Bush SRP 31D not producing sound.

[Spencervs]

Things seem to have taken a turn for the worse. I decided to unsolder the mains wire and cut it down to get rid of the solder melt marks in case we had an accident like the wires touching and going bang.

Fine, however it will not turn on now. I did have trouble getting the wire closer and did pull it a bit so maybe a wire snapped in the cable? I have wired it correctly and got a reading with the multimeter on the live of 240VAC, however the neutral was 0VAC; is that right? Checked the transformer and only one connector leading from the fuse shows voltage. How on Earth has this happened?

[julie_m]

The neutral of the mains should be at, or very close to, 0V. Earth and Neutral are usually joined, where the cable enters the house.

Measure (carefully!) volts across the primary of the power transformer, also each of the secondaries if you are seeing 240 on the primary. 0V on the primary with the mains on means a fuse or aomething else in series with it has failed. 240V on the primary and nothing on any secondary indicates a transformer fault.

You really should use rubber or heatshrink sleeving over the switch terminals, to prevent them from being touched by anyone or anything. Even insulating tape would be better than nothing.

[Spencervs]

ok, I got it back. I swapped the mains transformer for the one in the SRP31 I assume they have the same spec and its working again although if someone could recommend a new transformer I'd be gratefl as I was kinda hoping to restore the SRP31 too at a later date! Got no sound again from the SRP31D however so still at square one... gonna buy that resistor in a mo to see if it makes a difference, will also change the electrolytic capacitor like Graham said

[Station X]

Now you've got the mains transformer out, check the continuity of the windings. there my be nothing wrong with it.

[Spencervs]

Is that testing the resistance of each point? I measured them all and got 00.4 on the 200 ohm setting. Is this correct?

[Station X]

Measured them all with respect to where?

You should measure between the ends of each winding.

If there's no continuity the transformer's had it.

If there's continuity, the transformer will either work, or it will overheat, or it will smoke.

You should also check there's no continuity between the primary and secondary windings.

[Spencervs]

Well I've changed the resistors to the rightful 5.6K ones and have noticed the sound is quiet and tinny, never heard it this bad. Also replaced the other electrolytic capacitor and noticed that the rectifier measured 188VDC, isn't this way below what it should be?

I measured the transformer I put in and it seems to be 220V on the connector to the rectifier. As for the other transformer, how do I test for continuity? I am slightly confused on that point.

[Station X]

See post #146.

[Spencervs]

ok well I Ithink I have checked it although I am confused as I know nothing about primary and secondary windings or transformers in general. I put the multimeter on the setting with the speaker looking thing and touched with the red poker and the black on the output to rectifier and the other two outputs and got no beep... is this correct?

[Station X]

The primary winding goes to the mains and has taps for various voltages. The secondary winding goes to the rectifier and has a tap for the heaters.

We need to know the measured resistance of the windings. It's highly unlikely that all the windings are open circuit.

[Refugee]

I would just power the transformer with a lamp limiter and measure the secondaries with an AC volt meter. I bet it works fine.

We need to go thru (through) the whole job again long hand and make sure each step is complete before going on to the next one so that no more mistakes get made.

[reeltoreelrob]

Well, the suspense is killing me. Did you get it fixed

Regards,
Rob.

[Spencervs]

Hi guys, sorry for the wait!

I changed the other Plessey capacitor and changed the 560 ohm resistor for the correct 5.6K and the player seems to be working! It's producing nice nice sound! Only issue is the background hum which isn't too prominent but it wasn't there before and it gets louder when you turn the volume to higher levels. Could this be down to the 188V as opposed to the correct 220V being produced by the rectifier or a fault in the can capacitor which I have been told in the past can cause unwanted hum?

Also, as for the transformer, I'm going to have to claim idiocy here and say I have no idea how to measure the continuity... i.e. what exact points do I measure? I can't tell how many windings there are as they are hidden by the metal casing. Could I take a photo and ask you to guide me on that?

Sorry, I know I'm a bit of a novice at this.

[Spencervs]

just screwed it all back together and guess what? back to where I started! no sound again! What on earth has failed in this thing? checked all the dry joints too, I melted all the old solder to reseal the joints.

