Lifting Board For Component Replacement. 1971 Super Reverb

[keithb7]

Hi folks. I had a bit of a theory thought this morning. I have been servicing my 1971 Super Reverb. Changed all the tone circuit coupling caps, power supply caps, bias caps, and the RCA jacks. The
tremolo roach too. How do the pros do it? Is there any need to lift the board on this 71? I did not see any wires going under the main board. I did lift off the power section board under the dog house when
I did those caps , but not for any others on the main board. I simply heated up the joint, pulled up the old component leads, trimmed the new component leads, reheated the joint and pushed in
the new capacitor lead. Reflowed the hole and everything looks good. From the top side. I cannot see the bottom of the board, as I did not remove it. In earlier tweed amps I built there were
leads on the bottom side of the board. I don't believe there are any under the board on my 71. Am I correct here? Am I right to assume the board should be lifted on earlier circuits to ensure
any bottom wires don't become displaced when heating joints, yet not necessary on later models like my 71?

Some joints on my 71 have four or more leads going into 1 hole. It can be tight when trying to push in a new component again, after puling the old one out. What do you do to ease
installation in a crowded hole? I have been using longer needle nose pliers. Seems to work. Here is my 71 board for reference, before I changed any components.

The board on this one seems to be a 2 piece board. Can I assume the bottom board piece is solid and covers up all the connections so they do not potentially touch the chassis? The board does not
seem elevated. In the end, after I did the work, the amp sounds great and works fine. Thanks in advance for your replies. I am always learning more here every day.

[Jazz P Bass]

My answer: Yes to all of the above.

[Mick Bailey]

You've got it.

Boards with wires running underneath just need a little extra care. Sometimes a little pressure on the board can help to keep the wire in place, or wedge something underneath. I can't think of a situation offhand where I've needed to lift a board for regular maintenance or repair work.

[Tom Phillips]

…I simply heated up the joint, pulled up the old component leads, trimmed the new component leads, reheated the joint and pushed in the new capacitor lead. Reflowed the hole and everything looks good…

Better practice is to suck out the old solder and replace with new solder after the component leads are all back in place. The solder flux did its job when the original joint was made 45 years ago. It’s time to use new rosin core solder during your repair to produce a much better and higher reliability joint than the old heat & stab procedure will produce.

Yes. I know that heat & stab is common practice and it does seem to work. It’s a fast way to do experimenting too. However, when it is used for a final deliverable there is a much higher probability of problems down the line. I have personally fixed a lot of amps where the only problems were caused by poor soldering during previous repair work.

[52 Bill]

The only times that I have had problems with removing parts from the fiberboard is when the wire lead from an electrolytic cap was used as a jumper to another solder point or sometimes used as the grounding lead to the chassis. This is usually only found in the older amps.

The only way to deal with those cases is to clip the component lead above the board and hope that there will be enough space to fit an additional lead through the grommet.

[Justin Thomas]

Generally Fender would bend the wire over the eyelet to help keep it in place, at least on the BFs I've worked on. Anything is possible for later SFs though. I rarely if ever have to lift the main board except for as Tom described - solder blobs forming under eyelets and leaking out and shorting or rolling loose. I always empty the eyelet and start fresh. And it's amazing how much solder will fit in an eyelet, or how many leads will fit in an empty eyelet...

Two things I do to save eyelet space: I do not increase resistor wattage just because, unless I know it's cooking from excess current. And if I'm replacing an electrolytic cathode bypass cap, I will neatly solder the resistor around the legs of the cap so I only have to fit the cap lead in. You can get pretty creative sometimes... I have seen that F&T and a couple other companies are making the 25/25@25 caps with a single ground, just like the old Mallories. But they're pricey compare to two regular caps, so I don't use them. Just an option. Well, 3 things - I don't use Orange Drops. Them's leads is too fat.

Justin

[keithb7]

Great responses guys. Thanks for your comments. I will suck the joints dry in any future repairs, then refill with today's solder. I am learning as I go. All my amps seem to be running fine now, so darn it, I have nothing to work on for a while. I do quite enjoy tinkering. I keep swapping out pick ups and pots, switches in my guitars trying new things to satisfy my want to be working on electronics. Time to run another add on the local Craigslist for amp repairs. LOL.