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Yamaha PM430
Old 3 weeks ago
  #1
Yamaha PM430

Hi GS

I just bought this small Yamaha PM430 and are about to start working on it. It has been years since I last did something like this and wanted to ask you, fine people, for some advice.

1. I will re-cap this, starting with the PSU. What electrolytics are considered good for a project like this, and should I replace with the same values as the one already there? The largest caps on the powersupply are 1000uF 50v (for example). Would it be a good idea to replace the 47uF/16v on the preamp board with some Nichicon UVZ 47/25v? (I have a few from another project I did).

2. I will use the console for tracking drums. I need to install some kind of direct outputs on the channels. I do not know how to do it and I am not really sure where to tap the signal to feed whatever it will be. Advice on this would be appreciated. Any of you done this on a PM430 before?

Thanks in advance.

Richard
Attached Thumbnails
Yamaha PM430-img_3474.jpg   Yamaha PM430-img_3490.jpg   Yamaha PM430-img_3491.jpg  
Old 3 weeks ago
  #2
Lives for gear
 

I'm no expert but as far as I understand, there should be no problem with substituting electrolytics of higher voltage ratings as long as they are the same capacitance. I think there are scenarios where changing the capacitance level may be desirable (Jim Williams recommends some slight value differences for the coupling caps in the Peavey VMP2 and VC/L2, which I just got done recapping), but only if you know what you're doing, and almost certainly not in the PSU.
Old 3 weeks ago
  #3
Lives for gear
I would increase the capacitance in the PSU, 1000uf is low and higher capacitance will make your power rails more stable.

Looking at the schematic is always the first step. If you have it, post it, itโ€™s easier to give specific advice.

For the direct outs, I did this on a pm700 by tapping off one of the monitor sends using switching jacks. So if nothing is connected the signal still goes to the monitor send, but if you insert a 1/4โ€ cable then it interrupts the flow and goes to the direct out. It was unbalanced.

I think I tapped it right after the pot for the monitor send, or right after the cap after the op amp for the send. Schematic might jog my memory. You can also search GS for it, the info is all here. You need to add 100r resistors in series as well, I canโ€™t remember why exactly but itโ€™s in the pm700 direct out thread.

Good luck! Punchy little mixer.
Old 3 weeks ago | Show parent
  #4
Quote:
Originally Posted by Whoopysnorp View Post
.... but only if you know what you're doing, and almost certainly not in the PSU.
Thanks, I am really not an expert and for the most part, I do not know what I am doing.

I really want to understand more. When I study the schematic, questions come to mind at once.

1. Why are coupling caps 10uF?
2. Why 220ohm resistor in front of the first opamp and 47k to ground?

...that sort of thing.

Thanks again.

Richard
Attached Thumbnails
Yamaha PM430-skjermbilde-2020-11-08-kl.-18.10.32.jpeg   Yamaha PM430-skjermbilde-2020-11-08-kl.-18.11.14.jpg  
Old 3 weeks ago
  #5
Am I right when I say that the 10uf capacitor and the 47k resistor form a high pass filter?

That would give a cutoff frequency about 0,338Hz (according to an online calculator)

Richard
Attached Thumbnails
Yamaha PM430-skjermbilde-2020-11-08-kl.-18.44.34.png  

Last edited by Hayman; 3 weeks ago at 07:23 PM..
Old 3 weeks ago
  #6
Lives for gear
 

You're way ahead of me already. I'm going to shut up and listen for a bit, as I'm considering recapping my Sony MXP390.
Old 3 weeks ago
  #7
Lives for gear
You can replace the 1000/50 with 2200/50 Panasonic FC, they are 18 mm diam. and 7.5 mm lead spacing, see if those will fit. Yes you can replace the preamp board 47/16 ones with the 47/25 Nichicon UVZ, and you can use also those in the PSU (the ones at the bases of TR15 and TR16). For the rest of the PSU use any of the Panasonic F- series (FR, FM, FK, FC) you can find in the values you need. For the DC blocking bipolars, Nichicon Muse ES.
Old 3 weeks ago | Show parent
  #8
Lives for gear
Quote:
Originally Posted by Hayman View Post
Am I right when I say that the 10uf capacitor and the 47k resistor form a high pass filter?

That would give a cutoff frequency about 0,338Hz (according to an online calculator)

Richard
Yup.
Old 1 week ago
  #9
Hello again.
Have replaced some capacitors now. In the power supply, the main outs and one channel. Problem now is that I have lost audio signal completely. It seems that my +-22v are ok but my +-15 are not. They read close to nothing. As far as I can tell, the transistors (power supply) are ok. What should be the next thing to check?

Thanks
Richard
Old 1 week ago | Show parent
  #10
Two mistakes I did so far:
Replaced the 220uF capacitors in the powersupply with 470uF. Have changed them now to the correct value.
Inserted the ribbon-cable upside down for testing. Have corrected this too.
Richard
Old 1 week ago
  #11
These are my reading from power supply transformer (GA8029) to power supply PCB (AC).
Red1 24,06v
Red2 24,12v
Black 0,003v
Blue1 5,64v
Blue2 5,86v

Thanks
Richard
Old 1 week ago
  #12
Lives for gear
The +/-15 V is taken from the +/-22 V via simple voltage dividers where the series resistors (the 47R ones) are fusible (as you can see in the schematic), they may have gone when you inserted the cable the wrong way. Using 470u caps instead of 220u would have caused no problem.