It's really annoying because it will have good spells where it will just work and then bad spells where it won't but by the time you unscrew the thing to get to its insides it just works again. It's like it enjoys being moved around. To make it worse, the rectifier is also now showing the right 220v but the last couple of times it was 180-188v. Checked the voltage of the can capacitor too, that is 220v on the positive and 198v on the negative. The one time I caught it in the act it was V2 pin 1 if I remember started draining power but that's the only evidence I had, pure luck and coincidence that I caught it though

[Spencervs]

ok I've managed to catch it in the act! so lucky! found that the rectifier is producing 229v and I measured the valves too:

V1

1- 0v (Control grid triode)
2- 0v (Cathode triode)
3- 210v (Screen grid pentode)
6- 230v (Anode pentode)
7- 4v (Cathode pentode)
8- 0 (Control grid pentode)
9- 208 (Anode triode)

V2

1- 19v
2- 32v
3- 207v
6- 218v
7- 4v
8- 0v
9- 178v

tried taping the centre tag of the potentiometer with the multimeter and got no buzz at all

[Station X]

Checked the voltage of the can capacitor too, that is 220v on the positive and 198v on the negative.

What on earth are you doing? All voltages should be measured with respect to the chassis to which you connect the negative or black lead of your meter. The two positive tags of the capacitor should then have a positive voltage on them. I doubt there is a negative tag to measure on. If there is it'll be connected directly to the chassis and will measure ZERO volts.

tried taping the centre tag of the potentiometer with the multimeter and got no buzz at all

Why did you put tape on the tag?

Also, as for the transformer, I'm going to have to claim idiocy here and say I have no idea how to measure the continuity... i.e. what exact points do I measure? I can't tell how many windings there are as they are hidden by the metal casing. Could I take a photo and ask you to guide me on that?

Please read posts #150 and #151. Look at the circuit diagram too.

V1
1- 0v (Control grid triode)
2- 0v (Cathode triode)

No voltage on the cathode could indicate a problem with R5 or C4. Measure the resistance of R5 twixt valveholder pin and chassis. Check that C4 is the right way round.

[Spencervs]

There's no need to be rude. Like I said I have no experience in this or any prior knowledge and I think I've done a good job considering. Even if I have had blunders along the way (which is to be expected!), I have managed to follow most of your advice. You don't have to help me if you feel I'm being a problem, although your help is appreciated. Also taping is a spelling error on my part, I meant tapping. You know to do the buzz test like you told me to? And thanks for the info, I will look at the diagram. I didn't realise it would show the two windings.

gotta be R5 then... I deffinately got C4 in there ok, double checked polarity... will measure R5

[Glowing Bits!]

The next move with this unit is now to keep it unplugged.

Get hold of a circuit and study it very carefully (these units are not too complex in the circuit department) and follow the circuit on the unit itself while following the circuit, if that makes sense, this will make sure everything is where it is supposed to be (rule out things in the wrong place).

If the unit is powering up and making sound of some sort, the next move is to feel the temperature of the transformer, if it is slightly warm then it works, if it's very hot, consider another one.
If the unit still acts strange after checking everything, suspect the rectifier.

The golden question, does the sound fade, then come back at all or does it stay down?

[Spencervs]

Umm it stays dead for a while but after a while it will come back if you turn it off and on a few times. Sometimes it will phase back in itself while on but mostly you have to let it be for however long it wants. I'll give it a look at the diagram and match everything, I suspect the 0v on the cathode might be a problem however. I checked R5 and C4 (which is new) and they both seem fine. I think I might trace this line back too and test things out

[Glowing Bits!]

There could be many reasons why it is causing the sound to go, the first thing I would look at (previously discussed on this thread) would be the rectifier.
The only rectifiers I'm familiar with are the glass variety, when valve rectifiers start getting tired, the sound seems to go down in a step then comes back after a few minutes, the sound going down usually starts 10 minutes after the set has been fired up, whether solid state rectifiers do the same thing is another question.
The other thing you could try doing (somehow) is to wait for the sound to do it's 'going down' thing & look at the valves, the anode of a valve is the metal bit you can see through the glass, if it is trying to glow red (you need to be in a dark environment to see this), the amp is suffering a runaway condition.
The other thing to check would be the needle cartridge if it hasn't been replaced already.
If it becomes necessary to take pictures of how to test things with a multimeter, please get back to me, this may be more helpful than text alone!