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This TRIO-KA 9900 has been sleeping for 10 years! Let's wake her up!!

morfeora said:
The best thing you can do regarding the cables is to replace them with new, a bit of work but regarding.
The D1 is a diode that goes attached to the heat sink, reference STV-4H discontinued:
View attachment 1899601

"The only real substitute for a STV-4H diode is four 1N4004 diodes in series (or four UF4004 diodes)." Says EcoWars here:
https://audiokarma.org/forums/index...ubstitution-on-a-sx-838.741918/#post-10055673

Here is how he made them to be able to install them the same way as originals:
https://audiokarma.org/forums/index...v-3h-and-4h-diodes.279530/page-2#post-3446343

You will have to check also the drivers Q1 and Q2, from your pictures doesn't look like the originals. They can be replaced with the Sanyo 2SA1011 2SC2344 currently available in Bdent:
https://www.bdent.com/2sc2344-sanyo-audio-power-transistor.html
https://www.bdent.com/2sa1011-sanyo-audio-power-transistor.html

I just helped a friend in my city to restore his, amp also a KA-907 and we used these transistors. Worked pretty well. For my amplifier I used Toshiba 2SC4793 & 2SA1837, but they were a gift from our fellow member @Bratwurst7s as they are not available.

Going backwards in the amp, in the pre-driver section X00-2010-10 (B), also check Q15 to Q20, there is a big chance some of them are bad. You can replace them with Sanken 2SA1859/1859A & 2SC4883/4883A (you can find them in Digikey). This also done in my friend amp, without problems.

Good look in your restoration @KA907nKA9900, to restore mine toke me 4 months and also importing all the parts, so be patience :)
Cheers!
Click to expand...

Re-reading this and responding a second time.

Lots of gems in this post.

Thanks for being so detailed.

I wish I had come here as soon as my amplifier died. This forum kept showing up in my searches back then, but my thought then was raising the money to ship 25kg to @EchoWars and back....that is quite a sum...and so I never got around to do this

In the meantime I learnt a lot about electronics to be comfortable enough to play with it and attempt this restoration at much less cost to me and with the great satisfaction of doing it myself

But better late than never.

Thanks again.

I am budgeting 4 to 6 months to get everything back in order
 
reddish75 said:
A good idea of what to expect. Replacing those power supply caps looks a massive job in itself and looking at the photos it could be littered with black flag caps.

http://www.cdkands.com/ka907_1.html
Click to expand...

I see in that article, the author also picks up on the sloppy component installs like I mentioned before. There sure are a lot of messy things in that amp that I would need to straighten out, if it were mine lol.
 
reddish75 said:
Chem-wik desoldering braid is the only thing I use on vintage amplifiers, especially those which have already been worked on 2mm should do the trick. Desoldering pumps? I use those on output transistor pads where the board can take some punishment.

Solder stations? Look on ebay for a good used Weller or metcal. Dont forget tips.
Click to expand...

Is this your recommendation?
https://www.amazon.com/Chemtronics-Desoldering-Braid-Chem-Wik-10-50L/dp/B0019V5MAC

Are you advising against the use of desoldering pumps? Except on output transistor pads? What are output transistor pads? Please excuse my ignorance.

On the soldering stations, I will send you a PM with some links to options so you can advice me on the same
 
KA907nKA9900 said:
Is this your recommendation?
https://www.amazon.com/Chemtronics-Desoldering-Braid-Chem-Wik-10-50L/dp/B0019V5MAC

Are you advising against the use of desoldering pumps? Except on output transistor pads? What are output transistor pads? Please excuse my ignorance.
Click to expand...

This is what I use 2mm in width,

https://www.ebay.co.uk/itm/15m-Reel...250531&hash=item3f65b40f1c:g:4xMAAMXQNOZRCo6h

The link you posted is 2.5mm this doesn't seem a lot but its all about heating the braid quick enough to get it to suck the solder up and not ruin the solder pad.

With desoldering pumps they have their uses, for me not in vintage gear where the pcb's are generally more fragile than modern stuff. Output transistor pads I referred to are physically larger solder pads where larger component leads (output transistors in this case) solder too, these can typically take more heat from an iron so using a desoldering pump here rarely causes damage.
 
reddish75 said:
This is what I use 2mm in width,

https://www.ebay.co.uk/itm/15m-Reel...250531&hash=item3f65b40f1c:g:4xMAAMXQNOZRCo6h

The link you posted is 2.5mm this doesn't seem a lot but its all about heating the braid quick enough to get it to suck the solder up and not ruin the solder pad.

With desoldering pumps they have their uses, for me not in vintage gear where the pcb's are generally more fragile than modern stuff. Output transistor pads I referred to are physically larger solder pads where larger component leads (output transistors in this case) solder too, these can typically take more heat from an iron so using a desoldering pump here rarely causes damage.
Click to expand...
Thanks very much for the clarification/caution in the above
 
I am compiling a final shopping list from all the suggestions scattered across the 6 pages that make up this thread, hence the questions
 
rickl said:
This is exactly what I have and use.
Click to expand...
Thanks so much.

I've watched their video on YouTube.

I have never seen a repair man locally use that.

I've seen soldering stations but more commonly soldering irons.

I do very much appreciate the fact that I have been introduced to best practices and not just a hack of a repair.

This thread should be helpful to anyone with a Trio KA-9900 since such comprehensive repair threads are rare very much unlike the Kenwood KA-907.

Thanks again everyone whose contributed so far
 
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