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Old 14th Feb 2017, 4:44 pm   #41
ggg1234
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Default Re: Defiant MP4 with AT6 Turntable refurbish

Tag 1 goes to chassis
the resistance from chassis to pins 1, 2, 3 and 6,

1= 10k
2= 0 no reading
3= 10k
6= 0 no reading
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Old 14th Feb 2017, 5:26 pm   #42
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Default Re: Defiant MP4 with AT6 Turntable refurbish

If tag one goes to chassis, the reading to chassis should be close to zero ohms.

Are you sure there isn't a break in the wire?
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Old 14th Feb 2017, 6:00 pm   #43
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Default Re: Defiant MP4 with AT6 Turntable refurbish

Interesting that Defiant chose to put an upmarket autochanger in such a relatively basic record payer. An Autoslim would have done the job just as well.
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Old 14th Feb 2017, 8:47 pm   #44
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Default Re: Defiant MP4 with AT6 Turntable refurbish

Hi Graham

Been a long day I know but I checked those meter reading again and found that by touching the probes together I had not adjusted the Ohms adjust calibration screw to zero the meter for direct contact. Now 1 and 3 are indeed zero duh !!!

That said, I understand that as tag 1 is directly connected to the chassis it would also be 0ohms but a little confused as to why any other tag could be zero?

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Old 14th Feb 2017, 9:33 pm   #45
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Default Re: Defiant MP4 with AT6 Turntable refurbish

With the valves unplugged and the indicator lamp unscrewed (assuming that's possible) there should be no short-circuits (zero ohms) to chassis. The resistance may be just a few ohms though.

What is the type and voltage of the indicator lamp by the way?

Is there still infinite resistance (open circuit) between tag 2 and chassis?
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Old 14th Feb 2017, 10:06 pm   #46
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Default Re: Defiant MP4 with AT6 Turntable refurbish

Yes still no detectable movement on my old analog meter. I took the mini bulb out because it didn't light up when the sound went. So it's been out of its socket for all the readings all day.
However, I am expecting delivery tomorrow of my new DMM it may be better to wait for that and then take them all again?
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Old 15th Feb 2017, 8:52 am   #47
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Default Re: Defiant MP4 with AT6 Turntable refurbish

Morning Graham.

I'm just wondering whether the blown? indicator lamp acts as a fuse for the High Tension (HT) supply?

Check whether there's continuity between any of the transformer tags apart from those connected to the mains supply. We know that there must be continuity from chassis to tag 1 to tag 3, as that's the heater winding and the valves do light up.

Perhaps there's continuity between tags 2 and 6 or elsewhere?

The HT circuit might be tag 3 - indicator lamp - tag 6 - HT winding - tag 2 - anode (pin 9) of rectifier.

You could also check whether with power applied you get an AC voltage between tag 2 and tag 6.
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Old 15th Feb 2017, 11:45 am   #48
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Default Re: Defiant MP4 with AT6 Turntable refurbish

Morning Graham

Very interesting suggestions. Your HT with bulb as fuse does seem very possible. Back at the start of this issue, the first indication was no sound and the bulb went out. But I then removed the bulb which I think is a 6.3v e10 (don't know the wattage though as there are no visible markings on it) and it has been out since. Interestingly the bulb tests with continuity across it but doesn't light up when power is turned on. I don't have a power supply to check if it really does works tho.

With my old meter (which will have to do until my new one turns up today) I get the following readings:

As you rightly surmise the is indeed continuity between Chassis tag1 tag3 Heater circuit
Between tag2 and tag6 there is continuity.
With power on and bulb out there is circa 60v across tag2 and tag6
With power on and bulb in there is also circa 60v across tag2 and tag6

Not sure what that all means but it would seem at least some of the transformer is doing something/working?

regards
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Old 15th Feb 2017, 11:51 am   #49
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Default Re: Defiant MP4 with AT6 Turntable refurbish

also getting circa 140v across tag4 and tag2 (bulb out)
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Old 15th Feb 2017, 12:32 pm   #50
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Default Re: Defiant MP4 with AT6 Turntable refurbish

This looks good.

I suggest refitting the indicator lamp and the valves, then checking the AC voltage at rectifier pin 9 and the DC voltage at rectifier pin 3, both with respect to the chassis.

Only apply power briefly though for these tests, in case there are other faults which could damage the transformer.

You shouldn't be checking voltages on tag 4, as that has mains voltage on it.
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Old 15th Feb 2017, 1:24 pm   #51
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Default Re: Defiant MP4 with AT6 Turntable refurbish

well I flabbergasted !!! but so thrilled too. Thank you so much Graham your a star !!!

