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Old 2nd Mar 2017, 11:05 am   #141
Boater Sam
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Default Re: Defiant MP4 with AT6 Turntable refurbish

I have re-read this thread and we are no further on nor do we understand what the problem is, apart from exploring several blind alleys and being led up the garden path by unreliable voltage readings and ambiguous replies.

How can we sensibly continue when we have a bulb that did light, now doesn't but has to be in circuit to enable a transformer to get hot. How hot and how long it takes is unknown.
And what exactly is the fault?

It's all well and good helping but will we get an outcome, can the OP work it out or give us enough info?
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Old 2nd Mar 2017, 11:10 am   #142
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Default Re: Defiant MP4 with AT6 Turntable refurbish

I can see that the gloves are off this morning!

Graham.

Removing the indicator lamp disconnects the HT supply. The fact that the transformer still get hot under these conditions shows that it is not overheating due to supplying excess HT current.

Pull out the valves and remove the indicator lamp. Under these conditions the transformer won't be supplying any current at all and the only current will be magnetizing current in the primary. If the transformer still gets hot (allow it to cool before doing the test), then it probably has some short-circuited turns.
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Old 2nd Mar 2017, 12:23 pm   #143
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Default Re: Defiant MP4 with AT6 Turntable refurbish

Hi Graham

I really do appreciate your continued patience and putting up with the flack !!! I also understand my lack of knowledge must be frustrating for you all. But I do consider myself capable of defeating this record player fault. I have put the DMM back in its box and will now only supply analogue readings.

From my observations:

The lamp used to light when powered on but then stopped. It was only when I opened the cabinet to try to trace the fault that I found this loose resistor rattling around in the box. I think this is a red herring. Someone read it as 4 Mega Ohms and that this seemed very high for valve equipment and said that it was NOT part of the circuit that they could see. I and I think all of us agreed and have dismissed this as the cause.

I think that the resisters origin maybe from a previous owners 'mod' of installing the isolating transformer and that whilst doing so they left the resistor in the bottom as it would not have formed part of the 'mod'.

The heat of the transformer is a concern. Along the way, I initially hadn't touched this but when I did - that's when I noticed it was hot.

I have just removed the valves and the indicator lamp - It got 'hot' within 30 secs. Are we safe to assume that their is a primary winding fault even though the player still works fine?

Regards
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Old 2nd Mar 2017, 1:00 pm   #144
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Default Re: Defiant MP4 with AT6 Turntable refurbish

It does sound like the mains transformer is faulty. A transformer with no load on its secondary windings should stay lukewarm all day.

A faulty transformer could give low HT voltage (unfortunately we don't know what it should be) resulting in not enough HT current to light the indicator lamp. I calculate that the current drawn by the anode and screen grid of the pentode section of the UCL83 (5.8/390) is only about 15mA or about half what I'd expect.

Let's await a second opinion from one of the other contributors to this thread though.
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Old 2nd Mar 2017, 1:28 pm   #145
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Default Re: Defiant MP4 with AT6 Turntable refurbish

Quote:
Originally Posted by ggg1234 View Post
maybe from a previous owners 'mod' of installing the isolating transformer
Hold on a moment - I don't think we've established whether this is an original transformer or as has now been mentioned - it might be a substitute. This could all have been a waste of time chasing a fault that has been 'added' and is not part of the original player - hence the various confusions that have appeared.
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Old 2nd Mar 2017, 1:33 pm   #146
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Default Re: Defiant MP4 with AT6 Turntable refurbish

Thanks Graham.
The more I think about this issue with the unreliable and fluctuating voltage readings (I just cant be that bad) the more it does indicate to me an issue with this 'retro fitted modification' (the isolating transformer).

I think I will replace it anyway but lets see what others say?

Regards
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Old 2nd Mar 2017, 1:38 pm   #147
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Default Re: Defiant MP4 with AT6 Turntable refurbish

It might not be that easy to just go buy a small mains isolating transformer with a 45/90V heater winding from normal suppliers. It may have to be a donor from another record player. Dansette used them in their early models.
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Old 2nd Mar 2017, 1:45 pm   #148
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Default Re: Defiant MP4 with AT6 Turntable refurbish

Quote:
Originally Posted by vidjoman View Post
Quote:
Originally Posted by ggg1234 View Post
maybe from a previous owners 'mod' of installing the isolating transformer
Hold on a moment - I don't think we've established whether this is an original transformer or as has now been mentioned - it might be a substitute. This could all have been a waste of time chasing a fault that has been 'added' and is not part of the original player - hence the various confusions that have appeared.
Unfortunately, unless someone comes up with a similar player we have no way of knowing whether the transformer is an original or a replacement.

The question is "Is it faulty?" To my mind it is.

A replacement isn't going to be easy to source. It will need an 80V secondary to power the heaters and another secondary of indeterminate voltage connected is series with it to supply the HT.

It might be easier to convert the player to use 'E' series valves as a transformer for these could be easier to source.
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Old 2nd Mar 2017, 1:46 pm   #149
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Default Re: Defiant MP4 with AT6 Turntable refurbish

Is the transformer definitely a modification? The circuit diagram shown earlier in the thread shows a mains transformer. Would anyone go to the trouble of finding a transformer with the correct voltage for the two valve heaters and then fit it?

In strict financial terms the player probably isn't worth the outlay of having the transformer rewound, but that wouldn't stop many of us having invested so much time and effort into it already.

Edit



"It might be easier to convert the player to use 'E' series valves as a transformer for these could be easier to source."


I wonder whether this is a step too far for the OP?

