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Old 3rd Sep 2012, 6:30 pm   #181
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Default Re: Bush SRP 31D not producing sound.

We're back at post #144!

Meter on ohms range. You know where to connect the negative lead. Positive lead to the terminal of the transformer which goes to the rectifier. What reading do you get?

Please don't say "No reading", it's meaningless. The extreme cases are short circuit ie zero ohms and open circuit ie infinite ohms. Hopefully you'll see something in between these extremes.
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Old 3rd Sep 2012, 6:47 pm   #182
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Default Re: Bush SRP 31D not producing sound.

it seems ok now... unsoldered and shortened the mains wires as I had accidentally melted the plastic casing a bit when fixing other components, in fact this may have been the issue. However I am gonna run the tests that you recommended to me
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Old 3rd Sep 2012, 6:54 pm   #183
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Default Re: Bush SRP 31D not producing sound.

Quote:
unsoldered and shortened the mains wires as I had accidentally melted the plastic casing a bit when fixing other components, in fact this may have been the issue.
I don't see how this could have been the source of your problems. You said in post #180 that you were getting 240V AC on the primary winding. If there was a problem with the mains lead you wouldn't see a voltage there. Your actual words were "I am getting volts on the primary winding to the fuse bulb of 240ACV". I assume that means you saw a voltage on the primary winding?

Melted plastic on the mains lead won't cause a problem unless the bare wire touches the chassis or another wire. The mains lead wire would need to be broken to prevent mains current reaching the primary of the mains transformer.

By all means try the other tests, but I have a feeling that before long we're going to be back with having no voltage on the secondary again.
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Old 3rd Sep 2012, 7:16 pm   #184
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Default Re: Bush SRP 31D not producing sound!

Blimey. Ten pages with no progress, this must be some kind of UKVRR record.
Don't take this the wrong way, but given that things seem to be going round in circles, I stick with the advice I gave back at the beginning:

Quote:
Originally Posted by ben View Post
If none of this makes sense, I'd stop right there and get it to someone who has the required experience before you wreck it completely.
These are good units and it would be a shame to ruin this one. Well worth investing in a proper overhaul IMHO.
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Old 3rd Sep 2012, 7:19 pm   #185
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Default Re: Bush SRP 31D not producing sound.

Yes you're right there I saw a reading of 240V AC going to the fuse bulb from the primary winding

I have just done the tests as you described in #177 and all was fine, although the later tests I can't do as I cannot connect the rectifier, I'm still getting the same issue with the bright fuse bulb and no voltage to anything and only 40ACV going into the rectifier when I connect it.

and yes, Ben you are right. I am thinking of giving it to a professional, dunno where I can take it though is the thing. I want to see if I can just get it back to how it was first if that's even possible. Although if anyone can alert me to any service close to the Bromley area in Kent then I'd be thrilled. Also how much should it roughly cost to have one of these fixed? Money's a bit tight you see...

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Old 3rd Sep 2012, 8:25 pm   #186
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Default Re: Bush SRP 31D not producing sound.

So all the tests in post #177 work OK?

So as soon as you connect C16 and ONLY C16 the voltage to the rectifier drops to 40V AC?

That being the case C16 is breaking down at the working voltage and overloading the transformer.

----------------

If you can ship this to me in Ipswich and are willing to pay the return costs I can fix the amplifier for you or failing that tell you what's wrong with it. I'd only charge you for any replacement components. Check Parcels 2 go etc. They can be much cheaper than Royal Mail.
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Old 3rd Sep 2012, 9:14 pm   #187
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Default Re: Bush SRP 31D not producing sound.

yeah all of #177 tests worked ok, valves lit up, was getting 240V AC going to the wire. Just tested the player with the rectifier wired up and C16 removed, you were right! its registering the correct voltage now! However it makes a slight noise, should I assume its because the smoothing caps aren't connected? its hum from the speakers and some random crackle. fuse bulb also not lit. Hopefully changing C16 will put this on the path to be fixed! If problems get any more difficult I trust I can send the player to you?

Just a note, C16 might have even have been the cause for the death of the previous transformer. But one thought that comes to me, didn't we test C16 and C15 and find that the resistance indeed went to infinity? surely then they work? :/

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Old 3rd Sep 2012, 10:08 pm   #188
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Default Re: Bush SRP 31D not producing sound.

If ONLY C16 is connected, ther should be no hum from the speaker, because there's no electrical path to it. Slight hum could be explained by inductive pick up between the mains transformer and output transformer I suppose. Crackles I can't explain.

There's one more test you can try. Does your meter have a diode test function? If so measure the rectifier both ways. For this test, with the power off connect one lead to each end of the rectifier. Note the reading and reverse the leads, again noting the reading. You should read forward voltage one way and backward resistance the other.

See here, but expect different readings depending on the type of rectifier fitted:-

https://www.vintage-radio.net/forum/...58&postcount=1

You could also try the same thing with your meter on ohms range.

