Fidelity ? recordplayer

[Herald1360]

The Cossor output transformer will be better than the mains transformer, but its ratio is rather higher than optimum for a UL84 (4500ohm anode load rather than 2500ohm). That said, if it sounds OK it won't cause any damage to use it.

[kirstyd]

it seems to work ok with the Cossor transformer and the sound isn't to bad also the big cooked resistor is now only getting warm instead of hot so thats got to be a plus of course this transformer is a lot bigger than its own so i might just mount the bigger one in the cabinet and leave the old on in sit u for future reference or until something more suitable turns up

[Techman]

I think what you're saying in the above post is the best thing to do as regards leaving the old transformer in place and fitting the larger replacement near it - BUT, there's a few things to think about when doing this. It would be best if you could use at least one of the original metal chassis fixing points to hold the transformer. The reason for this is that if you are going to use wood screws to fix it to the inside of the case, you are going to have to think about them not being too long and coming through to the outside of the case. Infact, for safety insulation they shouldn't be screwed into the thin case woodwork at all. Also, with short wood screws there is a risk that the transformer could pull itself free due to its weight with this being a portable player which is going to be moved about and knocked. The transformer should not be mounted too close to, or above hot valves.

[Tim]

Originally Posted by Ed_Dinning

Ideally it should be a transformer from a set with a similar valve (UL84),

You can get replacement valve output transfomers from RS.

http://uk.rs-online.com/web/p/audio-...rmers/2106475/

I think primary connections 1-4 would be the most suitable. Your speaker is likely to be 3 ohms.

[Top Cap]

Looks like a HF16 though the HF18 and HF19 used the same circuit.
Info available here
http://www.service-data.com/search.p...&search=Search

[kirstyd]

Thanks guys. I was thinking of bolting the transformer to the speaker as there are holes on it that almost match. I just need to make them slightly larger, although I will look at getting a new one that's a bit more of a match for this machine. As I said earlier I got this machine purely for nostalgic reasons, once its up and running I wont be using it much, just to play the odd few singles now and again. Had a go at cleaning the filthy cabinet. If anyone is interested I did this with everyday washing powder [DAZ] its come up a treat

['LIVEWIRE?']

As a matter of interest, that universal o/p transformer (RS210-6475) N35A002F is also available from Vintage-Parts.com markhindes.easywebstore.co.uk

[Herald1360]

Just beware of the primary current rating for the RS TX. At 40mA it's a bit on the low side for many low voltage series heater valve types. An increase in cathode bias resistor may be needed for some.

[kirstyd]

Thanks guys, I will order one of these transformers. I may need a bit of advice when it arrives.

[kirstyd]

Hi everyone
well the new transformer arrived today .its roughly about the same size as the old one so it will fit in the same space the question now is what wires go where .The old one has two wires coming in from the amp and then two others going off to the speaker

[Herald1360]

Looking at the data sheet for the TX, the best match for 2.5K anode load and 3ohm speaker would be primary 1-3 (anode to HT) and secondary B-D (speaker).

However......

You will need to increase the value of the cathode resistor to bring the anode current down below 40mA. Chances are it will be considerably higher in its original design.

Anode current will be about 5mA less than cathode current so aim for a cathode current less than 45mA. Cathode current can be calculated from (cathode volts)/cathode resistor (ohms).

[Fidelity Fan]

The amplifier of this model looks the same as the Fidelity Model HF25. The big grey flaky resistor is 82 ohms 2 watts. The value of this was changed to 130 ohms on later production. It may be worth doing this to put less stress on the HT smoothing capacitors and the UL84. I once had one of these with an output transformer with an open circuit primary winding. It caused the 10k ohm 1/2w resistor across the HT capacitors to smoke.

[kirstyd]

yes the 10k ohm resistor has been getting hot i will do as you suggest and change the big resistor .I have installed the new transformer and the recordplayer is working reasonably well .

[Fidelity Fan]

That is good. I also remember that I once had a faulty UL84 causing the 10K resistor to smoke. Make sure that the HT smoothing capacitors are completely discharged before touching them. I still remember getting a very nasty shock from one of these when I was about 13.

[Herald1360]

The 10k resistor is in series with the output valve screen grid. If the O/P TX primary goes open, the valve current tries to go via the screen instead, hence the resistor cookery. If its value is OK, leave it. With a good TX back, it won't get hot any more. In similar amps where the screen goes direct to HT+, it will often glow red hot with the anode open circuited.

[Fidelity Fan]

I have noticed from the photos that it still has the original mains lead which is easy to connect the wrong way round in the plug. This should be replaced with the 3 amp double sheathed type to meet modern safety standards. The blue wire (neutral) should connect to the amplifier chassis when switched on and the brown (live) to the 82 ohm resistor.

[kirstyd]

I know what you mean about the mains lead, however I want to keep the thing looking [if nothing else] as original as possible.
As no one else but me will be using it, I am going to leave the flex as it is. I have made sure the plug is on the right way round [Neutral to chassis]

[kirstyd]

Hi guys .I have opened up this Fidelity again because although its now working its humming or should i say buzzing .With the volume turned right down there is just a very low hum you need to put your ear to the speaker to hear it .As the volume is turned up it starts to hum when the vol is up full the hum turns to a buzz .and the sound of the record playing is not very loud also when i touch the deck the buzz is reduced .Not sure of the model but it appears to have the same amplifier as the HF25 a very basic amp heres a few photos of it. In one of the photos i am pointing at the live side of the mains lead [you cant see the new output trans because its attached to the front panel next to the speaker it was to big to fit on the chassi.Forgot to say i have checked the cartridge and its fine.

[kirstyd]

this is a photo of the tag strip on the deck there appears to be no earth conection

[Nuvistor]

Its a live chassis player so a wire connected from the deck to the player amp chassis would possibly put 240vac on the deck, not good.
Has the player been working ok these last few months and gone faulty or has it been like this since May?
Frank