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Old 10th Feb 2017, 3:57 pm   #1
ggg1234
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Default Defiant MP4 with AT6 Turntable refurbish

Hi
I only joined yesterday and apologies if this is not posted correctly or in the wrong place. But please tell me if it is so I don't make the same mistake again.

I recently acquired a Defiant MP4 record player with a Garrard AT6 Turntable. My intention is to have a go at refurbing it.
I read the article on what to do first when acquiring these vintage valve machines in the reviving section of this site but have now come across an issue. It worked fine at first but has since stopped and I have found a component rattling around in the base. I am not an electronics expert but did as a kid play around with old valve equipment. it looks to me to be a resister (picture attached) which I think came from the triple bank of rotary pots (on/off volume and tone) on the front of the machine. I bought and downloaded the circuit diagram from this site but its been a long time since I could trace these things. with a view to safety first . . .I thought I would ask for a little help. My soldering skills are good.
Thank you.
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Old 10th Feb 2017, 5:13 pm   #2
Edward Huggins
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Default Re: Defiant MP4 with AT6 Turntable refurbish

That might have been a previously removed resistor.

When you say "refurbing it", what does this mean? Is there an electronic or mechanical fault with it other than maybe just tidying the cosmetics?

Let us know, this is a nice player?
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Old 11th Feb 2017, 9:38 am   #3
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Default Re: Defiant MP4 with AT6 Turntable refurbish

4 Megohms is a high value resistor even for valve circuits. If you have the circuit, it should be easy to find where it might have been.

It also doesn't seem to feature in any of the Defiant circuits in the sheet from up top cited for the MP4.
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Old 11th Feb 2017, 10:35 am   #4
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Default Re: Defiant MP4 with AT6 Turntable refurbish

Thank you guys for your responses.

It is indeed a lovely player standing on four original mid century legs. My 'refurbing' idea was to give it a good clean and service it as it all appeared to work quite well.

However, it has now stopped working (no sound) and some gentle dismantling revealed the valves heaters all still working but no sound. This resister was rattling around in the base. The discovery of the resister led me to think it may have become detached. I downloaded from top cited the wiring diagram but couldn't locate the part . . . . then I joined this blog. I have ordered up two valves just in case but I don't think it is them?

regards
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Old 11th Feb 2017, 12:25 pm   #5
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Default Re: Defiant MP4 with AT6 Turntable refurbish

Have you a multimeter? Some basic voltage checks and signal injection tests before replacing any item.
If there is no sound at all, not even a slight hum from the speaker, check if there is an external speaker switch, it may be dirty or even accidentally switch to the wrong position.
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Old 11th Feb 2017, 12:45 pm   #6
Edward Huggins
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Default Re: Defiant MP4 with AT6 Turntable refurbish

This uses UCL82 and UY85 valves, but they may not be the problem at all. You need to check the voltages from the cathode onwards from the UY85 rectifier valve as you may have an HT problem. Can you take a reading and let us know?
I still can't work out why you would want to gives this a "service" whilst it was previously working well - so assume you can read a circuit diagram and use a DMM?
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Old 11th Feb 2017, 4:03 pm   #7
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Default Re: Defiant MP4 with AT6 Turntable refurbish

Hi Edward

This model has UY85 and UCL83 (rather than UCL82) When I say 'service' I meant only the cleaning and lubricating the mechanical parts as the 'service' part.

I fear you may get a little frustrated with me as I only have my old analogue (radio shack) multimeter and am a little rusty at following the service diagram although I should be OK I think.
This leads me to ask perhaps what voltage readings I might expect to see from the cathode onwards?

Nuvister kindly suggests some basic Voltage and Signal injection tests the latter of which may be beyond my capability as I do not have a signal injector or scope.

I can hear no sound at all with the variable pots move in any direction. Touching the headshell wiring does nothing either. As too an external speaker switch . . I cant see anything that looks like one. I am posting some more pics should they be of any use/interest.

