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Vintage Audio (record players, hi-fi etc) Amplifiers, speakers, gramophones and other audio equipment.

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Old 6th Aug 2018, 2:14 pm   #1
ldadipscm
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Default HMV 2046 Volume stuck on Full

An elderly neighbour (he is not into modern technology whatsoever but loves his many vinyl albums) had a problem with very annoying crackling sound when adjusting the volume slider on his HMV 2046. He took advice from a friend of his to spray the slider with DP60, which he did. It wasn't me who suggested it but, to be honest (as a DJ who used vinyl records for many years) I would probably have suggested he try the same solution (or maybe an Air Duster type product).

After spraying into the slider area, the crackling stopped but the player had then become stuck on full volume instead and no end of sliding the control back and forth has cleared the problem, so his 2046 is presently unusable.

Can anyone advise whether the item is now fatally wounded or, preferably, if there is a possible solution to getting the volume adjustable again. He tells me that all the other features of the player still work fine, apart from the full volume problem.
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Old 6th Aug 2018, 3:42 pm   #2
Edward Huggins
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Default Re: HMV 2046 Volume stuck on Full

These sliders may have looked the part, but were often troublesome and, unlike a rotary potentiomenter, are not quite such an easy fix. Do you have sufficient experience to part dismantle this and try to restore the slider to what may be left of the track?
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Old 6th Aug 2018, 3:53 pm   #3
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Default Re: HMV 2046 Volume stuck on Full

Depending on what type of control it is, it may be replaceable or repairable. Another possibility is when cleaning the control he disturbed a connection and the bottom connection of the control is disconnected.

Edit. On a photo they look like slider controls, I never had much success cleaning that type, usually the slider started to feel sticky not a smooth travel. There are some types available, whether they would fit the HMV I don’t know.
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Last edited by Nuvistor; 6th Aug 2018 at 4:00 pm.
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Old 6th Aug 2018, 5:14 pm   #4
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Default Re: HMV 2046 Volume stuck on Full

I don't have a circuit for this player, but it strikes me that bad contact between the slider and the track won't give the symptoms described. It'd more likely result in complete silence.

Perhaps the track is broken internally or perhaps there's a bad external connection?
a few resistance checks will soon show what's what.

If the player is stereo, does the fault apply to both channels?
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Old 6th Aug 2018, 7:55 pm   #5
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Default Re: HMV 2046 Volume stuck on Full

Like Nuvistor, I would like to hope that the problem is just that the 0V / ground connection to the 'cold' end of the slider has been lost / fallen off / solder has cracked, especially if the slider is directly mounted on a PCB. Otherwise it sounds like the slider track has gone open circuit at the cold end.

If the control proves to be open circuit at one end then you might be lucky enough to find a log slider pot with the same value and same physical dimensions to replace it - there must have been a few standard sizes after all.
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Old 6th Aug 2018, 8:07 pm   #6
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Default Re: HMV 2046 Volume stuck on Full

Hi Edward. Not really but, with his permission, may try it as a last resort.
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Old 6th Aug 2018, 8:09 pm   #7
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Default Re: HMV 2046 Volume stuck on Full

Hi Frank. It is certainly a possibility that he could have disturbed a connection as I think he mentioned to me that the aerosol had a straw on the nozzle. I will ask him. Many thanks.
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Old 6th Aug 2018, 8:18 pm   #8
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Default Re: HMV 2046 Volume stuck on Full

Just found some on eBay, whether they would do the job is another question.

The player needs looking at and finding out exactly what has gone wrong.
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Old 6th Aug 2018, 8:19 pm   #9
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Default Re: HMV 2046 Volume stuck on Full

Hi. Thanks for your note agreeing with Nuvistor and adding more suggestions - much appreciated. I sourced an official Thorn/HMV 2046 circuit diagram manual which I downloaded and porinted for my neighbour, which may be helpful regarding open circuits if I can find someone local who has experience with repairing old radios. I will have a look at the manual with my neighbour. I also have seen an Ultra version of the 2046 (the Ultra 6046) - its identical apart from the badge. The 6046 I have seen is available for spares but also suffers from crackling of the volume slider.
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Old 6th Aug 2018, 8:23 pm   #10
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Default Re: HMV 2046 Volume stuck on Full

