Bush SRP31D - Restoration

[Edward Huggins]

Don't rush to replace the tone arm wiring harness. There is more cost and fiddly work to this than you might think! If you can see that some of those very fine wires are exposed to shorting, then coat them with a contact adhesive (Evostik) to provide an adequate enough insulation - even if only for the time being.

[Techman]

Originally Posted by sawleyram

I think what you are saying is that I need to be aware of the limited space at the point where the tonearm is joined at the pivot.

No, although that is a consideration.

It's the 'flexibility' of the very thin wire that's vitally important. The strands are as thin or thinner than the hairs on your head. As I said in my previous post, the wiring where it goes down through the pivot and bearing must be so thin and flexible that the motion of the arm is in no way impeded by it being there. Remember, it's the wall of the record groove that pulls the arm across the record and the wrong wiring will cause more record wear, possibly with skipping and jumping, thus needing increased tracking weight to compensate.

Every record player needs its tracking weight checking, as it can vary with time and also people fiddle with it and put it out, so you'll need to buy a gauge/balance for this regardless, particularly if the wiring or cartridge has been changed.

Keep soldering iron heat well away from the cartridge terminals as it will kill it stone dead in seconds.

[sawleyram]

Hi all, bit of an update on works so far. The stylus that came with the machine was probably past its best (based on sound reproduction) and very worn so I replaced this not long after it arrived. There was an immediate improvement to the sound quality which became crisper and a lot less 'crackly'.

I debated for a while about changing the tonearm cable at this point, but in the end I did decide the change it. The cable already in the machine was damaged in several places (as seen in my first post) and my temporary repair - although an improvement - wasn't something I wanted to leave. The cable kindly sent by Howard did have thicker insulation yes, but the actual wires (presumably tinned copper?) were of the same gauge and the same number of strands. They certainly weren't as thin as hair, so maybe the ones in the machine we're not original to begin with?

Changing the cable was fairly straightforward. I unsoldered from inside the machine first and worked from there, lastly unplugging the four connectors from the cartridge. I cleaned up each terminal inside the machine too. Routing the new cable was simple as there are two/three cable clips underneath the deck to help secure it. I made sure it was measured right and free from any moving parts.

The only minor problem I ran into was getting the replacement cable up into the tonearm as space is very tight at that point. I was very conscious of putting any sort of resistance on the tonearm's movement so it took a while to figure out the most appropriate route. I can happily say that the arm does now move freely, exerts no extra (noticeable) force onto records and returns home soundly at the end of play. I do need to find my tonearm scales ASAP though, just to make measurements and to prevent premature wear as already mentioned by others.

All in all the play is much improved. There is no hum anymore and sound reproduction is fantastic. I ended up listening to the entirety of my test record (Rachmaninov's beautiful Piano Concerto No.2!)

I should have said that I make wiring harnesses for classic cars as my job, so techniques for soldering and using wires are something I'd fairly confident on.

Pictures attached showing some stages of the works. The first showing the underside before works commenced, the second showing the replacement tonearm wire, the third showing the route the tonearm wire took after laying, the fourth a general view of the underside of the arm and the fifth showing a surprise I found lurking inside.

[Half a Mullard]

Many thanks for the update that looks good progress. You’ve made a very neat job with that wiring, well done!

I have dug out another of these players and checking both of mine and the original photo of your wiring they do look the same so I think it is safe to say that Bush designed it that way. These were a good quality player in the day and would have cost around £450 in today’s money.

Checking the tracking weight would be a good plan.

Also that looks an interesting find, I wonder how that got there!

[sawleyram]

Hi all, thought I'd post an update on this.

I replaced the tone arm wire very kindly supplied by another member of the forums with wire taken from an old mouse, as suggested by another member.

Although the wire sent to me did work without exerting any real surplus weight on the records, it had the unpredictable tendency to restrict the movement of the tone arm. I managed to locate an old serial mouse in the attic which used very fine wires. Unfortunately only two of the four colours were the same as the ones in the record player, but not really an issue as a took a photo and made a note.

The arm now moves across records freely all of the time.

The next issue (which I suspect is common) is finding the cause of inconsistent playing speeds. I have found records sometimes "warble", as in their pitch varies a bit like how you'd hear a worn/stretched cassette tape. It could be something simple like the motor taking a while to get up to speed, or it could be something to do with the drive wheel under the platter.

[Edward Huggins]

It is most likely to best a deformity of the Idler wheel ("Drive Wheel") known as "Flutter" and is very common. These can be restored.

[MurphyNut]

Originally Posted by Edward Huggins

It is most likely to best a deformity of the Idler wheel ("Drive Wheel") known as "Flutter" and is very common. These can be restored.

I had a slight deformity in my Idler wheel, which was causing this problem, I attached it to a drill and with it spinning at high speed pared the edge down with emery paper, kind of like using a lathe.
I didn't have to remove much to get it perfectly round again. The added befit, it removed the hard/shinny edge on the wheel and it now grips and runs smoothly on the inside of the turntable platter.