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Old 17th Jun 2012, 2:41 am   #1
Spencervs
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Default Bush SRP 31D not producing sound.

Hi guys, got this troublesome but in good condition SRP31D which has decided to just stop producing sound! It has done this before but normally it will be playing music then fade out to nothing. The turntable will be revolving but no sound will be being made. Now it won't work full stop. Tried putting a new cartridge on it but nothing happened, even touching the little wires made no buzz. I guess it's the amplifier at fault. What could it be?
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Old 17th Jun 2012, 6:04 am   #2
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Default Re: Bush SRP 31D not producing sound!

There is a round fuse bulb under the front lower control panel. It could be it is not firmly screwed in. I have had this problem and sounds similar. The red power light also goes out when this happens.
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Old 17th Jun 2012, 12:52 pm   #3
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Default Re: Bush SRP 31D not producing sound!

The fuse bulb is glowing brightly and the light bulb for the indicator is on too. Just tried unscrewing it and re-screwing it but has made no effect, also tried replacing the valves with a pair of ECL83s that I have spare. It's very off because the amp sounds like it should be working. I put my ear right up to the speaker and I heard a hum. What could have possibly gone wrong?
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Old 17th Jun 2012, 2:54 pm   #4
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Default Re: Bush SRP 31D not producing sound!

The fuse bulb in mine does not glow at all, so something must be causing a high current. Voltage checks around the power supply/output stages should point to the cause.

PS: Doesn't the D use ECL86s the original and C used ECL83s ?

Last edited by AC/HL; 17th Jun 2012 at 2:59 pm. Reason: Afterthought
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Old 17th Jun 2012, 3:02 pm   #5
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Default Re: Bush SRP 31D not producing sound!

Quote:
Originally Posted by Spencervs View Post
The turntable will be revolving but no sound will be being made. Now it won't work full stop.
You're none too clear in respect of the symptoms. Does "Now it won't work full stop" mean the turntable isn't working?
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Old 17th Jun 2012, 6:27 pm   #6
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Default Re: Bush SRP 31D not producing sound!

Good point, the sound isn't working but the turntable is. The amp does produce a quiet hum when you press your ear to the speaker but that's all it does and the valves light up (it takes ECL86s but I did wonder if it was the valves at one point so I replaced them briefly with spare ECL83s as I was told the circuitry for the SRP31D was pretty much the same as the SRP31 which takes the ECL83s). The sound used to work well then rarely fade out to nothing then after I turn it off and knock it where the valves are, it would produce sound again. Now it's not making sound at all.

It would be worth noting that the light next to the fuse that indicates that the machine is on fluctuates brightnesses,so some kind of power surges to the machine? What could have failed to make this happen?
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Old 17th Jun 2012, 6:42 pm   #7
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Default Re: Bush SRP 31D not producing sound!

Hi,
Using ECL83's in place of ECL86'smay cause the fuse lamp to glow due to high current drain as there is no guarantee that the pin connections (heaters apart) are the same on the different types of valve.

As has already been mentioned the C series of these players use ECL83's and the D series use ECL86's so the first thing to do is make sure that you have fitted the correct type of valves and hope that you have caused no further damage by trying the wrong type.

The metal rectifier is known to cause problems in these players so check that the HT on the +ve terminal of this device is around or above 200 volts DC, a reading of around 80 to 100 volts would indicate problems in this area.

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Old 17th Jun 2012, 6:53 pm   #8
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Default Re: Bush SRP 31D not producing sound!

Oh. I replaced the valves very quickly, they have the right ones now. Is the rectifier you speak of the same as the selenium rectifier? What is its purpose in the machine and what is HT and +ve?
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Old 17th Jun 2012, 7:16 pm   #9
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Default Re: Bush SRP 31D not producing sound!

The rectifier provides DC from the mains derived AC, and is used along with a capacitor, to supply the amplifier. The HT is the high voltage line for the valves. +ve refers to the positive DC output terminal of the rectifier. Measure the voltage across this.

If none of this makes sense, I'd stop right there and get it to someone who has the required experience before you wreck it completely.
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Old 17th Jun 2012, 7:24 pm   #10
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Default Re: Bush SRP 31D not producing sound!

I get it! Thank you. I imagine that the capacitor you speak of is the big can one? So if it measures 80-100V then it needs replacing?
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Old 17th Jun 2012, 8:35 pm   #11
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Default Re: Bush SRP 31D not producing sound!

No. Check the output of the metal rectifier, which will probably look like this:
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Old 18th Jun 2012, 1:07 am   #12
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Default Re: Bush SRP 31D not producing sound!

I can't find the metal rectifier at all, all I seem to have is a selenium one (which I am led to believe is the brown square object on the end)
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Old 18th Jun 2012, 6:47 am   #13
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Default Re: Bush SRP 31D not producing sound!

Just looked up this model on google, the square block to the far right is the rectifier, you should have around 200VDC after the rectifier (HT line).
Make sure all multimeter readings are taken with the black lead on the chassis, this is (or should be) the negative/return for everything,apart from the heaters, if it ain't, I'll be quite surprised!
Hope this helps to get the unit closer to working!
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Old 18th Jun 2012, 12:24 pm   #14
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Default Re: Bush SRP 31D not producing sound!

