I've just completed my latest repair of a Tannoy Reveal 6D monitor. It was making a crackling noise on start-up, which would last for ten or twenty minutes, if not more. The audio output would be cracking too. But it would go away and the sound would eventually be fine. I suspected capacitors. (Edit - my kids told me it was making a very annoying high pitched sound as well, but I couldn't hear that. I'll ask them if it's gone.)
Upon disassembly and diagnosis with an audio probe and separate amplifier I found that the crackling sound was not present at the output of the filter board...
Valden
Member
Last Activity: 04-27-2024, 04:56 PM
Joined: 09-27-2016
Location: New South Wales
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Re: Tannoy Reveal 6D
Hi Khron. The speakers on my Tannoy Reveal 8Ds have both lost their ‘spish-spish' highs too. Haven't managed to get them fixed yet. Hopefully it's the trim pots, which I have already had a fiddle with. I might just replace them.
My 6Ds are working pretty well at the moment. When the 8Ds crapped out a few weeks back I got serious about fixing the problem with the 6Ds reported in my last post. In that I thought the thermal fuse was playing up, but in the end I got the problem monitor working again by simply stripping it right down and cleaning...Leave a comment:
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Re: Tannoy Reveal 6D
This is a fresh post to this very helpful thread, seeking assistance with identifying the thermoswitch on the power board of my Tannoy Reveal 6D monitor.
Diagnosis: The music was fading out in one monitor, which was the master of the S/PDIF pair. The other monitor kept playing, so I suspected a problem with the audio or power circuit in the problem monitor. Upon inspection, I found that the trace between the transformer connector's pin 3 and the thermoswitch was broken. Soldering in a jumper wire to replace the trace got the monitor working again...Leave a comment:
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Re: Tannoy Reveal 6D
Ah, Variable Resistor! hehe.
Thanks.Leave a comment:
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Re: Tannoy Reveal 6D
It's not a voltage regulator? When I look at the schematic it's called VR1. And yes, it's rated at 1K (with no units, but Ohms it is! ). I'm happy to call it a trim pot, since that's what it's supposed to do.
Thanks for the advice on trying the contact adhesive. I have a can of CRC CO Contact Cleaner for such purposes. Expensive stuff! I've seen others using isopropyl alcohol.
I have to say, if I'd known that the main problem with this monitor would end up being the second surface mount component I lifted, I'd have been lifting...Leave a comment:
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Re: Tannoy Reveal 6D
Re the attenuated tweeter level, I had a look at signal strength at the voltage regulator on the filter board (the trim pot Khron mentioned) and compared the two monitors using the audio probe. The output from pin 14 of opamp 3 goes to pin 1 of the trim pot. With the good monitor the factory set output from the trim pot (pin 2) was a touch lower in volume than the input, to my ear. The trim pot appears to be adjusted fully clockwise, which appears to be fully attenuated, from fiddling with the one on the faulty monitor's filter board.
With the...Last edited by Valden; 10-12-2016, 02:31 PM.Leave a comment:
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Re: Tannoy Reveal 6D
Before I forget, Khron, thanks for your patience and assistance with this. It's been very good of you, to respond so helpfully to a new member's problem. I've really appreciated your advice and encouragement. 
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Re: Tannoy Reveal 6D
I rang Jaycar and to my surprise they said they had just the thing. But when I got there, just before closing, and showed the girl the surface mount cap I needed, she said. 'Oh, I don't think we have any of those!' I settled for the next best thing - a ceramic cap of 10nF and 50V rating.
The monitor is working! But, the high frequencies are significantly attenuated. Could it be the ring-in cap I'm using? I'll check the schematic to see if opamp 2 (IC2) has anything to do with the highs. The tweeter itself is fine. The highs problem moves with the...Leave a comment:
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Re: Tannoy Reveal 6D
I decided to focus on the surface mount components that were single points of failure in terms of creating a short between the negative rail and ground. I lifted one end of C18. Nope. The short's still there. What about C21? Holy crap! The short's gone. Connect it again with a molten strand of solder. The short is back. Break the strand? The short's gone again.
With a bit of luck this could be the fix. Now I'm on the scrounge for a 10nF SM ceramic capacitor.
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Re: Tannoy Reveal 6D
Thanks for the suggestion re cutting the tracks. I'll have to start calling it the Frankenfilter board.
The short/s I'm hunting for is/are present when the board is unpowered, as well as powered. Bewdy!
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I've been checking out the Brymen BM869S. There's a very interesting test video on YouTube, by Joe Smith.
[URL="https://youtu.be/K-4L2JarVxA"]https://youtu.be/K-4L2JarVxA[/URL]Re: Tannoy Reveal 6D
Thanks for the suggestion re cutting the tracks. I'll have to startLeave a comment:
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Re: Tannoy Reveal 6D 8D repair
Status update for repair of Tannoy Reveal 8D studio monitor.
I have confirmed that the power board is working, by using a dummy load to simulate the filter board being connected. In this configuration the two voltage regulators are supplying +15 and -15V, as they should. However, once the filter board is connected, voltage at the output of the negative voltage regulator drops from what should be -15V to -0.1V, relative to ground measured under the big caps on the power board. Measurements taken at the connector of the dismounted filter...Leave a comment:
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Re: Tannoy Reveal 6D
I played audio so I could trace the signal through the opamps, to find if any are not working. Seems a reasonable approach. Luckily, the 7915s are only $1.85. But, the electronics store up the road has only 13 of them. Might not be enough.
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Re: Tannoy Reveal 6D
Bugger. The Eagles killed the 7915 regulator!
I played my iPhone into the analog audio input on the filter board and the 7915 is now reading -0.5V at the output, just as it was before. Now it might not have been the audio that caused this, but that's the only thing I did. I'll buy a few more 7915s tomorrow and try to identify what's wrong on the filter board before playing audio into it. Sheesh!Leave a comment:
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Re: Tannoy Reveal 6D
Yes, the relocated and custom wired 7915 is producing -15V at the output. Having that working correctly makes diagnosing the other fault, up on the filter board by the looks of it, easier!...
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Re: Tannoy Reveal 6D
A quick test with that sacrificial stunt-double speaker shows that my voltmeter readings from my previous post play out as expected. The speaker cone sits still when hooked up to the tweeter pins. It pops out fully extended when connected to the woofer pins.Leave a comment:
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Re: Tannoy Reveal 6D
OK, this is interesting. I've checked voltage at the speaker connector pins. Red probe to positive speaker connector pin.
- with the good monitor, it's 0 for woofer and tweeter, with filter board connected.
- with the faulty monitor, its 14.9V for the woofer with the filter board connected. With filter board disconnected it's 0V.
- For the tweeter connector, it's -15V with filter board connected and -22.2V with the filter board disconnected.
Explain me that!
[b]Wait - I've found a problem with my temporary...
Last edited by Valden; 10-04-2016, 01:16 AM.Leave a comment:
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Re: Tannoy Reveal 6D
I've scraped goop off the even numbered pins of the three amp chips. I'm getting -37.1V at each pin 4, being the negative rail connection.Leave a comment:
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Re: Tannoy Reveal 6D
I proposed 'A shorted amp chip?' Probably not actually.
The amp chips' output is on pin 3. Pin 3 of the middle chip goes to one of the woofer connector pins. Pin 3 of the left chip goes to the other woofer connector pin. This suggests that the middle and left amp chips work in reverse phase. One pushes the cone while the other pulls.
Yep, from following the tracks, that is how the left amp chip works. While the audio input goes to the positive audio input pin 10 of the middle amp chip, it branches off and goes to the negative audio...Last edited by Valden; 10-03-2016, 11:46 PM.Leave a comment:
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Re: Tannoy Reveal 6D
The HF output is extending the test speaker too. The problem is affecting all the amplifiers.
The amplifiers run off the +/- 36V rails, not the regulated +/- 15V rails. Will look for a problem in the 36V rails.
- I'm getting 36.7V and -36.7V from the rectifier.
- looking at the LM3886 amplifier ICs, all three have 36.3V at supply pins 1 and 5 and 16V at audio output pin 3, except for the amp chip closest to speaker connectors, which has 0V at pin 3. A shorted amp chip?Last edited by Valden; 10-03-2016, 09:30 PM.Leave a comment:
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Re: Tannoy Reveal 6D
Khron asked 'Resistance between where the 7915's output should be, and pin 11 (of 14) / pin 8 (correction - pin 4 is ground) (of 8)? Answer - 976 ohm for all them. The 8 pin IC is labelled JR448AC LM833N. Another opamp? Google might know.
Edit - these measurement were taken with the 7915 back in circuit and apparently working.
The current challenge is, what's making the woofer cone extend outwards? This could be because the negative voltage rail is not reaching one of the amplifier chips. I'll try the stunt-double speaker with the...Last edited by Valden; 10-03-2016, 08:48 PM.Leave a comment:
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