Hi Graham

I forgot to thank you for the stero question - not thought of that. I will go round to see him tomorrow and see if I can get him to try one speaker at a time.
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Old 6th Aug 2018, 9:03 pm   #11
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Default Re: HMV 2046 Volume stuck on Full

Idadispcm, do either of you have a test meter (multimeter) available to you?
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Old 6th Aug 2018, 9:04 pm   #12
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Default Re: HMV 2046 Volume stuck on Full

Use the balance control to try each channel, don’t unplug the speakers, don’t want to cause damage.
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Old 6th Aug 2018, 9:12 pm   #13
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Default Re: HMV 2046 Volume stuck on Full

My dad used to have that exact same record player! I remember some of the selector buttons being mended with lengths of Bic pen tube and epoxy resin ..... The changer was about the last decent one BSR made, before they went all plasticky. Anyway.

It certainly sounds as though the earthy end of the volume potentiometer has become disconnected.

Quick reminder how a volume control works: The signal is fed in at the "top" or "clockwise" end, the carbon track is a resistance and the "bottom" or "anticlockwise" end is connected to chassis. The signal is tapped off from a selectable point on the track. The two lengths of track either side of the sliding contact form a potential divider, whose ratio is set by the position of the slider.

If the bottom end of the potential divider is disconnected, you just have a variable resistance feeding into the main amplifier. And since the input resistance into which it is feeding is greater than the resistance of the potentiometer track, it will see the lion's share of the voltage wherever the slider is positioned.

Both channels being affected equally suggests a wiring problem as opposed to a potentiometer problem (there are actually two carbon tracks in there, one for each channel, with a common mechanism for moving both sliders). It's unlikely (but not impossible) for you to have damaged them both in the same way.

Pictures?

P.S. Running the player with one or both speakers unplugged won't harm it (it's a transistor amplifier) but don't plug in or unplug a speaker while the unit is running -- that could cause damage if you are unlucky. Only change connections with the power switched off.
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Last edited by julie_m; 6th Aug 2018 at 9:17 pm. Reason: Added postscript.
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Old 6th Aug 2018, 9:17 pm   #14
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Default Re: HMV 2046 Volume stuck on Full

This now closed thread includes a useful inline copy of the relevant pages for the Ultra version (6046) from the RTVS book.

https://www.vintage-radio.net/forum/...ad.php?t=53096

It appears to show that the four sliders are PCB mounted, which gives me more hope that the problem may just be a cracked solder joint or broken PCB track at the 'low volume' end of the volume slider.
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Old 6th Aug 2018, 10:01 pm   #15
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Default Re: HMV 2046 Volume stuck on Full

Forum member valveman49 was last looking at the forum this morning, so still about and might be worth a PM -- maybe he still has the hi-res scans. From the less-detailed version in that thread, there seems to be just one common earth return from the controls PCB to the amplifier PCB; if a solder joint has failed at either end of that wire, it would certainly wind up running full chat with no way of turning it down.
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Old 7th Aug 2018, 11:00 am   #16
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Default Re: HMV 2046 Volume stuck on Full

OK - Noted and will do. Ta

Hi Julie
Many thanks for your detailed and very helpful advice (although I must admit some is far above my technical head). I will discuss everything (including your later post, which could be very relevant) with Allan when I see him this evening. Thanks again.

Hey you guys are all so very helpful. Your responses are all very much appreciated indeed.
Lawrence
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Old 7th Aug 2018, 10:41 pm   #17
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Default Re: HMV 2046 Volume stuck on Full

No worries. Anyway, as mentioned above, this is personal

If you search on the Internet for the phrase "potential divider", you'll find plenty of helpful articles. If you find a tutorial series, go back to the earlier sections on Ohm's Law and Kirchhoff's Laws, which you'll need to understand in order to get how the potential divider works. The only maths involved at this level is multiplication and division.

