SE/30 solder pad-problems while capacitor exchange

[retrofreak83]

Hi there,

I am currently recapping a SE/30. Unfortunately, some solder pads (and their environment) are completely gone away due to the leaked capacitors.

So I need to know where the caps C10, C9 and C6 can be connected alternatively.

As I am surely not the first one with this problem, I wonder if someone can provide me this information?

 

[phreakout]

Retrofreak83,

C6's positive polarity pad links up to Pin #7 on UB11; that's one of the Sound Chips.

C6's negative polarity pad links up with several components on the underside of the logic board. Most of the parts involved are C28-C81 (ceramic capacitors), R3-R43 (resistors) and all of the single leg connections (left side, not the two legs on the right side) of D4-D19 (diodes or transistors). Basically, what appears as a grid of traces/contacts on the underside of the logic board, any spot or component whose pad "beeps" during a continuity test will work fine for C6's negative pad.

C9's positive polarity pad again links up with the above C6's negative pad and Pin #1 on J12. By the way, you can tie in C6's negative pad with Pin #1 on J12, if you like. J12 is the clear white plastic 14-pin connector below C8-C10 on the top side of the logic board.

C9's negative polarity pad links up with Pin #7 on J12.

C10's positive polarity pad links up with one side of L17 and L11 (inductors) and Pin #14 on J12.

What I would do is use a digital multimeter that has an included "continuity tester", so you can trace out and verify what contacts will "beep", or indicate that they are tied in on the same circuit wiring. You can use either small (24 gauge) insulated non-braided wire or enamel-coated magnet wire (24-28 gauge) wire, like the kind used to wind torroids or loudspeaker wire coils. Just make sure it is "enamel-coated"; you don't want to short anything else out. You can solder the new wire to a contact located underneath the board and run the wire through the holes on the sides of the logic board. Then, either tape the wires down using blue painter's tape or hot-glue them in place to the tops of any square chips.

Good luck, have fun and report back on your success, failures or any concerns you may have.

73s de Phreakout. :rambo:

 

[JDW]

Ditto the Continuity-checker suggestion. Never recap a board without one, good traces or bad.

 

[retrofreak83]

Here we go again,

today I finished the repair, but now I got the "A Bright Horizontal Line in the Black Monitor"-symptom.

The HD starts, I hear some knicking out of the speaker but only the bright line appears.

As of the suggested solutions here

http://www.biwa.ne.jp/~shamada/fullmac/repairEng.html and the fact that I soldered my patch cables onto P1, is it possible that I P1 is the problem and I have to resolder it?

Or is it possible that not all of the recapped capacitors work like they should?

retrofreak

 

[JDW]

I got the "A Bright Horizontal Line in the Black Monitor"-symptom.

But is that white, vertical line on your CRT really 5mm in thickness? If so, then the problem lies within the Analog Board, not the logic board that you recapped. And if the Analog Board, it could be P1 or C15 or L2.

But if that white, vertical line on your CRT is about 1mm in thickness, then your problem is still on the Analog Board (not the logic board you recapped), and you need to focus your attention on resistor R19.

 

[phreakout]

JDW, it's a horizontal line, not vertical.

retrofreak83, I would look at possibly the second solution to your symptom on the SE/30 Repair Mac site; and that would be the Vertical Sweep IC at U2 (TDA1170A, 12-pin). If you would like a replacement, I've got one. I encountered the same problem on my SE-turned-SE/30's analog board. I tried replacing that IC, but the problem still existed. Eventually, I just replaced the analog board and all was good. But anyway, it is a good used part if you'd like to try replacing your original part. Send me a PM (private message) if you're interested.

I doubt the caps are the problem. The only thing to double-check is that all the caps were installed with the brown line side at the positive pad for each capacitor location (C1, C3 through C10, C12 and C13). Or even redo the soldering at each cap to rule out any bridging or shorts.

73s de Phreakout. :rambo: