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Old 11th May 2019, 7:14 pm   #1
Herald1360
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Default Dansette Bermuda

Got my hands on a Dansette record player for the first time ever! Not mine (I'm not particularly interested in any one-valve crystal cartridge machine) but it came into the Tewkesbury repair cafe this afternoon. Couldn't fix it on the spot- suspect knackered cartridge and possibly tired selenium rectifier, so I've brought it home to play with. After discussion with the owner I'm going to try the cheap route (Chinese cheapy plus preamp) at least to start with- it's easy to do it reversibly with the wooden box to mount a small circuit board on.


More to follow- I'm not stuck yet!
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Old 12th May 2019, 7:49 am   #2
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Default Re: Dansette Bermuda

Hi Chris
You may not need a preamp, those red and black Chinese cartridges have a fairly high output, or at least the one I bought did.

Mike
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Old 12th May 2019, 7:50 am   #3
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Default Re: Dansette Bermuda

I’ve used the Chinese Red Cheap Cartridge ( £2 )and didn’t need a preamp, plenty of output. Remember they don’t come with mounting bracket (£8).
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Old 12th May 2019, 7:59 am   #4
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Default Re: Dansette Bermuda

By the way, a version of the Chinese Cartridge having a 'flipover' LP/78 stylus is also available (without bracket!) from at least one e-bay selle.
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Old 12th May 2019, 9:32 am   #5
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Default Re: Dansette Bermuda

I had disappointing results running a Chinese Red Stylus cartridge into the similar amplifier (EL84 + selenium rectifier PSU) in a Dansette Major De Luxe. It was listenable only at full volume and if you huddled up close to the speaker.
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Old 12th May 2019, 1:54 pm   #6
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Default Re: Dansette Bermuda

I think the Chinese cartridges will work with singles, but may need full volume to be just about acceptable with LPs. It all depends on your expectation and the level of volume you require from an old record player. I've never actually tried one in a single valve record player, but I have got away with using the medium output crystal cartridge which is the BSR X5M on such players. The Chinese black with red stylus cartridges are extremely good for what they are and particularly for the price.
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Old 12th May 2019, 4:17 pm   #7
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Default Re: Dansette Bermuda

I'll knock up an opamp preamp anyway. Only one trimpot needed to dial in gain until it sounds about right.

Anyone know what the rated output of the Chinese ones is? An EL84 needs about 3.5V rms on g1 for a decent output.
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Old 12th May 2019, 5:42 pm   #8
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Default Re: Dansette Bermuda

Correction to my post #3, I didn’t use the red cheap cartridge on a single el84 amp, so I can’t confirm how well it would perform. It was used on a transistor amp, and it worked very well, sorry for any confusion.
I haven’t measured the out so I can’t give you any figures.
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Old 12th May 2019, 6:35 pm   #9
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Default Re: Dansette Bermuda

The output of these generic red chinese carts is not always stated, but I have seen c. 200mV, but no cm/sec velocity to deliver this is quoted.
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Old 12th May 2019, 9:08 pm   #10
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Default Re: Dansette Bermuda

I have a red and black Chinese cartridge on an ECL82 amp and there is too much signal, with the volume up to only 50% it is loud and going into distortion..

Mike
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Old 24th May 2019, 4:55 pm   #11
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Default Re: Dansette Bermuda

The player is now in working order, no preamp fitted yet.

Parts changed-

Cartridge. Chinese cheapy fitted with home made mounting clip folded up from tinplate.
Cartridge connectors. Used four D-type socket inserts.
Reservoir cap. Fitted Nichicon 33uF 400V.
Screen cap. Ditto
Cathode cap. Fitted random 22uF 50V.
Cathode resistor. Fitted 1W 150R for slightly easier life for EL84. (Old 120R was >180R).
Screen resistor. Fitted replacement 3k3. (Old one >3k9).
Tone cap. New 10n 630V fitted.
Rectifier. Fitted 1N4007//10n in series with 330R 6W.
Mains lead. Fitted two core sheathed type.
Mains plug. Nice old brown bakelite Volex Temco added to my stash, fitted reasonable black plastic modern one complete with a handy "3A fuse fitted" sticker.

