Black Sony STR-6060 (STR-6000) rebuild..

[pfunk951]

About a decade ago when I first got into STR-6060s, I had heard rumors that there existed this mythical receiver that was essentially a 6060, but had a black faceplate.. There wasn't (and still isn't) a lot of info out there on them, except that they are only in Japan and that they are very, very rare. Over the years, I found both aspects to be true.

Nonetheless, a restless heart never sleeps, and a long and tedious journey ended with success this weekend.

Upon receipt, the wood case had been obliterated- I literally peeled it off of the receiver. The good news is that after cleaning, the faceplate and lettering are in near showroom condition.. I'm getting tuner lights but no sound, a quick search revealed a blown fuse on the power supply board.. So it looks like my eagerness will have to transform into patience, as I wont hear this thing sing until I at least get the power squared away..

Due to the inoperative state, this build will be one step at a time- starting with the power supply boards.. I'll have to dust off the brain cells that helped me through this last time, but I'm confident that the content out there will get me squared away..

I'll have plenty of questions as this progresses, stay tuned and thanks in advance..!

MP

 

[OMGCat!]

That's very cool! I've never seen a black one or knew they existed.
Is it a 100v machine? That sucks about the wood case but excellent the face made it to you in perfect shape.

 

[pfunk951]

It showed up as 100v, but you just have to move a power bar over one slot and it's 117v.. Easy peasy.. I'm getting the PS caps on order now, I cant wait to get underway..

Looks like I'm only getting half the FM band that they get in the U.S.. Oh well!

 

[eedork]

That is a beautiful receiver!

 

[pfunk951]

First things first: Appearance.

Faceplate and knobs cleaned with water and light dish soap, then waxed with Meguiar's Ultimate liquid wax.

All 3 bulbs out, and replaced with LEDs. I tried white, but green is both the original color and looks the best. Pics of before, during, and my inspector validating the completed work:

 

[audiojones]

That is one gorgeous receiver, never even knew they existed! How come all the cool looking black options were only available overseas?

 

[Joe Nardy]

Yes, that is very pretty. It sounds like you're very familiar with these receivers but just an FYI...….. be very careful if you decide to clean the back side of the tuner dial glass. The lettering on some of these Sony STRs is fragile. It appears to be a water based decal like on model cars. I had a mishap with a STR-6055 when I immersed the glass in water and lost some of the lettering. It would be a shame to mess up the dial glass on that rare unit.

Thanks,
Joe

 

[captouch]

First things first: Appearance.

Faceplate and knobs cleaned with water and light dish soap, then waxed with Meguiar's Ultimate liquid wax.

All 3 bulbs out, and replaced with LEDs. I tried white, but green is both the original color and looks the best. Pics of before, during, and my inspector validating the completed work:View attachment 1775564 View attachment 1775565 View attachment 1775566

Beautiful black unit- good luck with the restore!

Can you provide a link to the green LEDs you used and whether/what mods were required to use them?

 

[eedork]

Yes, that is very pretty. It sounds like you're very familiar with these receivers but just an FYI...….. be very careful if you decide to clean the back side of the tuner dial glass. The lettering on some of these Sony STRs is fragile. It appears to be a water based decal like on model cars. I had a mishap with a STR-6055 when I immersed the glass in water and lost some of the lettering. It would be a shame to mess up the dial glass on that rare unit.

+1 - The same thing happened to me recently while cleaning up an STR-7065.

 

[pfunk951]

Audiojones- Good question, I really wish they were more prevalent. The process for obtaining it was difficult, confusing, and long, but in the end the Audio Gods must have smiled upon my fumbling efforts. I'm unaware of anyone else in the U.S. that has one..

Joe and eedork- Words of wisdom, even a damp cloth can lift these letters.. I cleaned the interior glass with damp Q-tips, going around the lettering. My Father-in-Law (certified Audiophile and collection partner) was thumbing through vinyl next to me while I cleaned it, and might have been alarmed if I threw myself out the window after rubbing off the "STR-6000" from the glass..

Captouch- stereolamps.com, and search for your unit. Zero mods, these are plug & play in the same sockets as the meter bulb and 2 fuse bulbs (pic attached).. If you don't know how to get these out, let me know and I'll write it up as it's not very straightforward- I bought 3 sets and am going to do the swap in some 6060s I have..

Power Supply caps due in tomorrow. I suppose that I need to get off my butt and start looking for a new case- I think it's a TAC-5E..?

Onward!

 

[pfunk951]

I'm finally underway..

After some partial and incorrect shipments from Mouser, I have finally got the PS and preamp circuits rebuilt. Had a couple of leaky caps come out, so I thought that might be the issue with the unit blowing the fuse- turns out that didn't fix it.. I've rebuilt a couple of these 6060s, but never brought one back from the dead, so I have a few questions:

Has anyone heard of these having transistor issues? I'm far from done with the recap/alignment, but I'm not seeing a "smoking gun" anywhere on the amp boards in the form of burned components.. I've got 80v coming off the rectifier bridge to the fuse, so all seems to be well with the transformer. When I put a new fuse in and power up, it immediately smokes the fuse with a loud tone out of the test speakers.. Too fast to check voltage off the speaker terminals..

