Technics SU-8077 Rebuild

[Ed Dumas]

It's rather simple with the Technics double transistors, if it's 2SA you use the KSA992, if it's 2SC you use KSC1845.

It all seems so simple when you lay it out like that!

Nicely done btw, very neat!

Thank you. I have had a good teacher!

Also, I have the luxury of being able to take my time. The only person waiting on this completion is me. I find the work is fascinating, and is a good mental break from my day job, so I look forward to it.

 

[jeromach]

Yes, it is zen, doing this, if at least there is no other pressure than your own person being excited about seeing the result.

And yes, it seems simple, but I can assure you, it only is once you found out....

 

[Ed Dumas]

Surprised to hear how "out of whack" those readings are for a couple reasons. A: It's had very little use since the servicing it received. B: It still sounds really good! Perhaps the servicing was not as extensive as you were lead to believe...

I am amazed at how fast all the parts arrived! I ended up ordering from both Mouser and DigiKey as I could not find everything exactly right at either place. Oh well. The first box from Mouser arrived about 1:00 today (Friday) when I ordered the parts on Wednesday evening. As I was working away, the second one from DigiKey arrived. Very impressive, especially considering the vast distances travelled (Texas and Ontario to Vancouver!) and that there were no errors, except mine!

Well I got finished the largest two boards today. These are the ones that are under the big brace on the right side of the amp. They are just to the right of the screwdriver and heat sink in this photo, looking to the back of the amp.



No real issues, except I discovered an error in my order (my fault). When I was creating the parts list, I missed a decimal place and ending up ordering a pair of 1000uF 63v capacitors when they should have been 6.3v. Too large to fit, so I will have to re-order. At least I take some comfort that it was not a bad decision, so much as bad eyesight. Such is life! I will save the order until near the end in case I find any other screw-ups.

I found the work that the service shop did a couple of years back. I was kind of in ignorant bliss back then about this sort of thing, so I just paid the bill and got on with my stereo assembly. But, I can see now what cost so much, and I bet it was all in shop time in diagnosis. The part changed out was a cable attachment similar to this one in this photo (long steel box).



There is a cable that attaches to the open slots on top. Something was amiss in that box, as you can clearly see it was changed out. You can tell from the soldering on the back of the circuit board, and the great amount of rosin left behind from the soldering. Just like in your shop, Drew, I can well imagine that it was all about just trying to figure out what was wrong. If I remember right, one side was cutting out, and there must have been a short in this unit that caused that. Diagnostics for something like this must be tough. Just thought you might like to know...

 

[jeromach]

Your mistake... which reminds me, did you order a 22uF bipolar cap? If so, it should be 220 if I recall well that this mistake was in the 8088 manual.

Both Mouser and Digi-Key are very professional companies. Not the cheapest, but I guess in the end it is cheaper to buy at one or two places than to spend hours on finding out where things are cheaper. And save on freight of course.
Ah, talking about distances, when I order from either of them it mostly will be here in less than two days too. And then it has crossed an ocean.

The "long steel box" is a switch. If you'd want to do this rebuild thoroughly in fact you should take them apart and clean them internally. Some job! But it will for now and in the foreseeable future prevent irritatingly small channel dropouts and spending time with finding out in what exact position the knob should be to let the thing play smoothly for another ten minutes. But perhaps, it you did not have these kind of problems before, just some deoxit will keep the devil away for a while. My experience in this is mixed, sometimes deoxit works, sometimes it really is necessary to take them apart. If you'd decice to clean them, then let me know, so I can give you some guidance (but it will set you back in time another couple of hours).

 

[Ed Dumas]

Your mistake... which reminds me, did you order a 22uF bipolar cap? If so, it should be 220 if I recall well that this mistake was in the 8088 manual.

Yes, I did order a 22uF cap. Thanks for letting me know. I am curious how someone came to reason that the manual has an error in it. Not that I do not trust you, I am just curious how someone got there. These kinds of things must be really hard to figure out. I appreciate the heads up, though! I will include that one in the next order, too!

As for the switches (aka "long steel box") I think maybe I had better spend the time now. Now that I think back on this amp over its life time, I think that has been an issue. This amp originally belonged to my father. I had chosen it for him, along with the speakers I now have, in 1979. When he passed away it ended up coming back to me, and is now the center of my sound system. But looking back, I think I have taken it in for my father a few times for that very same problem - one channel cutting out. I vaguely remember some technician telling me about contacts wearing and such. That must have been this issue. If you don't mind, I should work on that now while I have it apart. Better now than later, and a couple of extra hours I can deal with during my Spring Break.