I refitted the valves and indicator bulb and then measured the ac voltages at tag9 circa 140vac and DC voltage at tag3 circa 145vdc.

Whilst doing so I heard a crackle very faintly from the speaker so I re-assembled the record player and put a record in the auto changer. It dropped the arm swung across and it played. What can I say? Does this mean the lamp is the HT circuit fuse (it still doesn't light up by the way)?

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Old 15th Feb 2017, 2:25 pm   #52
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Default Re: Defiant MP4 with AT6 Turntable refurbish

It's good to know that the player is working again. We'd have probably got there sooner had we had the correct circuit diagram showing the wiring of the indicator lamp. Did the indicator lamp ever light up?

I don't like unexplained faults. At best this could have been down to dodgy contacts on a valve holder, indicator lamp holder, or a dodgy connection. At worst the transformer secondary has an intermittent open circuit. Time will tell.

If you want to continue enjoying your player without damaging it I suggest you do a couple of simple things.

Firstly measure the DC voltage w.r.t. chassis on pin 9 (the control grid of the pentode section of the UCL83. You should only see a fraction of a volt here.

Secondly change that Red/Yellow/Black Plessey electrolytic capacitor. These are notoriously unreliable. The replacement should have the same capacitance value and the same or higher working voltage as the original. This capacitor is polarised and the replacement must be fitted the correct way round. The old unit's ends are red and black, denoting +ve and -ve. The new unit will have the negative end marked by a series of minus signs.
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Old 15th Feb 2017, 4:31 pm   #53
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Default Re: Defiant MP4 with AT6 Turntable refurbish

Just getting used to my new meter - its hardly plug and play though. I bought an auto ranging one and that might have been a mistake. . . the display hardly settles especially near any emf sources (computer)

The mains indicator light never has come back on so I guess something not right there?

My new meter tell me the dcv on pin 9 (ucl83) is between 1.2 and 0.6vdc how does that sound?

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Old 15th Feb 2017, 4:35 pm   #54
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Default Re: Defiant MP4 with AT6 Turntable refurbish

The indicator light probably isn't designed to come on apart from a brief flash when excess current destroys it.

1.2 VDC on the control grid is a bit high. Disconnect C3 the grid coupling capacitor at the grid end and see whether the grid voltage drops to zero.
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Old 15th Feb 2017, 4:50 pm   #55
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Default Re: Defiant MP4 with AT6 Turntable refurbish

Just to double check do you mean this brown one (marked as 0.1 capacity) pic attached
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Old 15th Feb 2017, 5:57 pm   #56
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Default Re: Defiant MP4 with AT6 Turntable refurbish

I would think that the Red indicator light is nothing more that a "Pilot Light", an attractive feature on these types of players and nothing as sophisticated as a thermal/fused arrangement. This is such a basic circuit that I'm sorry to see the OP struggling with it.
Can I also comment that there is nothing "Plug and Play" (#53) about vintage electronics!
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Old 15th Feb 2017, 7:52 pm   #57
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Default Re: Defiant MP4 with AT6 Turntable refurbish

Hi Edward

Thanks for your comments. The red indicator light always used to come on when you switched on the power. Hence why I thought it was a power indicator.

It was only when it stopped coming on that these problems started. With the bulb back in the holder, even though it still doesn't light up on power, the player is now working and I have ordered one or two new parts (capacitor replacements) as suggested by others.

If you reread my post #53 you will see that my 'plug and play' comment was regarding my new meter (DMM) which arrived today and certainly not plug and play vintage electronics.

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Old 15th Feb 2017, 8:09 pm   #58
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Default Re: Defiant MP4 with AT6 Turntable refurbish

OK, now see your point! Is the "bulb" a normal lampbulb or a neon? Have you tested it's continuity and what's its rating (voltage)?
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Old 15th Feb 2017, 8:59 pm   #59
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Default Re: Defiant MP4 with AT6 Turntable refurbish

Hi Edward


I tested it on my old meter which has an audible bell which sounded so I assume there is no break in the filament. It is a typical small screw thread filament bulb with an e10 fitting and I think the voltage may be 6.3v. Or maybe 12v uNfortunately it is in too bad condition to decipher any writing on it as too voltage or wattage.
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Old 15th Feb 2017, 10:53 pm   #60
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Default Re: Defiant MP4 with AT6 Turntable refurbish

Edward. If there was a break in the filament the player wouldn't work, as the lamp is in series with the AC supply to the rectifier.

Graham. I'll get back to you tomorrow regarding the capacitor. I've no access to the circuit until I get home again.
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