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Bond glue issues and pictures

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restorer-john

restorer-john

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There were silver plated mechanism position switches inside.

If I never see another mode switch I will be a happy man. The only ones I have left are in my (3) DAT recorders and they are fine (and unobtainium).

VCRs. Wow, they were truly evil weren't they @solderdude ?

Here's one especially for you. Not a VCR, but the RF amps on a Sony DAT. Guaranteed every single one will fail due to leaking caps.

Looks OK out of the can doesn't it?
IMG_1258 (Small).jpeg


IMG_1262 (Small).jpeg


Let's get in close
IMG_1253 (Small).jpeg


Closer
IMG_1255 (Small).jpeg


Get rid of those horrible things!
IMG_1265 (Small).jpeg


IMG_1266 (Small).jpeg


IMG_1267 (Small).jpeg

Real caps installed... (just small enough to fit in the can too)
IMG_1259 (Small).jpeg
 

Wombat

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Sony made a huge thing of vibration damping inside their analogue and digital gear. Especially in their ES products, where every major large component was carefully attached, isolated or damped with various elastomers, insulators and other compounds.

I remember the first time hearing an amplifier heat-sink "sing" with a test tone and thinking if current can make a noise in a passive piece of aluminium, why can't that aluminium object when subjected to vibration, affect the current in some way? Surely a two way street?

Perhaps the capacitive coupling of the T03P collectors to the heatsink (earth) using the insulator as a dielectric was the issue, I don't know. All I know is Sony (and Yamaha) damp the heatsink fins with a bituminous encircling band on many of their products along with anti resonant measures such as masses cast in at different points along each heatsink fin.

I'm sure you (like all of us) have run your fingernail along heat-sink fins and listened to the sound...

And affect audio frequency signal in passive and active components in domestic use? I would love to see some evidence.

Even mechanical integrity for transportation or domestic use should not be an issue.

In poor designs or shoddy components, possibly.
 
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somebodyelse

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Thanks for the info. When I saw the EEVBlog entries on the KRK Rokit 6 active monitors I wondered whether it was a wider problem, although that instance was much faster acting than what you've described.
 

Thomas savage

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We've been discussing conductive adhesive issues in another thread.

Here's some pictures of what happens. All these items were either dead or dying and brown glue was the cause. Do not underestimate the mess this stuff can do. Your gear, regardless of brand can be a time-bomb.

The poor capacitor is essentially hermetically sealed to the phenolic PCB by the bond glue. It cannot vent even a tiny bit. The glue ages and corrodes the legs, the cap leaks electrolyte because of the corrosion going up the legs and into the cap itself. Cap loses an entire leg or it eats down the pcb hole and reacts with the PbSn and Cu and makes a big mess. Sometimes caps can shoot off like a bullet from this reaction. These days, more caps have a one-time vent on the top, but all smaller electros still have the vent on the rubber base.
View attachment 42104

View attachment 42106

Capacitor's legs eaten away from under the glue, completely invisible from either side. This is a small PSU in a vintage amp.
View attachment 42108

Get rid of those ancient caps and clean up the mess!
View attachment 42109

New Nichicon UFGs!
View attachment 42129

This is caused by the glue at the base, reacting with the tinned copper legs, not allowing venting at the cap base and the reaction travels up the inside of the sleeve to the top.
View attachment 42112
Same cap at base
View attachment 42111
That wretched glue loves to eat transistors too
View attachment 42113

Rebuilt. Even used an original perfectly matching Elna cap bracket from my NOS stock. Previous PSU filter cap on right was larger diameter. Holes were predrilled in the factory for the two sizes in 1974.View attachment 42146
Your so good at staring new threads , thanks John. Good discussions get lost and we lose the value of content when it springs up in threads as off topic diversions.
 

mjwin

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Great restoration job! I guess many of these products are truly "audio antiques" and deserve your loving attention in this way.

I wonder whether, most of the time, that horrid brown glue was just used to keep the taller components in place while they went through the flow soldering machine? I've never seen it used on products made in much smaller quantities & hand soldered.
 

sergeauckland

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Great restoration job! I guess many of these products are truly "audio antiques" and deserve your loving attention in this way.

I wonder whether, most of the time, that horrid brown glue was just used to keep the taller components in place while they went through the flow soldering machine? I've never seen it used on products made in much smaller quantities & hand soldered.

That was my guess too. The broadcast products I referred to above were all hand-soldered, as I also understand were Leak and early Quad boards. Components were held in by their lead-out wires, and the boards held on a jig and hand soldered, then the long leads clipped away, again by hand. No pick and place and flow soldering in that era, especially for products made in batches of 10-100.