Ah, talking about distances, when I order from either of them it mostly will be here in less than two days too. And then it has crossed an ocean.

Positively amazing if you think about it. I have wondered, with another HiFi friend, if these companies do not use robotics to get the orders out the door so fast. As for cost, I am not worried. I ordered about 90 parts to replace on this 8088, and the bill was less than $200, including shipping. That is a pretty darn good average, considering that that also includes the expensive filter caps. I will happily pay another $20 or so in potential savings to get these things here that fast, as well as guarantee that there are no fake parts, which has been an issue with capacitors in the past. Well worth it, in my books! Paying someone to do all this work would easily reach one thousand dollars Canadian, or more!

Thanks for the heads up on the 220 uF cap!

 

[jeromach]

Ok, I took my notes from the archive and there is more....

C701 in the manual = bipolar 22uF/16V, it should be bipolar 220uF/16v

then C121 and C122 = 10uF/16V in the manual, these should be 100uF/16V

voltages of course may be higher, as long as it fits.

Does the small power lamp still work? You might replace that as well, while you're there.
Now some folks would say, replace it with a LED, but in this case NO, do not do that, since the FL meters are using the same current source. They will not or only faintly be working after such a lamp transplant.
The (wire) lamp is 7,5V 75mA. These kind of lamps might be unobtainium, so if you replace it, make one yourself from the old wires and a regular wire lamp and use heat shrink to cover the leads.
Compare old and new diameter of the lamps, so you can use the existing rubber fitting. A smaller new lamp might be an option, you then can glue that in the rubber fitting.

Now for the switches, congrats, wise decision. But that is quite a story that I will elaborate on later.

 

[Ed Dumas]

C121 and C122 = 10uF/16V in the manual, these should be 100uF/16V

Yes, I see in my own notes that I saw the discrepancy and chalked it up to someone else putting in the wrong cap during some previous work. So, I put in the 10uF caps as the manual says, and then forgot to ask you about it. Good thing you remembered. I will order those as well in that final order as well.

Yes, I think the lamp still works, but I should do that as well, I guess. Now that you bring that up, I do remember seeing some other forums on 7.5 volt lamps now bring replaced with 8v lamps. I will order something like that too. Sounds like not such a big job. Thanks!

 

[jeromach]

To follow up, how do I know about all these errors in the service manuals and all those dirty tricks these nasty audio buggers will do on me...., read the story.

Btw, coincidentally it's about cleaning switches too!

http://audiokarma.org/forums/index.php?threads/diy-70s-technics-switches-cleaning.613109/

 

[jeromach]

Paying someone to do all this work would easily reach one thousand dollars Canadian, or more!

Any international mover you can recommend me?

 

[Ed Dumas]

To follow up, how do I know about all these errors in the service manuals and all those dirty tricks these nasty audio buggers will do on me...., read the story.

Wow! Tons of stuff in there to read and digest. I ordered some of that Robbe Grease, and I expect it will take some time to get here because it is coming from England. I couldn't find any over here, and I was not sure about substitutes. We shall see.

Btw, coincidentally it's about cleaning switches too!

So, both ends of the cable needs to be done then? At the board and at the face plate, right?

Any international mover you can recommend me?

Moving to Canada?

 

[jeromach]

Wow! Tons of stuff in there to read and digest. I ordered some of that Robbe Grease, and I expect it will take some time to get here because it is coming from England. I couldn't find any over here, and I was not sure about substitutes. We shall see.

So, both ends of the cable needs to be done then? At the board and at the face plate, right?

Moving to Canada?

Well, with these kind of wages.... Besides, I'm fed up with Europe, time for a change

You could still get Robbe grease? Cool, I didn't know better than that the company declared bankruptcy some time ago. Can you give me the link?

All switches need to be taken out and cleaned, the cable does not really need greasing, unless it doesn't go smoothly.

 

[Ed Dumas]

You could still get Robbe grease? Cool, I didn't know better than that the company declared bankruptcy some time ago. Can you give me the link?

I ordered the grease from this place:

https://www.align-trex.co.uk/robbe-precision-grease-and-teflon-1-5532.html

They specialize in model planes, helicopters and drones, but I am pretty sure it is the same grease. When I went to their site, they said they had one in stock. Now the site says "Out of Stock" and "Add Backorder." So, I think I got the last one. In fact, it might be the last one in a lot of places. The downside is that England is a LONG way from the West Coast of Canada, and it might be a while before I see it.

