3rd Sep 2012, 3:31 am | #161 |
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Re: Bush SRP 31D not producing sound.
ok, I've been tracing the circuit and got to a 470k resistor and I took it out and measured it and found it was reading something like 560k so I changed it for a new 470k and now the fuse bulb glows brightly! I don't understand why though... I made sure that the old resistor was meant to be 470k by the very faded colour bands, also according to the service manual 470k is the highest value resistors next to the potentiometers.
Should I carry on and check the other resistors? |
3rd Sep 2012, 8:26 am | #162 |
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Re: Bush SRP 31D not producing sound.
What was the component designation of the resistor you changed? Was it R7, R13 or R14?
If the fuse bulb glows brightly now, but didn't before, it could indicate a transformer fault or that excess current is being drawn from the transformer. Does the transformer feel hot to touch? Do C15 and C16 feel hot to touch? What's the HT voltage now? Meter on a DC volts range capable of measuring 250V or more. Negative (black) lead clipped to the chassis. Probe on positive (red) lead touching the positive tag of C16. Expect to see about 215V. Probe on positive (red) lead touching the positive tag of C15. Expect to see about 190V.
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3rd Sep 2012, 9:19 am | #163 |
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Re: Bush SRP 31D not producing sound.
I've just read through this entire thread and there's no logic to it whatsoever. Symptoms come and symptoms go, voltage readings change from post to post, the method of taking voltage and resistance readings is described several times.
It seems to me that we might as well start fault finding all over again starting at the power supply and then working back through the output stage, phase splitter, tone/volume controls and finally the cartridge. At the moment the fuse bulb is glowing brightly and the mains transformer is a replacement from another player. The rectifier and smoothing capacitors had been replaced before you got the player. Are the screws securing the wires of the mains lead to the mains plug pins tight? Are all soldered connections to the right of C15 on the diagram in good condition ie not dry joints? Is the voltage selector making good contact? Once you've checked these things measure the HT voltage as decribed in post #162. If the reading are very low try operating the mains switch several times in case it's not making good contact. If the fuse bulb glows brightly does it dim when either or both valves are unplugged? If you get good HT readings, monitor them for several hours, noting any substantial changes. We need to be sure that the power supply is working correctly before moving on to the output stage.
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3rd Sep 2012, 10:18 am | #164 |
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Re: Bush SRP 31D not producing sound.
Just a thought but having re-read some of the thread, when the voltages were checked on the smoother, it was recorded a voltage on the negative terminal (which Graham pointed out is incorrect). Coupled with the intermittent go/no go symptoms when the player is recased, are we looking at a faulty ground connection somewhere?
If the cap had no ground, the negative terminal would read close to the positive supply. Rob |
3rd Sep 2012, 10:20 am | #165 |
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Re: Bush SRP 31D not producing sound.
I'm guessing here that as the capacitor is a dual type (?) Spencer measured each terminal thinking that one must be pos, the other neg, and didn't realise that the can was the neg.
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3rd Sep 2012, 10:29 am | #166 |
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Re: Bush SRP 31D not producing sound.
Yes I agree but if you read through all the voltages posted, (if you have the time!) It sometimes appears that the circuit is in a working state whilst at others it throws up voltages that are clearly not correct.
So what I'm wondering is, are we looking for an intermittent connection as opposed to a component failiure. The main problem being is that bits have been replaced ad-hoc and we have no way of checking their correct replacement in terms of value or correct connection. If only the OP could get it to someone on here, half an hour on the bench would probably see it working. Rob |
3rd Sep 2012, 10:30 am | #167 | |
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Re: Bush SRP 31D not producing sound.
Quote:
It would be worth checking that the cap is tight in the clip and the clip is securely bolted to the chassis. EDIT. I've reposted the picture here, as it may aid us in describing how to take voltage readings.
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3rd Sep 2012, 2:07 pm | #168 |
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Re: Bush SRP 31D not producing sound.
had a look at the things that Graham told me to, I have noted that the mains switch is taking from the live 240 ACV and neutral taking 0 ACV. When I turned the machine on for a minute or so (scared to have it on any longer!) I did my measurements and then when I unplugged it, I felt the transformer and it had no temperature. I wpould also like to note that the transformer gives off a nasty smell and sounds like its burning. The recitfier seems to be taking in only 40 ACV and giving out 0 DCV. I then checked the dual can which you refer to and it gives nothing.
Also tried taking the valves out and the problem carried on. I would also like to point out that alarmingly when I turned the chassis the right way around there was some grease drips from the transformer! Isn't it a bit odd though that two transformers can prove dodgy in the same machine? Also, I checked all the joints by melting the solder and letting it re-set (making sure there was a tight connection too) Also the photo there is not a correct one, it is from an SRP31 which I had spare... I do have a nice updated photo of the SRP31D from before I started changing resistors and one after too I can post this again if its any use? Last edited by Spencervs; 3rd Sep 2012 at 2:17 pm. |
3rd Sep 2012, 2:21 pm | #169 |
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Re: Bush SRP 31D not producing sound.
It's odd that changing one resistor, which was slightly off value, is causing distress to the mains transformer. You must have introduced another fault somewhere.
