Can an amateur refurb and update a KA-7100?
- Thread starter neevo
- Start date
neevo
Super Member
If I tried to run the amp with only one of them in the De3, De4, De17 and De18 spots (14V 0.5W) with a DBT in series could it cause any issues for the amp? Didn't look like the amp powered on, so I think I'm ok, just wanted to make sure it couldn't cause any major issues if it had turned on. FYI the relay didn't clink, however I will replace the diodes with 2 before I fire it up again.
Also to be clear, I need to join these diodes together (series) to make them sum 28V 1W?
https://i.ytimg.com/vi/m4XxUi8nqbg/maxresdefault.jpg
Also can you help recommend a decent filter cap for the Nichicon KW 6800uF/50v power caps I've got? Might as well add them to the order to spread out the shipping cost.
The KSD1616A isn't ideal, but I'd not place a special order to get something different. I generally use out-of-production Zetex ZTX1056A's for relay drivers, but otherwise I'll use the KSC2690AY if a NPN is called for.
Stacking zeners also stacks the tolerance. You're better off (in this instance) simply using a 27V 1W zener (much of electronics is a matter of 'close enuff').
neevo
Super Member
That's good to know EW. Are diodes generally built to a standard eg I don't need audio grade?
If so would this 27v 1w option from a local electronics store work? Would certainly keep the recap on track vs having to shelve the recap for a better alternative.
http://www.jaycar.com.au/27v-1n4750-1-watt-zener-diode/p/ZR1427
I might also ask about the transistor to see if they have the sturdier option, otherwise I might leave it as is for the moment.
If so would this 27v 1w option from a local electronics store work? Would certainly keep the recap on track vs having to shelve the recap for a better alternative.
http://www.jaycar.com.au/27v-1n4750-1-watt-zener-diode/p/ZR1427
I might also ask about the transistor to see if they have the sturdier option, otherwise I might leave it as is for the moment.
No, diodes don't have an 'audio grade' however in the case of zeners they do come in different percentage tolerances, usually 5% (common) and 2%, (not so common). If I replace a zener in a sensitive part of a circuit I will generally use a 2%, often described as a 'precision zener', everything else gets a 5%.
I hope this helps.
<<<<Also to be clear, I need to join these diodes together (series) to make them sum 28V 1W?>>>>>
Yes, you solder the zeners in series. There are some photos here, the ones at the top are dead links but scroll further down: http://audiokarma.org/forums/index.php?threads/soldering-diodes-in-series.489336/
However, if EW recommends a 27v zener then that's what you should use. Also, that's good to know about the Qe34 sub, I'll update my list. Having something more robust there for the long run makes a lot of sense.
Yes, you solder the zeners in series. There are some photos here, the ones at the top are dead links but scroll further down: http://audiokarma.org/forums/index.php?threads/soldering-diodes-in-series.489336/
However, if EW recommends a 27v zener then that's what you should use. Also, that's good to know about the Qe34 sub, I'll update my list. Having something more robust there for the long run makes a lot of sense.
hopjohn
Silver Face
I'll stand by EW's 2015 recommendation for Qe34. He can argue with his own recommendation if he wants to.
Joe Smith Jr
Member
What is the broken piece or pieces in post #16?
The post says it's a cap? With a ginormous lead like that?
What the heck is that?
Joe
The post says it's a cap? With a ginormous lead like that?
What the heck is that?
Joe
The only thing I don't like about the 2SC3902T is that the leads are thicker than 'standard' and can mean opening up the PC board holes to get it fitted. And the leads are tough bastards and are like bending rebar. It would work fine, however, and I've used them from time to time. But if I had something else on-hand that would do the job, I'd not place a special order to get a replacement.
There's 100's of viable candidates for a relay driver. It's not a terribly critical selection.
There's 100's of viable candidates for a relay driver. It's not a terribly critical selection.
neevo
Super Member
What specs should I be searching EW? If I can avoid a specific order from Mouser that would have me $28.
Other than searching for that part number I'm not sure what I would need.
There were some on the auction site but I wasn't sure if that might be a cheaper version or something down spec.
Other than searching for that part number I'm not sure what I would need.
There were some on the auction site but I wasn't sure if that might be a cheaper version or something down spec.
neevo
Super Member
Good news!
It turns out my DBT wasn't working because I had misplaced a wire in the bulb holder. Probably a good thing given I had the wrong diodes in the power board.
Picked up some 27v 1W diodes from Jaycar, wired them all in. Found a incandescent bulb in the cupboard under the stairs and was ready for a test.
60w bulb went bright, then down to a very faint glow. LED on amp was lit and relay clicked
Power board complete. Minus the trimmers which I have purchased some wire for to extend 2 legs. Will do the trimmers once the board is mostly back together.
It turns out my DBT wasn't working because I had misplaced a wire in the bulb holder. Probably a good thing given I had the wrong diodes in the power board.
Picked up some 27v 1W diodes from Jaycar, wired them all in. Found a incandescent bulb in the cupboard under the stairs and was ready for a test.
60w bulb went bright, then down to a very faint glow. LED on amp was lit and relay clicked
Power board complete. Minus the trimmers which I have purchased some wire for to extend 2 legs. Will do the trimmers once the board is mostly back together.
Similar threads
- Sticky