Pretty much all the passive components really!

Pots blasted with Deoxit, now reasonably quiet. Hopefully volume control will shut up altogether with preamp fitted and no dc connection to grid.

It's a bit quiet on a classical LP, as might be expected.
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Old 25th May 2019, 11:23 pm   #12
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Default Re: Dansette Bermuda

Looks like it's coming on well Chris, great job.

Yes the LPs do tend to be a bit quiet, i can remember a friend popping round in the early 1980s i went downstairs to make a cup of tea, and when i came back my fidelity HF45 which was the much later model, with the TBA800 amplifier (which made a brief come back) bought from Woolworths in 1980 was on full volume with a carpenters LP on it.

The reason being, there was hardly any power in the volume at all, as if the volume was barely on number 4. But i knew exactly what to do if wanted to put this right and raise the roof, just put a Blondie single on

Paul
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Old 8th Jun 2019, 10:24 am   #13
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Default Re: Dansette Bermuda

Just to round this off.....


Preamp (x11 gain) knocked up on a bit of Verobard using a handy LF411 from the junk box plus a few other bits. Power from HT via 47k WW resistor and zener chain.



Sounds about as good as you would expect from a small elliptical speaker in a bare wooden box (rather boxy ) with no obvious nasty treble tracking issues and not a lot of bass.


Back to its owner via the Repair Cafe this afternoon.
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Old 8th Jun 2019, 11:37 am   #14
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Default Re: Dansette Bermuda

That's a fairly eleaborate circuit given what it's intended for. The main determinants of the ammount of "Bass" on these types of basic Dansettes are the efficiency of the cartridge and the degree of compliance of the speaker cone. These can vary considerably between production batches. If you get the right combination of an effective cartridge and a well suspended cone, the sound can be surprisingly "good" for what it is.
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Old 8th Jun 2019, 11:49 am   #15
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Default Re: Dansette Bermuda

You could add a bit of frequency selective feedback to the preamp to bring up the bass a bit. It's also possible that the input impedance is a bit low, and a 1M series resistor would improve things.
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Old 8th Jun 2019, 2:33 pm   #16
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Default Re: Dansette Bermuda

Dansette in particular, because of their cult status, but box record players in general, get a bit of stick because of their obvious shortcomings audio wise. You have to factor in time and place. We were just blowing off the post war cobwebs, and the mushrooming market for music for the younger generation needed cheap and cheerful equipment, freed from the family sitting room and the broadcasters choice of bands and orchestras. The MP3 player of it's generation.
Attempting to recreate modern audio standards is likely to turn into a merry go round of feedback and resonances. They are what they are.
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Old 8th Jun 2019, 7:20 pm   #17
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Default Re: Dansette Bermuda

Quote:
Originally Posted by paulsherwin View Post
You could add a bit of frequency selective feedback to the preamp to bring up the bass a bit. It's also possible that the input impedance is a bit low, and a 1M series resistor would improve things.

I did play with a 2M bias resistor in a simulation of the circuit and it dropped the -3dB point for a nominal 900pF cartridge from about 200Hz to 100Hz. I'd already built the preamp by then though, and the original Dansette amp input was 1M (the volume control pot) so I left it at 1M. I ran the sim to see if it provided any insight into why the preamp didn't work as built but that turned out to be just a solder splash between Veroboard strips.


A simple 1M series resistor would have dropped the gain by 6dB across the range whilst bringing down the -3dB frequency so I would have had to change the opamp gain setting as well to do that. As it stands you just start running into obvious distortion on a loud LP track with the volume wound up to max.



Too late now anyway, it's back with its (delighted) owners who donated £20 to the repair cafe as well as paying the £12 for the cost of parts used in the general repair.
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