If your eyes are glazing over, don't worry too much; you don't need to know in excruciating detail how barley and hops grow to enjoy beer. What you're looking for is a broken solder joint, or a loose quick-disconnect terminal, on a wire (my instincts are saying it probably will be black, but only because that's the colour I'd choose; and who knows what Thorn were thinking?) that should be connected between the largest expanses of copper on the controls PCB and amplifier PCB. It will be obvious when you see it, anyway. With any luck, resoldering just one connection or tightening up a push-on receptacle with a gentle tweak from a pair of pliers will be all it takes to have the old girl singing like a good'un again.

If you can't see an obvious disconnected wire, at least grab some photos of the internals and post them here. Somebody will be bound to spot something. You will need a multimeter to do the next round of tests, but even a cheap no-name one from a market stall (or online equivalent) will be more than adequate.

Anyway, we have some pretty strong circumstantial evidence but we need to establish something more concrete. I've got two suspects in particular in mind. So here's my suggested test schedule (subject to amendment by others if they spot any error or omission on my part):
  1. Plug both speakers in. Treble, bass and balance controls all at centre position, volume at minimum. Switch on power. Play record (given the nature of the fault, I suggest to use a compilation LP with many tracks on each side; such a record needs grooves that wiggle about less in order to fit so much music in, so need the volume control turned up higher than a shorter record with literally more wiggle room to sound as loud). Does volume control have any effect? Do treble and bass controls have any effect?
  2. Treble and bass to centre. Balance control to extreme left. What happens with sound level in each speaker? What effect does volume control have?
  3. Balance control to extreme right. What happens with sound level in each speaker? What effect does volume control have?
  4. Stop record, power off. Disconnect left-hand speaker. Treble, bass and balance all at centre, volume at minimum. Power on. Play record. Does volume control have any effect? What happens as balance control is moved from end to end and back?
  5. Stop record, power off. Disconnect right-hand speaker, connect left-hand speaker. T, B & B centre, V min. Power on. Play record. Does volume control have any effect? What happens as balance control is moved from end to end and back?
  6. Stop record, power off. Kettle on!
If the wiring diagram is accurate, and there is a single earth return between the controls PCB and the amplifier PCB which has somehow become disconnected, the controls should have little to no effect on the sound; with almost a full-strength signal going to each speaker irrespective where any of them be set. But if the balance control affects which speakers produce sound, that wire must be OK and the problem somewhere else. Similarly, if only one speaker is running flat-out all the time, it can't be that wire. But from the above tests with adjusting controls and disconnecting speakers, it should be possible to determine what is likely to be amiss, just from seeing what effects the controls are having in each state.

Do the tests (but don't take too long over them, as there is a slight risk of damage if the record player is run at too high a volume for too long. Don't worry too much about this, though; it should be able to withstand this abuse for rather longer than it takes to determine if or not moving a control made it louder, quieter or altered the timbre, and you can switch it off and leave it to cool down for a few minutes between tests) and post your findings -- I'm sure I'm not the only one keen to see them. Doesn't everyone love a good detective story?
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Old 8th Aug 2018, 9:06 am   #18
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Default Re: HMV 2046 Volume stuck on Full

Hi Graham
Alan (owner of the HMV 2046) confirmed last evening that, using the balance slider, the sound does come out of both speakers and furthermore, when the balance fader is pushed fully to the left, the sound disappears from the right speaker (and vice versa).
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Old 8th Aug 2018, 9:10 am   #19
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Default Re: HMV 2046 Volume stuck on Full

Sirius Hardware.

Yes, happy to confirm that I do myself possess a multimeter and it is in good condition.

Kind regards
Lawrence
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Old 8th Aug 2018, 9:23 am   #20
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Default Re: HMV 2046 Volume stuck on Full

Hi Julie

Once again, sincere thanks for the trouble you are going to in suggesting things to check in order to try and isolate the actual fault. My plan is to meet up with Alan as soon as I can to go through your list but it will be a few days now before we can get together. I work during the day (Mon - Fri) so can only see him in the evenings but I have to attend a meeting tonight and then Alan tells me that he is away from Thursday to Saturday.

I will progress your suggestions and those of the other members who are all offering excellent suggestions and advisce, as soon as I can.

[As a CAMRA member and a fan of 'who dunnits?' and love a cuppa',
I appreciate your humourus asides, too!]

Cheers.
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