ODS Maintainability Strategy

[donvan]

I am currently building sub-boards for my first amp build, a 183, and I'm just thinking ahead about wiring to and from these boards. From the photos I've seen it looks like it would be a fairly involved process if one ever needed to replace a component that requires accessing the bottom of these boards once the amp is fully wired. The boards have wires going to multiple sides so again it looks difficult to get to the bottom. So here are a couple of questions regarding the preamp board:

1) What is the best way to access the bottom of the preamp board? Disconnect wires from only one side? Or all sides? Leave wires attached to board and disconnect them from the chassis components?

2) Is there anything that can be done during the wiring phase that makes future access easier? I'm not sure what that would be but you never know. Longer wires are probably not a good idea.

Just curious how you experienced builders and repair people go about these things.

Thanks,
Don

[norburybrook]

I am currently building sub-boards for my first amp build, a 183, and I'm just thinking ahead about wiring to and from these boards. From the photos I've seen it looks like it would be a fairly involved process if one ever needed to replace a component that requires accessing the bottom of these boards once the amp is fully wired. The boards have wires going to multiple sides so again it looks difficult to get to the bottom. So here are a couple of questions regarding the preamp board:

1) What is the best way to access the bottom of the preamp board? Disconnect wires from only one side? Or all sides? Leave wires attached to board and disconnect them from the chassis components?

2) Is there anything that can be done during the wiring phase that makes future access easier? I'm not sure what that would be but you never know. Longer wires are probably not a good idea.

Just curious how you experienced builders and repair people go about these things.

Thanks,
Don

personally I would think it would be mainly electrolytic caps that would need changing in the amps lifetime. I really doubt you'd need to be changing wires that run to and from the board. All the components are top mounted so can be replaced without too much trouble if needs be.

just my 2 cents.

M

[pompeiisneaks]

As I recall with mine, most of the replaceable components are in top solder-able positions. I know wires can be tricky themselves, but I don't know of wires failing, usually fuses and components fail before the wires themselves. Basically if a cap or resistor fails you can easily heat the joint, remove the solder and pull it out and replace it and re-solder. Am I missing something else in the question though? the under board stuff is all just jumpers etc. They shouldn't be removed or need to be replaced as far as I can think of.

~Phil

[dorrisant]

As Phil said, the eylets will nullify the need to access the bottom of the board in most cases. Usually it is easy enough to remove the pots, jacks and switches from the chassis and roll the board over towards the tube sockets. No desoldering. Seems like you do this quite a bit if you do many repairs.

[donvan]

I don't foresee wires going bad but ...
Components like electrolytics are on the top and connecting wires (jumper wires) are on the bottom of the boards. I would think that when removing a bad cap, the connecting wire on the bottom could come out of the eyelet and you would then need to access the bottom. Therefore I was wondering the best way to access the bottom.

Since the preamp board has external wires coming to it on all sides, I couldn't imagine any way to roll the board without temporarily removing the external wires that come to it from at least 1 or 2 sides.

It sounds no one has had to access the bottom.

[pompeiisneaks]

You should always wrap the under connecting wires in a U shape around the eyelet so it takes some force for them to be bent up and to fall out of the eyelet. This makes a good permanent physical connection and the solder is just a mechanical glue to hold the joint together. This also means swapping components is easier as well. If they're falling out the bottom, then yes it would be a big PITA to deal with, but so far on mine I've had to swap a few components when I realized I did something wrong and the jumpers and wires stayed put.

~Phil

[donvan]

Thanks Phil, that's a good tip.

[erwin_ve]

If for maintainance you replace a component from the top, how do you make sure you still got a good mechanical connection?

[Mr. dB]

The insulator board directly underneath the eyelet board should hold the wires in place. Just like in a Fender.

[pompeiisneaks]

If for maintainance you replace a component from the top, how do you make sure you still got a good mechanical connection?

I basically create a U shape in the leads and push them in and flex them as best I can outwards, It's not perfect, but it works for me. I sometimes use a small tip of a screwdriver etc to get the lead to bend around the eyelet but it's best effort at that point. I can tell if it worked well or not if it's just loose there wobbling or if it tends to stand up on it's own.

Ideally you have a great connection, in the real world, I'm sure occasionally I've got more of a solder bridge in some of those joints. That's also why it's best to get shiny solder joints

~Phil

[erwin_ve]

If for maintainance you replace a component from the top, how do you make sure you still got a good mechanical connection?

I basically create a U shape in the leads and push them in and flex them as best I can outwards, It's not perfect, but it works for me. I sometimes use a small tip of a screwdriver etc to get the lead to bend around the eyelet but it's best effort at that point. I can tell if it worked well or not if it's just loose there wobbling or if it tends to stand up on it's own.

Ideally you have a great connection, in the real world, I'm sure occasionally I've got more of a solder bridge in some of those joints. That's also why it's best to get shiny solder joints

~Phil

Phil thanks for your reply. That was basically how I did this. Recently I abonded it. I had some crackling noise after putting some stress on the PI trimmer because my screwdriver stretched/bent the trimmer. After sucking away and cleaning the old solder and reflow of new solder it was gone.
It is giving me some serious thoughts on the reliabilty on parts(trimpots) that are not easy on the mechanical connection in a full eyelet built.

[pompeiisneaks]

Yeah I agree I've had more than one problem with trim pots an eyelets, they don't 'bend' well, and getting them to align well and stay was a nightmare, but I finally got it. I had to do 3 on that last ods build, on on FET and two on the board.

~Phil