Installing new input jacks

[greco]

A friend of mine has asked me to consider replacing the 2 input jacks on his Fender M 80 amp. The present jacks are in bad shape as they don't hold the plug securely and hence the signal cuts in and out or there is no signal at all.

I suggested that he might want to replace the existing plastic, enclosed, board mounted jacks with open Switchcraft jacks.

I have found a turorial on the internet about doing this replacememt on a Fender Hot Rod Deville and it seems reasonably straight forward.

My main concerns are:

1) I don't want to try something that might be more challanging than I expected.

2) Obviously, I don't want to harm his amp in any way.

2) I don't want to end up with his amp humming (or some sort of "new" unwanted noise).

3) Getting the correct jacks for the job. Are the replacement jacks the typical "normally open" mono 1/4 inch jacks or something more sophisticated (i.e., the jacks that have the feature to open/close an additional circuit?

4) I am assuming that the Switchcraft jacks would need to be fully insulated from the chassis.

Any comments related to, or in addition to, the above concerns would be appreciated.

If this is not the type of thing a relative newbie to electronics should be trying....please don't hesitate to say it. My friend is quite happy to take the amp to a tech.

Thanks for your comments.

Peace

Dave

[sliberty]

Plastic enclosed jacks are very common, and not "inherently evil" in any way. The plastic enclosed jacks on my 1972 HiWatt are original and work perfectly.

I don't know what sort of jacks the M 80 uses, but they are probably readily available. I would simply replace them with the same type and be done with it. Open up the amp, and unsolder one of them. Then you'll be able to look for a suitable replacement.

The only trick with unsoldering a baord mounted jack is to be careful. You don't want to overheat the baord because that can make the copper pads lift off of the board. So, use a solder solker to remove most of the solder, and then gently remove the jack.

I believe that you should be able to get the right jacks at http://www.tubesandmore.com

[iaresee]

Plastic enclosed jacks are very common, and not "inherently evil" in any way. The plastic enclosed jacks on my 1972 HiWatt are original and work perfectly.
+1 -- the Marshall enclosed jacks and the Switchcraft are both very nice, plastic housing, enclosed jacks. The enclosed jacks can be a little easer to work with if you need to isolate the chassis from the ground on the jack.

Post a picture of the jack and the board. We can give you more information on a replacing it that way.

4) I am assuming that the Switchcraft jacks would need to be fully insulated from the chassis.
It's possible. You can test it: using a DMM set to continuity beep mode touch a probe to some metal on the chassis near the jack. Then use the other probe to touch the sleeve connector on each jack you intend to replace. If the DMM beeps you've got a continuous path and it means ground on the jack needs to tied to the chassis.

[greco]

Here is a pic of the jacks:
http://i263.photobucket.com/albums/ii136/Davido-08/InputJacks1.jpg

[iaresee]

Interesting. I've never seen jacks like that before. Are they in a custom enclosure? How many pins on the bottom of the board? See if you can get Wild Bill or mhammer to read this thread -- they've seen more jacks than I have and might be able to tell you who makes 'em. I can't, sorry.

[greco]

This is not a custom enclosure AFAIK.

Stock Fender M 80 1 x 12" combo (unless a previous owner modded it).

We have not removed the board as yet, so I can't comment on the number of pins from each jack.

This close-up shot might help. The mark on the jack on the left is a scratch, not a crack in the housing.

http://i263.photobucket.com/albums/ii136/Davido-08/InputJackscloseup.jpg

Dave

[Hamm Guitars]

Use a dental pick or similar instrument to reach insude the jack from the 1/4" hole and bend the tip tong back in place.

[dwagar]

+1, a fast, simple, no cost solution.

I had to do this on my wireless belt pack. My fault, I was using a cord with right angle jacks (because I play a LP). Bent the piece back into place, replaced the one end with a proper straight jack, and it's been fine ever since.

[greco]

Use a dental pick or similar instrument to reach insude the jack from the 1/4" hole and bend the tip tong back in place.

"tip tong"......has a nice ring to it

Thanks for this suggestion. The plastic collar of the jack (on the front panel of the amp) has also been broken. However, the dental pick approach is worth a try as a quick fix.

I have been going through the Mouser catalog (on a CD) to see if I can match to this part. It is literally like trying to find a jack in a haystack (of 1532 pages)

Cheers

Dave

[sliberty]

Here you go:

http://www.catalinaguitars.com/catalog2/product_info.php?cPath=66_86_94&products_id=442

[greco]

sliberty....Thanks for the link...I saw that pic also.

http://i263.photobucket.com/albums/ii136/Davido-08/M80Jack.jpg

The pins didn't look the same as in the close-up pic that shows 4 pins in a row ...if I'm correct.

Dave

[sliberty]

The only way to really be sure what you need is to remove the part from the board. Then, you can call the vendor who claims he has the correct parts for the M 80, and describe what your part looks like (maybe you'll even find a part number on it), and he can confirm what he's got.

[keeperofthegood]

Those also look stereo and not mono. The top contact looks in a position for the ring and not the tip. Being semi-transparent or even pop-offable (those look to be melted pins, use a small drill bit to cut the melt tops off, then it's easy to crazy glue back later), or Id suggest sliding in a stereo plug and seeing if the top contact meets the tip or ring.

*edit* I do mean that the clear plate is a cover that can be removed for easy viewing of the internals of the jack.

[sliberty]

Check http://www.angela.com. Click on the Connector link,a nd scroll down to the bottom. There is a Fender jack that looks promising.

[greco]

Thanks sliberty...they sure look like the ones !

and are "murder to find" according to Angela.com

Dave