Technics SU-V6 restoration and upgrades - anything for preventative maintenance?

leesonic

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I have a Technics SU-V6 on it's way here. I'm going to do my usual work on it : new caps, WIMA films in the signal path, removing and regreasing the outputs, new trimmers, that sort of thing. But I was wondering what else should I do do it, either as upgrades or preventative maintenance? I have a short list of things :

- OA90 diodes seem to have reputation for going bad. Maplin Electronics in the UK (very reputable) has them for £1.39 each (which is about $1.80). I can get these sent here for free, so should I just go ahead and swap them all out?

- OP amps. There's an NJM4559 in the phono stage and an AN6552 in the tone stage. Preliminary searching here on AK show OPA1612 and OPA2134 as suitable replacements, but I might be mistaken. Is it worth replacing these?

- I already have the six fusible resistors down for replacement. R651-654 100R, R655-656 330R.

Anything else I should be concerned about? Small signal transistors?

Lee.
 
I wouldn't worry about the diodes until they go bad. Maybe have a few on hand. As far as the opamps, install sockets and put ceramic bypass caps on each supply (keep the cap as close to the pin as possible, ground side doesn't matter). See which opamp you like the most. I prefer the OPA2134.
 
I wouldn't worry about the diodes until they go bad. Maybe have a few on hand. As far as the opamps, install sockets and put ceramic bypass caps on each supply (keep the cap as close to the pin as possible, ground side doesn't matter). See which opamp you like the most. I prefer the OPA2134.

I saw values of 10nF floating around, does that sound right for the supply bypass? I've also seen (and used) some 470uF caps on an opamp inside a Kenwood tuner. Any advantage of using these instead of (or as well as) the ceramic caps?

Can the 2134 be used to replace both the phono and tone control opamps?

Lee.
 
I saw values of 10nF floating around, does that sound right for the supply bypass? I've also seen (and used) some 470uF caps on an opamp inside a Kenwood tuner. Any advantage of using these instead of (or as well as) the ceramic caps?

Can the 2134 be used to replace both the phono and tone control opamps?

Lee.
0.1uF should be fine. As far as the larger caps, I don't know. It depends if there is already local decoupling with that size of cap. The ceramics are important for stabilization.
Short answer, yes, you can use it both places. I would still recommend looking at the circuit you are putting it in for loading and impedance and swapping opamps to see which ones you like best.
 
The tone circuit is fairly simple - I dropped a new opamp into the tone section on my V6 and it worked wonders. Be very careful with the phono board as it contains some JFETs - I havent yet auditioned mine but have heard others say that its great. The Technics fusibles dont usually give you any problems (unlike some sansui and other ones) I would leave these alone unless you have problems.
 
Well, it arrived, but very poorly packaged. I just contacted the seller (eBay) to see what the next step it. I mean, I can fix the insides, but I can't bash out a dented front panel. The front panel took a hit, and got pushed over the the right, which could be adjusted. They took the knobs off, probably to stop further damage, they were just rattling around in a plastic bag.

Technics SU-V6 shipping damage 01.jpg

Technics SU-V6 shipping damage 02.jpg

Technics SU-V6 shipping damage 03.jpg

Technics SU-V6 shipping damage 04.jpg

Technics SU-V6 shipping damage 05.jpg
 
Too bad about the cosmetics. Don't know what the shipper was thinking just using paper for insulation. Guess he was desperate to cash in on the over-exagerrated eBay shipping calculator
 
Maybe. I've been on that side of the deal where shipping ends up taking most of the meat off the bone. But a slightly larger box with a layer of Styrofoam would have worked. Styrofoam is a good absorber of impacts, that's why there's a big lump of it behind your front bumper cover.

Am I being crazy asking for a refund?
 
Not in my book. You paid for the thing without the damage. Would you have given the same amount in its current condition?
 
I agree - if that damage wasn't present or shown in the original description, then I'd ask for a return / refund as well. Like it or not, it's the seller who controls packing, and shipping method, so it's for them to dispute any shipping damage with their (sub-contracted) courier. It's not the buyer's responsibility.
 
Sorry to see the damage, those are nice amps. The last three items I've purchased on Ebay have arrived poorly packed and damaged. Takes a lot of fun out of the hobby
 
I'm seeing if I can work out a partial refund with the seller. They did write back last night and told me to send it back, but I wanted to try working on one of these.

Lee.
 
Mostly cosmetic.... those switches (selectors) remote steer the actual switches that are near the input jacks (better s/n)

Do check the pots thoroughly for damage/cracks... iirc these implicated the NFB on the power amp. - incl tone bypass sw.

The big issue with these amps are dirty selector switches (often affecting one or both channels)

As for power amp, check offset and bias as per manual.

The new class A light is probably blown too... these are 12viirc

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Preventitive - do look at main pcb for dry joints (regulators and drive/pre drive transistors are a place to look, as is associated resistors)

On mine I put 2SA1494 and 2SC3858 outputs, mainly in case of accidental speaker wire shorts... I've had a few ppl carelessly do this. (Cause a short)

Other than all of that, all should be fine.
 
If replacing the speaker relay - drop-in replacement is: Omron G4W-2212P

As per SVI2004A - I too replaced output transistors with a full set of Sanken 2SA1494's and 2SC3858's - due to the original right channel Toshiba's being shorted

The the SU-V6 is an easy amp to work on - with not too many Electrolytics to replace when recapping
 
OK, I started working on this over the weekend. The insides were pretty dusty, but nearly all of it came off with some compressed air. Here is the "before" picture :

Technics SU-V6 01.jpg

Here is the tone control board before and after. There really aren't that many caps to replace in this amp. I fitted a gold plated socket and replaced the 4558 op-amp with a 2134, adding caps to decouple the power supply rails on the back of the board.

Technics SU-V6 02.jpg

Technics SU-V6 03.jpg

Technics SU-V6 04.jpg

Before and after pics of the phono preamp board, which also has the regulated power supply for this and the tone board. There were a lot of caps with shrunken covers on here, probably due to the hot-running regulator transistors. I added some heatsinks to these. Op-amp was changed as above.

Technics SU-V6 05.jpg

Technics SU-V6 06.jpg

Cleaning up the glue on the power amp board. Underneath the main caps, it looked like one of them had been getting hot, there was evidence of heat burn on the board (arrowed). I wonder why? There were also a couple of hot-running resistors at the back (circled) that had been cooking the board. These go to the regulated supply, I will get some newer larger wattage ones, and mount them off the board.

Technics SU-V6 07.jpg

Lee.
 
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Lee - great to see that you have started and completed a couple of boards on your SU-V6 - do like the idea of bolting on small heatsinks on the regulator transistors of the input/phono EQ PCB - :thumbsup:
If changing out the trimmer-pots - would recommend Bourns 3296W - certainly made it easier to adjust spot-on - also went with UCC 10000u 63V (ESMH630VNN103MR50T) for the main PSU filter caps
Looking forward to seeing more of your great work on this amp
 
Those yellow circled ones are actually metal film resistors. I wouldn't change them, they're far superior to the usual carbon type alternatives.
 
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