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Old 21st Apr 2024, 9:28 pm   #1
paul1962
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Default Dansette Junior Deluxe Question

Hello Everyone,

You could say Captain Confused is back again

I have a Dansette Junior Deluxe with according to the board and also the descriptive schematic for the model, is the 14-2 type amplifier. This one uses the Electrostatic type of speaker, just for clarification.

This board as as far as I can tell, is original and hasn't had any previous works done on it, but I am finding some rather strange situations with it, which I will detail below.

Firstly, the valve choices on this board. It has the UY85 Rectifier valve, which is both in the player and also listed in the schematic, but whereas the schematic states a UCL83 valve, actually fitted is a UL41. I can find nowhere that states the UL41 as an equivalent to the UCL83 and this is confusing.

Is there any kind soul that can explain whether this is the right valve fitted ?

Also, the videos I can find online, shows a couple of extra capacitors that this board doesn't seem to have and just for the icing on the cake, where one disc capacitor should be on the board found online, there is a tag wire that looks as though it has been cut off but not been unsoldered, which on the non electrostatic speaker type, was (or should have been) a 0.005 uF disc capacitor.

The fault that I'm trying to correct on this amp is one of a crackle, almost like either a dry solder joint, or loose connection somewhere, together with a low output from the player. The deck motor is supplying 82v from the motor to the board and when the crackle (or arcing noise) is heard, this increases by around 2 v.
So far, I have replaced the 3 smoothing caps (32,16 and 25uF in the can which had leaked badly) and also the old wax type .005uF that decided to dump it's wax all over the circuit board. How the hell this was working without going bang is beyond my comprehension, but the hum was horrendous, that's for sure.

Over to you good knowledgable people.
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Old 21st Apr 2024, 9:41 pm   #2
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Default Re: Dansette Junior Deluxe Question

The UL41 is a single pentode on a B8A base whereas the UCL83 is a Triode Pentode on a B9A base they are in no way equivalents.

The fact you are also missing a couple of capacitors suggests the board you have is a single stage amplifier not the 2 stage amplifier that would use the UCL83.

Pictures would help us to identify the correct circuit.

Cheers

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Old 22nd Apr 2024, 12:12 am   #3
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Default Re: Dansette Junior Deluxe Question

Many thanks for your reply Mike, I have some pics for you to have a look. Please excuse the state of the track side of the board, I did say the caps had leaked everywhere and that is old wax deposits that are yet to be cleaned off.
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Old 22nd Apr 2024, 12:29 am   #4
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Default Re: Dansette Junior Deluxe Question

I should just add, that I believe this to be the correct schematic for the actual board in the player.

Last edited by Station X; 22nd Apr 2024 at 6:26 am. Reason: Forum rule B8.
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Old 22nd Apr 2024, 5:56 am   #5
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Default Re: Dansette Junior Deluxe Question

It is not possible for the ul41 to work in place of the UCL 83. The connections to the pins are very different, and the ul41 has 8 pins whilst the ucl83 has 9 pins, so the socket won't match.

Looking at the board I think it has been extensively modified. For starters the ul41 base in your picture doesn't seem original to me, compared to the rectifier end. Also someone seems to have soldered connections from the tracks to the matching pins on the replacement UL 41 b8a base. I hope this makes sense so far.

How to go forward from here?. If you retain the ul41, you will still have poor performance due to the single amplification stage. For me, returning this to the original is a no brainer. What's unclear is how much damage to the board has been done. If it's been butchered, the nuclear option would be to redo it on an aluminium base with point to point wiring. Alternatively, I think someone sells ready made PCBs for Danette's but I've never used them and for such a simple circuit is hardly worthwhile.

Hope this helps
I'm sure other more knowledgeable people will chime in if I'm wrong.

Gabriel
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Old 22nd Apr 2024, 8:32 am   #6
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Default Re: Dansette Junior Deluxe Question

Another factor is the cartridge.

Single stage amplifier record players rely on having high-output cartridges fitted to their turntables. These produce significantly more audio voltage while playing a record and this mostly makes up for the lower gain of the simpler amplifier. The end result can be a bit disappointing, but these were the cheaper models...

With a single stage amplifier, you are tied to high output cartridges. The really bad news is that not only are they no longer being made, those in existence whether fitted to players or new ones left in stock are all dying. The higher output voltage was achieved by using a more strongly piezo-electric material, Rochelle Salt. Rochelle salt is hygroscopic and absorbs water from humidity in the atmosphere. ochelle salt is also water-soluble, and the active elements in these cartridges have been slowly turning themselves to sludge. There are some still left in working condition, but not many. Finding another one if yours isn't good will be difficult.