In the meantime, I am almost done with the capacitors on the SU-8088. I have about 6 left, and then can turn my attention to the cleaning bits. The C4 cap, is this the one that is on the side of the amp for the ground? Looks like it to me, but there is no label.

 

[Ed Dumas]

Well, with these kind of wages.... Besides, I'm fed up with Europe, time for a change

Okay, given a beer or two, I could turn that one little statement into an entire evening discussion, easy! There are so many questions I would like to ask. If you make it out our way, maybe I will get a chance.

Speaking of which, where in Canada are you planning to move to? Is there a set date, or are you just beginning the process, or just wishing? I have found that so many people that come here are really not prepared for the vastness of our nation, or the large differences in culture across the land. From where I am, we can drive due East for 7 long, long days or more before we hit the ocean on the other side of Canada. And that does not even take into account the vastness of the North. If you are really coming out here, make sure you give some thought to the kind of life you want when you arrive, such as dense city, quieter suburbs, remote rural, cold north, flat prairie, mountainous West, history in the East, forests of BC, lakes of Manitoba, rain in Vancouver, snow in Ontario, bugs on the prairies, and so on. The differences are so great that it is worth trying to figure it out before you get here, to save some more moving costs afterwards.

 

[jeromach]

Apart from the bugs on the prairies all suggestions seem fine to me!

Well, it wasn't particularly serious, but, who knows.
I am Dutch, but in my old days I travelled a little across the world and I lived in Hungary and Cyprus.
All that was more than 10 years ago and to be honest, I miss it....

So, you might convince me to come over

Do they say that in Canada too, the grass is always greener at the neighbours'?
Yeah, I know there is more to it then just packing a container and move over.
Still, that's more or less what I did in Cyprus. I bought two cars in England, put them in a container together with some furniture etc., took a plane with the family and the cats and lived there for some 8 months or so.
Nice experience, but when I moved to Budapest I was quite relieved

 

[jeromach]

The C4 cap, is this the one that is on the side of the amp for the ground? Looks like it to me, but there is no label.

Probably, but I am not sure. The C004 is a 330uF 6,3V cap, so if the one on the side is the same, then most likely it is a

 

[Ed Dumas]

Well, it wasn't particularly serious, but, who knows.

Too bad. Our loss. We have our share of anti-immigration folks here, too, and I like to remind them that Canada is SERIOUSLY underpopulated. We have substantially more land than our neighbour to the South (30-40% more land?) and we have only 10% of their population. We seriously need more people to sustain our nation. Too many folks don't see that. Bring them on!

BTW I was serious about the bugs on the prairies. You know how most people are concerned about mosquitoes? Where I was born in Northern Alberta, our mosquitoes were carrying cattle away!

Check out this video. Makes you just love our Wet Coast, doesn't it?

 

[jeromach]

Meanwhile, in Holland;

I have my projects too....

And yes, seven switches... Ed, did you take yours out already?

Ah, this Technics SA-700 is ready now btw, I'm test driving it with Italian progressive rock over a Technics SL-10;

 

[Ed Dumas]

I was away a couple of days visiting my mother. Back now.

Today, I took out and cleaned the four switches that are located on the boards. I cannot mount them back in yet, as I am waiting on the Robbe's Miracle Grease coming from England. Might be a few days yet on that. I will get to the other 7 switches at the front plate probably tomorrow.

I found putting the switches in a small plastic container and doing an alcohol rinse first helped. It kept all the little pieces together, and the alcohol helped take the old grease away. Then I could do the more thorough scrub of the rails with chrome polish and keep the parts contained.



I found the first two switches that I did to be actually not bad at all. They looked to me like one had already been done, and maybe one had been replaced. So, I was figuring it would be a breeze and then I encountered the third and fourth switches. They required more scrubbing on the rails. Sigh... But, I think the alcohol helped melt the old dried grease.

While I have this amp apart, can I replace the speaker cable connectors to something that is more modern, like spade connectors? Might be kind of tough, though, trying to find something to fit onto the board in the same way. Do you know if anyone has done this before?

 

[Ed Dumas]

Ah, this Technics SA-700 is ready now...

Nice amp, BTW! My wife had one of those before we met.

 

[perokl]

Hello, thank you for this thread, I successfully recaped my SU-8077 according to your instructions, cleaned all switches, set all voltages and washed the old dust.
It sounds now like new!
Now I have one problem - the fl meter is very dimm. When I turn the volume up it begin a Little to flicker. I checked the wiring, it looks like it's OK.
Has anyone ever had such a problem?