Regards
Graham
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Old 11th Feb 2017, 6:03 pm   #8
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Default Re: Defiant MP4 with AT6 Turntable refurbish

Refurbing is a shortened form of Refurbishing
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Old 13th Feb 2017, 3:36 pm   #9
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Default Re: Defiant MP4 with AT6 Turntable refurbish

Hi camtechman

Refurbing is indeed refurbishing. Any ideas on the 'voltages' I need to see?

Regards
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Old 13th Feb 2017, 5:03 pm   #10
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Default Re: Defiant MP4 with AT6 Turntable refurbish

That amp looks to have a mains isolating transformer on the RHS, if so that's good. Looks a decent sized speaker too. The are only 4 wires to the UY85 - 2 for the heater, cathode and anode. The cathode reading should be around 180-210V.
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Old 14th Feb 2017, 11:50 am   #11
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Default Re: Defiant MP4 with AT6 Turntable refurbish

Hi Edward

Thanks for you assistance.
I have measured the voltage on the valve base of the UY85 (valve out) and pin 4, which I believe is the Cathode, to the chassis only reads 80v?

I assume the heater circuits of both valves are ok as my (non technical) observations show the valves go brighter for a second or two when switched on then fall back to a more normal 'glow' thereafter.

One thing it showed me for sure is that I need a DMM and not my old radio shack analogue and I will now buy one.(any suggestions on make welcomed)

Graham
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Old 14th Feb 2017, 12:08 pm   #12
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Default Re: Defiant MP4 with AT6 Turntable refurbish

HI Edward

I must correct my last post as I misread the data sheet and I see pin 4 is one of the heater pins. Pin 3 which is the Cathode has no reading at all.

Graham
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Old 14th Feb 2017, 1:06 pm   #13
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Default Re: Defiant MP4 with AT6 Turntable refurbish

Anything on pin 9? The voltage here will be AC.
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Old 14th Feb 2017, 1:14 pm   #14
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Default Re: Defiant MP4 with AT6 Turntable refurbish

I'm assuming this is similar to the Defiant R209.
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Old 14th Feb 2017, 1:17 pm   #15
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Default Re: Defiant MP4 with AT6 Turntable refurbish

Hi Graham

(Measured with both valve out) on pin 9 about 20v?
regards
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Old 14th Feb 2017, 1:25 pm   #16
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Default Re: Defiant MP4 with AT6 Turntable refurbish

Hi Graham,
I downloaded the sheets from the 'up top site' and must admit to being a little confused. I think its closer to the R209 but the wording says all three sp1 R209 and Hf1 are two valve but my reading of the diagrams tells me only the SP1 is two valves the other two show three?. The label on mine shows it as an Defiant MP4, where am I going wrong?
Regards
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Old 14th Feb 2017, 1:32 pm   #17
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Default Re: Defiant MP4 with AT6 Turntable refurbish

What you're seeing on the circuit diagram is two valves within the same envelope. Note the dashed lines along the sides of the envelope symbol. So the physical valve count is two.

Are you measuring pin 9 (the anode) with your meter set to AC volts? Next step is to unplug the UY85 (the other valve will go out) and check pin 9 again.

EDIT. I see you've done that. Let me have a think.
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Old 14th Feb 2017, 1:36 pm   #18
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Default Re: Defiant MP4 with AT6 Turntable refurbish

Trace the wire from pin 9 back to the mains transformer secondary. Is there a voltage on the transformer tag?

Have you identified pin 9 correctly? Pins number clockwise when looking from under the chassis.
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Old 14th Feb 2017, 1:36 pm   #19
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Default Re: Defiant MP4 with AT6 Turntable refurbish

The circuit diagram will appear to show 3 valves, but the UCL83 is 2 valves in one glass envelope. As I thought from your photo, the circuit shows it's mains isloated with a 90V tap for the 2 valve heaters at 45V each. Check the cathode again, which on the diagram in Post #14 is Pin 3.
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Old 14th Feb 2017, 1:37 pm   #20
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Default Re: Defiant MP4 with AT6 Turntable refurbish

Are maybe V1A and V1B on said circuit diagram two halves of one valve?
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