Technics amplifer thermal compound okay for power IC

[MaccAu]

Hi

I got a second SU-G50, as i messed my other one up. This second one is dusty with some grime. I plain to clean it with IPA, fit new grease compound, oil the fan motor.

I have some left over in a small jar Wakefield 120-2 thermal compound. I used it on my SU-V8. Mfg date is 041114, so i hope its not too old, looks fine to me upon looking at it.

Would it be okay to use on an amplifer IC on the heatsink?

As for the fan motor, I was thinking of some silicone oil?

Thanks in Advance Sam

http://www.wakefield-vette.com/reso.../thermal-management-accessories-wakefield.pdf

 

[Ian Finch]

Any goop thin enough to spread evenly to all points as you tighten the screws should be fine. Some types, on standing, separate into their component oil and powdered alumina so stir or squeeze the tube a lot to remix but be very careful to prevent dust particles, grit etc. getting into the compound and preventing an ideal fit of the surfaces. The idea is actually to bring them into closest contact, the compound only filling voids due to imperfect flatness. It's nowhere near as good as the metal at heat transfer, so less is best, with only a small bead of excess showing around the edge.

Good luck, BTW, with any Technics Hybrid repair - replacement modules are often fakes or low grade refurbs.

Never use silicone oil near motors or contacts. It's not for bearing lubrication and the further away from electronics the better, really. You can use any mineral oils but those bearings will be worn if they need oil, so a general purpose oil say, ≥ 30 SAE might suit. A new fan may be the right choice though.

 

[Welcome]

Also replace that relay. Those DEC parts with tape on top tend to go REAL bad.

 

[MaccAu]

Any goop thin enough to spread evenly to all points as you tighten the screws should be fine. Some types, on standing, separate into their component oil and powdered alumina so stir or squeeze the tube a lot to remix but be very careful to prevent dust particles, grit etc. getting into the compound and preventing an ideal fit of the surfaces. The idea is actually to bring them into closest contact, the compound only filling voids due to imperfect flatness. It's nowhere near as good as the metal at heat transfer, so less is best, with only a small bead of excess showing around the edge.

Good luck, BTW, with any Technics Hybrid repair - replacement modules are often fakes or low grade refurbs.

Never use silicone oil near motors or contacts. It's not for bearing lubrication and the further away from electronics the better, really. You can use any mineral oils but those bearings will be worn if they need oil, so a general purpose oil say, ≥ 30 SAE might suit. A new fan may be the right choice though.

Hi Ian
Thank you for the reply and help.
I will use just enough, noticed factory setup there was a fair bit of it showing around the top and bottom, down onto the board. I think too much interferes with heat transfer. I;ll give the amp a complete clean out, before install IC.

The Technics Hybrid is the original, it was a one owner amp, i had to fix dry joints in it when I got it, was very dusty with no display. I plain to give her a make over. The other Technics SU-G50 will be parts, including another hybrid IC, volume pots, relay etc.

The motor is well secured and i looked no dust, and I think its fine, though would u mean singer oil?

My friend told me of a better fan -Mabuchi RF310T-11400 5.9v ? maybe at WES, not sure Element14 would have it

Also replace that relay. Those DEC parts with tape on top tend to go REAL bad.

Hi Welcome thanks for the reply and help
Yes, actually i had one go in the other G50 amp and used an old 1984 V4X relay, not a DEC brand, maybe i should change the DEC in this one? 24vdc

 

[Ian Finch]

Singer oil is thin, 20 SAE unless it's changed recently. The synthetic oil used in engines is around 40 SAE. The oil in automotive differential gears is about 90 SAE. 'lots of places to find a few drops of machine oil but the choice is yours.

