Dansette HI-FI

[ms660]

Out of interest what is the voltage output of the replacement mains transformer that was fitted?

Lawrence.

[Station X]

250 Volts AC.

[Station X]

Originally Posted by Edward Huggins

I think the version of the "Hi Fi" just (very thoroughly!) serviced with ECL82s used a 9" x 6" speaker. The ECL86 version had an 8" round. I've never heard a side-by-side comparisom. Edward

Yes. This version has an oblong speaker.

[Station X]

Job completed.

I'll give the player a few hours soak testing, to see if any other faults show up, before returning it to its owner.

[ms660]

Looks like it's been on here before?

https://www.vintage-radio.net/forum/...ad.php?t=63446

Lawrence.

[Station X]

Well spotted.

It's quite clear from pictures of an unmolested unit later in that thread that the mains transformer, rectifier and dropper resistance aren't original.

The changing of the 220k resistor in the amp, which is the subject of the present thread, is mentioned. It's a pity a brand new one wasn't fitted.

I wonder how many hands it's passed through before it ended up with Dave?

[Edward Huggins]

Originally Posted by Station X

Yes. This version has an oblong speaker.

Oblong? Well, that's a first! Maybe sometimes Oval, more usually Elliptical - but now Oblong.....Edward.

[Herald1360]

Unusual, maybe, but not outside the full definition of oblong:

http://www.merriam-webster.com/dictionary/oblong

[ms660]

The loudspeaker frame can be oblong too.

Lawrence.

[Station X]

OK. I apologise for any distress my use of the word "oblong" may have caused.

The speaker has an oval shaped cone. I did not actually measure it.

[ms660]

No distress for me, a loudspeaker is an object in it's entirety, round, square, oblong, whatever etc.

Lawrence.

[newstart]

Thanks to all those who responded to my Dansette HI-FI problem. Panic over ! Graham, STATION X moderator came to my rescue with his unrivalled knowledge and put matters right. A great big thankyou to Graham. Once again the aroma of warm rexine and wood......Priceless !!
Regards....Dave.

[Station X]

Thanks David.

I'm not sure about the unrivalled knowledge bit! I struggle with anything more complex than a valve record player or radio.

Enjoy using your player.

Graham.

[D_S_J_R]

I'm no good on valve amps (or detailed solid state work either - cough - ) but I can advise on the Garrard should it need some work - they usually all do by now. The main thing is general lubrication and in particular, the trippawls on the main 'auto cam' under the platter, which were lubricated when new and this dries off. If the amp was serviced before, then it may have been dealt with then with any luck. Loads here and also on Vinyl Engine about servicing these and related models (the Autoslim mechanism ran for fifteen years or more on a wide range of models, with only detailed mods as the years went on).

[Station X]

It's been more than five years since I repaired this player for the OP, but recently he contacted me to say it had stopped working again. He said that when he turned it on smoke started emerging from the grilles and it was coming from the mains transformer, naturally he turned the player off. I told him to bring the player round to me and I'd take a look at it.

With the player on the bench I removed the amplifier from the cabinet. Fortunately these players have long inter-connecting leads and is possible to work on and operate the amplifier with it stood on the top front of the cabinet.

With suspected transformer burn outs the first thing I do is to remove all loads from the secondary windings. The LT winding was isolated by unplugging the valves and unscrewing the indicator lamp. The HT winding was isolated by unsoldering one of the wires going to the AC tags on the bridge rectifier. Mains was then applied via a Variac, the transformer got warm, but did not smoke.

Transformers don't generally fail spontaneously, failure is due to another component being faulty and this was what I checked out next. With the rectifier in circuit I tested the junctions using the diode test function of my DMM and found that one of the junctions was short-circuit both ways. This was confirmed with the rectifier totally disconnected from the circuit. While the rectifier was out I applied HT to the circuit from an external supply and found that there were no shorts across the HT rails; and the smoothing capacitors weren't leaking electrically. I found a suitable rectifier in the junk box and, after testing it, I fitted it to the player.

On applying mains the player worked, but not for long!! The transformer did indeed smoke, so I switched off.

I located a suitable transformer here:-

https://primarywindings.com/product/pwht07/

I opted for the drop through version and it took a couple of weeks to arrive.

I mentioned before that neither the rectifier or mains transformer were original to the player. The transformer was a Radiospares Continental with the HT secondary winding rated at 250V 60mA. On removing it I could see that the chassis had been rather crudely hacked to get the fixing bolts to fix. The new transformer easily fitted into the cut out in the chassis and I drilled four new fixing holes for it. On wiring in the new transformer the player worked once again and the transformer stayed cool.

The HT voltage was a bit low though and I attributed this to the non-original 1.5k wire wound anti-surge resistor which was probably fitted to keep the HT current down to 60mA. I replaced the resistor with one of 1k and the voltage at the centre tap of the output transformer primary measured 184VDC with 180VDC on the anodes of the pentodes.

I soak tested the player for several hours working through my LP collection. No more faults came to light and the new mains transformer stayed cool. I refitted the amplifier to the cabinet and it's ready for collection by the OP.

[Station X]

No circuit diagram for the ECL82 version of The Dansette HiFi has come to light, but I did reverse engineer the circuit at the time of the previous repair. However as the mains transformer was not original I don't know what the HT secondary winding voltage of the correct transformer was. Neither do I know whether an anti-surge resistor was fitted or what its value was.

So if any forum member has an unmolested version of this player perhaps they could check the voltages on the output transformer and see whether an anti-surge resistor is fitted.......

[buggies]

There is a ECL82 circuit discussed in this video if you can ignore their advertising. They do mention that the mains transformers burn.
https://en-gb.facebook.com/vintageau...17328732440961

[John10b]

Thanks George for link and information it provides.
John

[joebog1]

This is a good story Graham. I like your work over whoever did the first work.

Joe

[Kentode]

It's the electrical equivalent of Trigger's broom!

But , what great provenance the forum has generated for it. I look forward to seeing it on the Antiques Roadshow...