This all suggests you'd be better off with a 2-stage amplifier if you have the choice as what to restore it as. Medium and lower output cartridges use man-made ceramic elements such as Lead-Zirconium Titanate which can still be found and are available new form China.

If you're stuck with a single stage valve amplifier, some people have added small, transistor, preamplifiers to make up the gain shortage. This gets a bit messy because you also have to arrange a power supply to feed the transistor circuit.

At the moment, availability of different choices of cartridge are a much stronger constraint than anything else. This says that a logical approach would be to identify the type of cartridge you have and whether it's viable, then go from there.

David
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Old 22nd Apr 2024, 10:45 am   #7
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Default Re: Dansette Junior Deluxe Question

In addition to the valid comments already made, as I understand it the amplifier is working but crackling, it’s possible the output transformer is breaking down and would need replacing.
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Old 22nd Apr 2024, 12:56 pm   #8
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Default Re: Dansette Junior Deluxe Question

Well ... thank you all for your insights ... I honestly thought I was going mad for a minute, Once again, you have helped me along the way

I do agree that the best way forward at this stage is to just write off this amplifier board and put it back to it's original 2 stage amplifier.

This is for more than one reason. Firstly, after cleaning all the old wax off of the trace side of the board, i can now see that it appears that the B8A base has indeed been cut through the board and without some kind of support, even if I was to change the base back to a B9A type, it would only be held in place by the tags rather than through the board as per the UY85 base. Then I would need to obtain the correct UCL83 and assuming that the output transformer is possibly starting to give out (as per Juhn 10b's possible theory), then to return this board back to anywhere near original specs is not a viable option when I could probably replace the whole amplifier unit more cost effectively.

Once again ... I thank you all and wish you all well.

Kindest Regards
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Old 22nd Apr 2024, 1:24 pm   #9
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Default Re: Dansette Junior Deluxe Question

The fact that it's (or was...) a Dansette may help you decide.

Dansettes were the players that best fitted teenagers' budgets. They were pretty much rock bottom prices and engineered down to such. They did make a graded series of models, each targeted at different price points, for those with a bit more to spend.

Consequently, a lot of people have golden memories of their first record player which are locked to the name Dansette. Now much older, they are no-longer impecunious and they're getting a bit wistful. They've been mining a seam of old LPs and 45s in their attics and thinking about playing them again, and the fun they used to have. Their solution is simple - they need a Dansette again.

Consequently, Dansettes are in demand and this has an inevitable effect on current prices. This effect is so strong that machines which were much better back in the day can now be bought for significantly less than anything with a Dansette badge.

As yours has been mucked about with, why not muck about with it some more?

I'd make sure it has a ceramic cartridge in it with a stylus which can be found easily. I might buy and stash a job-lot of styli.

I'd definitely go for a two-stage amplifier. ECL series dual valves aren't made any longer, but ECC83 and EL84 are, so the availability of spares is better out into the future. This would tempt me to two separate valves, with an outside chance I'd go for push-pull just for the hell of it.

If you've got to restore an amplifier which is so efficiently destroyed, you're really building a new one. If you're not locked into 100% originality, you get a free choice, so where do you stop?

Good audio coming out of an ordinary sized box has a shock factor and can impress even non-technical people quite a lot. I found this out when my neighbour heard a Hacker Herald I'd restored. He'd never heard that from a portable transistor radio. Now he has one and enjoys the surprise factor on people visiting his garage/guitar group meeting place.

You could treat it as an opportunity for a bit of fun.

David
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Old 22nd Apr 2024, 1:28 pm   #10
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Default Re: Dansette Junior Deluxe Question

The amplifier in the Dansette Junior Deluxe has a two-stage circuit using an UCL83 and a UY85. The Amplifier in a Dansette Junior (i.e. not the De Luxe version) has a single-stage EL84, but if it is a very early version, it may use an UL41.
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Old 22nd Apr 2024, 1:47 pm   #11
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Default Re: Dansette Junior Deluxe Question

It's very unusual for any record player to use a UY85 and UL41, as they are different generations of valve. The UY85 would normally be paired with a UL84 in a single stage amp, while the UL41 would be paired with a UY41.
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Old 22nd Apr 2024, 2:09 pm   #12
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Default Re: Dansette Junior Deluxe Question

I was thinking the same, David. I'd probably turn it into a Mullard 3-3, provided there's enough space in there for a mains transformer.