If you can remove the case on the relay, wiping the contacts when lightly clenched together, with small strips of card soaked in IPA slipped several times between them, works wonders unless there is severe pitting of the surfaces. Try prising the bottom lip of the cover away from the base moulding on either side with an inverted flathead nail or hooked steel wire. If it's actually bonded, just replace as recommended by Welcome - there will be several drop-in replacement types out there but DEC is no more. Check pin spacings of this, for example: http://www.altronics.com.au/p/s4195d-8a-24vdc-dpdt-pcb-mount-relay/

 

[MaccAu]

Singer oil is thin, 20 SAE unless it's changed recently. The synthetic oil used in engines is around 40 SAE. The oil in automotive differential gears is about 90 SAE. 'lots of places to find a few drops of machine oil but the choice is yours.

If you can remove the case on the relay, wiping the contacts when lightly clenched together, with small strips of card soaked in IPA slipped several times between them, works wonders unless there is severe pitting of the surfaces. Try prising the bottom lip of the cover away from the base moulding on either side with an inverted flathead nail or hooked steel wire. If it's actually bonded, just replace as recommended by Welcome - there will be several drop-in replacement types out there but DEC is no more. Check pin spacings of this, for example: http://www.altronics.com.au/p/s4195d-8a-24vdc-dpdt-pcb-mount-relay/

Hi Ian
Thanks again for the help and link.
My brothers might have oil like that as they do their own repairs on the cars.

Since the pcb is grimy (not the clean pcb in the photo), i shall check the relayand clean it carefully.
I found a part with the spacings from the dec website same pins same distance.
[IMGDEAD]http://i68.tinypic.com/5vrbyr.jpg[/IMGDEAD]

 

[Ian Finch]

Yep, standard like the Altronics type pic. but only one set of contacts. Omron will make a decent unit anyway if you prefer a new replacement. This looks just right for the job, with good current rating: G2RG2A424DC - OMRON ELECTRONIC COMPONENTS - General Purpose Relay, G2R Series, Power, Non Latching, DPST-NO, 24 VDC, 8 A | element14 Australia

 

[MaccAu]

Hi Ian,
Thanks for the link, I shall get one as a spare..

I redid the grease, appears to be a gap, between IC and heatsink, it was like that with the factory one in the above pic with lots more grease

Mine , i hope isnt too little
[IMGDEAD]http://i67.tinypic.com/1495vk6.jpg[/IMGDEAD]

 

[Ian Finch]

Assuming some of the white grease was there before mounting, you seem to be a bit light on compound this time. Pull it off squarely, without sliding about and smearing, then inspect for voids. Add a little more along the centre line, closest to where it may have been lacking and refit.

The "bead" I mentioned is a small excess - a witness to full coverage but I don't see one in your pic.

 

[MaccAu]

Hi Ian,

When I fitted the IC there was a thin layer of white covering it, but maybe too thin, the white grease you see in the middle is the new grease, i completely cleaned the heatsink.

Maybe its best i fit it again with some grease. I ran if from 3 -5 at volume 2, very little heat, though its cooler this time of year.

Initially it was working on one channel and I thought darn I shouldve changed the relay but i had just added a pair of cheap bananas on the cheap Technics speakers i am using to test, so maybe the fault was with the speaker, has been perfect.

? worth taking off to check the grease? i dont want to have too little. looking over it i see only some white.

 

[Ian Finch]

I would nip it up straight after a hot session and see if there is any ooze as you do so. If not, better spring it off the heatsink and inject a little more as suggested.

 

[MaccAu]

Thanks Ian

After a run, unscrew the IC and see if there is any grease missing, and if there is, touch it up a little more, seems more on a certain side of the IC other side is good.

 

[MaccAu]

Hi Ian

IC is good
though upon start up there is no sound on one speaker but adjusting volume or bass seems to bring it around?

Does this sound like a relay?

 

[Ian Finch]

Hi
I've known relays to go bad, losing contact intermittently or even completely because of dirty, pitted surfaces and that's why they need cleaning or replacement. It won't happen with a new or clean relay and to check operation when there is music playing and it has an opaque cover, you can use a "stethoscope" to listen when the contacts close to hear if that coincides with restoring sound or not. A crude stethoscope can be as simple as a light screwdriver - blade on the relay case and the handle touching in your earlobe - works fine and is usually quite safe using plastic handle drivers.
However, I don't get the impression that's quite the problem here, if you can get it to work by jacking up the volume. If the second channel also worked when you gave the relay a whack, that would confirm a relay problem. Have you replaced the relay yet and does it click after powering up?

