Bush SRP 41 Advice

[popmirrorman]

Hello all
After receiving good advice here before i'm back again, hope someone can help. I have a Bush SRP 41 portable record player with the original Monarch deck. I replaced the Cart recently for BSR SC12m. Listed to an LP all the way through and it sounded great.

2 weeks later, after transporting the unit to another house on the back seat of my car (transit screws engaged) when i turned the power/volume switch on this morning i was greeted with a few seconds of loud crackling - very much like the sound of a dirty pot. The crackling abruptly stopped after maybe 2 or 3 seconds and now there is no volume at all. The power light on the front is still glowing, just no sound.

Has anyone any idea where i should look first?

Thank you for reading.
Ian

[Edward Huggins]

Sounds like a failure in the power supply. Measure the voltage output from the rectifier and the mains transformer secondaries. Check also the DC output from the large value capacitor fed by the rectifier. A Service Sheet for this is available from the Link at the top RHS of this page.

[popmirrorman]

Thanks Edward. I will look into how to go to about be this and report back eventually.
Ian.

[Nickthedentist]

Edward's advice is good.

The pilot light is operational, so the mains transformer is being energised and basically working.

What we need to look at next is the power supply to the amplifier.

With the red lead of your multimeter meter clipped to a chassis connection (e.g. where the mains earth connection attaches), and set to measure DC volts, measure each side of the fuse with the black probe.

If all's well, there should be about 26V on both sides of it.

Do you have the service sheet?
https://www.service-data.com/product.php/7042/1041/m17042

Note that these transistorised amps, while super-reliable in their day, are now getting tricky to fix due to internal short circuits developing in the transistors, and replacement transistors which are still OK being hard to find. Hopefully your fault may be something "silly" like a poor contact in the fuseholder etc.

[popmirrorman]

Thanks for elaborating nick, that makes things a bit clearer for a starting point. I'll do the test this weekend and let you know.
Thank

[Michael Maurice]

There are two versions of the SRP41, one which uses a transformer coupling the bases of the output transistors, the later one being all DC coupled.

If yours is the later one, there is a 50R preset pot RV5 for the quiescent current, it has a habit of going o/c. Replace it. It may have already damaged the output transistors.

However there is a 500mA fuse in the power line to the amplifier, you might be lucky and find that its blown in which a replacement should bring it back to life, but you MUST replace that preset.

You might not be able to find a 50R preset, in which case use a 100R in parallel with a 100R fixed resistor.

[popmirrorman]

Thanks Michael. I think this particular one is the latest model as it ha no wire and plug for stereo, just the socket.

[ajgriff]

All sound advice but my first thought would be a loose connection caused by vibration during transportation. Worth just checking the security of the tag connections to the cartridge before going too much further.

Alan

[popmirrorman]

Thanks. I did check the tags as I thought the same but they are all fine.

[popmirrorman]

Here is how it looks inside. The circuit board seems a little gunky but nothing else obvious to my untrained eye. Did notice some browning at the connection of the larger capacitor. More photos to follow. I can't see the fuse that was mentioned above.

[popmirrorman]

More photos here. Thanks for your help so far
Ian.

[John10b]

That looks like the amplifier, you need to check the psu which is housed behind the speaker front panel, to undo front panel you will find three screws along the bottom, hope that helps.
John

[popmirrorman]

Thanks John. I'll have a look.

[Edward Huggins]

I can see a change-on-sight red/yellow Plessey cap in there. PSU= Power Supply Unit where the fault may be.

[John10b]

PSU picture attached.
John

[popmirrorman]

Have accessed psu. Photos attached. Not sure what I am looking for or how to utilize my multimeter. I'm assuming you can't tell much from just looking.

Cheers
Ian

[paulsherwin]

Nothing obviously wrong there. Check the DC voltage coming out of the power supply with your meter. If it's plausible and stable then the fault is elsewhere.

[John10b]

I presume your psu looks like the picture I sent you, if so, check the fuse.
When checking for faults, you, look, listen and smell, sometimes the fault is very obvious.
John

[popmirrorman]

Hi John. My psu is the same as your picture except there is no fuse and no fuse holder so assume it was never there.

Latest update is that there is no power at all to the player - no light comes on and the turntable does not function. Thoughts from here?

[Analogue man]

This may be an obvious suggestion but have you checked the fuse in the plug?