Blew my 1060 during adjustments

[Keith Baran]

So, I just completed recapping a 1060, everything went great and it sounded great. I began to adjust the DC offsets. I completed the first channel and everything dialed in perfect. Then I moved over to the other channel. I had my meter attached to J714 and J718. As I was making the adjustment I was at a bad angle to adjust R730 so I nudge the unit over a bit and one of my meter probes touched the chassis, SNAP!!. I replaced the blown fuse but now when I turn it on my dim bulb tested glows bright. This is out of my league, does anyone have suggestions on where and how to start troubleshooting what I fried?
Any suggestions would be much appreciated.
Regards
Keith

 

[bktheking]

Pull the outputs on the channel you were working on and test them.

 

[Keith Baran]

Thanx bktheking, will do , hopefully this week. I was thinking to start there, not because I had some technical logic to do so but just a guess. LOL
Thanx again

 

[Blue Shadow]

Sorry for your loss. Everyone has done this, if they go inside with meter probes. Get some mini-grabbers for your next attempt. I'm sure they have saved me a number of times after I learned my lesson and got some.

 

[The Fuxtor]

Yup! Been there dun that! Start checking transistors on that channel.... Start with the output transistors and work back till you find the blown one

 

[Bert 1100]

Sorry to hear about that........so many posts on AK warning to use mini grabber probes or to insulate all but the very tip of the probe....

I began to adjust the DC offsets

For information, there is no DC offset adjustment on the 1060.
You can adjust the idle current and the clipping balance. The latter requires an oscilloscope to do.

 

[Keith Baran]

Sorry to hear about that........so many posts on AK warning to use mini grabber probes or to insulate all but the very tip of the probe....

For information, there is no DC offset adjustment on the 1060.
You can adjust the idle current and the clipping balance. The latter requires an oscilloscope to do.

It was the power amp adjustments. step 6.1 LOL never made it to 6.2 . My scope was ready but alas, my carelessness put a halt to that step

 

[Keith Baran]

Yes, I was using mini grabbers. I was connected not to the resistor but to J714 and J718. Then my mini grabbers were attached to my Fluke meter leads. I moved the unit to get a better angle to adjust the pot and forgot the meter leads were on the bench about 6 inches away from the unit and I moved the chassis right up against the meter leads.
It really is a bummer because this unit was in REALLY bad shape. So I had it all apart washing circuit boards, re-wiring, changing parts and this only being my second attempt at refurbishing an amp I thought to myself " Man this thing will probably never work again", but it did and it was Rockin! until my stupid, lame move. Oh well it can help develop my troubleshooting skills.
Thanx for everyone's input. Hope I get some time to work on it this week.

 

[eizner23]

Can one adjust dc offset with DBT in circuit to prevent such a disaster?

 

[Bert 1100]

After a rebuild and changing lots of components, yes you can do a first adjustment with the DBT in line.
But the final adjustment needs to be done on full line voltage, or it will not be fully correct.
And shorting something out in the amp can blow things up whether it is on DBT or not. Plenty of energy in the main caps to do damage.

 

[Keith Baran]

I'll say, lots of energy, the spot on the chassis where the probe toughed looks like a model rocket just took off and left a blast area

 

[AnalogueBen]

Hi Keith,

I know how disappointing this is, happened to me when I went to adjust the bias for the first time in my 1060, grounded a probe...
I took out a driver on the left channel as a tech found for me, I rushed out and got some replacements of ebay which after being replaced didn't sound right. I eventually found an original set of drivers but they were the ones from a later model marantz without the "spaceship" heatsinks, part 607 instead of 606 and 960 instead of 959. You can refit the original heatsinks easily.
Hope you trace the problem with out to much difficulty.
Ben

 

[Keith Baran]

All right, finally had some time to work on the blown 1060, I removed the output transistors, and guess what..... Blown, shorted, So at this point I really don't want to change the type so I checked on mouser for a replacement for these Hitachi 2SC897 the replacement I came up with is a On Semi Mj21194G on Mouser, below is the link, what do you guys think? OK ?
https://www.mouser.com/ProductDetai...=/ha2pyFadujEihMqaz/hhkq6TQqOjR1kS1vnU717vwU=

 

[Richs_Trains]

On Semi Mj21194G

Used them in my 1060 rebuild and they worked perfect and sound great. Bought a set of the originals also, but they were from China and was kinda afraid to use them. The Mouser one's were good. Rich

 

[airtime]

I would bet that everyone on this forum has blown at least one, or more amps doing just that. I know I have!

Now I just throw a box of steel washers in there and send it off to someone that knows what there doing. No but really, I just can't do that kind of work anymore. I do wish you the best of luck fixing the 1060 back up. And this time use rubber probes ;-)

 

[Keith Baran]

Thanks for all the input and condolence's LOL. While I wait for transistors from Mouser I'm making some mini grabbers , meter leads, and alligator clips that are completely insulated except for the point of contact , What's hard to swallow is that I had everything very safe except when I wasn't thinking and moved the 1060 to get a better angle to tweak the pot and pushed the 1060 right into the tip of the meter lead

 

[airtime]

One trick I've done in a pinch was use some electrical tape on the probe lead. Just leaving the very tip exposed. Sometimes you can't get the spring hook probe to lock onto what you're testing.

Or my all time favorite, just tack solder a piece of wire onto the solder pad you're testing. This way your probe is in a safer position and will not slip off and take out a months worth of work. This works well for those spots you need to hold the probe onto for more than a quick test or is hard to wiggle a probe into safely once the unit is live. That little bit of solder blem is FAR better than removing a bunch of blown transistors!!!!! I've even tacked a wire onto the lead ends of resistors on the top end of a PCB to avoid further destruction or disassembly.

 

[llwhtt]

I just got a 1060 in for repair yesterday, blows the line fuse. Two bad outputs so far.

Craig

 

[Keith Baran]

I am ordering transistors this weekend, I thought I may as well replace the trimmer pots also, any suggestions on a Mouser part # for R723,R724,R729,R730

Thanks
Keith