KA-9100 restoration just maybe

[SicMan]

 

[Fredrik 1977]

Haha i like steve buscemi

 

[Fredrik 1977]

OK! got the caps! so i did the last part of the amp! had to pull the rectifierboards a third time, hopefully the last time!!!!




and a last picture of this masterpiece design



Amp itself Fully restored! been looking forward to this moment!!
had to snatch 11screws from a scrap receiver to cover all the missing ones.
Its got a new relay and all new electrolytics.
Also its got all new diodes and transistors on rectifier pcb's cleaned faceplate and knobs. Switches cleaned.
Oh then there was 2 new fuses and powercord.
Also professionally home made grill to cover damages in woodcasing.
And to top it off new thermalgrease. And a modified basspot






And i set the dc offset at 0V after beeing powered up for 40 min
hooked up speakers and cd. how does it sound you ask?
well....only two words come to mind and those are HOLY SHIT!
this is a very good sounding amplifier!
Ike&Tina - Proud Mary at around 2W



now i only have to mess with the woodcase a little.

 

[Fredrik 1977]

Thanks for the motivation! ...I think. Niiiiice job!

hope it helps! i can promise you wont be dissapointed once yours is finished!

I talked to the owner and he wanted to refurbish the woodcase himself..so i just fitted the grill i made earlier (they are on some picture back in the thread).
he will paint the grill once finished with the veener.




he´s heading this way as we speak...so once he is finished with the case i will get some pictures of the complete masterpiece pcb layout amp that sounds awesome.

i´ll post the pics once he is done. a before and after sort of thing.

 

[Goldie99]

Nice metalwork too - you're obviously a man of many talents !
Great job & great read - thanks.

 

[Fredrik 1977]

I think there's going to be one very pleased owner!

the look on his face indicated that you are right by 100%

 

[Fredrik 1977]

Nice metalwork too - you're obviously a man of many talents !
Great job & great read - thanks.

well thank you i like working with my hands, not the office type of guy. since i work at a mechanical workshop with some very cool machinery i do some "homework" when needed! made parts for you name it, airguns, cars, speakers, and yes amplifiers.

and you might have noticed....i love 70´s hifigear.
this stuff just gotta be fixed up to spec! non negotiable. future generations must have the chance to hear these classic pieces

 

[JimmyEJames]

Very nice Fredrik 1977
Very very nice
There is still hope
JJ

 

[Fredrik 1977]

and to all the KA-9100 owners out there....your lucky to have this piece of history on your hands! take care of it.
this amp really means business. when brought up to spec.

 

[Fredrik 1977]

this is the state she was in. no powercord, blown fuses and VAC selector set to 110V probably hooked up to 230VAC.
and wrong speaker relay.


She is now fit for fight to meet the coming 40years. after a refurbish and total recap.







well owner very happy, and so am i

i didnt get any pic of the grill i made. but it looks good to me in the pic´s

 

[1old_wizard]

Sweet !!!. What did you stain it with??

 

[Fredrik 1977]

Sweet !!!. What did you stain it with??

im not the owner of the amp, i restored the amp itself and made a grill to cover the damage in the wood cabinet, the owner himself did the sanding and whatnot on the wood. he mailed the final pictures.
he is happy as a sailor on relieve in bangkok ...it did sound awesome! im a little jealous

 

[Salty Guy]

Michael Percy Audio and Parts Connexion both sell the Nichicon 10,000uf 63V KG Gold solder lug caps (40mm x 80mm). The difference between the stock 12,000uf and replacing them with 10,000uf means nothing.

While that protection board is out, you'd be making a big mistake not to replace Qz1 and Qz2. Matter of fact, whenever I have this board out I replace ALL the semiconductors on it. All new diodes and transistors. It's just too difficult to remove to trust that you won't have an intermittent issue with a 40 year-old part.

QUESTION: Is it acceptable to upgrade the stock 12,000uf with 15,000uf replacements??? I've read on couple of the other KA9100 restoration threads that the Nichicon Gold Tune 15,000's were used likely do to the exact dimensions and fitment in the brackets.

TIA for any input here...

 

[gort69]

Is it acceptable to upgrade the stock 12,000uf with 15,000uf replacements???

Yes it is. It will be even "more" acceptable when - since the diode boards are separated from the filter caps - you upgrade the rectifier diodes with something a bit sturdier, such as UF5404. And even better yet if you address the increased load on the power switch by either bridging both halves together and/or adding a relay or a triac.

I've read on couple of the other KA9100 restoration threads that the Nichicon Gold Tune 15,000's were used likely do to the exact dimensions and fitment in the brackets.

True. But that luxury is kind of expensive. Last I checked those were about 25 ea plus shipping. There are cheaper options, but they require a bit of creativity.

 

[Salty Guy]

Yes it is. It will be even "more" acceptable when - since the diode boards are separated from the filter caps - you upgrade the rectifier diodes with something a bit sturdier, such as UF5404. And even better yet if you address the increased load on the power switch by either bridging both halves together and/or adding a relay or a triac.



True. But that luxury is kind of expensive. Last I checked those were about 25 ea plus shipping. There are cheaper options, but they require a bit of creativity.

My KA 9100 was gifted to me by brother in law for helping him move all his furniture from one house to another. Being a gift, and because I'm building (hopefully) a high quality vintage hifi listening system around it, I don't mind the expensive Gold Tune cap option. I've purchased a minty KP-9010 and an already serviced KT-7500 to marry to my KA-9100. I'm excited because I've read good things about this amp phone stage. Looking forward to getting it this tank of an amp up and running so I can begin to experiment with difference between a MC and a HOMC cartridge. Plan to research any phono stage mods to help here.

Honestly, I think it's way above my skill level, but I'm enjoying the research and hopefully one day can make it happen. I suspect the power relay is fried on this amp, so the Triac route is likely in it's future. The main filter caps upgrade and rectifier board maintenance are what I'm currently researching. So far everything I've seen suggests this amp is not a learner project. At this point I've only popped the hood a couple times and read every thread I can find. By far my strongest skill is in clicking the "But It Now" button. HaHaHa

I appreciate the response Sir.

 

[Semanon]

As noted, increasing the value of the filter caps should cause no problem. There may be additional inrush current that could strain the power switch, so a relay or triac could be added to lower the strain. It seems power switch failure has not been an issue on the KA-9100, buy ymmv.