Last edited by PaulR; 2nd Mar 2017 at 1:53 pm.
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Old 2nd Mar 2017, 2:24 pm   #150
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Default Re: Defiant MP4 with AT6 Turntable refurbish

Hi All

To me I originally thought of it as a later mod because of the state of the fixings and lacquer (pic attached) but it could also have been a replacement for a faulty one or a later repair to original. I have been working off the Defiant R209 circuit diagram which I bought off up top site (but I don't think it is allowable to post it here?)

Regards
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Old 2nd Mar 2017, 2:53 pm   #151
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Default Re: Defiant MP4 with AT6 Turntable refurbish

I can't remember whether we have discussed the cartridge in the player. The original one most likely would be intended for mono records and would destroy any stereo records played with it. Stereo cartridges are available and something suitable would need to be obtained and fitted before the player could be used properly. Whatever is obtained this will never be hi-fi and would only really be suitable to play records that are not valuable.

Obviously the amp needs sorting out first but this is something to bear in mind.

Can you tell us what cartridge is already there and post some photographs?
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Old 2nd Mar 2017, 3:14 pm   #152
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Default Re: Defiant MP4 with AT6 Turntable refurbish

Hi PaulR

Its an ACOS GP 67 - LG (or IG) twin sided cartridge with SJ1 and SJ2 stylus's. It is from an intermediate (MK1/MK11) Garrard AT6 Turntable. It only has two wires indicating mono I believe.

Regards
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Old 2nd Mar 2017, 4:22 pm   #153
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Default Re: Defiant MP4 with AT6 Turntable refurbish

That appears to be a mono only cartridge so will need replacing with something more suited if you want to play stereo records without damage.

However, one thing at a time, concentrate on the amplifier first.
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Old 2nd Mar 2017, 4:35 pm   #154
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Default Re: Defiant MP4 with AT6 Turntable refurbish

If you decide to continue you will need a stereo cartridge as clydeuk says. I have recently bought a NOS Ronette 105 for around £20. If you would like more details send me a PM, but you will need to decide what to do about the amp first. One upside is that it is quite a good autochanger. I assume you have a rubber mat for it


Paul
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Old 2nd Mar 2017, 4:41 pm   #155
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Default Re: Defiant MP4 with AT6 Turntable refurbish

Quote:
Originally Posted by Station X View Post
It does sound like the mains transformer is faulty. A transformer with no load on its secondary windings should stay lukewarm all day.

A faulty transformer could give low HT voltage (unfortunately we don't know what it should be) resulting in not enough HT current to light the indicator lamp. I calculate that the current drawn by the anode and screen grid of the pentode section of the UCL83 (5.8/390) is only about 15mA or about half what I'd expect.

Let's await a second opinion from one of the other contributors to this thread though.
That's my current conclusion also Graham, I too worked out the UCL83's current as only around 15mA, as it stands the HT seems to me to be to low, that fits in with the bulb not lighting up.

Lawrence.
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Old 2nd Mar 2017, 5:07 pm   #156
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Default Re: Defiant MP4 with AT6 Turntable refurbish

If the transformer is indeed faulty (and that's the way it's looking ) then it could be rewound. Forum members Ed_Dinning and murphymad have the wherewithal to do this.

The type of shaver socket used in bathrooms contains a safety isolating transformer having a secondary with 110 and 230 V tappings, and rated 20 VA -- probably just about enough for your needs. If you can get hold of such an item cheaply (car boot sale, online auction, building site where a hotel is being refitted .....) then it won't hurt to experiment; if you can get two transformers, so much the better, just split the power dissipation between them by using one for the heaters and the other for the HT.

You will need to add a resistor in series between the 110 V tapping and the valve heaters, to drop the excess voltage; you can work out the value using Ohm's Law, since you know the current through it will be 0.1 A.

If the valves are UCL83 (with 38 V heater, not UCL82 with 45 V heater) and UY85, they could have the heaters rewired in parallel and powered from the two ends of an 18-0-18 V, 200 mA (at least) transformer. You would still really need a transformer to supply the HT; the transformer might have been added as a last-minute requirement to a design that was originally supposed to have been live-chassis.
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Old 2nd Mar 2017, 6:24 pm   #157
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Default Re: Defiant MP4 with AT6 Turntable refurbish

We now seem to have a consensus that the transformer is at fault.

I would suggest that the OP asks Ed Dinning for a quote for a rewind. There can be no harm in asking.
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Old 2nd Mar 2017, 7:01 pm   #158
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Default Re: Defiant MP4 with AT6 Turntable refurbish

Thank you everyone.

I do feel quite happy with a re-wind if it can be done. I will contact Ed and see if he wishes to quote.

I guess it will cost a bit and more than it's worth but I remember a line from a film where 'an old chap was planting some trees knowing he would never shelter in their shade' quite relevant I think.

I'll report back in due course.

Kind regards
Graham

It will be a great relief
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Old 2nd Mar 2017, 7:24 pm   #159
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Default Re: Defiant MP4 with AT6 Turntable refurbish

All I can say is that Plessey used this type of small "tropicalised" mains transformer in earlier Defiant (and Regentone) models. These also had "U" series valves in 2 stage amplifier configuration.

If a re-wind is considered, the HT secondary specification will need to be determined.
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Old 2nd Mar 2017, 8:15 pm   #160
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Default Re: Defiant MP4 with AT6 Turntable refurbish

Remember that if it's NOT the original transformer then a rewind will be the same as this one. It MUST be checked as an original component or you will be back to square one.
I'm sure that a transformer could be wound to the original spec, if the details are known.
I said way back that this has the look of a Philips transformer with the bitumen coating, and that makes it suspicious in my view. I may be wrong as I don't think I've serviced any Defiant record players.
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