Quote:
Originally Posted by Spencervs View Post
I can't find the metal rectifier at all, all I seem to have is a selenium one
"Metal Rectifier" is a generic term used fairly loosely to cover just about any static rectifier that isn't thermionic or silicon / germanium.

They will all have some sort of metal case or heatsink in their construction to allow heat to be conducted, convected or radiated away from the device.

Both the one in your player and the pictured one are contact cooled types. Others have multiple fins for air cooling.
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Old 18th Jun 2012, 3:26 pm   #15
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Default Re: Bush SRP 31D not producing sound!

Looking at this again, if this is a 31D then the ECL83's will not work and should not be fitted because the pin out is different.

If you've put ECL83's in this and tried it, then those valves are probably dead now. Valves are hardy, but if you put current in at the wrong pin and it ends up on the wrong grid, it won't take long!

http://www.r-type.org/exhib/aai0108.htm

http://www.r-type.org/exhib/aaa0034.htm

Are they lit up? Silly question I know, but they are in parallel and if one isn't lit, swap the ECL86's over and see if the unlit valve lights in the other socket.If one does not light in either socket and the other does, you have found your problem! If neither valve lights in one socket, then look at that socket and wiring to it. If they are both out, then it's either the transformer, the wiring or both valves. If the lamp across the valve heaters is lit. then check both valves.

I don't know whether one or both ECL86's have bitten the dust, but the amplifier is not working now and it stopped with them in it. They may be OK, I don't know.

How loud is the hum from the speaker? There should be volts on both the smoothing capacitors, which are linked by R19 (Bush manual.)

Now, the $100 question : Are you OK with the electronic side of it. If you are and you have a meter, then come back and tell us. If you want to learn, buy a meter from Maplin and we'll take you through it. The other option is to get one of us to take a look.

Cheers,

Steve P.
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Old 18th Jun 2012, 8:53 pm   #16
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Default Re: Bush SRP 31D not producing sound!

Just had a look at the valves, both ECL86s are glowing, so I assume they are fine. Speaker hum is quite quiet, you can hear a quiet hiss if you listen out for it and my ear can hear hum from around 15cm away although before it stopped working there wasn't really any hiss or hum.

I will be honest, I am not that advanced in my knowledge of electronics but I wouldn't mind learning if that's OK
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Old 18th Jun 2012, 9:12 pm   #17
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Default Re: Bush SRP 31D not producing sound!

Glowing does not mean a valve is OK. It means the heaters are working - nothing more.

Go and get a meter and a few good tools from Maplin. Also, despite the fact that it uses ECL83's rather than the ECL86's, you can download the data from here..

http://www.service-data.com/product.php/638/1039

Cheers,

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Old 29th Jun 2012, 11:40 am   #18
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Default Re: Bush SRP 31D not producing sound!

Right, sorry for the slow reply there! I got myself a multimeter and tested the rectifier as asked before. I found when opening this record player (which I had never done before due to the nuts being too tight) that the rectifier and can capacitor have been replaced since its manufacture. In fact the two components have been replaced post 1989 as it said it was made in Germany. I tested the connector with the grey wire leading to the transformer (I assumed this was the line to the valves as the red wire went to the speaker section) with the meter set to 750 ACV and got a reading in the 220s. I was told to measure it in DCV but when I did, I got negative numbers! so was I reading the wrong bit? Also I had the black lead on the chassis
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Old 29th Jun 2012, 8:47 pm   #19
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Default Re: Bush SRP 31D not producing sound!

Now you've got a meter, we may get somewhere.
The gray lead you're referring to looks pink on the pic, this is going to the right connection on the rectifier, this is AC HT (high woltage) from the transformer, the red wires on the left is where we will be taking readings from, if you're getting 220v from the red wires, this tells us the rectifier is serving it's purpose.
It is now worth noting that all voltage readings will be taken in DC, unless otherwise advised.
One of the red wires should go to the capacitor next door to the rectifier, while the other should go to the speaker transformer (centre tap for push-pull).
There should be two wires coming off the speaker transformer to the anodes of the output valves (pin 6), with the black meter lead to chassis, the meter set to the 1000vDC range, carefully find pin 6 and measure the voltage on both valves (both pin 6), it should be around 210vDC.
If, so far, you've managed to find the anode and taken a measurement, please get back to us the the result, then it's time to go further with it.
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Old 30th Jun 2012, 9:51 pm   #20
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Default Re: Bush SRP 31D not producing sound!

OK. Very confused, tried to test the rectifier with the multimeter again from the red wire and I got nothing! No reading whatsoever except for a one blipping on the screen then vanishing to zero again, but there wasn't even a noise of electricity connecting yet the bulb was working in the machine. I did however take off the wire that connects the cartridge of the tone arm to the amplifier as it was making things extremely difficult due to its inability to allow me to pull out the chassis. The fault is not that of the multimeter as I tested a battery with it and it gave me the correct DCV. What on earth is going on?
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