 

[MaccAu]

Hi Ian,

All good a strong click on power up. I never cleaned it, and the board was rather dusty, i think the owners mustve stored it in a garage or shed. Maybe i could clean the relay.

I shall try giving the relay case a whack and see if that brings the problem channel around upon start up, as it plays fine after then.

Can i clean those motorised volume controls with contact cleaner? The spare G50 front end is in much better condition. Relay on that is an old Technics SU-V4X relay.

I did the mods with the speaker cable that the Tech did on my other G50. Terminals were harder to solder , but first see if issue is relay with the whack

 

[MaccAu]

Update
I turned it on no sound on that channel, so i tapped gently the top of the relay case and the sound came on properly, and now is good on both

I pinch off the case and clean the relay with deoxit and cotton bud? I am tempted to order a new one but if i can clean it i might get a bit more mileage if its the relay?

 

[Welcome]

No, replace it completely. Your problem is present on all relays of this type, and they are beyond saving. There are a wide variety of modern drop-in replacements and they are cheap - expect to pay around $2.

 

[MaccAu]

No, replace it completely. Your problem is present on all relays of this type, and they are beyond saving. There are a wide variety of modern drop-in replacements and they are cheap - expect to pay around $2.

Hello Welcome,

Thank you for the reply, so cleaning it would only be a short term thing. I got had my original DEC cleaned and I got a few years out of it in my other G50.

Ian sugguested this one which I found. A nice brand also, though everything is made in SE Asia these days, i guess to keep costs down
G2RG2A424DC - OMRON ELECTRONIC COMPONENTS - General Purpose Relay, G2R Series, Power, Non Latching, DPST-NO, 24 VDC, 8 A | element14 Australia

 

[Welcome]

Wow, that wasn't a cheap shop. I would use this, though: 9-1393243-9 - TE CONNECTIVITY / SCHRACK - General Purpose Relay, Power PCB Relay RT2 Series, Power, Non Latching, DPST-NO, 24 VDC, 8 A | element14 Australia

I have lots of personal experience with this exact part and it works great in amplifiers. Usually total drop in, too. This looks like the six pin type, so sometimes you have to cut the two innermost pins to fit it on the board. Those pins are the NC (normally closed) pins, you need the outermost, NO (normally open) pins.

Omron relays are equally good, but more expensive because of brand recognition I suppose.

My theory is that the DEC relays go extra bad due to the sticker allowing moisture to get in, or possibly the glue itself on it, making the contacts corroded. I've had to replace lots of relays in various amplifiers, and the majority of them have been of this type.

 

[MaccAu]

Wow, that wasn't a cheap shop. I would use this, though: 9-1393243-9 - TE CONNECTIVITY / SCHRACK - General Purpose Relay, Power PCB Relay RT2 Series, Power, Non Latching, DPST-NO, 24 VDC, 8 A | element14 Australia

I have lots of personal experience with this exact part and it works great in amplifiers. Usually total drop in, too. This looks like the six pin type, so sometimes you have to cut the two innermost pins to fit it on the board. Those pins are the NC (normally closed) pins, you need the outermost, NO (normally open) pins.

Omron relays are equally good, but more expensive because of brand recognition I suppose.

My theory is that the DEC relays go extra bad due to the sticker allowing moisture to get in, or possibly the glue itself on it, making the contacts corroded. I've had to replace lots of relays in various amplifiers, and the majority of them have been of this type.

Hello Welcome, thank you for the recommendation, and wow its nice to see it is Austrian made. I like TE products, I use the pins and adaptors. That is good i can just cut the extra pins. Its great you know the part very well and used it

I think that must be the reason with DEC problem, as something seems to mess them up. DEC mustve been use a lot back then. I dont know why but the earlier Technics amplifers I have from the 80s they used Matsushita relays, but I think the G50 is early 90s maybe.