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Beomaster 2400 touchpad issue - it's not working, pins are touching!!!

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Irata
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Irata posted on Sat, Jan 28 2017 3:49 PM

ok guys, I need some help please.

i just completed a full cap and lamp replacement from Martin. I also did the 2 large caps, and that seems to have remedied my muffled channel issue. 

Now the problem. 

When I install the touchpad panel, none of the "buttons" work. I've taken it apart and reinstalled everything multiple times. Quadruple checked that all pins are aligned and touching. 

All inputs are functional and switchable with the remote. All inputs are functional and switchable when I use my finger, or touch the "fork" that rests against the pin with a screwdriver. 

I have two functional 2400s, so I swapped touchpad panels. Both work exactly as they should on the other one, but neither function on this one. 

WHAT AM I MISSING?

is there anything else that makes this function other than a strictly mechanical connection between the forks and the pins?

I feel like I'm going insane. 

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Irata
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Irata replied on Sat, Jan 28 2017 8:43 PM

I've done some more digging, but haven't come up with anything

I have 12-13 volts at the collector of all the input selector transistors. But I don't have -6 at the base of TR22, which I think I need. On my working 2400 I have -6v at the standby pin and the base of TR22. 

The non-working one shows 0 at the base. I've replaced it even though it seemed to test ok out of circuit. 

I have 15v at the positive and 13v at the negative of c86, 13-14v at both ends of r128

15v at the positive of c71

nothing at either end of c87, the base of tr22, or the standby pin.

Can anyone smarter than me tell me where to look next?

i can't figure out why all the inputs work with my finger or the remote, but not the contacts of the touch pads. 

Irata
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Irata replied on Sun, Jan 29 2017 3:17 PM

Ok, I've replaced all the sensitouch transistors on the off chance it was disrupting the circuit. No dice. Same issue.

I've cleaned all the touch pins and forks, there is absolutely no issue whatsoever with their contacting cleanly and with tension.

Why in the world does this work with my finger, flawlessly I might add, but it is literally dead through the touch panel?

All caps and lamps per Martin have been replaced, so it can't be some weird lamp wattage nonsense.

I noticed in Martin's directions that the C71 polarity varies. I am 90% certain I put it in the same way, and it corresponds with the markings on the board, and I'm getting 15V at it. Is there any chance it should be installed against the markings on the board? I hesitate to switch it because I don't want to blow anything up, and I'm pretty sure it's in the right way. I was absolutely sure when I did it, but now that there's this weird issue it makes me question it.

Anyone?

Irata
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Irata replied on Sun, Jan 29 2017 4:10 PM

Here's a comparison of readings from the working and non-working 2400s. Don't know if this is directly related to my touchpad issue, but it seems likely. If anyone can help me figure out why I'm getting different readings at the standby pin, I'd sure appreciate it.

Dillen
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Dillen replied on Sun, Jan 29 2017 4:52 PM

I'd say a shorted B-E on the transistor, or the touchpads bronze-fork shorting to R129 (bent resistor).
But keep in mind, that the emitter should have a 9V AC signal - not a DC.
If the problem affects all sensitouch pads, then more likely a problem around TR7 on the volume control board.
Is TR7 powered and oscillating?
If so - perhaps a broken L1 on the volume control board - or no connection to it.

Martin

Irata
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Irata replied on Sun, Jan 29 2017 6:00 PM

Thanks Martin. TR7 seems to be working, it reads the same on both machines.

New wrinkle that I've discovered. Everything seemed to be working fine before I replaced the 2 large filter caps, I used 6800uf 35V Nichicons.

Now it seems that the relay is stuck open (or closed). When I use my finger to select an input from standby, the relay really doesn't click anymore. It switches, but there's no click. The working one has a very audible click and visible movement.

ALSO, PROBABLY A MUCH LARGER ISSUE- In standby, the filter caps on the non-working one are reading and I think they shouldn't. The left is showing -31.5 and the right is reading 31.5.

On the working one the large filter caps don't read anything in standby. Once an input is selected, THEN the left shows -31.5, and the right 31.5.

I replaced the wires exactly as removed, and I replaced as I went along to make sure I didn't hose anything up. AND YET, I've hosed everything up.

Any brilliant insight?

Irata
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Irata replied on Sun, Jan 29 2017 6:52 PM

How about a bad OD1 rectifier?

The 2 neutrals are each reading 23.4 AC at the rectifier, and of course at the relay. This is in standby as well as operating modes.

On my working 2400, they don't read 23.4 UNTIL it's out of standby.

Workable hypothesis?

Irata
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Irata replied on Sun, Jan 29 2017 7:14 PM

Just to confirm I replaced the large caps right...

The yellow and blue wires go to the negative of the left cap, the red and orange go to the positive of the right cap, and the blacks basically bridge between the + and - of the two.

That's how it was when I took it apart, and how it is on my working example. It's just not functioning like it should anymore.

Irata
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Irata replied on Sun, Jan 29 2017 7:59 PM

Went to look into your L1 suggestion...

Neither of my 2400s have an L1. They do have an odd looking TR21.

They're both the 3 IC versions, which unfortunately don't align with the schematics I have.

Dillen
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Dillen replied on Sun, Jan 29 2017 9:19 PM

If it is still working if operated from the remote control - then it points to two faults at the same time.

TR7 on the early (1-IC) volume control version corresponds to TR21 on the later (3-IC). Check that it produces a nice AC sine.

With the amplifiers rectifier (+/- 31V) powered at all times and no relay clicking, the standby circuit must also be checked.
It seems to be unable to cutoff power to the relay coil.
Bad IC9, TR31, TR32, D55?
Are the tonecontrol indicator lights on?
Volume indicator lights on?

Martin

Irata
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Irata replied on Sun, Jan 29 2017 10:38 PM

Checking the AC sine is going to be beyond my equipment and expertise unfortunately. 

I will check IC9, TR31, TR32, and D55. 

Yes, once out of standby, all the lights are operational. 

Irata
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Irata replied on Sun, Jan 29 2017 11:59 PM

So I'm using my working 2400 as a comparison, and it appears that all those components read about the same.

I figured out that LI is the same on mine... TR21 (TR7) checks out on both machines.

TR31 is what I replaced initially to get this one back up and running. It seems to be ok still. I pulled TR32, and it appears to be good as well.

IC9 returns the same results across both machines. Same for D55.

Argh.

Dillen
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Dillen replied on Mon, Jan 30 2017 6:43 AM

Perhaps the relay itself.
Are its contacts still closed with the Beomaster disconnected from mains?

Martin

Irata
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Irata replied on Mon, Jan 30 2017 1:31 PM

It was the relay. I went to listen again, because I knew I could hear it trying to kick the relay over, and it was. I could hear it sending a signal to open/close the the relay. I was doing it a few times, trying to determine if I could see the contact move just the slightest bit, and then it popped open!

For the uneducated like me, is this something that needs to get cracked open and the contacts cleaned? It looks like there's just a plastic cover that can be taken off.

So it seems that the open relay issue has been solved, which brings me right back to the sensitouch controls not responding.

Irata
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Irata replied on Mon, Jan 30 2017 1:35 PM

I put it all together again in the hopes that the relay issue solved my problem, but it didn't.

I can operate everything with my finger, and the remote control, but not with the control panel.

I've cleaned all the pins and contacts, and replaced all the transistors related to the sensitouch pins.

Since there's access from the front, where you can see that the contacts are all aligned, with the slightest contact on an input fork with the tip of a screwdriver triggers the input selections.

It's like there's an invisible force field between the cover and the pins.

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