S.
 
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Don Hills

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Sal1950

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Definitely not a, "Badur the Butcher." (Inside joke. I replaced a technician many years ago and his name was Badur and so we nicknamed him as Badur the Butcher.")
Around my circles we refer to them as "hammer mechanics " or " Primitive Pete's" LOL

Here's some pictures of what happens. All these items were either dead or dying and brown glue was the cause.
Is the "brown glue" you refer to the universal product used or were/are there better options that some manufacturers have used?
Sorry if this is dumb question, I have zero knowledge in this area.

BTW, thanks so much for this posting, an interesting insight into your passion.
 

Newk Yuler

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Is silicone caulk a suitable cap glue? Or perhaps a similar professional product made specifically for that purpose? I have some new-ish equipment using what looks like it although IIRC it may just be used to bind caps or other components together at the sides.
 
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mjwin

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Is silicone caulk a suitable cap glue? Or perhaps a similar professional product made specifically for that purpose? I have some new-ish equipment using what looks like it although IIRC it may just be used to bind caps or other components together at the sides.
Silicones are used quite a bit. But they're not caulking grade, & definitely non-acetoxy,(or you'll end up with the same problem as the brown glue!) I've used Loctite Tempflex 5145, which is certified electronics grade. You'll also see Hot-melt EVA products used a lot, too. The near-instantaneous setting time makes them ideal for tacking components together during assembly.
 
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restorer-john

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Is the "brown glue" you refer to the universal product used or were/are there better options that some manufacturers have used?

Pretty much all the major brands had problems with brown glue. Whether the glue was from a single supplier and it took years for the problem to become apparent, I'm not sure. A bit like Takata airbags, except not so serious.

In the mid 90s Yamaha made a big thing about using a completely different bond adhesive on large passives and it was white, silicone-like in texture and has given me no problems apart from removal.

The most serious issues tended to occur on old Sansui gear as they used huge amounts of the glue and their phenolic PCBs seemed to feed whatever reaction was occurring- often they are beyond repair.
 

Doodski

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If I never see another mode switch I will be a happy man. The only ones I have left are in my (3) DAT recorders and they are fine (and unobtainium).

VCRs. Wow, they were truly evil weren't they @solderdude ?

Here's one especially for you. Not a VCR, but the RF amps on a Sony DAT. Guaranteed every single one will fail due to leaking caps.

Looks OK out of the can doesn't it?
View attachment 42169

View attachment 42170

Let's get in close
View attachment 42171

Closer
View attachment 42172

Get rid of those horrible things!
View attachment 42173

View attachment 42174

View attachment 42175
Real caps installed... (just small enough to fit in the can too)
View attachment 42176
Sony camcorders are also known to have those leaky corroding caps in them too. I've seen many that have gone bad.
 
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Sal1950

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Humm, What's your opinion of the condition of this glue ? TIA
IMG_1696.JPG
IMG_1701.JPG
 
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Doodski

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To the eye the adhesive doesn't appear to be baked yet or have any capacitor leakage. Is there a issue with the amp?
 
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restorer-john

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Humm, What's your opinion of the condition of this glue ?

It looks fine at this stage. Have a close look at the legs of components where they are in contact with the glue for corrosion.

The far right capacitor tops are bulging a little due to the glue seal around the cap base with the PCB. Normal gassing off can make them appear swollen. People panic when they see that, but it's not a problem.
 
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Killingbeans

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Sony camcorders are also known to have those leaky corroding caps in them too. I've seen many that have gone bad.

Yeah, those caps are just horrible. Also not audio related: Sega made a handheld gaming console called 'Game Gear' in the 90's, and it used them extensively. The consoles all need a full recapping to be the slightest bit functional.
 

Sal1950

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It looks fine at this stage. Have a close look at the legs of components where they are in contact with the glue for corrosion.

The far right capacitor tops are bulging a little due to the glue seal around the cap base with the PCB. Normal gassing off can make them appear swollen. People panic when they see that, but it's not a problem.
No problem with amp, a GFA-5400, plays perfectly. The last time I opened it bias and DC offset measured within spec and a tiny tweak had things perfect..

Hmm. 1990s Adcom. Those kind of concerns are constantly in the back of my head, too. Like huge potentially failing caps. :(
Only one of the big monoblocks suffered from defective caps, the rest have performed stellar into quite old age.
I've got 5 running here, all in original condition
 

pdb

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What a great thread A few minutes of reading already gave soo many good tips / and valuable information - Per (DK)
 
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