Refurbishing a Technics SU-8080 - worth it and where are the gotchas?

Yes its a beast.

The crackling could be the relay but could as equally be a small signal transistor going south. The noise started on once the unit had got warmed up. You will need to sort this before doing a recap.

I will find the SM and refresh myself on what the issue could be.

See the "pre out / main in" sockets at the back? Pull the jumpers and run an RCA lead from the pre out to another amplifier. Then run a very low level sound source into the main in - under both of these tests the noise will only be present in one stage of the amplifier - let us know which test has the noise.
 
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I recall a friend bought one new back in the day, went over to have a few beverages and was impressed
with the amp but don't have the foggiest memory what else was being used.

Must have been the star of the group good luck bring it back.
 
Let us know you have done your testing of the seperate stages of the amplifier.

You actually have the 2SA798 "double transistors" at the input to your Main amp stage (TR301 & TR302). My guess is that these are the problems. They get noisy & fail with age. They look as attached. You could test these once they warm up with a short burst of freeze spray which will either make the noise better or worse - but will make it change.

These can be replaced with a pair of matched-hfe KSA992's bonded together for thermal bonding.

If you arent sure how to do this you may be best getting a tech to do it. Otherwise we can guide you thru the steps. You ideally need a component tester (ie a cheapo like this will work fine) soldering iron, solder, side-cutter pliers, heatshrink of the right size, and about 20 or so new KSA992s ordered from say Mouser.

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okay so i tried isolating the pre and the amp within the SU-8080 and guess what.... I can't reproduce the crackling in the right channel. I did tighten my speaker connectors for the right speaker in case it was a bad connection and although nothing seemed loose that no matter how hard or long I drove the bloody thing that all was working just fine. In fact it sounded quite amazing.

That being said, I think it is pretty safe to say that I can share my capacitor/components list here and get some feedback?

I'll still replace the speaker relay since it is such a PITA and I may even order the transistor set that slimecity has suggested just as a precaution.

My next question is then.... what should I do next?
 
OK - so its an intermittent fault....it will be back at some point.

I would replace the speaker relay and also the two 798's as a preventative measure. And then just do a full switch clean & recap.

Thats all I did on mine.
 
Do you know where I can find a replacement power switch knob ? Mine got all banged up so it would be nice to get one that is in decent shape.

Slimecity or ryuuoh are either one of you okay with reviewing my cap/transistor list when I finish compiling it? Plan to order everything from mouser.

Btw what relay do I order since I don’t know the specs of it?

Thanks
 
On the Protection and Main Amplifier Selector Board page of the service manual, you can see the footprint of the relay. It's 24 volts coil, and I see that 10 amps contact rating is the norm for this amp. Look for a printed circuit (pc) through hole solder pin relay that matches. These relays are getting harder to find. A few years ago I bought two relays from a shop on ebay called classic audio service, and got two relays branded "finder" that had the proper voltage, current rating and pinout.
The power switch cap on mine was replaced with a fairly ugly cap, but at least it was black. I've been toying with the idea of 3d printing one.
For caps, I went with what was appropriate, ie low leakage and non polar are going to be the special ones. I wouldn't obsess over low ESR these days, as Japanese caps are pretty good across the range of their caps in this regard.
 
Ah okay I gotcha. I better rip into that amp soon then it what you’re saying :). I actually really like the sound of this amp MORE than my Pioneer SX-3800. My SX-3800 sounds muted by comparison. Admittedly however, my SX-1050 receiver is still king in our home but the technics is absolutely a keeper for me.
 
I can share my Mouser cap list if you still need them. I recently did mine and it made a huge improvement.
TBH, it's not as refined and tube-like as my M2, but I still think it's a keeper and WELL worth your time. It is a bit clinical/forward, but better bass than my M2, honestly.

Not sure that it is a well known amp judging by the market price. Personally, I love the dual mono design, face plate and knobs, and overall balance of the controls.
I have the ST-8080 too and it just adds a touch of class color to the combo.

I plan to replace the speaker binding posts some day. The original design is horrible. Use heavy gauge speaker wire, or risk the wires pulling out.

Recap wasn't bad, but under the tone board was a bit touchy. Congrats and please keep us posted on the progress.
 
I can share my Mouser cap list if you still need them. I recently did mine and it made a huge improvement.
TBH, it's not as refined and tube-like as my M2, but I still think it's a keeper and WELL worth your time. It is a bit clinical/forward, but better bass than my M2, honestly.