C16 may test OK on the tiny voltage from your meter, but it could be breaking down when high voltage is applied to it. If you decide to replace it you may have to use two capacitors with their negatives connected to chassis, as cans are no longer widely available,
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Old 3rd Sep 2012, 10:21 pm   #189
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Default Re: Bush SRP 31D not producing sound.

I didn't have C16 connected to the player when the rectifier was working ok. When I connect C16 with nothing else (not even C15) the fuse bulb glowsand I get the same fault occur. I took out the can and found it isn't a replacement at all, it just looks shiny. Hidden under the metal clamp that holds it to the player it says Mar 64 which I assume is March 1964. Now I found a can on ebay that is 50uf - 50uf and 500V is that an ok replacement? my one from the player says the following

"50-50uf
RED OUTER
275V MAX WKG
350V SURGE
CE 634/20

MAR 64"

this is the one on ebay that I found

also I believe the multimeter does have a diode setting, is it the one you use to test fuses with the triangle and a line almost like a pause symbol?
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Old 3rd Sep 2012, 10:35 pm   #190
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Default Re: Bush SRP 31D not producing sound.

We shouldn't be discussing eBay items here. The one you've linked to will do the job. Don't forget to connect the negative terminal to the chassis though. The red and yellow tags should be connected as per the original can.

If you look at the post I linked to you'll see that the meter selector switch is set to diode test. The feature isn't designed for testing fuses. The meter shown is a Fluke. The symbol on your meter may be different. Read the manual.
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Old 3rd Sep 2012, 10:53 pm   #191
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Default Re: Bush SRP 31D not producing sound.

ok that's fine, by the negative terminal I assume you mean the third pin? also checked the rectifier with the diode test and have gotten 1.598 when done red/black and then 1.059 when done black/red does this suggest that the rectifier is in working order?
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Old 3rd Sep 2012, 10:58 pm   #192
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Default Re: Bush SRP 31D not producing sound.

The negative tag is the one that isn't coloured red or yellow.

I can't deduce anything from your readings because you haven't given any units. If they're not indicated on the display, your manual should tell you what they are. What readings do you get on the resistance range?
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Old 4th Sep 2012, 12:06 am   #193
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Default Re: Bush SRP 31D not producing sound.

On the ohm setting it was 3.11k both ways. I'm not entirely sure where the manual for the multimeter is so cannot say what the diode setting is measured in. I'll try and find it tomorrow but I fear its been disposed of at some point.
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Old 4th Sep 2012, 1:58 am   #194
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Default Re: Bush SRP 31D not producing sound.

I am pretty sure the rectifier has survived some distress and is likely to be OK.

What do you have that could be used as a limiter? I am thinking about a 10K 10W resistor or 15W bulb from a broken microwave or fridge.

Use it as a lamp limiter between the rectifier and the smoothing capacitor and post the DC voltages on the capacitor and the rectifier and let's see what we get.
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Old 4th Sep 2012, 8:16 am   #195
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Default Re: Bush SRP 31D not producing sound.

The easiest option might be to temporarily replace the rectifier with a 1N4007G diode which is available from Maplin for about 40 pence.

If the fuse lamp still glows then obviously the fault will be with C16.

Connect unmarked end of diode to transformer and marked end to C16,
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Old 5th Sep 2012, 2:16 am   #196
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Default Re: Bush SRP 31D not producing sound.

Dear Mr Spencer, please could you take up Graham's offer to fix this unit before it ends up as scrap.
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Old 6th Sep 2012, 7:20 pm   #197
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Default Re: Bush SRP 31D not producing sound.

Seconded! I admire your perseverence, but at the very least, I think you need someone with more experience at your side to help you with this. Otherwise it could be a huge waste of effort and money, which would be sad after coming so far.

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Old 7th Sep 2012, 2:32 pm   #198
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Default Re: Bush SRP 31D not producing sound.

Quote:
Originally Posted by Nickthedentist View Post
Otherwise it could be a huge waste of effort and money...
And, frankly, an easy source of electrocution which I'm surprised hasn't happened yet.
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Old 7th Sep 2012, 2:58 pm   #199
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Default Re: Bush SRP 31D not producing sound.

There is a good chance the selenium rectifier has gone leaky and passing AC to C16, it won't like that and it will certainly turn up the fuse bulb! If you can detach the whole chassis, put it into a stout cardboard box and send it to me. (PM me for my address). Provided the transformers are OK I will get it to sing for you even if a part or full rebuild is required. I will let you know what problems I have encountered so that you can learn from the experience and put you in a better position for when you tackle the next one. No charge - I will even contribute the postage costs back to you - can't be fairer than that. Hopefully a fully working unit will be returned to you and all you will have to do is make sure the cartridge and wiring is ok. P.S. If you decide to send, make sure the valves are well protected in their own cushion-wrappings.
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Old 7th Sep 2012, 3:08 pm   #200
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Default Re: Bush SRP 31D not producing sound.

I'd get Spencer to send the cartridge and stylus to you too, so that you'll know they're OK. Otherwise I can see this thread running for another 100 posts.

200 not out!
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