Marantz 1060 Rebuild - IT'S NOT LOOKING GOOD - P700 Amplifier Board

[@alexw890]

Man that’s a tough one. I have limited experience as well but every single time I’ve been stumped like this, it’s ended up being a problem I caused with the work I did. Keep at it!

[@PrimeHiFi]

Just spitballing here but I’ve seen those orange ceramic caps short before so maybe check those. Quadruple check for bridged solder joints under a magnifying glass and also make sure the trimmers are of the right value too. I’ve made that mistake before. Hook a scope to the output to see if it’s oscillating and also measure bias to see if that’s skyrocketing. Make sure there is no continuity between the collectors of the outputs and the heatsink too. Also verify all wiring downstream of the amp board is solid. Looking forward to an update. Don’t give up!

[@PossibleAudio]

I'll never give up. Just taking a rest for my back, shoulders and hands. I'm making notes from everyone and will get back to it in a another couple of days. I'm looking forward to figuring out the issue and coming up with a solution.

[@robertdestefano1409]

my brother I am not an expert I did however work for Harmon Kardon in the 80's and was trained by very experienced technicians. one the old timers (funny how it's always an old-timer) anyway he said a scope is your best friend. it does the work of many pieces of test equipment at once. seeing the signal, noting the dc levels, verifying offsets and bias currents. the calibrations of the amp (bias and offset) will often fail at some point in a defective ckt. see these signals during the calibration will often show the defective component. in your case since the components were removed and reinstalled perhaps in error you put R43 for example where R44 should go .i that case removing every part and testing will not show anything wrong. they may just be in the wrong place. additionally, some boards are mislabeled by the manufacturer so if you're following that blindly it can also jam you up. use your video of before you took apart. there may be a clue. and one more thing you seem to have overcome some personal physical issues. don't let a manmade piece of crap beat you now. remember Rocky "THERE AIN'T NO CANT" ask Mr. Carlson , Xray tony or shangoo those brothers never quit., so you're not allowed two. good luck you got this. bob

[@Abeille30]

The first thing that comes to my mind would be the cleaning of the flux you did previously, you removed the solder to make it clean, so it's maybe possible you forgot a bridge behind or something got put together in extra; i would pause the video footage and recheck it.

[@timbucktoonotforyou.8442]

You must be a very patient man. Good luck with it.

[@PossibleAudio]

I must say... My gushing river of enthusiasm has turned into a trickling creek. The thought of stripping the board and starting over with a new replacement board isn't making me very happy.

[@robertarchuletta2498]

@@PossibleAudio I would hold off on that. The effort you put into that is amazing. You workmanship is second to none

[@robertarchuletta2498]

I highly doubt that the board is bad. It being a single sided board. Unless perhaps there a hairline crack in one of the etches. But that would be pretty obvious. Are you measuring any funky voltages on the board when it's in the circuit?

[@kylesmithiii6150]

@@robertarchuletta2498 @PossibleAudio I agree with you. I have been in similar situations. I don't suggest that you use a dim bulb greater than 100W in this troubleshooting. You will find the root problem(s), I am sure, just keeping narrowing down the possibilities following the schematics. Best of luck. (sorry to say but wear eye protection in case a capacitor blows up while you are troubleshooting - been there done that).

[@jrumiano]

Start checking the traces on the board. Use a schematic to help test/verify component connections. There may a cracked trace in the PCB.

[@davidgranic2509]

Been there. Always ends with a cracked trace. Run a continuity check using the pins to track it down

[@stormriderkaos]

I work on old-timey tube gear and I've been there too. Sometimes (rarely) the board material itself has gone conductive. Truly painful diagnostic routine. My theory is that the board takes on moisture and when conductance occurs it lays down a track of impurities that is near impossible to remove from the board. If there's only one or two such tracks one might be able to locate them via test equipment, cut the board traces and jumper with wires.

[@Geoduck.]

Take a day off and then try once more. Wishing you well finding the gremlins. It's likely you know there are new P700 PCB boards on eBay for our 1060 amps.

[@frankgeeraerts6243]

What a nice looking rebuild! WHAT's the problem ? Are those big transistors put in the correct place ? Is there a faulty trace ...? Anyway there must be a reason and I think you will find the cause .... Have a very nice day and give yourself some time let it be and to think about it .often time helps to find the solution . PS ..years ago I had a similar problem and when retesting components , all were testing good , then I discoverd that a resistor that tested good was failing when being used real under load conditions ........

[@robertarchuletta2498]

So is it blowing fuses or getting hot? The board appears to be single sided . Only thing I can think of is that the problem is in a different stage or maybe what you thought was a good transistor is actually a faulty one. Maybe a bad junction does not show up until it's under a bit of a load.

[@TrevorsBench]

I'm not sure what the issue is. I went to the AK forum and you say 'dead short'. What's shorted? Are you going by the indication of the 40w bulb in the DBT? If so, 40 watts is a small bulb. I say upsize it to a 100w bulb and see what happens. It's a quasi complementary design and it may not be happy until it sees full rail voltage. Have a voltmeter on the B+ and monitor with both the 40w and larger bulbs. Also, check for 1/2 rail voltages before the speaker output capacitors, it should be there between the two output transistors. Hope this helps

[@PossibleAudio]

Hey Trevor. I assumed there's a short from the BRIGHT 40w dim bulb and low voltages. Measuring about 3v on B+ with the 40w dim bulb in circuit. With the amplifier module out of circuit I get 70v at B+ with 40w dimm bulb (DARK). I'll increase the bulb to 100w and see what happens.

[@TrevorsBench]

@@PossibleAudio Might just be hungry for current

[@PossibleAudio]

Went to a 116w bulb... No joy. Higher voltages by a little over double and extra heat on the left side of the board. R748 is hitting 125f degrees and that's the hottest component I can find.. It tested as 0.5 Ohms in circuit.

[@TrevorsBench]

@@PossibleAudio It's odd that R748 is getting hot and not R750 as they are in series and the same value. That might be a clue. There is no low impedance path for current to flow from the junction of R748 and R750 to allow a imbalance like this. The speaker output is disconnected, right? You measured R748 and it's 0.5 ohms? It should be 0.24 ohms.Try swapping places of the output transistors H003 and H004 to rule those out. Could be the bias is WAY high on this channel and drawing excessive current. I'm thinking the bias may be incorrect and turning on the outputs too much which is giving you high current draw

[@PossibleAudio]

I pulled out a new Multimeter. Now is a better time than ny to get used to a new tool. I turned the trimmer pots on the left channel until they maxed out both directions. No change. I remeasured R747, R748, R749, R750. They all read 0 ohms. It's strange because they start out at close to 0.3 ohms and slowly drop to 0.I They also measured at 0.5 before installed which I found really strange. swapped the outputs H001 & H002. I've tried a 40w, 75w and 116w of bulbs. No speakers are connected. I'm baffled by this whole outcome. Total of 80+ hours on 1 board. I'm so bull headed when I start something, getting myself to stop is difficult.