Not sure that it is a well known amp judging by the market price. Personally, I love the dual mono design, face plate and knobs, and overall balance of the controls.
I have the ST-8080 too and it just adds a touch of class color to the combo.

I plan to replace the speaker binding posts some day. The original design is horrible. Use heavy gauge speaker wire, or risk the wires pulling out.

Recap wasn't bad, but under the tone board was a bit touchy. Congrats and please keep us posted on the progress.
Its been a while but yes, if you can share your list with me that would be immensely appreciated. I've been away from AK for a while but I'm back and ready to tackle some of the work needed to get this thing singing perfectly. Not sure if it actually needs a recap or not. No leaking caps anywhere but that bloody crackling is annoying after playing it for about 30 minutes or so...

Thanks.
 
If it's crackling, my money is on a transistor. I had a Marantz 2230 that had a horrible crackling noise and it turned out to be a preamp transistor.
 
Well I decided to go back and take a peek at the Technics again and give it a deep cleaning of all rotary selectors and those pesky push buttons with a triple treatment of Deoxit and “exercised” them for a good 100+ actuations and fired her up. Still had a bit of a cracking on the tape selector so I got into it again to clean it some more and I think my issues are completely resolved. Took a magnifying glass to the relay and no arcing marks at all on the contacts and they appear new still. Looks like the switches and buttons on the SU-8080 are a pain but with enough persistence I think I just spared myself a full rebuild for now.

Currently running the amp at decent levels for the next few hours to see if the problem has gone away or if it is just pure luck that it’s working perfectly now.
 
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Ah alas I finally managed to get the Technics to fail. After performing perfectly for a few weeks that the output finally has developed an AC hum which means the power supply filtering circuits are dried out and worn. So many amps to fix in the upcoming months...

The amp still sounds great but when there is silence I can so hear that AC hum....
 
I rebuilt an SU-8088 a few years back... very very well-built amp with potted transformer, etc. I recapped the whole beast. I see the 8080 has dual transformers, very nice. The amp was solid as a rock, but TOO neutral sounding for me... I just couldn't get excited about it, much as I wanted to... I couldn't seem to get it to bring music alive like some other amps. YMMV, I'm sure with some speakers it would excel.
 
I'm compiling and updated BOM list from Mouser to replace all electrolytics with PW series Nichicon caps but there are a few things I'm struggling with.
1. For the 4 main filter caps the original Panasonic caps (part #: ECET55R103Y) is no longer available. What is a suitable replacement for an exact fit?
2. For the electrolytics that are less than 4.7uF I was thinking of putting in WIMA stacked film caps since less electrolytics = better
3. For the non-polar caps can I also sub in film caps? My understanding is that film caps can be used for low uF values, are not polarity dependent (meaning it can be put in place of a polarized electrolytic) and can ALSO satisfy non-polar electrolytic requirements.
4. Are there any particular caps that I should focus on putting in Nichicon KL (low leakage) caps? I've rebuilt a few Pioneer receivers and Pioneer CLEARLY states that some caps MUST be low leakage ones.
5. Speaker relay - Any suggestions as to which one from Mouser would be a DIRECT fit? I've read that there are problems with the relay and should be refurbished or replaced since I"m already in there changing all the caps out.

Thanks!
 
First post Hi!

Stevescivic - reading your post with a lot of interest as I also have a Technics SU-8080 which I've actually owned for about 20 years but only recently realised just how good it is and worth restoring.

I'm about to carry out a similar restoration with mine and am following the advice and recommendations people are offering you with your project. My SU-8080 is fully operational at the moment, but I do worry how long it will last as it is full of dusty fluff and has had substandard repairs carried out when I first obtained it - it was used as a TV stand in a non-operational state for a long time before I got it for nothing...

Anyway, to get back on topic with your project, I've found the relay you are looking for on Digikey, but there are limited stock available, and these were found on the UK site. I read on another forum that the relay is marked HC2a-P-DC24V and after much research and studying datasheets, this relay is now obsolete. I believe it is a DPDT (form C) type relay (non-latching). However there is an equivalent HC2-HP-DC24V-F or HC2E-HP-DC24V-F (sealed amber) Panasonic relay which is in limited stock on Digikey.uk.

Hopefully this is of assistance to you, but please double check the specifications of the relay to ensure it is indeed suitable for your project - might be worth cross-checking with your own relay if it is the same or similar part number (printed on the actual component).

Look forward to reading the next update cheers!
 
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