Turn off the motor with switch S2. Pull out the valves. Unscrew LP1 Disconnect the rectifier from the secondary winding of the mains transformer. Apply mains power and measure the AC voltage across the secondary of the mains transformer. That's between chassis and the point you disconnected the rectifier from. What voltage do you measure? Is there still smoke and heat from the transformer? EDIT. Yes please do post a recent picture of the actual chassis. Then we'll know that we're singing from the same hymn sheet.
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3rd Sep 2012, 2:49 pm | #170 |
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Re: Bush SRP 31D not producing sound.
aha! I found that it seems to work normally. I am reading 240 ACV from the line to the rectifier, I also measured the end of the wire to the rectifier and it too measured 240 ACV. There is a slight buzz sound though, but surely that's normal?
Also here's the photo of the record player before fiddling. I can take new ones if it's any good. http://s2.photobucket.com/albums/y8/...t=IMGP0501.jpg Last edited by Station X; 3rd Sep 2012 at 3:16 pm. Reason: Thumbnail added. |
3rd Sep 2012, 3:03 pm | #171 | ||
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Re: Bush SRP 31D not producing sound.
From post #168.
Quote:
Quote:
You need to check very carefully for dodgy connections and wires shorting out to places they shouldn't be. What voltages are you getting on the dual can now?
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3rd Sep 2012, 3:37 pm | #172 |
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Re: Bush SRP 31D not producing sound.
when I reconnect the rectifier, I get the fuse bulb glowing again. Is it not possible that the rectifier is dodgy? it has in the past thrown lower voltages than it should do... perhaps changing the resistor was the last stress it could handle? I find this all very odd. This player defies logic. I would have thought if the rectifier is dodgy then it wouldn't cause a bright fuse bulb but rather just stop the current there? unless there's some kind of feedback? With the rectifier connected I get an input of 40-50 ACV and the same from the transformer, however without the rectifier I am getting an output from the transformer of 240 ACV
Dual can is connected directly from the rectifier so I wouldn't get anything if it's disconnected I imagine |
3rd Sep 2012, 3:52 pm | #173 |
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Re: Bush SRP 31D not producing sound.
Another good thought, what's the chance of R23 causing a problem? I am aware of these going high over time but that would not normally affect things.
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3rd Sep 2012, 3:55 pm | #174 |
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Re: Bush SRP 31D not producing sound.
Something else for Spencer to try.
get your multimeter out, stick it on the highest ohms setting, disconnect the filter caps C15 & C16 & check them the same as a resistor, it should read infinite ohms. One is now wondering if these caps could be dragging everything down somehow. |
3rd Sep 2012, 4:01 pm | #175 |
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Re: Bush SRP 31D not producing sound.
I wasn't aware that Spencer had disconnected the rectifier from the transformer. I know I asked him to do it, but he said the player was working normally. Our ideas about what working normally means obviously differ.
It looks like the transformer is healthy. So with the rectifier disconnected the next thing to check is the smoothing capacitors. This can be done as described by Glowing Bits! Meter on resistance range. Negative lead of meter to chassis. Positive lead to each tag of the can in turn. Reading should start low, but rise to near infinity as the caps charge from the meter's internal battery. While you've got R23 disconnected check its resistance.
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3rd Sep 2012, 5:40 pm | #176 |
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Re: Bush SRP 31D not producing sound.
ok, tested C15 and C16, they reach the 20M setting and infinite, tested the resistor too and I noticed that it struggles to reach the 3.3k but it does reach it eventually. dunno if this is an issue, it seems to me though that the rectifier is the problem?
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3rd Sep 2012, 6:01 pm | #177 |
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Re: Bush SRP 31D not producing sound.
You cannot assume that the rectifier is the problem.
Try the following. Motor off. Leave the rectifier and capacitors disconnected for the moment. Screw in LP1. Check that you still have about 220V AC on the lead going to the rectifier and that everything is cool and smokeless. Plug in any valve. ie valve and LP1 plugged in. Check that you still have about 240V AC on the lead going to the rectifier and that everything is cool and smokeless. Plug in the other valve ie both valves and LP1 plugged in. Check that you still have about 240V AC on the lead going to the rectifier and that everything is cool and smokeless. These tests should prove whether of not you have a problem with Low Tension (LT) current overloading the transformer.
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3rd Sep 2012, 6:09 pm | #178 |
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Re: Bush SRP 31D not producing sound.
Let's assume that all worked, that LP1 and the valves all light up and everything is cool with the AC voltage on the secondary around 240V AC.
Reconnect C16 to the rectifier but make sure no other leads or components are connected to C16. Measure the DC voltage across C16. Black lead of meter to chassis (I shalln't repeat that again) and red lead to the terminal of C16 which is connected to MR1. What voltage do you see? Is everything cool?
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3rd Sep 2012, 6:13 pm | #179 |
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Re: Bush SRP 31D not producing sound.
Next move if all is OK.
Reconnect R23 between C15 and C16, but make sure the only other connection to C15/C16 is to the rectifier. This effectively isolates the power supply from the HT load. What DC voltage do you see across C15 and C16? Is everything cool?
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3rd Sep 2012, 6:23 pm | #180 |
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Re: Bush SRP 31D not producing sound.
I just don't understand this player... I tried to test the transformer again but it seems the secondary winding is dead. I am getting volts on the primary winding to the fuse bulb of 240ACV but am getting nothing on the secondary winding to the rectifier. I can't believe how illogical this is! I know for a fact that last time it was showing 240ACV beore when the rectifier was disconnected! what can be causing the last two transformers to go?
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