I suppose I need to get all the caps in to rule them out, but just wanted to know if there are any usual suspects in the circuitry that could cause an overload of that 6v fuse.. Here's a pic of the preamp board for those who love the poly caps

Thanks again!

 

[Moving Ahead]

So you're not using a DBT?

 

[pfunk951]

Ha, not yet, but it looks like this weekend's project is making one! It'll buy me some time while Mouser gets me sorted out, I'm still a dozen caps shy on my order..

Mike

 

[pfunk951]

Quick update,

Left channel 2SD88 Transistors are shot, I'm swapping in some NTE MJ15003 this weekend. This is my first go-round with these transistors, anybody have opinions on them?

I'm hoping that no other damage was done, we'll find out..!

Onward!

 

[captouch]

Something caused the original transistors to blow. You aren’t afraid to blow the new ones?

Did you ever build the DBT?

 

[pfunk951]

Indeed, there's something afoot that has caused the dominoes to fall.. With the help of the schematic and another freshly rebuilt(and operating!) 6060, I've started searching upstream, and It appears that there are problems in the Circuit Protection Board that feeds the amp channels.

So far, I've found that R777, a 12k resistor that feeds the good channel, is reading properly. I verified the same readings off of the good 6060 unit. Meanwhile, its counterpart, R677- which feeds the bad channel, is reading 63.5 ohms- which is flamboyantly low. Testing upstream and downstream of this suspect resistor is showing good readings on all the rest of the resistors, so I -may- have isolated a problem that could have been sending way too much voltage to the dead amp board. Is this sound logic?

I'm pondering whether I should just swap the Circuit Protection Boards, get the transistors in, and bring it up on the DBT.. I am STILL waiting on many of the caps from Mouser, so I'm reluctant to bring it up prior to dropping in the new electrolytics..

This has been a challenging rebuild! All comments appreciated..

Mike

 

[pfunk951]

She's got a pulse!!!

This morning I got the 4 output transistors installed, and Mouser decided to ship me another partial order- enough to complete the PS and protection boards.. I dropped the caps in, pulled out the variac, whipped up a DBT that would make the Fire Marshall pass out, and slowly brought up the voltage..

At 80 volts the DBT started glowing brighter- brighter than on the test Sony 6060 that I was using as a baseline.. I held the voltage there, and sent in some Steely Dan through the AUX to see if I could move a signal through the amps.. Out of the speakers came Babylon Sisters, and I nearly hit the roof.. I removed the speaker wires, and took some readings- way too much DC offset on both channels.. Not wanting to push my luck, I powered down..

My plan is to get the rest of the caps in, and retry this exercise.. The capacitors I've pulled so far have been in bad shape, and I still have both amp boards to go, so I figure they all need to get refreshed in order to eliminate variables..

Today was a good day.

 

[rswojo]

Some thoughts.

You mentioned excessive DC offset. The 6060 is cap coupled so you will see DC on the speaker terminals without a load.

You mentioned a 6A fuse. That fuse should be a 5A fuse, not 6A.

I have a 6060 parts unit that I bought from an AK member a few years ago. It had a bad volume pot but I tried it out once before I removed the MPX board, face plate and power switch. In case you need it.

That is a beautiful machine, I like the black toggles/silver accents and the knurled knobs are a few years ahead of their time. Your inspector is cute too, she/he looks like my little inspector.

 

[pfunk951]

rswojo- Thanks, you are correct- that's a 5A fuse.. My little inspector has been by my side the whole time, and appears to be both confused and amazed that I plugged a lightbulb into one of my receivers..

Update: The recap is finished, the new output transistors are in, and I brought it up on the DBT.. Sound from both channels is good, but slightly distorted on the Left Channel (this is the one that had bad output transistors in it.. Also, the left output transistors are running noticeably hotter than the right.. So I have some issues that are still lingering, and I'm going to need some help/guidance from the gurus.. Here's the skinny:

1. Upon startup, the DBT Lights up and dims, but then starts glowing moderately again. It glows significantly brighter than the "control" 6060 that I put on the DBT next to it.. This bring up a question: Am I safe to start checking voltages while this is powered on with the DBT inline? That extra glow is telling me something must still be shorted in there- maybe on the left channel. I understand the DBT is eating up the amps, but I'm skiddish and I don't want to fry anything.. Note: I've been doing light restore jobs on amps for some time now, and somehow never used a DBT.. This thing is pretty neat!

2. After the full recap, DC offset drops to the single digits on both channels after being switched on for 30 seconds, but the left channel will have spikes up into the .060-.100 volt range.. I only replaced the output transistors, is this a sign that the other transistors on the board are malfunctioning?

Please let me know if there's anything I'm missing. So far it's come back to life, and I don't want to do anything that will cause the magic smoke to appear..

Thanks!!

MP

 

[rswojo]

I am nowhere near an expert but I had a 6055 with blown outputs. After I replaced the outputs I had to replace 4-5 small signal transistors upstream. Then I still had high offset voltage and replaced a blown emitter resistor to fix that. I just started pulling, testing and replacing transistors starting with the ones nearest to the outputs.

That said I'm sure someone will have a better method for troubleshooting this but the point is when the big boys go they take a few of their little friends along.

Keep it on the dim bulb until you are done.