Kenwood KR9600 dc offset... adjustment?

[eiraved]

A complete recap of the KR9600 is a challenge, even for an experienced pro.

 

[Anonky]

A complete recap of the KR9600 is a challenge, even for an experienced pro.

Forgive my ignorance: but what is the difficulty with it? Desoldering and replacing them doesn’t sound that complicated. Time consuming yes, but what am I not following? Appreciate the advice

 

[spark1]

If you go forward, keep a log of each component removed, with its part number (eg C32, TR04, etc), part description (eg 100uf/50V cap, 2SC458 transistor), orientation info, and a description of the replacement part (eg Nichicon UKL, 100uf/50V). Organize this info by board/section.

Work on and finish one board or section at a time. Take plenty of pics beforehand showing wiring connections, etc, and both pics and notes regarding disassembly process. Keep screws, clips, washers etc together, organized by board and section (eg power supply board, bottom cover, etc.). Divvy up all of the new components by board/section, setting aside all but those pertinent to the board/section being worked on.

After each board or section is completed, turn unit up on a DBT to assure no shorts, and then play-test on full power to identify any audible problems.

If you do not replace variable resistors, test them before using them as part any adjustment process.

Be 100% sure of the pin-out of any replacement transistors and of the transistors being replaced. Then check/confirm again!

 

[spark1]

Access is difficult, and a good rebuild involves more than just cap replacement.

There are lots of threads about 9600 restoration here at AK. Here is a succinct one:

https://audiokarma.org/forums/index.php?threads/kenwood-kr-9600-opinions.476368/

 

[Anonky]

Access is difficult, and a good rebuild involves more than just cap replacement.

I see. I’m in the process of finding the right workbench to set up a solder station on then I’m going to assess where to go from there. I’m tempted to just fix the offset and let it ride but considering the parts in this unit that are unobtanium I am worried shortly after some regular use, something would fail and fry the trio packs or something to that effect. Outside of recap, the triac switch mod looks within my abilities too and is the only mod I wish to pursue at this time.

The boards on this look easier to access than the pioneer qx949 I’m battling what to do with, so I feel like this is a better one to try servicing first. I will take your advice and be very methodical about it if I proceed. Just can’t stomach a $500+ bill from a shop, and I’d like to learn this skill so that I can continue to restore these units.

 

[Anonky]

Quoted: "Just can’t stomach a $500+ bill from a shop, and I’d like to learn this skill so that I can continue to restore these units."

My response is more a generic one and not directed your quote, but it looked like a good segue for my thoughts on this subject.

When you get immersed in this hobby, you'll quickly understand why shops charge what appear to be exorbitant rates. Usually, when someone posts an exorbitant rate, the EE experienced will jump in and say "That's too much!". Yeah but ...that's because they have experience and know exactly where to look for the issue and have the skills to fix it. Experience/education doesn't come cheap and neither does a brick and mortar lease. As an anecdote, I can earn more per hour at In & Out Burger than I can performing restorations ...seriously. But money is not why I do it.

I think it's great you've decided to embark upon this hobby yourself. As @SicMan told me early on -- something along the lines of -- you won't soon forget this after you get it up and running. New skills breed confidence.

Relative to your query regarding buying a cap kit from the auction site...you'll learn more if you order them yourself. It'll force you to reference what's already on the boards. The more you see it, the more familiar and comfortable you'll feel when you repair it.

With regard to my quote about the charge, I didn’t mean that in a sense that I do not value the work they do. I understand the time it takes both in present and from past experience. I just would rather keep that cost to a minimum and pick up the skill myself. Learn something new! Sounds fun.

 

[eiraved]

I see. I’m in the process of finding the right workbench to set up a solder station on then I’m going to assess where to go from there. I’m tempted to just fix the offset and let it ride but considering the parts in this unit that are unobtanium I am worried shortly after some regular use, something would fail and fry the trio packs or something to that effect. Outside of recap, the triac switch mod looks within my abilities too and is the only mod I wish to pursue at this time.

The boards on this look easier to access than the pioneer qx949 I’m battling what to do with, so I feel like this is a better one to try servicing first. I will take your advice and be very methodical about it if I proceed. Just can’t stomach a $500+ bill from a shop, and I’d like to learn this skill so that I can continue to restore these units.

You'll soon find that a full recap/resto of a KR9600 is close to what you encountered with the Pioneer. @spark1 has given a great step by step approach to follow on the restoration process on post #26.

 

[GOYA]

The TA200W power packs are not fragile devices. I have seen one survive shorting the output to ground. (Don't ask how I know this) But undoubtedly, they are not bulletproof and they are indeed pricey and not easily available. That being said, I would discourage using the KR-9600 as a unit to learn on. Surely you can find a lesser amp or receiver to gain confidence and skill in working on electronics.
That being said, whenever you DO work on (or have someone work on) the 9600 power amp boards, make sure to replace the input capacitors (Ce2 and Ce13) with a single film capacitor of high quality. See here: https://audiokarma.org/forums/index.php?threads/kenwood-kr-9600-my-next-big-project.715070/page-2