HELP! HK-770 AMP FROM THE UK...complete with barn spiders !

OK some more forward, less backward... Under the category of OH BY THE WAY I made a little copper buss bar, from the driver heatsink to the metal mount of the driver , thinking that would disperse MORE HEAT... I made it.. and for a few minutes it was working OK.. then the LEFT started mis behaving.. ( thank you DBT AGAIN ) . There is .5 of a volt from heatsink to chassis on the LEFT ONLY.. the Right is FINE 0.00V. So I'm thinking I have a bad mica isolator or a lead WAY TO CLOSE to the heat sink. In other news, I did recap the drivers, WOW what a difference.. NICE FAT FULL LOW END.....New PS caps ordered.. more to come.
 
How about a nice front shot so those who don't know it, can see what it really looks like. As for spiders and roaches, I have had them in my machines and it freaks my wife out to the point of fainting, when I just reach in and grab them right out with my fingers.
 
It's getting HAPPIER I did find A 1UF 3.9 K network that had fallen victim to the ACID / GLUE.. which was FINE till I moved it ~ 4K and PINK the lead of the resistor let go RIGHT AT THE RESISTOR BODY....
This lead me on a 1 hr search for a 3.9K... closest I has was 3.3 K so in it went..... The right is still the problem child ( post removing the heatsink , cleaning, replacing ALL the insulators, new goo.. et al ) .. it ran for ~ 2hr stable as you please then the right started making that static sound and bias went away.. post cool down it's happier.. so I'm HOPING that network was part of the issue !

Bubba,, here you go !







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And the crowd goes BOOOO ! Hard failure on the RIGHT CHANNEL.... USUALLY the amp does recover from this symptom after a cool down.. but not this time.
It powers up, comes out of protection BUT NOW it has a frying egg sound in the right, no bias , in the right...AND the unit consumes about 2X as much as compared to it at idle ( according to the DBT ) .The right still made audio + frying background.
I've printed out the correct scheme's & going to lift some parts out & test, starting with fuse resistors..... COVER ME I'm GOING IN !
 
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This is just FRUSTRATING.. pulled all fuse resistors out AND most emitter resistors.. all AOK... put it back together works.... SHEESH
 
Sucker that big is enough to kill a home sale. I've had larger spiders in my life.
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maybe resoldering helped fix a circuit.
 
I've re soldered that particular board 2X. ( used the Hakko to pull old solder out & resolder with FRESH ) . BUT i think ...maybe a lead was crusty enough just not to take the solder, so the pull ,test, re bend, stuff it back in was enough for a a PROPER connection.. because all the intermittent behavior was getting on my last nerve...Hooked up my CA 3K to the HK and beat it to DEATH for 2 hrs. While that was happening....I busted apart an old PC supply to harvest some heatsink material.... 8 of my PS caps arrived.. So there will be MORE......
 
New Driver board caps & additional heatsinks..... AND it
s behaving well !
 

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Things NOT to do on an HK 770 PRIOR to coffee......
Sometime in it's life Q-413 was replaced with a 2N5551 Which was RUNNING BLAZING HOT !, so hot I made a copper heatsink.. which , helped BUT I KNEW it was wrong
this WAS a 2SA666A (c) , I looked at the transistor swap post that John provided and a a KSC3503D was a valid cross.....and thru all my Sansei rebuilds I had a PAIR !
The issues was I was still getting the intermittent frying egg sound, but only for a few seconds then POOF it auto fixed itself.... So SWAP HO & away I went. BUT the silkscreen on the board is WRONG.
It marks the collector on the WRONG POSITION ! So after the swap I powered up and the DBT did it's job, and prevented a smoke show. After COFFEE and some research & doodling I realized the BASE and collector were swapped !... so in again and NOW it works, I had to do a bunch of trace repair & reenforcement, but that's all good now & works.

The leads on the 2N5551 were at full length , and looks like it was recently swapped.. but the leads got SO HOT the silver looked like discolored chrome headers.


KSA-1381 Is this the correct mate for KSC3503D ?
 
WELL WELL The first run on the HK off " life support " and WOW.....I dd have to reset the bias due to full AC mains... and the DC offset has drifted for the same reason.. but I can live with a TEENY DC thunk when turning on the speakers... First impressions, this amp has no idle noise..... the noise floor is in the dirt.... I played Some Ghost in the Shell ( soundtrack from the Anime series, which are OUTSTANDING RECORDINGS of some hard music to record , from Tyco drums to itty bitty bells....This ampi is FAST, no smudge in the detail... and it will do 100 WPC into 8 ohms ALL DAY LONG.....I am STUNNED how really good this amp is, there is more to be done but it is detail, heatsink & OCD upgrades.
So WOO HOO, really pleased with this amp......
 
NOTHING is worse than spiders in audio gear.

I bought a Sansui SR series turntable once and opened it up and a huge black spider ran at me, it was in there with its smaller buddy, so they got extinguished with some bug spray. Bastards.
used to have Black Widow Spiders in everything living in Phoenix. When it seemed time i would go on a hunt on the outside of the house looking under everything. Would find lots. I used to spray em with bug killer but they would die this slow icky death slowly spinning their way to the ground where i would usually step on em. They were still dangerous.
One day in the garage working on a amp I surprised one that was not there two hours before. Their webs are a dead give away and i find one next to my leg. (in shorts). I had the contact cleaner in my hand and sprayed it. It dropped like a rock. I think the cold got it. Didn't kill it but quicker to the soul of my sandals. New weapon of choice on widows.
 
I've re soldered that particular board 2X. ( used the Hakko to pull old solder out & resolder with FRESH ) . BUT i think ...maybe a lead was crusty enough just not to take the solder, so the pull ,test, re bend, stuff it back in was enough for a a PROPER connection.. because all the intermittent behavior was getting on my last nerve...Hooked up my CA 3K to the HK and beat it to DEATH for 2 hrs. While that was happening....I busted apart an old PC supply to harvest some heatsink material.... 8 of my PS caps arrived.. So there will be MORE......
Where R you buying your caps if I might ask?? Seems your thinking corrosion on a joint makes sense. It would work for a bit then sputter. But you would think you would have found that with the freeze spray..
 
Ok waiting for the last few chicklets to arrive BUT I'm considering this amp GOOD TO GO..... I could get a bit more OCD on the heatsink BUT no. Next will be the HK 825 PRE...
 
So, i just got a Silver SA5050 which I think is identical to the HK770. No power light, I replaced a blown 2A fuse and the light now works, but no sound from either channel. There's a slight thump when I operate the speaker switch. No signs of any burnt components, so I guess I'll start resoldering in case of dry joints and replace the fuse resistors - but how do I tell which ones they are vs normal resistors?
 
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