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Thread: EBS HD-Series amps don't use thermal grease in their folded heat sink stacks?

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    Senior Member nevetslab's Avatar
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    EBS HD-Series amps don't use thermal grease in their folded heat sink stacks?

    While going thru preventative maintenance on our rental inventory, I brought over some EBS TD-650 Bass Amps for scrutiny. From a few years ago, I recall EVERY HD series amp we had (HD350, HD650), all using an aluminum base plate to which the MosFET's are mounted, then a set of 4 aluminum fins are folded up (0.090" thk) and screwed down thru the base plate & into the chassis to form a heat sink assembly. And, NO thermal grease used anywhere in the assembly. Two M5 PHMS hold it all together. Now, I know there are from Sweden, and it's relatively cold up there, but, really! Is it just because these are Musical Instrument products, that the laws of thermal dynamics don't apply?

    Ah, well, pays me to pull them apart and grease 'em up, then have to get the white grease off me that has learned to leap great distances onto your fingers and elsewhere.

    And, I get to play thru them for a while to make sure all is well inside. Great sounding amps!!

    Click image for larger version. 

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    Last edited by nevetslab; 12-02-2018 at 09:52 PM. Reason: Added photos
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    Pix or it didn't happen.

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    Old Timer J M Fahey's Avatar
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    1) please post schematics if you have them available.
    And gut pictures, specially showing heatsinks.

    2) if you have perfect metal to metal contact, you get better thermal contact that way than adding any paste in between.

    Grease + metallic oxide (usually zinc oxide) is better than nothing at all, which means trapped air between not perfectly mating surfaces, but if contact is perfect, grease + mineral load actually degrades it.

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    Juan Manuel Fahey

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    Senior Member nevetslab's Avatar
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    Quote Originally Posted by J M Fahey View Post
    1) please post schematics if you have them available.
    And gut pictures, specially showing heatsinks.

    2) if you have perfect metal to metal contact, you get better thermal contact that way than adding any paste in between.

    Grease + metallic oxide (usually zinc oxide) is better than nothing at all, which means trapped air between not perfectly mating surfaces, but if contact is perfect, grease + mineral load actually degrades it.
    My apologies on leaving out the photos. I've added them to the initial post. The smallest folded fin at the top of the stack would be the most questionable as to flatness. You do make a good point, though not having a microflat anymore to check the flatness, all I have to go by is the sense of any tendency to rock side to side where it's placed. I haven't actually run thermal tests on the assemblies to see what the difference is as sensed by the MosFET's. This addition of thin layer of silicon grease is from experience with heat sinks in various power amp designs over the years of manufacturing. One would NOT install power xstrs to heat sinks without a thin layer of grease on isolated heat sinks, nor without the best non-grease insulator affordable in the budget, or use mica without thin layer of grease between the xstr's mtg surface and the insulator, & insulator to heat sink.

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    I need to check and see if there is a non-disclosure agreement with EBS when I obtained the service doc's on the HD350 and the Fafner TD650. I don't have the service doc's on the standard TD650, though I'd be guessing the power amp assy is the same, without pulling the cover off the Fafner model.

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    Servcie Doc's for EBS Fafner TD650

    Quote Originally Posted by nevetslab View Post
    I need to check and see if there is a non-disclosure agreement with EBS when I obtained the service doc's on the HD350 and the Fafner TD650. I don't have the service doc's on the standard TD650, though I'd be guessing the power amp assy is the same, without pulling the cover off the Fafner model.
    I didn't find a NDA involved with the Service Doc's I had received back in 2010, so I guess I can share them.

    FafnerTD650_Svc Docs-1.pdf
    Bias Alignments.pdf
    Compressor-Bias.pdf

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