 14049
Location: Province de Québec, Canada
I'll use this jack ;


https://www.tubesandmore.com/products/S-H902


Top
Profile
Post subject: Re: Blues Jr replacement jack
Posted: Wed Oct 01, 2014 9:07 am
Offline
Aspiring Musician
Aspiring Musician

Joined: Sun Jun 30, 2013 9:59 am
Posts: 420
I was looking at that one, too. (That exact one, actually.) I have the switchcraft jacks, tho. So I guess I'll use those once my fiber washers arrive.


Top
Profile
Post subject: Re: Blues Jr replacement jack
Posted: Wed Oct 01, 2014 10:44 am
Offline
Rock Icon
Rock Icon
User avatar

Joined: Fri Feb 05, 2010 4:31 am
Posts: 14049
Location: Province de Québec, Canada
DarkPenguin wrote:
I was looking at that one, too. (That exact one, actually.) I have the switchcraft jacks, tho. So I guess I'll use those once my fiber washers arrive.



Not sure you need some fiber washer .Here's how to know .

Can you take some reading with meter on ohms scale ?

Put one meter's probe on face plate ,( where no paint for good contact ) other meter's probe on filter caps negative side wich go the the ground or any parts going to amp ground.

If you have some reading , very low ohms ( best is "0" ohms or close ) this mean faceplate is the amp ground and you do not need fiber washer .Use Switchcraft with no fiber washer

If reading is few thousand ohms and more ..., face plate is isolated from the amp ground and you need fiber washer .


Top
Profile
Post subject: Re: Blues Jr replacement jack
Posted: Wed Oct 01, 2014 12:16 pm
Offline
Aspiring Musician
Aspiring Musician

Joined: Sun Jun 30, 2013 9:59 am
Posts: 420
shimmilou wrote:
DarkPenguin wrote:
...I've switchcraft jacks laying around if that is a good idea...


What are you waiting for? :wink:

You probably should isolate the jack from the chassis with a fiber shoulder washer and fiber flat washer.

Image


I'm not sure I have the right jacks for this. Do I need the ones with the tip shunt bit?


Top
Profile
Post subject: Re: Blues Jr replacement jack
Posted: Wed Oct 01, 2014 12:35 pm
Offline
Rock Icon
Rock Icon
User avatar

Joined: Fri Feb 05, 2010 4:31 am
Posts: 14049
Location: Province de Québec, Canada
DarkPenguin wrote:
n Do I need the ones with the tip shunt bit?



YES . Jack with a shorting contact to ground , if not , lot of noise in the amp .

And about ohms reading ?


Top
Profile
Post subject: Re: Blues Jr replacement jack
Posted: Wed Oct 01, 2014 1:13 pm
Offline
Aspiring Musician
Aspiring Musician

Joined: Sun Jun 30, 2013 9:59 am
Posts: 420
0 ohms and I need to buy a new switchcraft.


Top
Profile
Post subject: Re: Blues Jr replacement jack
Posted: Wed Oct 01, 2014 2:09 pm
Offline
Rock Icon
Rock Icon
User avatar

Joined: Fri Feb 05, 2010 4:31 am
Posts: 14049
Location: Province de Québec, Canada
DarkPenguin wrote:
0 ohms and I need to buy a new switchcraft.



You don't need fiber isulating washer , just regular jack with normally close contact like this one ;


https://www.tubesandmore.com/products/W-SC-12A


Top
Profile
Post subject: Re: Blues Jr replacement jack
Posted: Wed Oct 01, 2014 3:30 pm
Offline
Aspiring Musician
Aspiring Musician

Joined: Sun Jun 30, 2013 9:59 am
Posts: 420
Have one of those arriving whenever Mammoth gets around to sending me my order. Thanks for the help!


Top
Profile
Post subject: Re: Blues Jr replacement jack
Posted: Wed Oct 01, 2014 8:51 pm
Offline
Rock Icon
Rock Icon
User avatar

Joined: Tue Jun 29, 2010 1:20 pm
Posts: 9640
Location: Indiana
Some plastic jacks are isolated from the chassis, and some have a metal piece near the top for contact to the chassis. Check the ones that are installed, and if there is no metal tab that contacts the chassis on the stock jacks, I would use the isolation washers with the Switchcraft jacks. I assumed that the OP is referring to the metal, traditional type Switchcraft jacks.

The chassis holes for these plastic jacks are the perfect size for the isolation washers, the shoulder washer fits in the hole, centering the Switchcraft jack.

Connecting the Switchcraft jacks to the chassis could cause noise, or it might be OK. It would be easy enough to try both ways and see. I used the isolation washers for my HRDlx.

_________________
---> "The amp should be SWITCHED OFF AND UNPLUGGED before you do this!" <---

Por favor, disculpe mi español, no se llega a la práctica con mucha frecuencia.


Top
Profile
Post subject: Re: Blues Jr replacement jack
Posted: Wed Oct 01, 2014 9:09 pm
Offline
Rock Icon
Rock Icon
User avatar

Joined: Tue Jun 29, 2010 1:20 pm
Posts: 9640
Location: Indiana
The amp chassis is always ground, so you will read low ohms from the chassis to ground of the power supply and other ground positions, that's not the point. The point is to isolate the jack itself from the chassis, to prevent a ground loop. The negative lead of the jack will connect to its own ground point, and in many modern amps, that ground should not connect to the chassis (a second ground), creating a loop. The ground pin of the amp's electrical plug is connected to the chassis, note the difference between the symbol of that ground compared to the symbol of the ground for the negative lead of the jack.

Having said that, the BJr III schematic shows the input jack negative connected to the chassis, while the previous BJrs do not. So, it might not matter, but it definitely won't hurt to use the fiber washers, and IMO would be better to use the washers.

_________________
---> "The amp should be SWITCHED OFF AND UNPLUGGED before you do this!" <---

Por favor, disculpe mi español, no se llega a la práctica con mucha frecuencia.


Top
Profile
Post subject: Re: Blues Jr replacement jack
Posted: Thu Oct 02, 2014 1:12 am
Offline
Rock Icon
Rock Icon
User avatar

Joined: Fri Feb 05, 2010 4:31 am
Posts: 14049
Location: Province de Québec, Canada
shimmilou wrote:
The amp chassis is always ground, so you will read low ohms from the chassis to ground of the power supply and other ground positions, that's not the point. The point is to isolate the jack itself from the chassis, to prevent a ground loop.

Not in my opinion, plastic jacks are use because printed cicuit is build by robot . Robots can't use Switchcraft type jacks , you need a human worker and it cost more and ask more time .

The negative lead of the jack will connect to its own ground point, and in many modern amps, that ground should not connect to the chassis (a second ground), creating a loop. The ground pin of the amp's electrical plug is connected to the chassis, note the difference between the symbol of that ground compared to the symbol of the ground for the negative lead of the jack.

I show to Dark Penguin how to do do some reading in ohms to see if front panel is at the "right " ground ,in other word at the amp 's circuit common. His answer is yes . Switchraft jack can be use here like in any Blackface or Silverface amp

.


Top
Profile
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 23 posts ]  Go to page 1, 2  Next
Go to page 1, 2  Next

All times are UTC - 7 hours

Fender Play Winter Sale 2020

Who is online

Users browsing this forum: No registered users and 2 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum

Search for:
Jump to: