Xr600c mixer amp, advice.

[Tassieviking]

I seem to have confused you with what I wanted you to do, I meant to ask you to measure across each capacitor separately.
The arrows were there to show which capacitors I wanted you to test.
From the results you got it does prove there is a problem with the power supply for the +-52V and the +- 15V supply.
These share the same transformer winding, I am suspecting a power diode might be at fault, hopefully not the transformer.
The next tests you need to do is measure the AC voltage from the transformer to the PCB, and then the diodes, followed by capacitors for this section.

Measure the AC voltage coming from the transformer, the wires should be red-red/yellow-red.
Measure red to red/yellow, red/yellow to red, the red with yellow wire is the ground wire and the two red wires should be about 37Vac to the red/yellow wire.
If you have about 37 Vac on both of these then the transformer is ok. It should be about 74 Vac from the red to red wire as well.
If there is a plug on the AC wires, unplug it and measure the voltages, the problem could be a bad solder joint on the PCB.

If the AC from the transformer is good, then we keep going.
Measure across C26, there should be about 52 Vdc across this capacitor.
Measure across C30, there should be about 52 Vdc across this capacitor as well.

If you have the two 37 Vac supplies but not the two 52Vdc supplies then I would think you have a faulty diode or two.
If you don't have 52 Vdc across C26 then I think diode CR16 or CR17 might be faulty.
If you don't have 52Vdc across C30 then I think diode CR18 or CR19 might be faulty.
These diodes are 6 Amp 200V diodes

If you measure each capacitor for DC Volts and AC Volts it makes it easier to find the fault, there should be no or hardly any AC voltage across the capacitors.
You can also measure across the diodes CR16, CR17, CR18, CR19, Measure AC and DC for each one please.

[Oldmactech]

Thank you very much.
I will take those measurements Tonite.
I did discover one diode cr11 and it’s companion Cr 13 on the riser that contains the output transistors. Cr11 passes voltage in both directions (tested in circuit so not sure it’s a good test). Cr13 does not pass voltage in both directions.

I also found some very old flux on the same board that was bridging two traces. Doubt that would have killed the diode but pretty near to it. Cleaned off the flux.
Thanks again.

[Oldmactech]

Ok, here’s some measurements.

power supply red to yellow 33.6vac both sides, 67.3vac red to red

c41 0vac
15.7 vdc
c42 0vac
15.9 vdc
c43 0vac
0vdc
c44 0vac
0vdc
cr16 28.7vac
36vdc
cr17 lead to short to probe from top
cr18 30.8 vac
-25.5vdc
cr19 lead to short to measure from top
c30 11.1vac
26.1vdc
c26 .6vac Hard to get a probe on from top
-25.6vdc
If it matters the entire preamp section is disconnected from the power side.

[Tassieviking]

I think that some diodes are blown in the bridge rectifier, and possibly also CR13 and CR11, They are all the same so I would replace all of them.
It should be full wave but I think you are getting more like half wave.
Cr11, Cr13, CR15,CR17, CR18,CR19,
Personally I would also replace C35 and C36 as well, but at least test them.
If you replace the big capacitors, pull the old ones and measure the diameter and pin spacing, then get some the same diameter and pin spacing, at least 55v and 4700uF or bigger.
I don't know if you would need capacitors with leads or pins, you would have to remove one to find out.
You need to re-measure C43 and C44 since you got 0V, previously you got "C43 and C44 5.9 ACv 10.9 DCv", across both I presume.

I think the 16V power supply is fine, so ignore that from now on.

With 33.6V ac from the transformer you should get approx 47Vdc after the bridge rectifier (33.6 x 1.14), maybe a bit more with the 5000uF capacitors if they were good.
Google full wave bridge rectification (ac x 1.41) and half wave rectification (ac x 0.705) if you want more information on that.
Please understand that I am giving the best advice I can, but I have problems with memory because of strong medication for a bone disease.

[Oldmactech]

Many thanks for the help, especially during medical problems.

the schematic calls for P600d diodes. Shopping around is there a particular flavor of these diodes I need to purchase?

thanks again.

[Helmholtz]

P600D is a 6A/200V general purpose rectifier diode.

https://www.vishay.com/docs/88692/p600a.pdf

[Oldmactech]

Thanks to all. I’ll order a 6 pack of p600d diodes. I’m seeing 200v, up to 1000v, which is correct?

I must admit I’m not anxious to remove the “big capacitors.” I started to de-solder one last pm and using solder wick I partly destroyed a solder pad. They seem to be mechanically attached as well as soldered in. I think my tip got to hot not used to working with old leaded solder.

I’ve been all over this thing, is it odd that there is nothing that looks burned or damaged and the solder joints seem good?

[Tassieviking]

I am pretty sure any general purpose diodes that handle 6 Amps and 200 volts or more will be fine.
I would consider getting a solder sucker to remove solder from components, they work great for me.
I don't know what country you are in but in Australia they are fairly cheap and easy to get.
Look for one with an aluminium body and Teflon tip at least
They are just a big spring loaded syringe, press the button and the plunger goes back and sucks up the solder.

https://uk.farnell.com/multicomp-pro...older%20sucker

[Helmholtz]

Thanks to all. I’ll order a 6 pack of p600d diodes. I’m seeing 200v, up to 1000v, which is correct?

The "D" stands for the 200V version.

[Oldmactech]

Thanks for the clarification. And your patience.
I own a couple of the solder suckers. There are gobs of solder on this thing so I’m going to have to figure out how to get the caps out without rendering the whole thing useless.

I’ll likely install diodes first in hope that the Caps are good…..

thanks again.

[Delta362]

For those solder joints that are tough, try using a little bit of the SMT removal alloy. Just add it like you were going to solder a joint. A little goes a long way with this. It blends with the existing solder and drastically lowers the melting point. Makes it so much easier to remove items that have large amount of heatsink type surface (such as ground connections on PCB mounted filter caps). Also works great when removing ICs. Just remember when the part is removed to apply solder to the hole and wick everything out nice and clean. You do not want to leave it there as your next solder joint won't be strong if you do.

https://www.amazon.com/gp/product/B017ROFFEW/

[Oldmactech]

Ok, so I replaced all the p600d diodes and tested with my simple light bulb limiter in circuit. Immediately the light bulb went full brightness. (Previously I had had stayed on but dim).

Did a short something while de-soldering, re-soldering?

I did connect a speaker via the output Jack for a second and the hideous noise is gone but replaced with a 60 cycle hum. Didn’t leave it on too long and will test for ac/dc on the jacks later. Ran out of time.

[Oldmactech]

I pulled the 5000uf capacitors and tested them with my multimeter.
One is apparently bad so I would like to replace it (or both.)
Mouser and or other don’t seem to have anything similar.
Attached is a picture, any search tips would be appreciated.

[g1]

Mouser and or other don’t seem to have anything similar.
Attached is a picture, any search tips would be appreciated.

Those are not the modern typical values. Search for 4700uF at 63V (or 80V).

[Tassieviking]

The pins on that capacitor looks very different, can you get a better picture of the mounting pins ?
The most critical part is that the new capacitor has the correct spacing of the pins so they fit into the PCB you have.
As long as the two electrical (plus and minus) leads fit into the holes and the diameter of the capacitor is not to big to fit onto the PCB it should be good.
Higher capacitance and higher voltage rating is fine, as long as both capacitors are the same value.
You might have to use a hot glue gun to mount the new caps if you cant get ones with the extra mounting pins for mechanical strength.

They look like snap in capacitors to me but need a better photo of the leads.

Measure the distance between the leads and search from there.

https://au.element14.com/w/c/passive...df_f1000002_bv