Given the prices these Danettes are fetching, it seems that there is a whole industry centred around their refurbishment. You can even get replica cabinets now.

Having said this, I've never worked on one myself.
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Old 22nd Apr 2024, 7:51 pm   #13
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Default Re: Dansette Junior Deluxe Question

Quote:
Originally Posted by Edward Huggins View Post
The amplifier in the Dansette Junior Deluxe has a two-stage circuit using an UCL83 and a UY85. The Amplifier in a Dansette Junior (i.e. not the De Luxe version) has a single-stage EL84, but if it is a very early version, it may use an UL41.
I should add that in the EL84/UL41 version, the rectification is via a Contact Cooled device, no valve is used.
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Old 22nd Apr 2024, 8:16 pm   #14
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Default Re: Dansette Junior Deluxe Question

Odd you should mention a 3-3! I did exactly the same thing with an old Dansette way back in the 70's when my brother presented me with a tatty example with a duff output transformer. There was plenty of room in the cabinet so I built a 3-3 amp and changed the cartridge to a medium output ceramic type. Also fitted a better speaker. It sounded great so fitted an extension speaker socket which allowed it to drive a dual cone Hi Fi speaker. Many successful parties were had......I later built another 3-3 and converted it to stereo, the speaker on the record player forming the left channel and the external speaker forming the right. OK they weren't matched but it gave a pretty good account of itself.
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Old 22nd Apr 2024, 8:28 pm   #15
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Default Re: Dansette Junior Deluxe Question

Given that the originality has already been lost, it may make more sense to fit a modern solid state amp. These are available as modules for almost nothing from Chinese eBay sellers.
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Old 23rd Apr 2024, 8:43 am   #16
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Default Re: Dansette Junior Deluxe Question

However, if you do build a replacement valve amp, please give a thought to subsequent technicians who may have to work on it in the future, and paste the new circuit diagram inside the box! It would solve the mystery that you have been trying to unravel here...
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Old 23rd Apr 2024, 4:20 pm   #17
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Default Re: Dansette Junior Deluxe Question

We might be going off-topic into a bit of exotica here. This simple 2 stage amp can be made good as long as the heater voltage from turntable motor is giving 90V from the tap on the winding.
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Old 29th Apr 2024, 7:52 pm   #18
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Default Re: Dansette Junior Deluxe Question

Hello everyone,

I have an update and also a question in regards cartridge type (high or low output).

I have managed to obtain the correct board with valves, changed all caps and it is fitted and working.
I have fitted a medium output cartridge, but the volume seems lacking and there is distortion. I have also tried an original BSR SC5M known to be in good working order with the same result.

The badly modified amp that was in it, had a high output TC8 (which was also knackered) and now I have the correct UCL83 amp fitted, I was wondering if any of you good people may know which type of cartridge was the original fitment.

If someone could advise, it would be greatly appreciated.

Kind Regards
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Old 29th Apr 2024, 8:07 pm   #19
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Default Re: Dansette Junior Deluxe Question

Is the distortion there at all volume levels or only towards maxium? Have you checked the HT voltage against the circuit value? I would have thought that a medium output cartridge would be OK with a two-stage amp. What about the output transformer? The speaker? Eliminate all this first before swapping cartridges. If the output transformer is the original, it might have been overrun when the UL41 was shoehorned into the circuit. The UCL83 has an anode current of around 30mA whereas the UL41 is 45mA. The transformers are minimally rated so it might have been damaged....shorted turns will give a distorted output. If you have any output transformers you can try (almost anything will do for testing as long as it's rated adequately), it will prove the point.
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Old 29th Apr 2024, 8:19 pm   #20
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Default Re: Dansette Junior Deluxe Question

Quote:
Originally Posted by Sideband View Post
Is the distortion there at all volume levels or only towards maxium? Have you checked the HT voltage against the circuit value? I would have thought that a medium output cartridge would be OK with a two-stage amp. What about the output transformer? The speaker? Eliminate all this first before swapping cartridges.
Hello Sideband

The distortion is on max volume only, almost like an overdriven effect (based on my experience as a guitarist). when I touch the cartridge wires, the amp almost blows my head off, but with cartridge output, next to nothing, almost like 1/4 volume. This is what makes me question the cartridge output voltage. This is with a brand new medium output cartridge and also a good known BSR original one.

I should just add that the board and all components were changed complete as a unit, with output transformer and valves also.

Last edited by paul1962; 29th Apr 2024 at 8:30 pm.
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