Edit: TBH I'd take the opportunity to replace those resistive dividers with 7815/7915 regulators, that will give you a much cleaner and stable supply for the opamps.
Old 1 week ago | Show parent
  #13
Thanks,
Are you saying that those 47R resistors might be blown?
Richard
Old 1 week ago
  #14
Lives for gear
Yes, if you still have the +/-22 but not the +/-15, well, they're what's between the two voltages.
Old 1 week ago | Show parent
  #15
Iยดm a little confused. There are two fuses that are listed as 47ohm 45mA. Should I replace those?
Thanks
Richard
Old 1 week ago
  #16
The fuses are all 1A/250v. They seem to be ok. I don't have those values available. Only 750mA and 2A.
Richard
Old 1 week ago
  #17
Lives for gear
They're not fuses but fusible resistors, i.e. special resistors basically guaranteed to fail to open without catching fire. You should replace them with the same thing (*), or remove the voltage dividers altogether (those and the 3k3) and use standard 3-terminal regulators, as suggested above.

(*) Edit: 145 mA across 47R is ~1W, so you need something like this.
Old 1 week ago
  #18
Thanks again.
It is those white ones you refer too, right? They are marked 45mA 47Rk Micron 99.
Attached Thumbnails
Yamaha PM430-47r.jpg  
Old 1 week ago
  #19
Lives for gear
Yes, but I think it's 145mA, it's what it says in the schematic too, no?
Old 1 week ago
  #20
Lives for gear
Those are likely them. You can measure them, if there is infinite resistance then you know they are blown (broken, not passing voltage).

If they are the problem, you should be able to read 15v between ground and one leg of those resistors.

Also, note how they are mounted. They are elevated from the pcb on purpose. If you replace them, make sure to mount the new ones the same way, it prevents damage to the pcb in the event of catastrophic failure.

Also, how do you know the transistors are fine? You mentioned it earlier in one of your posts.
Old 1 week ago
  #21
Lives for gear
One more thing, it is also possible you have a cold solder joint or two somewhere that is stopping the 15v rails from working.
Old 1 week ago | Show parent
  #22
Yes, It says 145mA in the schematic.
Old 1 week ago | Show parent
  #23
Thanks,
I read -22v and 0v on the first.
22v and 0V on the second.
13v and 13v on the last one.

As for checking the transistors, I just put my meter in diode mode and checked base-collector and base emitter. It read about 6 volts on both so I figured that it was ok.

Richard
Old 1 week ago | Show parent
  #24
I learn something new every day. Thanks.
Old 1 week ago | Show parent
  #25
Lives for gear
Quote:
Originally Posted by Hayman View Post
Thanks,
I read -22v and 0v on the first.
22v and 0V on the second.
13v and 13v on the last one.

As for checking the transistors, I just put my meter in diode mode and checked base-collector and base emitter. It read about 6 volts on both so I figured that it was ok.

Richard
That's correct and it confirms that they are blown. Not the last one, which I guess is the 3R9 in the 12V supply, right? And I guess you mean 0.6V... If you measured the transistors without removing them from the PCB you may get the wrong reading, but in any case the fact that you do get the +/-22 V supplies suggests that they are fine.

The next thing after fixing the supply will be to see if the rest of the circuit survived the reversed polarity... The blown resistors may have saved the standard opamps, but the ones fed directly from the +/-22 V supplies may be damaged. That's the NE80100 at the outputs, which are actually proprietary Yamaha discrete opamps. Fingers crossed because those will be hard to find, and if you do they won't be cheap. I've found the schematic though and it wouldn't be difficult to make reasonable clones on little PCBs, but I don't know if you'd be up for such complications...
Old 1 week ago
  #26
It was a stupid mistake. I actually had marked the ribbon left and right.
Old 1 week ago | Show parent
  #27
Itโ€™s bedtime in Norway now. Will check out the 7815/7915 tomorrow. Donโ€™t really know how that works, but I have some regulators somewhere. Thanks to all. Richard
Old 1 week ago
  #28
Lives for gear
If youโ€™ve blown the Yamaha discreet op amps you may be doing yourself a favour, because they suck. I replaced some of mine with cheap build yourself kits (maybe $20 each) and the master outs sounded much better. Only thing is only one or two of the ones on the market can take 22 or 24 volts, most stop at 16 or 18.

If yours are blown Iโ€™ll look up which ones I used and let you know.
Old 1 week ago
  #29
Lives for gear
Quote:
Originally Posted by Hayman View Post
Itโ€™s bedtime in Norway now. Will check out the 7815/7915 tomorrow. Donโ€™t really know how that works, but I have some regulators somewhere. Thanks to all. Richard
See attached. Notice the different pinout, the 7815 goes 1, 2, 3 = Input, GND, Output and the 7915 goes 1, 2, 3 = GND, Input, Output. The Ins and Outs correspond to the fusible resistors, so you can place the regulators there, but I don't see the 3k3 resistors nearby, so you may need to drill little holes in the PCB to make the GND connections (they don't have to go where the 3k3 resistors are, you just need to connect them to ground).

Edit: forgot to mention that with 1W power dissipation and no heatsink those regulators will work fine but will get quite hot, I'd use some small TO-220 heatsinks, like these, so you don't burn your fingers if you touch them.
Attached Thumbnails
Yamaha PM430-pm430-regs.png  
Old 1 week ago
  #30
Thank you for all your help.

I have some new regulators that I wonder if I can use?

LM337KC (negative regulator)
LM317T (positive regulator)
LM350T (positive regulator)

Richard
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