Bush SRP31D Rectifier Modification Help Please

[_Cosmic_]

..and thanks to Mullard for the heads up about the tag strips. They are very very hard to source....
I had seen that company mentored before but although the strips are very inexpensive I recall that the postage they charge makes it uneconomical to buy small amounts of anything.

[Half a Mullard]

Glad to see everything coming together, thanks for updating us. Personally I don't think the slight increase in voltage should do any harm, it certainly doesn't want to be 240 or more but I think that should be OK. I'd be interested in what others think though. The criticality is the current through the output transformer. You have spaced the components out well and kept them away from the tone controls which should reduce hum.

Cricklewood are good for odd bits but yes, its probably better to order a few bits and pieces at a time to save on the postage.

[_Cosmic_]

I set up the lounge workshop again today...
and at the same time unexpectedly quick, the recently bought srp31d arrived...as expected it was a pile of junk..the seller said it was working..the stylus was twisted (not in transit) so it wasn't, it was really dirty so I spent most of the day cleaning it...its looking better already...I ordered a new stylus for it and managed to twist the stylus shaft with round nosed pliers in a vice and got it to play..the tone is quite nice actually..if I cant get my monarch to play at the right speed on the player I'm working on I will swap the decks over....

Back to the plot....

[_Cosmic_]

My 223V might be a little too high as I noticed this afternoon that after about 30 minutes switched on the was running a bit hot. Both sides on top of the valves and to the RHS above the new resistor.
At present I don't know why. I will take it apart tomorrow and find out exactly what's heating up.
I think it might be a good idea to try and get the voltage down to what it should be..215V.
I think it might be a good idea to wire some resistors in parallel (series would take up too much room) and was wondering what the best way to calculate what resistances to to add to my 220R to bring the present 223V down to 215V.
The electronics company I am buying parts from sell 10 watt resistors in these resistances...22R, 0R1, 0R22,0R47, 1R, 4R7,10R, 47R, 100R, 220R, 470R.

I noticed a Dutch (or German) teenager doing this when replacing a selenium rectifier in a vintage radio with diodes on youtube a few weeks ago.

I know the calculation for 2 in parallel is R1*R2/R1+R2 but I'm not half good enough to work this sort of thing out to calculate what R2 would be I dont think.

Would anyone be able to come to the rescue I wonder?

Judging from my experiments so far changing from a 220R to 100R raised the voltage from 200V to 213V (with the dim bulb tester attached)=13volts

[Edward Huggins]

There should be very little wrong with your BSR "Monarch" UA16 to get it running OK. If the motor is running and the idler wheel is sound, there's only cleaning of the stepped pulley, the turntable inner rim and the idler-to-pulley alignment to attend to. As to record players advertised as "working", please don't get me started on that......!

[Half a Mullard]

It certainly wouldn't do any harm to get the voltage down a little. I'm pretty sure I ended up with 330 ohm ( would need to take apart to check). If it were me, I'd use a bit of trial and error with different resistors around those values to get the voltage about right. Better a bit on the low side and you wont notice the difference. I also agree about "working"!
These are nice players and worth the effort.

[ms660]

As far as I can make out there's no mains input voltage given for the DC output voltage that's quoted in the manual.

Lawrence.

[MurphyNut]

Originally Posted by _Cosmic_

..and thanks to Mullard for the heads up about the tag strips. They are very very hard to source....
I had seen that company mentored before but although the strips are very inexpensive I recall that the postage they charge makes it uneconomical to buy small amounts of anything.

They can be found easily on ebay and quite cheap, they're often in long strips you can cut to whatever size you want.

[_Cosmic_]

So Howard, it looks like mine will end up about there too doesn't it.
As you see by the list I posted, the company doesn't do values between 220R and 470R so any ideas how you would make up to 370R using my existing 220R resistor and another in parallel. ie how do you calculate the value of the additional resistor? Would any engineers care to enlighten us please?

[_Cosmic_]

Yes Ed, I thought I had done most of that!! But thanks to you I went through it all again and even brasso'ed the spindle. I used a fine emery board to slightly clean the idler rim as it looked a bit shiny again, I lube'd everything that looked like it needed it and alcohol'ed the inner rim on the pattern again with a clean cloth to make sure it was spotless. I checked the position of the idler wheel against the stepped positions on the motor spindle and it was aligned correctly.
I think its fixed it..well its certainly better than it was as it was getting slower and slower over the last couple of weeks.
Whatever I missed the first time round its thanks to you for prompting me to do it all again.
Much appreciated.

[_Cosmic_]

Yes Clive thanks for that. I did see the long strips but i needed the small ones with the little bracket on. Can we mention websites like ebay now? When I read the rules when I joined it said you couldn't, they have probs changed in the last 20 years!!
Actually I did get mine from the Chinese looking man on Ebay with the beardy thing who sent my order within a couple of days so that was great.
Thanks for the heads up and taking an interest.

