Bush SRP 31D not producing sound.

[robjkmannering]

With all the generous offers of free repair, it would be foolish not to accept. Now, where did I leave that faulty Roberts Mullard module? Perhaps someone would repair that....

Rob

P.S. I have a spare mains transformer for this that I will happily donate free if it should be required in repair by another member.

[steve_gus]

Hi,

I too think Spencer has done his best, but sometimes expert help is a better option.

Best regards,

Steve.

[Spencervs]

Oh wow guys thanks! would the chassis only be needed or should I send the entire thing?

[Michael Maurice]

I think the consensus is that you should send the whole thing, so that it can be repaired and fully tested.

That way it will be returned in a good working order for you to use and enjoy.

[Glowing Bits!]

I'll second that.

[Station X]

Two weeks of silence. Spencer hasn't contacted me. I wonder if he's contacted Top Cap?

[Spencervs]

Hi (Please do NOT keep addressing with "Hey", it's rude) sorry for the quietness there, have a lot going on these days. I sent the chassis to Top Cap last week. I was going to send the entire thing but Top Cap said it wasn't necessary, will soon see I suppose. I'll report what happens with it... really hope I haven't ruined it! :S

[Station X]

Excellent. We look forward to reading Top Cap's report.

[Top Cap]

Having received the amplifier chassis from Spencer, I did a visual check. Only component misplaced was C4 round the wrong way, cathode bias decoupler with its positive terminal to chassis. The insulation on the wiring was not looking too good so a rewire was planned.
Main smoothing block required a 35mm horizontal clip and was fitted. Valves appeared to be good with no shorts and good emission.

Prior to re-wiring I did some quick checks, starting with the mains transformer which was isolated and run up off load.
All outputs were correct and no apparent distress.
However the outputs disappeared when the chassis was inverted and the fault was traced to poor/broken contact on mains selector socket. This was made of the same brittle material sometimes found on old paxolin octal valve holders and to get around this problem the transformer was hard wired for 240V operation. Soak test showed no signs of over heating so attention was then directed at the selenium rectifier. This measured 100k one way and 74k the other way so was replaced by a new tag strip, silicon diode and surge limiter.
During re-wire some tags fell off both valve sockets whilst trying to unwrap old components and wiring. Replaced both with porcelain high temperature types.
After that a run up of the amplifier on the variac showed all was fine, HT pretty spot on with the circuit and the scope showed excellent balanced drive to the output pentodes, no doubt helped by the new 47k resistors in the phase inverter.

Now on its way back for Spencer to re-fit into the cabinet.

[G8UWM-MildMartin]

Excellent news!
Although I've had nothing to contribute, I'd been reading with bated breath.
With the replacement components being of better quality than the originals, I'd expect the amplifier, at least, to last more than another 50-odd years.

[Station X]

Well done Top Cap. The dodgy voltage selector seems to have been a major problem which was masking other faults. The mains transformer came from another player.

[Spencervs]

I got the chassis yesterday and fitted it all back together and it sounds amazing. No fading as of yet and all seems to be functioning properly.

The only issue is there is still the small background hum which is noticeable and is probably a ground wire not connected well enough maybe? or actually do you think it could be the tiny wires from the cartridge as they are loose and odd? However I doubt I'm going to do anything about that because it sounds great as it is.

Thanks so much everyone for your help despite the annoyingly and painfully long topic (sorry about that!) and a massive thank you to Les for taking the time to fix it for me and reporting the issues/fixes.

[Darren-UK]

You don't want loose connections on the cartridge or you'll get crackling and intermittent output.

Otherwise low background hum is quite normal with many record players; providing a record played at low volume will drown it out I wouldn't worry about it.

[Nickthedentist]

Spencer,

You're a very luck chap... Les' diagnostic skill and workmanship is superb, and you have a better-than-new machine now.

Three cheers for Les! I was wondering when this thread would end.

Nick.

[Spencervs]

Yes indeed! I feel very privilaged to have it all working. I actually can't believe Les managed to fix it! I was sure when the fuse bulb started glowing that it was completely gone. I had nightmares of having to throw it in the skip... imagine that! but yes, thanks so much guys, seriously wouldn't know what to do without you all

[Darren-UK]

Originally Posted by Spencervs

I had nightmares of having to throw it in the skip

Had you have done so, someone would've found it, rescued it, joined the forum and then started a thread about it .

[paolo]

Been following this thread with a great deal of interest having the C model myself. So glad that it has had a happy ending! Hum is just part of the charm of valve equipment so unless it is absolutely ruining the music, turn it up and enjoy

Paul