| Author | Message | ||
| Rory Coupland (bigjilm) Username: bigjilm Registered: 06-2013 |
Hi Im rusty on my schematics, help needed. I am trying to decipher the DB-2 board on a 2275-130 (specifically which of the 5x 20uf capacitors are which: C34,35,36,42,43). On the board I see two chips in their large heatsinks, and one small 8-pin "IC-8 LMM58" but I cannot apply / see an 8-pin symbol on the schematic, or indeed see the 2 chips either. Very strange: Im tearing my hair out trying to match my caps to C numbers you see.  Many thanks, RC | ||
| Rory Coupland (bigjilm) Username: bigjilm Registered: 06-2013 |
The DB-2 "driver board" if you divide above diagram into quarters is in the TOP RHS 1/4. | ||
| Mike Kaus (mm210) Username: mm210 Registered: 05-2006 |
That's LM1458 and the IC is BOTH of those little triangle. That's the two halves of the dual op amp. If you look, they are numbered and then add in the +16v and the -16 volt contacts and you get 8. If you look, they are both numbered IC8. Mike. | ||
| Rory Coupland (bigjilm) Username: bigjilm Registered: 06-2013 |
Aha.. I was so confused about where pins 4 and 8 were I thought it must be two of godonlyknows what else! Ok: so looking at the dual opamp in the board, it has a 'dip' in one end. Where is pin 1 and pin 5 inrelation to this 'dip'? Im getting closer to ID'ing these goddam caps!! my soldering iron's been sitting waiting to pounce for 3 days, old 5 caps removed and new ones ready. So close! thanks, rc | ||
| Mike Kaus (mm210) Username: mm210 Registered: 05-2006 |
Here's the pinout of a 1458  | ||
| Rory Coupland (bigjilm) Username: bigjilm Registered: 06-2013 |
Ok great- now I can try and find these damn two caps that -on the schematic- suggest to me, a 'pair' ie C35 and C36 (that join to pins 1 and 7 of the 1458. Are these the two you referred to as the 'driver pair' you mentioned Mike? these two Ive been trying to locate for days now. | ||
| Christophe (vignau) Username: vignau Registered: 06-2011 |
You can change this LM 1458 dual OP. It is VERY cheap ( 0.6 ?). I spent 1 year finding a trouble in my 2275-130, this OP was in short and every things was a mess, and very difficult to diagnose. |
Tue, 03/25/2014 - 09:54
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