[Boulevardier]

Originally Posted by _Cosmic_

any ideas how you would make up to 370R using my existing 220R resistor and another in parallel. ie how do you calculate the value of the additional resistor? Would any engineers care to enlighten us please?

You won't make up 370R by putting anything in parallel with 220R. To make 370R you must put a 150R in series with your 220R.

Mike

[John10b]

Cricklewood have a decent range of resistors, worth taking a look.
John

[Half a Mullard]

Yes, agreed Cricklewood have the range including the 330 ohm - prices are reasonable but agree you have the postage on top. Good service though.

https://www.cricklewoodelectronics.c...rs.html?page=2

As others have said the ones you have wont work in parallel. Best, I would suggest, to use a single resistor of the right value. You could do a temporary connection until you are happy with the result, then solder in place as you did with the first one.

[Nuvistor]

Originally Posted by Boulevardier

You won't make up 370R by putting anything in parallel with 220R. To make 370R you must put a 150R in series with your 220R.

Mike

To add to the info from Mike.
To calculate resistors in parallel read the end section of this page.

http://www.vintage-radio.com/repair-...resistors.html

[_Cosmic_]

I'm back!!

After waiting for about a week I took delivery of 5 x 330R ceramic 10W resistors.

After previously reading advice given on the forum I had previously ordered other values that proved to be of no use at all in my case.

To get my new diode rectifier circuit voltage from 223V down to the recommended 215V (or slightly less) Howard said he thought he used a 330R so of course I ordered some of those.

I couldn't wait for them to arrive. As soon as they got here I removed the 220R's from my newly constructed terminal strip(s) and added a 330R in its place.

I have by now accumulated 3 SRP 31D's in various states of disrepair.
I have removed the selenium rectifier in all 3 after testing the voltage outputs, one of which was only delivering 52V DC (28V at one point) instead of 215V DC.

All 3 now have terminal strips and a diode/330R series resistor arrangement installed as described earlier. They are all now delivering voltages of 210-212V that is a near perfect result for me. So thanks to Howard for the advice on what he thought he used in his project.
Here are the images associated with this project.
Here is an image is from one of the amplifiers delivering a very low voltage.
I am getting better at installing the new circuit strips.
All the components are spaced our and well away from tones controls etc.
I guess I could have put head shrink insulating on the components to finish things off but I don't have any of that and everything is sturdy and not going to move so very safe.

In between all this I have been repairing other problems, such as repairing 3 electrostatic tweeters that now seem to work great and add so much to the sound, fixing the motor auto shut off on the UA16 and other spring or lube associated problems such as premature tonearm lifting before the end of a record. All fixed and working nicely all thanks to help and encouragement from our vintage radio members.
There are still things to fix and problems to solve but for this thread I'm pretty happy with it..unless the experts say it isn't very good.

Thanks to all for watching this thread.

I will post a thread showing how to repair your Grundig electrostatic tweeters when I get time. I have the photos ready.
I now have 2 complete SRP 31D's that sound fabulous both having different sound characteristics, I think its because they each have different carts. I will post a thread about this too. I have one amp ready to fit back into a cleaned up case and to attach a UA16 to when I acquire one from somewhere. What will I do with them all? I don't think I could bear to part with them for a long time to come.

Cosmic Chris

[_Cosmic_]

Here's a couple of images of my two just about renovated SRP 31D's.
The spare (not visible - it's underneath the 'old' BSR at the moment): along with the wrong deck ('old' BSR, supplied with it. The cabinet is nice and clean now and I just need a UA16 to put in it. This 'old' BSR needs renovating when I get time. Was this fitted to another model such as the SRP 31C I wonder?

[Techman]

The value of the resistor is variable and is dependent on the state of the valves, so it's not an exact science and those of us that work on these things keep a stock of the various values, so no problem in getting the exact voltage required, but it sounds like you've got it near enough - better slightly lower than too high!

Bush originally gave the HT voltage for the early version of this player as 220 volts, but revised this later to 215 volts with no apparent circuit changes - you may ask why that would be.

Many of these players have been found still working at below 40 volts HT, but they sound very 'thin'!

[_Cosmic_]

Yes, thanks for that.
I love learning about the history of products. When I'm working away trying to solve problems and fixing mechanisms etc, I often think I would have loved to have been involved building these. Compared to modern electronics they are very basic in that they even have a small terminal block inside the cabinet that connects the motor to the transformer tap, but the soldering work is so sturdy and well done that its fantastic to see they have lasted all this time. However the mechanisms on the BSR monarch series are very complex and its totally amazing to get inside and see them operate. I haven't quite had the courage to strip one right down and re-lubricate it all for fear of not getting it back together again or accidentally losing a vital part. I might strip down my spare to see what happens.....
I hope everyone who lands on this thread can follow everything and get their SRP 31D's working again...
Cosmic

[_Cosmic_]

The image I previously described as my 'old' deck is in fact the BSR UA14